Internet Engineering Task Force INTERNET-DRAFT H Harney (SPARTA) U Meth (SPARTA) A Colegrove (SPARTA) G Gross (IdentAware) draft-ietf-msec-gsakmp-sec-06.txt SPARTA, Inc., IdentAware Security Expires: December 1, 2004 June 2004 GSAKMP Status of this memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as ``work in progress''. The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Abstract This document specifies the Group Secure Association Key Management Protocol (GSAKMP). The GSAKMP provides a security framework for creating and managing cryptographic groups on a network. It provides mechanisms to disseminate group policy and authenticate users, rules to perform access control decisions during group establishment and recovery, capabilities to recover from the compromise of group members, delegation of group security functions, and capabilities to destroy the group. It also generates group keys. INTERNET-DRAFT GSAKMP June 2004 Copyright Notice Copyright (c) The Internet Society (2004). All Rights Reserved. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 2] INTERNET-DRAFT GSAKMP June 2004 Contents 1 Overview 9 1.1 GSAKMP Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 9 1.2 Document Organization . . . . . . . . . . . . . . . . . . . . . . . 10 2 Terminology 10 3 Security Considerations 13 3.1 Security Assumptions . . . . . . . . . . . . . . . . . . . . . . . 13 3.2 Related Protocols . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.2.1ISAKMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.2.2FIPS Pub 196 . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.2.3LKH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.2.4Diffie-Hellman . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.3 Denial of Service (DoS) Attack . . . . . . . . . . . . . . . . . . 15 3.4 Rekey Availability . . . . . . . . . . . . . . . . . . . . . . . . 15 3.5 Proof of Trust Hierarchy . . . . . . . . . . . . . . . . . . . . . 15 4 Architecture 16 4.1 Trust Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 4.1.1Components . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 4.1.2GO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 4.1.3GC/KS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 4.1.4Subordinate GC/KS . . . . . . . . . . . . . . . . . . . . . . . 17 4.1.5GM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 4.1.6Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . 19 4.2 Rule-Based Security Policy . . . . . . . . . . . . . . . . . . . . 19 4.2.1Access Control . . . . . . . . . . . . . . . . . . . . . . . . . 20 4.2.2Authorizations for security relevant actions . . . . . . . . . . 21 4.3 Distributed Operation . . . . . . . . . . . . . . . . . . . . . . . 21 4.4 Concept of Operation . . . . . . . . . . . . . . . . . . . . . . . 22 4.4.1Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . 23 4.4.2Creation of a PT . . . . . . . . . . . . . . . . . . . . . . . . 23 4.4.3Creation of a Group . . . . . . . . . . . . . . . . . . . . . . 24 4.4.4Discovery of GC/KS . . . . . . . . . . . . . . . . . . . . . . . 24 4.4.5GC/KS registration policy enforcement . . . . . . . . . . . . . 24 4.4.6GM registration policy enforcement . . . . . . . . . . . . . . . 25 4.4.7Autonomous Distributed GSAKMP Operations . . . . . . . . . . . . 25 5 Group Life Cycle 27 5.1 Group Definition . . . . . . . . . . . . . . . . . . . . . . . . . 27 5.2 Group Establishment . . . . . . . . . . . . . . . . . . . . . . . . 28 5.2.1Standard Group Establishment . . . . . . . . . . . . . . . . . . 28 5.2.1.1Request to Join . . . . . . . . . . . . . . . . . . . . . 30 5.2.1.2Key Download . . . . . . . . . . . . . . . . . . . . . . . 31 5.2.1.3Request to Join Error . . . . . . . . . . . . . . . . . . 33 5.2.1.4Key Download - Ack/Failure . . . . . . . . . . . . . . . . 33 5.2.1.5Lack of Ack . . . . . . . . . . . . . . . . . . . . . . . 35 5.2.2Cookies - Group Establishment with Denial of Service Protection 36 5.2.3Group Establishment for Receive-Only Members . . . . . . . . . . 38 5.3 Group Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . 39 5.3.1Group Management . . . . . . . . . . . . . . . . . . . . . . . . 39 Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 3] INTERNET-DRAFT GSAKMP June 2004 5.3.1.1Rekey Events . . . . . . . . . . . . . . . . . . . . . . . 39 5.3.1.2Policy Updates . . . . . . . . . . . . . . . . . . . . . . 40 5.3.1.3Group Destruction . . . . . . . . . . . . . . . . . . . . 40 5.3.2Leaving a Group . . . . . . . . . . . . . . . . . . . . . . . . 40 5.3.2.1Eviction . . . . . . . . . . . . . . . . . . . . . . . . . 40 5.3.2.2Voluntary Departure without Notice . . . . . . . . . . . . 40 5.3.2.3De-Registration . . . . . . . . . . . . . . . . . . . . . 41 5.3.2.3.1Request to Depart . . . . . . . . . . . . . . . . . . 41 5.3.2.3.2Departure_Response. . . . . . . . . . . . . . . . . . 42 5.3.2.3.3Departure_ACK . . . . . . . . . . . . . . . . . . . . 43 6 Security Suite 44 6.1 Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 6.2 Definition Suite 1 . . . . . . . . . . . . . . . . . . . . . . . . 44 7 GSAKMP Payload Structure 45 7.1 GSAKMP Header . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 7.1.1GSAKMP Header Structure . . . . . . . . . . . . . . . . . . . . 46 7.1.1.1GroupID Structure . . . . . . . . . . . . . . . . . . . . 48 7.1.1.1.1UTF-8 . . . . . . . . . . . . . . . . . . . . . . . . 48 7.1.1.1.2Octet String. . . . . . . . . . . . . . . . . . . . . 49 7.1.1.1.3IPv4 Group Identifier . . . . . . . . . . . . . . . . 50 7.1.1.1.4IPv6 Group Identifier . . . . . . . . . . . . . . . . 50 7.1.2GSAKMP Header Processing . . . . . . . . . . . . . . . . . . . . 51 7.2 Generic Payload Header . . . . . . . . . . . . . . . . . . . . . . 53 7.2.1Generic Payload Header Structure . . . . . . . . . . . . . . . . 53 7.2.2Generic Payload Header Processing . . . . . . . . . . . . . . . 53 7.3 Policy Token Payload . . . . . . . . . . . . . . . . . . . . . . . 54 7.3.1Policy Token Payload Structure . . . . . . . . . . . . . . . . . 54 7.3.2Policy Token Payload Processing . . . . . . . . . . . . . . . . 55 7.4 Key Download Payload . . . . . . . . . . . . . . . . . . . . . . . 55 7.4.1Key Download Payload Structure . . . . . . . . . . . . . . . . . 56 7.4.1.1Key Datum Structure . . . . . . . . . . . . . . . . . . . 58 7.4.1.2Rekey Array Structure . . . . . . . . . . . . . . . . . . 59 7.4.2Key Download Payload Processing . . . . . . . . . . . . . . . . 60 7.5 Rekey Event Payload . . . . . . . . . . . . . . . . . . . . . . . . 61 7.5.1Rekey Event Payload Structure . . . . . . . . . . . . . . . . . 61 7.5.1.1Rekey Event Header Structure . . . . . . . . . . . . . . . 63 7.5.1.2Rekey Event Data Structure . . . . . . . . . . . . . . . . 64 7.5.1.2.1Key Package Structure . . . . . . . . . . . . . . . . 65 7.5.2Rekey Event Payload Processing . . . . . . . . . . . . . . . . . 65 7.6 Identification Payload . . . . . . . . . . . . . . . . . . . . . . 67 7.6.1Identification Payload Structure . . . . . . . . . . . . . . . . 67 7.6.1.1ID_U_NAME Structure . . . . . . . . . . . . . . . . . . . 69 7.6.2Identification Payload Processing . . . . . . . . . . . . . . . 70 7.6.2.1ID_U_NAME Processing . . . . . . . . . . . . . . . . . . . 71 7.7 Certificate Payload . . . . . . . . . . . . . . . . . . . . . . . . 71 7.7.1Certificate Payload Structure . . . . . . . . . . . . . . . . . 71 7.7.2Certificate Payload Processing . . . . . . . . . . . . . . . . . 72 7.8 Signature Payload . . . . . . . . . . . . . . . . . . . . . . . . . 73 7.8.1Signature Payload Structure . . . . . . . . . . . . . . . . . . 73 7.8.2Signature Payload Processing . . . . . . . . . . . . . . . . . . 75 Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 4] INTERNET-DRAFT GSAKMP June 2004 7.9 Notification Payload . . . . . . . . . . . . . . . . . . . . . . . 76 7.9.1Notification Payload Structure . . . . . . . . . . . . . . . . . 76 7.9.1.1Notification Data - Acknowledgment (ACK) Payload Type . . 79 7.9.1.2Notification Data - Cookie_Required and Cookie Payload Type79 7.9.1.3Notification Data - Mechanism Choices Payload Type . . . . 80 7.9.1.4Notification Data - IPv4 and IPv6 Value Payload Types . . 81 7.9.2Notification Payload Processing . . . . . . . . . . . . . . . . 81 7.10Vendor ID Payload . . . . . . . . . . . . . . . . . . . . . . . . . 82 7.10.1Vendor ID Payload Structure . . . . . . . . . . . . . . . . . . 82 7.10.2Vendor ID Payload Processing . . . . . . . . . . . . . . . . . 83 7.11Key Creation Payload . . . . . . . . . . . . . . . . . . . . . . . 84 7.11.1Key Creation Payload Structure . . . . . . . . . . . . . . . . 84 7.11.2Key Creation Payload Processing . . . . . . . . . . . . . . . . 85 7.12Nonce Payload . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 7.12.1Nonce Payload Structure . . . . . . . . . . . . . . . . . . . . 86 7.12.2Nonce Payload Processing . . . . . . . . . . . . . . . . . . . 87 8 GSAKMP State Diagram 88 9 IANA Considerations 91 9.1 IANA Port Number Assignment . . . . . . . . . . . . . . . . . . . . 91 9.2 Initial IANA Registry Contents . . . . . . . . . . . . . . . . . . 91 9.2.1GSAKMP Group Identification Types . . . . . . . . . . . . . . . 91 9.2.1.1Amending formula for GSAKMP Group Identification Types . . 92 9.2.2GSAKMP Payload Types . . . . . . . . . . . . . . . . . . . . . . 92 9.2.2.1Amending formula for GSAKMP Payload Types . . . . . . . . 92 9.2.3GSAKMP Exchange Types . . . . . . . . . . . . . . . . . . . . . 92 9.2.3.1Amending formula for GSAKMP Exchange Types . . . . . . . . 93 9.2.4GSAKMP Policy Token Types . . . . . . . . . . . . . . . . . . . 93 9.2.4.1Amending formula for GSAKMP Policy Token Types . . . . . . 93 9.2.5GSAKMP Key Download Data Item Types . . . . . . . . . . . . . . 93 9.2.5.1Amending formula for GSAKMP Key Download Data Item Types . 93 9.2.6GSAKMP Cryptographic Key Types . . . . . . . . . . . . . . . . . 94 9.2.6.1Amending formula for GSAKMP Cryptographic Key Types . . . 94 9.2.7GSAKMP Rekey Event Types . . . . . . . . . . . . . . . . . . . . 94 9.2.7.1Amending formula for GSAKMP Rekey Event Types . . . . . . 94 9.2.8GSAKMP Identification Classification . . . . . . . . . . . . . . 94 9.2.8.1Amending formula for GSAKMP Identification Classification. 95 9.2.9GSAKMP Identification Types . . . . . . . . . . . . . . . . . . 95 9.2.9.1Amending formula for GSAKMP Identification Types . . . . . 95 9.2.10GSAKMP Certificate Types . . . . . . . . . . . . . . . . . . . 95 9.2.10.1Amending formula for GSAKMP Certificate Types . . . . . . 96 9.2.11GSAKMP Signature Types . . . . . . . . . . . . . . . . . . . . 96 9.2.11.1Amending formula for GSAKMP Signature Types . . . . . . . 96 9.2.12GSAKMP Notification Types . . . . . . . . . . . . . . . . . . . 96 9.2.12.1Amending formula for GSAKMP Notification Types . . . . . 97 9.2.13GSAKMP Acknowledgment Types . . . . . . . . . . . . . . . . . . 97 9.2.13.1Amending formula for GSAKMP Acknowledgment Types . . . . 97 9.2.14GSAKMP Mechanism Types . . . . . . . . . . . . . . . . . . . . 97 9.2.14.1Amending formula for GSAKMP Mechanism Types . . . . . . . 98 9.2.15GSAKMP Nonce Hash Types . . . . . . . . . . . . . . . . . . . . 98 9.2.15.1Amending formula for GSAKMP Nonce Hash Types . . . . . . 98 Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 5] INTERNET-DRAFT GSAKMP June 2004 9.2.16GSAKMP Key Creation Types . . . . . . . . . . . . . . . . . . . 98 9.2.16.1Amending formula for GSAKMP Key Creation Types . . . . . 99 9.2.17GSAKMP Nonce Types . . . . . . . . . . . . . . . . . . . . . . 99 9.2.17.1Amending formula for GSAKMP Nonce Types . . . . . . . . . 99 10Acknowledgments 99 11References 100 11.1Normative References . . . . . . . . . . . . . . . . . . . . . . . 100 11.2Informative References . . . . . . . . . . . . . . . . . . . . . . 100 A APPENDIX A -- LKH Information 102 A.1 LKH Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 A.2 LKH and GSAKMP . . . . . . . . . . . . . . . . . . . . . . . . . . 103 A.3 LKH Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 A.3.1LKH Key Download Example . . . . . . . . . . . . . . . . . . . . 104 A.3.2LKH Rekey Event Example . . . . . . . . . . . . . . . . . . . . 105 B APPENDIX B -- Change History (To Be Removed from RFC) 106 B.1 Changes from GSAKMP-00 to GSAKMP-01 February 2003 . . . . . . . . . 106 B.2 Changes from GSAKMP-01 to GSAKMP-02 June 2003 . . . . . . . . . . . 107 B.3 Changes from GSAKMP-02 to GSAKMP-03 August 2003 . . . . . . . . . . 107 B.4 Changes from GSAKMP-03 to GSAKMP-04 October 2003 . . . . . . . . . 107 B.5 Changes from GSAKMP-04 to GSAKMP-05 February 2004 . . . . . . . . . 111 B.5.1Major Modification/Reorganization of Specification . . . . . . . 111 B.5.1.1Key Terms and Payloads Modified . . . . . . . . . . . . . 111 B.5.2Modification By Section . . . . . . . . . . . . . . . . . . . . 112 B.6 Changes from GSAKMP-05 to GSAKMP-06 May 2004 . . . . . . . . . . . 115 Authors Addresses 120 Full Copyright Statement 121 Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 6] INTERNET-DRAFT GSAKMP June 2004 List of Figures 1 GSAKMP Ladder Diagram . . . . . . . . . . . . . . . . . . . . . . . 29 2 GSAKMP Ladder Diagram with Cookies . . . . . . . . . . . . . . . . 37 3 GSAKMP Header Format . . . . . . . . . . . . . . . . . . . . . . . 46 4 GroupID UTF-8 Format . . . . . . . . . . . . . . . . . . . . . . . 49 5 GroupID Octet String Format . . . . . . . . . . . . . . . . . . . . 49 6 GroupID IPv4 Format . . . . . . . . . . . . . . . . . . . . . . . . 50 7 GroupID IPv6 Format . . . . . . . . . . . . . . . . . . . . . . . . 51 8 Generic Payload Header . . . . . . . . . . . . . . . . . . . . . . 53 9 Policy Token Payload Format . . . . . . . . . . . . . . . . . . . . 54 10 Key Download Payload Format . . . . . . . . . . . . . . . . . . . . 56 11 Key Download Data Item Format . . . . . . . . . . . . . . . . . . . 57 12 Key Datum Format . . . . . . . . . . . . . . . . . . . . . . . . . 58 13 Rekey Array Structure Format . . . . . . . . . . . . . . . . . . . 60 14 Rekey Event Payload Format . . . . . . . . . . . . . . . . . . . . 61 15 Rekey Event Header Format . . . . . . . . . . . . . . . . . . . . . 63 16 Rekey Event Data Format . . . . . . . . . . . . . . . . . . . . . . 64 17 Key Package Format . . . . . . . . . . . . . . . . . . . . . . . . 65 18 Identification Payload Format . . . . . . . . . . . . . . . . . . . 68 19 Unencoded Name (ID-U-NAME) Format . . . . . . . . . . . . . . . . . 70 20 Certificate Payload Format . . . . . . . . . . . . . . . . . . . . 72 21 Signature Payload Format . . . . . . . . . . . . . . . . . . . . . 74 22 Notification Payload Format . . . . . . . . . . . . . . . . . . . . 77 23 Notification Data - Acknowledge Payload Type Format . . . . . . . . 79 24 Notification Data - Mechanism Choices Payload Type Format . . . . . 80 25 Vendor ID Payload Format . . . . . . . . . . . . . . . . . . . . . 82 26 Key Creation Payload Format . . . . . . . . . . . . . . . . . . . . 84 27 Nonce Payload Format . . . . . . . . . . . . . . . . . . . . . . . 86 28 GSAKMP State Diagram . . . . . . . . . . . . . . . . . . . . . . . 88 29 A. 1: LKH Tree . . . . . . . . . . . . . . . . . . . . . . . . . 102 30 A. 2: GSAKMP LKH Tree . . . . . . . . . . . . . . . . . . . . . . 103 Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 7] INTERNET-DRAFT GSAKMP June 2004 List of Tables 1 Request to Join (RTJ) Message Definition . . . . . . . . . . . . . 30 2 Key Download (KeyDL) Message Definition . . . . . . . . . . . . . . 32 3 Request to Join Error (RTJ-Err) Message Definition . . . . . . . . 33 4 Key Download - Ack/Failure (KeyDL-A/F) Message Definition . . . . . 34 5 Lack of Ack (LOA) Message Definition . . . . . . . . . . . . . . . 35 6 Cookie Download Message Definition . . . . . . . . . . . . . . . . 36 7 Rekey Event Message Definition . . . . . . . . . . . . . . . . . . 39 8 Request_to_Depart (RTD) Message Definition . . . . . . . . . . . . 41 9 Departure_Response (DR) Message Definition . . . . . . . . . . . . 42 10 Departure_ACK (DA) Message Definition . . . . . . . . . . . . . . . 43 11 Group Identification Types . . . . . . . . . . . . . . . . . . . . 47 12 Payload Types . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 13 Exchange Types . . . . . . . . . . . . . . . . . . . . . . . . . . 48 14 Policy Token Types . . . . . . . . . . . . . . . . . . . . . . . . 55 15 Key Download Data Item Types . . . . . . . . . . . . . . . . . . . 57 16 Cryptographic Key Types . . . . . . . . . . . . . . . . . . . . . . 59 17 Rekey Event Types . . . . . . . . . . . . . . . . . . . . . . . . . 62 18 Identification Classification . . . . . . . . . . . . . . . . . . . 68 19 Identification Types . . . . . . . . . . . . . . . . . . . . . . . 69 20 Certificate Payload Types . . . . . . . . . . . . . . . . . . . . . 73 21 Signature Types . . . . . . . . . . . . . . . . . . . . . . . . . . 75 22 Notification Types . . . . . . . . . . . . . . . . . . . . . . . . 78 23 Acknowledgment Types . . . . . . . . . . . . . . . . . . . . . . . 79 24 Mechanism Types . . . . . . . . . . . . . . . . . . . . . . . . . . 80 25 Nonce Hash Types . . . . . . . . . . . . . . . . . . . . . . . . . 81 26 Types Of Key Creation Information . . . . . . . . . . . . . . . . . 85 27 Nonce Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 28 GSAKMP States . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 29 State Transition Events . . . . . . . . . . . . . . . . . . . . . . 90 Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 8] INTERNET-DRAFT GSAKMP June 2004 1 Overview 1.1 GSAKMP Overview Protecting group information requires the definition of a security policy and the enforcement of that policy by all participating parties. Controlling dissemination of cryptographic key is the primary mechanism to enforce the access control policy. It is the primary purpose of GSAKMP to generate and disseminate a group key in a secure fashion. GSAKMP separates group security management functions and responsibilities into three major roles: 1) Group Owner, 2) Group Controller Key Server, and 3) Group Member. The Group Owner is responsible for creating the security policy rules for a group and expressing these in the Policy Token. The Group Controller Key Server (GC/KS) is responsible for creating and maintaining the keys and enforcing the group policy by granting access to potential Group Members (GM) in accordance with the Policy Token. To enforce a group's policy the potential Group Members need to have knowledge of the access control policy for the group, an unambiguous identification of any party downloading keys to them, and verifiable chains of authority for key download. In other words, the Group Members need to know who potentially will be in the group and to verify that the key disseminator is authorized to act in that capacity. In order to establish a Group Secure Association (GSA) to support these activities, the identity of each party in the process MUST be unambiguously asserted and authenticated. It MUST also be verified that each party is authorized, as defined by the Policy Token, to function in his role in the protocol (e.g., GM or GC/KS). The security features of the establishment protocol for the SA include - Group policy identification - Group policy dissemination - GM to GC/KS SA establishment to protect data - Access control checking GSAKMP provides mechanisms for cryptographic group creation and management. Other protocols may be used in conjunction with GSAKMP to allow various applications to create functional groups according to their application-specific requirements. For example, in a small-scale video conference the organizer might use a session invitation protocol like SIP [RFC 2543] to transmit information about the time of the conference, the address of the session, and the formats to be used. For a large-scale video Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 9] INTERNET-DRAFT GSAKMP June 2004 transmission, the organizer might use a multicast announcement protocol like SAP [RFC 2974]. This document describes a useful default set of security algorithms and configurations, Security Suite 1. This suite allows an entire set of algorithms and settings to be described to prospective group members in a concise manner. Other security suites MAY be defined as needed and MAY be disseminated during the out-of-band announcement of a group. Distributed architectures support large scale cryptographic groups. Secure distributed architectures require authorized delegation of GSA actions to network resources. The fully specified Policy Token is the mechanism to facilitate this authorization. Transmission of this Policy Token to all joining GMs allows GSAKMP to securely support distributed architectures and multiple data sources. Many-to-many group communications require multiple data sources. Multiple data sources are supported because the inclusion of a policy token and policy payloads allow group members to review the group access control and authorization parameters. This member review process gives each member (each potential source of data), the ability to determine if the group provides adequate protection for member data. 1.2 Document Organization The remainder of this document is organized as follows: Section 2 presents the terminology and concepts used to present the requirements of this protocol. Section 3 outlines the security considerations with respect to GSAKMP. Section 5 describes the group management life-cycle. Section 6 describes the Security Suite Definition. Section 7 presents the message types and formats used during each phase of the life-cycle. Section 8 defines the state diagram for the protocol. 2 Terminology The following terminology is used throughout the GSAKMP paper. Requirements Terminology: Keywords "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT" and "MAY" that appear in this document are to be interpreted as described in [RFC 2119]. Certificate: A data structure used to verifiably bind an identity to a cryptographic key (e.g., X.509v3). Compromise Recovery: The act of recovering a secure operating state Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 10] INTERNET-DRAFT GSAKMP June 2004 after detecting that a group member cannot be trusted. This can be accomplished by rekey. Cryptographic Group: A set of entities sharing or desiring to share a GSA. Group Controller Key Server (GC/KS): A group member with authority to perform critical protocol actions including creating and distributing keys and building and maintaining the rekey structures. As the group evolves, it MAY become desirable to have multiple controllers perform these functions. Group Member (GM): A Group Member is any entity with access to the group keys. Regardless of how a member becomes a part of the group or how the group is structured, GMs will perform the following actions: - Authenticate and validate the identities and the authorizations of entities performing security relevant actions - Accept group keys from the GC/KS - Request group keys from the GC/KS - Enforce the cooperative group policies as stated in the group policy token - Perform peer review of key management actions - Manage local key Group Owner (GO): A Group Owner is the entity authorized for generating and modifying an authenticatable policy token for the group, and notifying the GC/KS to start the group. Group Policy: The Group Policy completely describes the protection mechanisms and security relevant behaviors of the group. This policy MUST be commonly understood and enforced by the group for coherent secure operations. Group Secure Association (GSA): A GSA is a logical association of users or hosts that share cryptographic key(s). This group may be established to support associations between applications or communication protocols. Group Traffic Protection Key (GTPK): The key or keys created for protecting the group data. Key Datum: A single key and its associated attributes for its usage. Key Encryption Key (KEK): Key used in an encryption mechanism for wrapping Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 11] INTERNET-DRAFT GSAKMP June 2004 another key. Key Handle: The identifier of a particular instance or version of a key. Key ID: The identifier for a key that MUST stay static throughout the life-cycle of this key. Key Package: Type/Length/Data format containing a Key Datum. Logical Key Hierarchy (LKH) Array: The group of keys created to facilitate the LKH compromise recovery methodology. Policy Token: The policy token is a data structure used to disseminate group policy and the mechanisms to enforce it. The policy token is issued and signed by an authorized Group Owner. Each member of the group MUST verify the token, meet the group join policy, and enforce the policy of the group, (e.g., encrypt application data with a specific algorithm). The group policy token will contain a variety of information including: - GSAKMP protocol version - Key creation method - Key dissemination policy - Access control policy - Group authorization policy - Compromise recovery policy - Data protection mechanisms An example of a policy token is specified in [HCLM00]. Rekey: The act of changing keys within a group as defined by policy. Rekey Array: The construct that contains all the rekey information for a particular member. Rekey Key: The KEK used to encrypt keys for a subset of the group. Subordinate Group Controller Key Server (S-GC/KS): Any group member having the appropriate processing and trust characteristics as defined in the group policy that has the potential to act as a S-GC/KS. This will allow the group processing and communication requirements to be distributed equitably throughout the network (e.g., distribute group key). The optional use of GSAKMP with Subordinate Group Controller Key Servers Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 12] INTERNET-DRAFT GSAKMP June 2004 will be documented in a separate paper. Wrapping KeyID: - The Key ID of the key used to wrap a Key Package. Wrapping Key Handle: The key handle of the Key used to wrap the Key Package. 3 Security Considerations In addition to the specification of GSAKMP itself, the security of an implemented GSAKMP system is affected by supporting factors. These are discussed here. 3.1 Security Assumptions The following assumptions are made as the basis for the security discussion 1. GSAKMP assumes its supporting platform can provide the process and data separation services at the appropriate assurance level to support its groups. 2. The key generation function of the cryptographic engine will only generate strong keys. 3. The security of this protocol is critically dependent on the randomness of the randomly chosen parameters. These should be generated by a strong random or properly seeded pseudo-random source. 4. The security of a group can be affected by the accuracy of the system clock. Therefore, GSAKMP assumes that the system clock is close to correct time. If a GSAKMP host relies on a network time service to set its local clock, then that protocol must be secure against attackers. The maximum allowable clock skew across the group membership: policy configurable, with a default of 5 minutes. 5. As described in the message processing section, the use of the Nonce value used for freshness along with a signature is the mechanism used to foil replay attacks. 6. GSAKMP does not provide identity protection. 7. The group's multicast routing infrastructure is not secured by GSAKMP, and therefore it may be possible to create a multicast flooding denial of service attack using the multicast application's data stream. Either an insider (i.e. a rogue GM) or a non-member could direct the multicast Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 13] INTERNET-DRAFT GSAKMP June 2004 routers to spray data at a victim system. 8. The compromise of a S-GC/KS forces the re-registration of all GM under its control. The GM recognizes this situation by finding the S-GC/KSs certificate on a CRL as supplied by a service such as LDAP. 9. The compromise of the GO forces termination of the group. The GM recognizes this situation by finding the GOs certificate on a CRL as supplied by a service such as LDAP. 3.2 Related Protocols GSAKMP derives from two (2) existing protocols: ISAKMP [MSST98] and FIPS Pub 196 [FIPS 196]. In accordance with Security Suite 1, GSAKMP implementations MUST support the use of Diffie-Hellman key exchange [DH77] for two party key creation and MAY use Logical Key Hierarchy (LKH) for rekey capability. 3.2.1 ISAKMP ISAKMP provides a flexible structure of chained payloads in support of authenticated key exchange and security association management for pairwise communications. GSAKMP builds upon these features to provide policy enforcement features in support of diverse group communications. 3.2.2 FIPS Pub 196 FIPS Pub 196 provides a mutual authentication protocol. 3.2.3 LKH GSAKMP relies upon a rekey capability, i.e., LKH, to enable group recovery after a compromise [RFC 2627]. 3.2.4 Diffie-Hellman A Group may rely upon two party key creation mechanisms, i.e., Diffie-Hellman, to protect sensitive data during download. The information in this section is borrowed heavily from [IKEv2] as this protocol has already worked through similar issues and GSAKMP is using the Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 14] INTERNET-DRAFT GSAKMP June 2004 same security considerations for its purposes. This section will contain paraphrased sections of [IKEv2] modified for GSAKMP as appropriate. The strength of a key derived from a Diffie-Hellman exchange using specific p and g values depends on the inherent strength of the values, the size of the exponent used, and the entropy provided by the random number generator used. Security Suite 1 defined in section 6, based on [IKEv2] Group 2, with a strong random number generator and an exponent no less than 200 bits is sufficient to use for 3DES. An implementation should make note of this conservative estimate when establishing policy and negotiating security parameters. Note that these limitations are on the Diffie-Hellman values themselves. There is nothing in GSAKMP which prohibits using stronger values nor is there anything which will dilute the strength obtained from stronger values. In fact, the extensible framework of GSAKMP encourages the definition of more Security Suites. It is assumed that the Diffie-Hellman exponents in this exchange are erased from memory after use. In particular, these exponents MUST NOT be derived from long-lived secrets like the seed to a pseudo-random generator that is not erased after use. 3.3 Denial of Service (DoS) Attack This GSAKMP specification addresses the mitigation for a distributed IP spoofing attack (a subset of possible DoS attacks) in section 5.2.2, Cookies. 3.4 Rekey Availability In addition to GSAKMP having the capability to do rekey operations, GSAKMP MUST also have the capability to make this rekey information highly available to GMs. The necessity of GMs receiving rekey messages, requires the use of methods to increase the likelihood of receipt of Rekey Messages. These methods MAY include multiple transmissions of the rekey message, posting of the rekey message on a bulletin board, etc. Compliant GSAKMP implementations MUST support retransmission of rekey messages. 3.5 Proof of Trust Hierarchy As defined by [HCM], security group policy MUST be defined in a verifiable manner. GSAKMP anchors its trust in the creator of the group, the GO. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 15] INTERNET-DRAFT GSAKMP June 2004 The Policy Token explicitly defines all the parameters that create a secure verifiable infrastructure. The GSAKMP Policy Token is issued and signed by the GO. The GC/KS will verify it and grant access to GMs only if they meet the rules of the Policy Token. The new GMs will accept access only if 1) the token verifies, 2) the GC/KS is an authorized disseminator, and 3) the group mechanisms are acceptable for protecting the GMs data. 4 Architecture This architecture presents a trust model for GSAKMP and a concept of operations for establishing a trusted distributed infrastructure for group key and policy distribution. GSAKMP conforms to the IETF MSEC architectural concepts as specified in the MSEC Architecture document [HW05]. GSAKMP uses the MSEC components to create a trust model for operations that implement the security principles of mutual suspicion and trust anchors. 4.1 Trust Model 4.1.1 Components The trust model contains four key components: - Group Owners (GO), - Group Controllers / Key Servers (GC/KS), - Subordinate GC/KS (S-GC/KS), and - Group Members (GM). The goal of the GSAKMP trust model is to derive trust from a common trust anchor for a group. All security relevant decisions and actions implemented by GSAKMP are based on information that ultimately is traceable to and verified by a core trust anchor. There are two pieces of the trust anchors for GSAKMP, the GO (policy creation authority) and the PKI root that allows us to verify the GO. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 16] INTERNET-DRAFT GSAKMP June 2004 4.1.2 GO The GO is the policy creation authority for the group. The GO has a well defined identity that is relevant to the group. That identity can be of a person or of a group trusted component. All potential entities in the group have to recognize the GO as the individual with authority to specify policy for the group. The policy reflects the protection requirements of the data in a group. Ultimately, the data and the application environment drives the security policy for the group. The GO has to determine the security rules and mechanisms that are appropriate for the data being protected by the group keys. All this information is captured in a policy token (PT). The GO creates the PT and signs it. 4.1.3 GC/KS The GC/KS is authorized to perform several functions: key creation, key distribution, rekey, and group membership management. As key creation authority, the GC/KS will create the set of keys for the group. These keys include the Group Traffic Protection Keys (GTPK) and first tier rekey keys. There may be second tier rekey trees if a distributed rekey management structure is required for the group. As the key distribution (registration) authority, it has to notify the group of its location for registration services. The GC/KS will have to enforce key access control as part of the key distribution and registration processes. As the group rekey authority, it performs rekey in order to change the group's GTPK. Change of the GTPK limits the exposure of data encrypted with any single GTPK. Finally, as group membership management authority, the GC/KS can manage the group membership (registration, eviction, de-registration, etc.). This may be done in part by using key tree approaches such as Logical Key Hierarchies (LKH). 4.1.4 Subordinate GC/KS A subordinate GC/KS is used to distribute the GC/KS functionality across multiple entities. The S-GC/KS will have all the authorities of the GC/KS except one: it will not create the GTPK. It is assumed here that the group Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 17] INTERNET-DRAFT GSAKMP June 2004 will transmit data with a single GTPK at any one time. This GTPK comes from the GC/KS. Note that relative to the GC/KS, the S-GC/KS is responsible for an additional security check: the S-GC/KS must register as a member with the GC/KS, and during that process it has to verify the authority of the GC/KS. 4.1.5 GM The GM has two jobs - make sure all security relevant actions are authorized and properly use the group keys. During the registration process, the GM will verify that the PT is signed by a recognized GO. In addition, it will verify that the GC/KS or S-GC/KS engaged in the registration process is authorized, as specified in the PT. If rekey and new PTs are distributed to the group, the GM will verify that they are proper and all actions are authorized. The GM is granted access to group data through receipt of the group keys This carries along with it a responsibility to protect the key from unauthorized disclosure. GSAKMP does not offer any enforcement mechanisms to control which GM are multicast speakers at a given moment. This policy and its enforcement depend on the multicast application and its protocols. However, GSAKMP does allow a group to have one of three Group Security Association multicast speaker configurations: - There is a single GM authorized to be the group's speaker. There is one multicast application SA allocated by the GO in support of that speaker. The PT initializes this multicast application SA and identifies the GM that has been authorized to be speaker. All GM share a single TPK with that GM speaker. Sequence number checking for anti-replay protection is feasible and enabled by default. This is the default group configuration. GSAKMP implementations MUST support this configuration. - The GO authorizes all of the GM to be a group speaker. The GO allocates one multicast application SA in support of these speakers. The PT initializes this multicast application SA and indicates that any GM can be a speaker. All of the GM share a single TPK and other SA state information. Consequently, some SA security features such as sequence number checking for anti-replay protection can not be supported by this configuration. GSAKMP implementations MUST support this group configuration. - The GO authorizes a subset of the GM to be a group speaker (which may be the subset comprised of all GM). The GO allocates a distinct multicast application SA for each of these speakers. The PT identifies the Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 18] INTERNET-DRAFT GSAKMP June 2004 authorized speakers, and initializes each of their multicast application Security Associations. The speakers still share a common TPK across their SA, but each speaker has a separate SA state information instance at every peer GM. Consequently, this configuration supports SA security features such as sequence number checking for anti-replay protection or source authentication mechanisms that require per speaker state at the receiver. The drawback of this configuration is that it does not scale to a large numbers of speakers. GSAKMP implementations MAY support this group configuration. 4.1.6 Assumptions The assumptions for this trust model are: - the GCKS is assumed to be never compromised, - the GO is assumed to be never compromised, - the PKI, subject to certificate validation, is assumed to be trustworthy,, - The GO is capable of creating a security policy to meet the demands of the group, - the compromises of a group member will be detectable and reported to the GO in a trusted manner, - the subsequent recovery from a compromise will deny inappropriate access to protected data to the compromised member, - no security relevant actions depend on a precise network time, - that there is confidentiality, integrity, multicast source authentication and anti-replay protection mechanisms for all GSAKMP control messages, 4.2 Rule-Based Security Policy The trust model for GSAKMP revolves around the definition and enforcement of the security policy. In fact, the use of the key is only relevant, in a security sense, if it represents the successful enforcement of the group security policy. Group operations lend themselves to rule-based security policy. The need for distribution of data to many endpoints often leads to the defining of those authorized endpoints based on rules. For example, all IETF attendees Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 19] INTERNET-DRAFT GSAKMP June 2004 at a given conference could be defined as a single group. If the security policy rules are to be relevant, they must be coupled with validation mechanisms. The core principle here is that the level of trust one can afford a security policy is exactly equal to the level of trust one has in the validation mechanism used to prove that policy. For example, if all IETF attendees are allowed in then they could register their identity from their certificate upon check in to the meetings. That certificate is issued by a trust anchor (PKI root) that is authorized to identify someone as being an IETF attendee. The GO could make admittance rules to the IETF group based on the identity certificates issued from trusted PKIs. In GSAKMP, every security policy rule is coupled with an explicit validation mechanism. For interoperability considerations, GSAKMP requires its supporting PKI implementations MUST be compliant to RFC 3280. If a GM public key certificate is revoked, then the entity that issues that revocation SHOULD signal the GO, so that the GO can expel that GM. The method that signals this event to the GO is not standardized by this specification. A direct mapping of rule to validation mechanism allows the use of multiple rules and PKIs to create groups. This allows a GO to define a group security policy that spans multiple PKI domains, each with their own Certificate Authority public key certificate. 4.2.1 Access Control The access control policy for the group keys is equivalent to the access control policy for the multicast application data the keys are protecting. In a group, each data source is responsible for ensuring that the access to the source's data is appropriate. This implies that every data source should have knowledge of the access control policy for the group keys. In the general case, GSAKMP offers a suite of security services to its applications, and does not prescribe how they use those services. GSAKMP supports the creation of GSAs with multiple data sources. It also supports architectures where the GC/KS is not itself a data source. In the multiple data source architectures GSAKMP requires that the access control policy is precisely defined and distributed to each data source. The reference for this data structure is the GSAKMP Policy Token [ref TBD]. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 20] INTERNET-DRAFT GSAKMP June 2004 4.2.2 Authorizations for security relevant actions A critical aspect of the GSAKMP trust model is the authorization of security relevant actions. Security relevant actions include - download of group key, rekey, and PT creation and updates. These actions could be used to disrupt the secure group and all entities in the group must verify that they were instigated by authorized entities within the group. 4.3 Distributed Operation Scalability is a core feature of GSAKMP. GSAKMP's approach to scalable operations is the establishment of S-GC/KSs. This allows the GSAKMP systems to distribute the workload of setting up and managing very large groups. Another aspect of distributed S-GC/KS operations is the enabling of local management authorities. In very large groups, subordinate enclaves may be best suited to provide local management of the enclaves' group membership, due to a direct knowledge of the group members. One of the critical issues involved with distributed operation is the discovery of the security infrastructure location and security suite. Many group applications that have dynamic interactions must "find" each other to operate. The discovery of the security infrastructure is just another piece of information that has to be known by the group in order to operate securely. There are several methods for infrastructure discovery: - Announcements - Anycast - Rendezvous points / Registration One method for distributing the security infrastructure location is to use announcements. The SAP is commonly used to announce the existence of a new multicast application or service. If an application uses SAP[Ref RFC 2974] to announce the existence of a service on a multicast channel, that service could be extended to include the security infrastructure location for a particular group. Announcements can also be used by GSAKMP in one of two modes - Expanding Ring Searches (ERS) of security infrastructure and expanding ring searches for infrastructure discovery. In either case, the GSAKMP would use a multicast broadcast that would slowly increase in its range by incremental multicast hops. The multicast source controls the packet's multicast range Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 21] INTERNET-DRAFT GSAKMP June 2004 by explicitly setting its Time To Live count. An expanding ring announcement operates by the GC/KS announcing its existence for a particular group. The number of hops this announcement would travel would be a locally configured number. The GMs would listen on a well know multicast address for GC/KSs that provide service for groups of interest. If multiple GC/KSs are found that provide service, then the GM would pick the closest one (in terms of multicast hops). The GM would then send a GSAKMP Request to Join message (RTJ) to the announced GC/KS. If the announcement is found to be spurious then that is reported to the appropriate management authorities. The ERA concept is slightly different from SAP in that it could occur over the data channel multicast address, instead of a special multicast address dedicated for the SAP service. An expanding ring search operates in the reverse order than the ERA. In this case, the GM is the announcing entity. The (S-)GC/KSs listen for the requests for service, specifically the RTJ. The (S-)GC/KS responds to the RTJ. . If the GM receives more than one response, it would either ignore the responses or send NACKs based on local configuration. Anycast is a service that is very similar to ERS. It also can be used to provide connection to the security infrastructure. In this case, the GM would send the RTJ to a well-known service request address. This anycast service would route the RTJ to an appropriate GC/KS. The anycast service would have security infrastructure and network connectivity knowledge to facilitate this connection. Registration points can be used to distribute many group relevant data, including security infrastructure. Many group applications rely on well known registration points to advertise the availability of groups. There is no reason that GSAKMP could not use the same approach for advertising the existence and location of the security infrastructure. This is a simple process if the application being supported already supports registration. The GSAKMP infrastructure can always provide a registration site if the existence of this security infrastructure discovery hub is needed. The registration of S-GC/KSs at this site could be an efficient way to allow GM registration. GSAKMP infrastructure discovery can use whatever mechanism suits a particular multicast application's requirements, including mechanisms that have not been discussed by this architecture. However, GSAKMP infrastructure discovery is not standardized by this version of the GSAKMP specification. 4.4 Concept of Operation This concept of operation shows how the different roles in GSAKMP interact to set up a secure group. This particular concept of operation focuses on a secure group that utilizes the distributed key dissemination services of the Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 22] INTERNET-DRAFT GSAKMP June 2004 S-GC/KS. 4.4.1 Assumptions The most basic assumption here is one or more trustworthy PKI for the group. That trusted PKI will be used to create and verify security policy rules. There is a GO that all GMs recognize as having group policy creation authority. All GM must be securely pre-configured to know the GO public key. All GMs have access to the GO PKI information, both the trusted anchor public keys and the certificate path validation rules. There is sufficient connectivity between the GSAKMP entities. - The registration SA requires that GM can connect to the GC/KS or S-GC/KS using either TCP or UDP. - The rekey SA requires that the data layer multicast communication service be available. This can be multicast IP, overlay networks using TCP, or NAT tunnels. - GSAKMP can support many different data layer secure applications each with unique connectivity requirements. 4.4.2 Creation of a PT The GO creates and signs the Policy Token for a group. The policy token contains the rules for access control and authorizations for a particular group. The PT consists of the following information: - Identification - this allows an unambiguous identification of the PT and the group, - Access Control Rules - these rules specify who can have access to the group keys, - Authorization Rules - these rules specify who can be a S-GC/KS, - Mechanisms - these rules specify the security mechanisms that will be used by the group, this is necessary to ensure there is no weak link in the group security profile, for example, for IPSec, this could include Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 23] INTERNET-DRAFT GSAKMP June 2004 SPD/SAD configuration data - Source authentication of the PT to the GO - the PT is a CMS signed object and this allows all GMs to verify the PT 4.4.3 Creation of a Group The PT is sent to a potential GC/KS. This can occur in several ways, and the method of transmittal is outside the scope of GSAKMP. The potential GC/KS will verify the GO signature on the PT to ensure that it comes from a trusted GO. Next, the GC/KS will verify that it is authorized to become the GC/KS, based on the authorization rules in the PT. Assuming that the GC/KS trusts the PT, is authorized to be a GC/KS, and is locally configured to become a GC/KS for a given group and the GO, then the GC/KS will create the keys necessary to start the group. The GC/KS will take whatever action is necessary (if any) to advertise its ability to distribute key for the group. The GC/KS will then listen for RTJs. The PT has a sequence number. Every time a PT is distributed to the group the group members verify that the sequence number on the PT is increasing. The PT lifetime is not limited to a particular time interval, other than by the lifetimes imposed by some of its attributes (e.g. signature key lifetime). The current PT sequence number is downloaded to the GM in the "Key Download" message. Also, to avoid replay attacks, this sequence number is never reset to a lower value (i.e. rollover to zero) as long as the group identifier remains valid and in use. The GO must preserve this sequence number across re-boots. 4.4.4 Discovery of GC/KS Potential GMs will receive notice of the new group via some mechanism: announcement, Anycast, registration look-up. The GM will send an RTJ to the GC/KS. 4.4.5 GC/KS registration policy enforcement The GC/KS may or may not require cookies, depending on Denial of Service environment and the local configuration. Once the RTJ has been received, the GC/KS will verify that the GM is allowed to have access to the group keys. The GC/KS will then verify the signature on the RTJ to ensure it was sent by the claimed identity. If the checks succeed, the GC/KS will ready a Key Download message for the GM. If not the GC/KS can notify the GM of a non-security relevant problem. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 24] INTERNET-DRAFT GSAKMP June 2004 4.4.6 GM registration policy enforcement Upon receipt of the Key Download message, the GM will verify the signature on the message. Then the GM will retrieve the PT from the Key Download message and verify that the GO created and signed the PT. Once the PT is verified as valid, the GM will verify that the GC/KS is authorized to distribute key for this group. Then the GM will verify that the mechanisms used in the group are available and acceptable for protection of the GMs data (assuming the GM is a data source). The GM will then accept membership in this group. The GM will then check to see if it is allowed to be a S-GC/KS for this group. If the GM is allowed to be a S-GC/KS AND the local GM configuration allows the GM to act as a S-GC/KS for this group, then the GM changes its operating state to S-GC/KS. The GO needs to assign the authority to become a S-GC/KS in a manner that supports the overall group integrity and operations. 4.4.7 Autonomous Distributed GSAKMP Operations In autonomous mode, each S-GC/KS operates a largely self-contained sub-group for which the Primary-GC/KS delegates the sub-group's membership management responsibility to the S-GC/KS. In general, the S-GC/KS locally handles each Group Member's registration and de- registration without any interaction with the Primary-GC/KS. Periodically, the Primary-GC/KS multicasts a Re-Key Event message addressed only to its one or more S-GC/KS. After a S-GC/KS successfully processes a Rekey Event message from the Primary-GC/KS, the S-GC/KS transmits to its sub-group its own Rekey Event message containing a copy of the group's new GTPK and policy token. The S-GC/KS encrypts its Rekey Event message's sub-group key management information using Logical Key Hierarchy or a comparable re-key protocol. The S-GC/KS uses the re-key protocol to realize forward and backward secrecy, such that only the authorized sub-group members can decrypt and acquire access to the new GTPK and policy token. The frequency at which the Primary-GC/KS transmits a Re-Key Event message is a policy token parameter. For the special case of a S-GC/KS detecting an expelled or compromised group member, there is a mechanism defined to trigger an immediate group re-key rather than waiting for the group's re-key period to elapse. See below for details. Each S-GC/KS will be registered by the GC/KS as a management node with responsibility for GTPK distribution, access control policy enforcement, LKH tree creation and distribution of LKH key arrays. The S-GC/KS will be registered into the primary LKH tree as an endpoint. Each S-GC/KS will hold an entire LKH key array for the GC's LKH key tree. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 25] INTERNET-DRAFT GSAKMP June 2004 For the purpose of clarity the process of creating a distributed GSAKMP group will be explained in chronological order. First, the Group Owner will create a policy token that authorizes a subset of the group's membership to assume the role of S-GC/KS. The GO needs to ensure that the S-GC/KS rules in the policy token will be stringent enough to ensure trust in the S-GC/KSs. This policy token is handed off to the primary GC. The GC will create the GTPK and initial LKH key tree. The GC will then wait for a potential S-GC/KS to send a Request to Join (RTJ) message. A potential S-GC/KS will eventually send an RTJ. The GC will enforce the access control policy as defined in the policy token. The S-GC/KS will accept the role of S-GC/KS and create its own LKH key tree for its sub-group membership. The S-GC/KS will then offer registration services for the group. There are local management decisions that are optional to control the scope of group members that can be served by a S-GC/KS. These are truly local management issues that allow the administrators of an S-GC/KS to restrict service to potential GMs. These local controls do not effect the overall group security policy, as defined in the Policy Token. A potential Group Member will send an RTJ to the S-GC/KS. The S- GC/KS will enforce the entire access control policy as defined in the PT. The GM will receive an LKH key array that corresponds to the LKH tree of the S-GC/KS. The key tree generated by the S-GC/KS is independent of the key tree generated by the GC/KS., they share no common keys. The GM then has the keys it needs to receive group traffic and be subject to rekey from the S-GC/KS. For the sake of this discussion let's assume the GM is to be expelled from the group membership. The S-GC/KS will receive notification that the GM is to be expelled. This mechanism is outside the scope of this protocol. Upon notification that a GM that holds a key array within its LKH tree is to be expelled the S-GC/KS does two things. First the S-GC/KS initiates a de-registration exchange with the GC/KS identifying the member to be expelled. (The S-GC/KS proxies a Group Member's de- registration informing the GC/KS that the Group Member has been expelled from the group.) Second, the S-GC/KS will wait for a rekey action by the GC/KS. The immediacy of the rekey action by the GC/KS is a management decision at the GC/KS. Security is served best by quick expulsion of untrusted members. Upon receipt of the de-registration notification from the S-GC/KS the GC/KS will register the member to be expelled. The GC/KS will then follow group procedure for initiating a rekey action (outside the scope of this protocol). The GC/KS will communicate to the GO the expelled members Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 26] INTERNET-DRAFT GSAKMP June 2004 information (outside the scope of this protocol). With this information, the GO will create a new PT for the group with the expelled GM identity added to the excluded list in the groups access control rules. The GO provides this new PT to the GC/KS for distribution with the Rekey Event Message. The GC/KS will send out a rekey operation with a new PT. The S- GC/KS will receive the rekey and process it. At the same time, all other S-GC/KSs will receive the rekey and note the excluded GM identity. All S-GC/KSs will review local identities to ensure that the excluded GM is not a local member. If it is, then the S-GC/KS will create a rekey message. The S-GC/KSs must always create a rekey message, whether the expelled Group Member is a member of their subtrees or not. The S-GC/KS will then create a local rekey message. The S-GC/KS will send the wrapped Group TPK to all members of its local LKH tree, except the excluded member(s). 5 Group Life Cycle The management of a cryptographic group follows a life-cycle: group definition, group establishment, and security relevant group maintenance. Group definition involves defining the parameters necessary to support a secure group, including its policy token. Group establishment is the process of granting access to new members. Security relevant group maintenance messages include rekey, policy changes member deletions, and group destruction. Each of these life-cycle phases is discussed in the following sections. The use and processing of the optional Vendor ID payload for all messages can be found in Section 7.10. 5.1 Group Definition A cryptographic group is established to support secure communications among a group of individuals. The activities necessary to create a Policy Token in support of a cryptographic group include - Determine Access Policy - identify the entities that are authorized to receive the group key. - Determine Authorization Policy - identify which entities are authorized to perform security relevant actions, including key dissemination, policy creation, and initiation of security management actions. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 27] INTERNET-DRAFT GSAKMP June 2004 - Determine Mechanisms - define the algorithms and protocols used by GSAKMP to secure the group. - Create Group Policy Token - format the policies and mechanisms into a Policy Token and apply the GO signature. 5.2 Group Establishment GSAKMP Group Establishment consists of three mandatory-to-implement messages, the Request to Join, the Key Download, and the Key Download Ack/Failure. The exchange may also include two OPTIONAL error messages, the Request to Join Error and the Lack_of_Ack messages. Operation using the mandatory messages only is referred to as "Terse Mode", while inclusion of the error messaging is referred to as "Verbose Mode". GSAKMP implementations MUST support Terse Mode and MAY support Verbose Mode. Group Establishment is discussed in Section 5.2.1. A group is set in Terse or Verbose mode by a policy token parameter. All (S-)GC/KSs in a Verbose mode group MUST support Verbose mode. GSAKMP allows Verbose mode groups to have GMs that do not support Verbose mode. Candidate GMs that do not support Verbose mode and receive a RTJ-Error or Lack-of-Ack message must handle these messages gracefully. Additionally, a GM will not know a prior that it is interacting with the (S)-GC/KS in Verbose or Terse mode until the Policy Token is received. For Denial of Service protection, a Cookie Exchange MAY precede the Group Establishment exchange. The Cookie Exchange is described in Section 5.2.2. Regardless of mode, any error message sent between component members indicates the first error encountered while processing the message. 5.2.1 Standard Group Establishment After the out-of-band receipt of a Policy Token, a potential Group Controller Key Server (GC/KS) verifies the token and its eligibility to perform GC/KS functionality. It is then permitted to create any needed group keys and begin to establish the group. The GSAKMP Ladder Diagram, Figure 1, is presented to illustrate the process of establishing a cryptographic group. The left side of the diagram represents the actions of the GC/KS. The right side of the diagram represents the actions of the GMs. The components of each message shown in the diagram are presented in sections 5.2.1.1 - 5.2.1.5. The Request to Join message is sent from a potential GM to the GC/KS to request admission to the cryptographic group. The message contains key creation material, freshness data, an optional selection of mechanisms, and Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 28] INTERNET-DRAFT GSAKMP June 2004 CONTROLLER Mandatory/ MESSAGE MEMBER Optional !<-M----------Request to Join-------------! ! ! !--M----------Key Download--------------->! ! ! !--O-------Request to Join Error--------->! or ! ! !<-M----Key Download - Ack/Failure--------! ! ! !--O------Lack of Acknowledgment--------->! ! ! !<=======SHARED KEYED GROUP SESSION======>! Figure 1: GSAKMP Ladder Diagram the signature of the GM. The Key Download message is sent from the GC/KS to the GM in response to an accepted Request to Join. This GC/KS-signed message contains the identifier of the GM, freshness data, key creation material, encrypted keys, and the encrypted Policy Token. The Policy Token is used to facilitate well-ordered group creation and MUST include the group's identification, group permissions, group join policy, group controller key server identity, group management information, and digital signature of the GO. This will allow the GM to determine whether group policy is compatible with local policy. The Request to Join Error message is sent from the GC/KS to the GM in response to an unaccepted Request to Join. This message is not signed by the GC/KS for two reasons: 1) The GM, at this point, has no knowledge of who is authorized to act as a GC/KS and so the signature would thus be meaningless to the GM, and 2) Signing responses to denied join requests would provide a denial of service potential. The message contains an indication of the error condition. The possible values for this error condition are: Invalid-Payload-Type, Invalid-Version, Invalid-Group-ID, Invalid-Sequence-ID, Payload-Malformed, Invalid-ID-Information, Invalid-Certificate, Cert-Type-Unsupported, Invalid-Cert-Authority, Authentication-Failed, Certificate-Unavailable, Unauthorized-Request, Prohibited-by-Group-Policy, and Prohibited-by-Locally-Configured-Policy. The Key Download Ack/Failure message indicates Key Download receipt status at the GM. It is a GM-signed message containing freshness data and status. The Lack_of_Ack message is sent from the GC/KS to the GM in response to an invalid or absent Key Download Ack/Failure message. The signed message contains freshness and status data and is used to warn the GM of impending Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 29] INTERNET-DRAFT GSAKMP June 2004 eviction from the group if a valid Key Download Ack/Failure is not sent. Eviction means that the member will be excluded from the group after the next Rekey Event. The policy of when a particular group needs to rekey itself is stated in the Policy Token. Eviction is discussed further in Section 5.3.2.1. For the following message structure sections, details about payload format and processing can be found in Section 7. Each message is identified by its exchange type in the header of the message. Nonces MUST be present in the messages unless synchronization time is available to the system. 5.2.1.1 Request to Join The exchange type for Request to Join is eight (8). The components of a Request to Join Message are shown in Table 1. Table 1: Request to Join (RTJ) Message Definition Message Name : Request to Join (RTJ) Dissection : {HDR-GrpID, Key Creation, [Nonce_I], [VendorID], : [Notif_Mechanism_Choices], [Notif_Cookie], : [Notif_IPValue]} SigM, [Cert] Payload Types : GSAKMP Header, Key Creation, [Nonce], [Vendor ID], Signature, [Certificate], [Notifications] SigM : Signature of Group Member Cert : Necessary Certificates, zero or more {}SigX :Indicates fields used in Signature [] : Indicate an optional data item As shown by Figure 1, a potential GM MUST generate and send an RTJ message to request permission to join the group. As defined in the dissection of the RTJ message, this message MUST contain a Key Creation payload for KEK determination. When synchronization time is not available to the system as identified by the Policy Token, a Nonce payload MUST be included for freshness and the Nonce_I value MUST be saved for later use. An OPTIONAL Notification payload of type Mechanism Choices MAY be included to identify the mechanisms the GM wants to use. Absence of this payload will cause the GC/KS to select appropriate default Policy Token specified mechanisms for the Key Download. In response, the GC/KS accepts or denies the request based on local configuration. indicates the GC/KS actions that will determine if the RTJ will be acted upon. The following checks SHOULD be performed in the order presented. In this procedure, the GC/KS MUST verify that the message header is properly formed and confirm that this message is for this group by checking the value Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 30] INTERNET-DRAFT GSAKMP June 2004 of the GroupID. If the header checks pass, then the identity of the sender is extracted from the Signature payload. This identity MUST be used to perform access control checks, find the GMs credentials (e.g. certificate) for message verification, and MUST also be used in the Key Download message. Then the GC/KS will verify the signature on the message to ensure its authenticity. The GC/KS MUST use verified and trusted authentication material from a known root. If the message signature verifies, the GC/KS then confirms that all required payloads are present and properly formatted based upon the mechanisms announced and/or requested. If all checks pass, the GC/KS will create and send the Key Download message as described in section 5.2.1.2. NOTE: At any one time, a GC/KS MUST process no more that one (1) valid RTJ message from a given GM per group until its pending registration protocol exchange concludes. If the GM receives no response to the RTJ within the GM's locally configured timeout value, the GM SHOULD resend the RTJ message up to three (3) times. If any error occurs during RTJ message processing, and the GC/KS is running in Terse mode, the registration session MUST be terminated and all saved state information MUST be cleared. The OPTIONAL Notification payload of type Cookie is discussed in section 5.2.2. The OPTIONAL Notification payload of type IPValue may be used for the GM to convey a specific IP value to the GC/KS. 5.2.1.2 Key Download The exchange type for Key Download is nine (9). The components of a Key Download Message are shown in Table 2: In response to a properly formed and verified RTJ message, the GC/KS creates and sends the KeyDL message. As defined in the dissection of the message, this message MUST contain payloads to hold the following information: GM identification, Key Creation material, encrypted Policy Token, encrypted key information, and signature information. If synchronized time is not available, the Nonce payloads MUST be included in the message for freshness. If present, the nonce values transmitted MUST be the GC/KSs generated Nonce_R value and the combined Nonce_C value which was generated by using the GC/KSs Nonce_R value and the Nonce_I value received from the GM in the RTJ. If two party key determination is used, the key creation material supplied by the GM and/or the GC/KS will be used to generate the key. Generation of this key is dependant on the key exchange, as defined in Section 7.11, Key Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 31] INTERNET-DRAFT GSAKMP June 2004 Table 2: Key Download (KeyDL) Message Definition Message Name : Key Download (KeyDL) Dissection : {HDR-GrpID, Member ID, [Nonce_R, Nonce_C], Key Creation, (Policy Token)*, (Key Download)*, [VendorID]} SigC, [Cert] Payload Types : GSAKMP Header, Identification, [Nonce], Key Creation, Policy Token, Key Download, [Vendor ID], Signature, [Certificate] SigC : Signature of Group Controller Key Server Cert : Necessary Certificates, zero or more {}SigX :Indicates fields used in Signature [] : Indicate an optional data item (data)* : Indicates encrypted information Creation Payload. The Policy Token and key material are encrypted in the generated key. The GM MUST be able to process the Key Download message. indicates the GM actions that will determine how the Key Download message will be acted upon. The following checks SHOULD be performed in the order presented. In this procedure, the GM will verify that the message header is properly formed and confirm that this message is for this group by checking the value of the GroupID. If the header checks pass, the GM MUST confirm that this message was intended for itself by comparing the Member ID in the Identification payload to its identity. After identification confirmation, the freshness values are checked. If using Nonces, the GM MUST use its saved Nonce_I value, extract the received GC/KS Nonce_R value, compute the combined Nonce_C value, and compare it to the received Nonce_C value. If not using Nonces, the GM MUST check the timestamp in the Signature payload to determine if the message is new. After freshness is confirmed, the signature MUST be verified to ensure its authenticity, The GM MUST use verified and trusted authentication material from a known root. If the message signature verifies, the key creation material is extracted from the Key Creation payload to generate the KEK. This KEK is then used to decrypt the Policy Token data. The signature on the policy token MUST be verified. Access control checks MUST be performed on both the GO and the GC/KS to determine both their authorities within this group. After all these checks pass, the KEK can then be used to decrypt and process the key material from the Key Download payload. If all is successful, the GM will create and send the Key Download - Ack/Failure message as described in section 5.2.1.4. The Policy Token and Key Download payloads are sent encrypted in the KEK generated by the Key Creation payload information using the mechanisms Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 32] INTERNET-DRAFT GSAKMP June 2004 defined in the group announcement. This guarantees that the sensitive policy and key data for the group and potential rekey data for this individual cannot be read by anyone but the intended recipient. If any error occurs during KeyDL message processing, regardless of whether the GM is in Terse or Verbose mode, the registration session MUST be terminated, the GM MUST send a Key Download - Ack/Failure message, nd all saved state information MUST be cleared. If in Terse mode, the Notification Payload will be of type NACK to indicate termination. If in Verbose mode, the Notification Payload will contain the type of error encountered. 5.2.1.3 Request to Join Error The exchange type for Request to Join Error is eleven (11). The components of the Request to Join Error Message are shown in Table 3: Table 3: Request to Join Error (RTJ-Err) Message Definition Message Name : Request to Join Error (RTJ-Err) Dissection : {HDR-GrpID, [Nonce_I], Notification, [VendorID]} Payload Types : GSAKMP Header, [Nonce] Notification, [Vendor ID] In response to an unacceptable RTJ, the GC/KS MAY send a Request to Join Error (RTJ-Err) message containing an appropriate Notification payload. Note that the RTJ-Err message is not a signed message for the following reasons: the lack of awareness on the GM's perspective of who is a valid GC/KS as well as the need to protect the GC/KS from signing messages and using valuable resources. Following the sending of an RTJ-Err, the GC/KS MUST terminated the session and all saved state information MUST be cleared. Upon receipt of an RTJ-Err message, the GM will validate the following: the GroupID in the header belongs to a group to which the GM has sent an RTJ, and, if present, the Nonce_I matches a Nonce_I sent in an RTJ to that group. If the above checks are successful, the GM MAY terminate the state associated with that GroupID and Nonce. The GM SHOULD be capable of receiving a valid KeyDownload message for that GroupID and Nonce after receiving an RTJ-Err for a locally-configured amount of time. 5.2.1.4 Key Download - Ack/Failure The exchange type for Key Download - Ack/Failure is four (4). The components of the Key Download - Ack/Failure Message are shown in Table 4: Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 33] INTERNET-DRAFT GSAKMP June 2004 Table 4: Key Download - Ack/Failure (KeyDL-A/F) Message Definition Message Name : Key Download - Ack/Failure (KeyDL-A/F) Dissection : {HDR-GrpID, [Nonce_C], Notif_Ack, [VendorID]}SigM Payload Types : GSAKMP Header, [Nonce], Notification, [Vendor ID], Signature SigM : Signature of Group Member {}SigX :Indicates fields used in Signature In response to a properly processed KeyDL message, the GM creates and sends the KeyDL-A/F message. As defined in the dissection of the message, this message MUST contain payloads to hold the following information: Notification payload of type Acknowledgment (ACK) and signature information. If synchronized time is not available, the Nonce payload MUST be present for freshness, and the nonce value transmitted MUST be the GMs generated Nonce_C value. If the GM does not receive a KeyDL message within a locally configured amount of time, the GM MAY send a new RTJ. If the GM receives a valid LOA (see section 5.2.1.5) message from the GC/KS before receipt of a KeyDL message, the GM SHOULD send a KeyDL-A/F message of type NACK followed by a new RTJ. The GC/KS MUST be able to process the KeyDL-A/F message. indicates the GC/KS actions that will determine how the KeyDL-A/F message will be acted upon. The following checks SHOULD be performed in the order presented. In this procedure, the GC/KS will verify that the message header is properly formed and confirm that this message is for this group by checking the value of the GroupID. If the header checks pass, the GC/KS MUST check the message for freshness. If using Nonces, the GC/KS MUST use its saved Nonce_C value, and compare it to the received Nonce_C value. If not using Nonces, the GC/KS MUST check the timestamp in the Signature payload to determine if the message is new. After freshness is confirmed, the signature MUST be verified to ensure its authenticity, The GC/KS MUST use verified and trusted authentication material from a known root. If the message signature verifies, the GC/KS processes the Notification payload. If the notification type is of type ACK, then the registration has completed successfully and both parties SHOULD remove state information associated with this GM's registration. If the GC/KS does not receive a KeyDL-A/F message of proper form, is unable to correctly process the KeyDL-A/F message, the Notification payload type is any value except ACK, or if no KeyDL-A/F message is received within the locally configured timeout, the GC/KS MUST evict this GM from the group in the next policy-defined Rekey Event. The GC/KS MAY send the OPTIONAL Lack_of_Ack message if running in Verbose Mode as defined in section 5.2.1.5. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 34] INTERNET-DRAFT GSAKMP June 2004 5.2.1.5 Lack of Ack The exchange type for Lack of Ack is twelve (12). The components of a Lack of Ack Message are shown in Table 5: Table 5: Lack of Ack (LOA) Message Definition Message Name : Lack of Ack (LOA) Dissection : {HDR-GrpID, Member ID, [Nonce_R, Nonce_C], Notification, [VendorID]} SigC, [Cert] Payload Types : GSAKMP Header, Identification, [Nonce], Notification, [Vendor ID], Signature, [Certificate] SigC : Signature of Group Controller Key Server Cert : Necessary Certificates, zero or more {}SigX :Indicates fields used in Signature [] : Indicate an optional data item If the GC/KSs local timeout value expires prior to receiving a KeyDL-A/F from the GM, the GC/KS MAY create and send a LOA message to the GM. As defined in the dissection of the message, this message MUST contain payloads to hold the following information: GM identification, Notification of error, and signature information. If synchronized time is not available, the Nonce payloads MUST be present for freshness, and the nonce values transmitted MUST be the GC/KSs generated Nonce_R value and the combined Nonce_C value which was generated by using the GC/KSs Nonce_R value and the Nonce_I value received from the GM in the RTJ. These values were already generated during the Key Download message phase. The GM MAY be able to process the LOA message based upon local configuration. indicates the GM actions that will determine how the LOA message will be acted upon. The following checks SHOULD be performed in the order presented. In this procedure, the GM MUST verify that the message header is properly formed and confirm that this message is for this group by checking the value of the GroupID. If the header checks pass, the GM MUST confirm that this message was intended for itself by comparing the Member ID in the Identification payload to its identity. After identification confirmation, the freshness values are checked. If using Nonces, the GM MUST use its save Nonce_I value, extract the received GC/KS Nonce_R value, compute the combined Nonce_C value, and compare it to the received Nonce_C value. If not using Nonces, the GM MUST check the timestamp in the Signature payload to determine if the message is new. After freshness is confirmed, access control checks MUST be performed on the GC/KS to determine its authority within this group. Then signature MUST be verified to ensure its authenticity, The GM MUST use verified and trusted authentication material Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 35] INTERNET-DRAFT GSAKMP June 2004 from a known root. If the checks succeed, the GM SHOULD resend a KeyDL-A/F for that session. 5.2.2 Cookies - Group Establishment with Denial of Service Protection This section defines an OPTIONAL capability that MAY be implemented into GSAKMP when using IP based groups. The information in this section is borrowed heavily from [IKEv2] as this protocol has already worked through this issue and GSAKMP is copying this concept. This section will contain paraphrased sections of [IKEv2] modified for GSAKMP to define the purpose of Cookies. An optional Cookie mode is being defined for the GSAKMP to help against DoS attacks. The term "cookies" originates with Karn and Simpson [RFC 2522] in Photuris, an early proposal for key management with IPSec. The ISAKMP fixed message header includes two eight octet fields titled "cookies". Instead of placing this cookie data in the header, in GSAKMP this data is moved into a Notification payload. An expected attack against GSAKMP is state and CPU exhaustion, where the target GC/KS is flooded with Request to Join requests from forged IP addresses. This attack can be made less effective if a GC/KS implementation uses minimal CPU and commits no state to the communication until it knows the initiator potential GM can receive packets at the address from which it claims to be sending them. To accomplish this, the GC/KS when operating in Cookie mode, SHOULD reject initial Request to Join messages unless they contain a Notification payload of type "cookie". It SHOULD instead send a Cookie Download message as a response to the RTJ and include a cookie in a notify payload of type Cookie_Required. Potential GMs who receive such responses MUST retry the Request to Join message with the responder GC/KS supplied cookie in its notification payload of type Cookie, as defined by the optional Notification payload of the Request to Join Msg as defined in section 5.2.1.1. This initial exchange will then be as shown in Figure 2 with the components of the new message Cookie Download shown in Table 6. The exchange type for Cookie Download is ten (10). Table 6: Cookie Download Message Definition Message Name : Cookie Download Dissection : {HDR-GrpID, Notif_COOKIE_REQUIRED, [VendorID]} Payload Types : GSAKMP Header, Notification, [Vendor ID] The first two messages do not affect any GM or GC/KS state except for communicating the cookie. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 36] INTERNET-DRAFT GSAKMP June 2004 CONTROLLER MESSAGE MEMBER in Cookie Mode !<--Request to Join without Cookie Info---! ! ! !----------Cookie Download--------------->! ! ! !<----Request to Join with Cookie Info----! ! ! !-------------Key Download--------------->! ! ! !<-----Key Download - Ack/Failure--------! ! ! !<=======SHARED KEYED GROUP SESSION======>! Figure 2: GSAKMP Ladder Diagram with Cookies A GSAKMP implementation SHOULD implement its GC/KS cookie generation in such a way as to not require any saved state to recognize its valid cookie when the second Request to Join message arrives. The exact algorithms and syntax they use to generate cookies does not affect interoperability and hence is not specified here. The following is an example of how an endpoint could use cookies to implement limited DoS protection. A good way to do this is to set the cookie to be: Cookie = | Hash(Ni | IPi | ) where is a randomly generated secret known only to the responder GC/KS and periodically changed, Ni is the Nonce value taken from the initiator potential GM, IPi is the asserted IP address of the candidate GM. The IP address is either the IP header's source IP address, or else if it is present then the IP address contained in the optional Notification "IPvalue" payload. should be changed whenever is regenerated. The cookie can be recomputed when the "Request to Join with Cookie Info" arrives and compared to the cookie in the received message. If it matches, the responder GC/KS knows that all values have been computed since the last change to and that IPi MUST be the same as the source address it saw the first time. Incorporating Ni into the hash assures that an attacker who sees only the Cookie_Download message cannot successfully forge a "Request to Join with Cookie Info" message. This Ni value MUST be the same Ni value from the original "Request to Join" message for the calculation to be successful. If a new value for is chosen while there are connections in the process of being initialized, a "Request to Join with Cookie Info" might be Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 37] INTERNET-DRAFT GSAKMP June 2004 returned with other than the current . The responder GC/KS in that case MAY reject the message by sending another response with a new cookie or it MAY keep the old value of around for a short time and accept cookies computed from either one. The responder GC/KS SHOULD NOT accept cookies indefinitely after is changed, since that would defeat part of the denial of service protection. The responder GC/KS SHOULD change the value of frequently, especially if under attack. An alternative example for Cookie value generation in a NAT environment is to substitute the IPi value with the IPValue received in the Notification payload in the RTJ message. This scenario is indicated by the presence of the Notification payload of type IPValue. With this substitution, a similar calculation as described above can be used. 5.2.3 Group Establishment for Receive-Only Members This section describes an OPTIONAL capability that may be implemented in a structured system where the authorized (S-)GC/KS is known in advance through out-of-band means and where synchronized time is available. Unlike Standard Group Establishment, in the Receive-Only system, the GMs and (S-)GC/KSs operate in terse mode and exchange one message only: the Key Download. Potential new GMs do not send an RTJ. (S)-GC/KSs do not expect Key Download - ACK/Failure messages and do not remove GMs for lack or receipt of the message. Operation is as follows: upon notification via an authorized out-of-band event, the (S)-GC/KS forms and sends a Key Download message to the new member with the Nonce payloads ABSENT. The GM verifies - the ID payload identifies that GM - the timestamp in the message is fresh - the message is signed by an authorized (S)-GC/KS - the signature on the message verifies When using a Diffie-Hellman Key Creation Type for receive-only members, a static-ephemeral model is assumed: the Key Creation payload in the Key Download message contains the (S-)GC/KS's public component. The member's public component is assumed to be obtained through secure out-of-band means. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 38] INTERNET-DRAFT GSAKMP June 2004 5.3 Group Maintenance The Group Maintenance phase includes member joins and leaves, group rekey activities, policy updates, and group destruction. These activities are presented in the following sections. 5.3.1 Group Management 5.3.1.1 Rekey Events A Rekey Event is any action, including compromise report or key expiration, that requires the creation of a new group key and/or Rekey information. Once an event has been identified (as defined in the group security policy token), the GC/KS MUST create and provide a signed message containing the GTPK and Rekey information to the group. Each GM who receives this message MUST verify the signature on the message to ensure its authenticity. If the message signature does not verify, the message MUST be discarded. Upon verification the GM will find the appropriate Rekey download packet and decrypt the information with a stored Rekey key(s). If a new Policy Token is distributed with the message, it MUST be encrypted in the old GTPK. The exchange type for Rekey Event is five (5). The components of a Rekey Event message are shown in Table 7: Table 7: Rekey Event Message Definition Message Name : Rekey Event Dissection : {HDR-GrpID, ([Policy Token])*, Rekey Array, [VendorID]}SigC, [Cert] Payload Types : GSAKMP Header, [Policy Token], Rekey Event, [Vendor ID], Signature, [Certificate], SigC : Signature of Group Controller Key Server Cert : Necessary Certificates, zero or more {}SigX :Indicates fields used in Signature (data)* : Indicates encrypted information [] : Indicate an optional data item Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 39] INTERNET-DRAFT GSAKMP June 2004 5.3.1.2 Policy Updates New policy tokens are sent via the Rekey Event message. These policy updates may be coupled with an existing rekey event or may be sent in a message with the Rekey Event Type of the Rekey Event Payload set to None(0) (see section 7.5.1. A policy token MUST NOT be processed if the processing of the Rekey Event message carrying it fails. Policy token processing is type dependent and is beyond the scope of this document. 5.3.1.3 Group Destruction Group destruction is also accomplished via the Rekey Event message. In a Rekey Event message for group destruction, the Sequence ID is set to 0xFFFFFFFF. Upon receipt of this authenticated Rekey Event message, group components MUST terminate processing of information associated with the indicated group. 5.3.2 Leaving a Group There are several conditions under which a member will leave a group: eviction, voluntary departure without notice, and voluntary departure with notice -- or De-Registration. Each of these is discussed in this section. 5.3.2.1 Eviction At some point in the group's lifetime, it may be desirable to evict one or more members from a group. From a key management viewpoint, this involves revoking access to the group's protected data by "disabling" the departing members' keys. This is accomplished with a Rekey Event, which is discussed in more detail in section 5.3.1.1. If future access to the group is also to be denied, the members MUST be added to a denied access control list, and the policy token's authorization rules MUST be appropriately updated so that they will exclude the expelled GM(s). After receipt of a new PT, GMs SHOULD evaluate the trustworthiness of any recent application data originating from the expelled GM(s). 5.3.2.2 Voluntary Departure without Notice If a member wishes to leave a group for which membership imposes no cost or responsibility to that member, then the member MAY merely delete local Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 40] INTERNET-DRAFT GSAKMP June 2004 copies of group keys and cease group activities. 5.3.2.3 De-Registration If the membership in the group does impose cost or responsibility to the departing member, then the member SHOULD de-register from the group when that member wishes to leave. De-Registration consists of a three-message exchange between the GM and the member's GC/KS: the Request_to_Depart, Departure_Response, and the Departure_Ack. Compliant GSAKMP implementations for GMs SHOULD support the De-Registration messages. Compliant GSAKMP implementations for GC/KSs MUST support the De-Registration messages. 5.3.2.3.1 Request to Depart - The Exchange Type for a Request_to_Depart Message is thirteen (13). The components of a Request_to_Depart Message are shown in Table 8. Table 8: Request_to_Depart (RTD) Message Definition Message Name : Request_to_Depart (RTD) Dissection : {HDR-GrpID, GC/KS_ID, [Nonce_I], Notif_Leave_Group, [VendorID]} SigM, [Cert] Payload Types : GSAKMP Header, Identification, [Nonce], Notification, [Vendor ID], Signature, [Certificate] SigM : Signature of Group Member Cert : Necessary Certificates, zero or more {}SigX :Indicates fields used in Signature [] : Indicate an optional data item Any GM desiring to initiate the De-Registration process MUST generate and send an RTD message to notify the GC/KS of its intent. As defined in the dissection of the RTD message, this message MUST contain payloads to hold the following information: the GC/KS identification and Notification of the desire to leave the group. When synchronization time is not available to the system as defined by the Policy Token, a Nonce payload MUST be included for freshness, and the Nonce_I value MUST be saved for later use. This message MUST then by signed by the GM. Upon receipt of the RTD message, the GC/KS MUST verify that the message header is properly formed and confirm that this message is for this group by checking the value of the GroupID. If the header checks pass, then the identifier value in Identification payload is compared to its own, the GC/KSs identity, to confirm that the GM intended to converse with this GC/KS, the GC/KS who registered this member into the group. Then the identity of the sender is extracted from the Signature payload. This identity MUST be used to confirm that this GM is a member of the group serviced by this GC/KS. Then the GC/KS will confirm from the Notification Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 41] INTERNET-DRAFT GSAKMP June 2004 payload that the GM is requesting to leave the group. Then the GC/KS will verify the signature on the message to ensure its authenticity. The GC/KS MUST use verified and trusted authentication material from a known root. If all checks pass and the message is successfully processed, then the GC/KS MUST form a Departure_Response message as defined in section 5.3.2.3.2. If the processing of the message fails the de-registration session MUST be terminated and all state associated with this session is removed. If the GC/KS is operating in Terse Mode, then no error message is sent to the GM. If the GC/KS is operating in Verbose Mode, then the GC/KS sends a Departure_Response Message with a Notification Payload of type Request_to_Depart_Error. 5.3.2.3.2 Departure_Response - The Exchange Type for a Departure_Response Message is fourteen (14). The components of a Departure_Response Message are shown in Table 9. Table 9: Departure_Response (DR) Message Definition Message Name : Departure_Response (DR) Dissection : {HDR-GrpID, Member_ID, [Nonce_R, Nonce_C], Notification, [VendorID]} SigC, [Cert] Payload Types : GSAKMP Header, Identification, [Nonce], Notification, [Vendor ID], Signature, [Certificate] SigC : Signature of Group Member Cert : Necessary Certificates, zero or more {}SigX :Indicates fields used in Signature [] : Indicate an optional data item In response to a properly formed and verified RTD message, the GC/KS MUST create and send the DR message. As defined in the dissection of the message, this message MUST contain payloads to hold the following information: GM identification, Notification for acceptance of departure, and signature information. If synchronization time is not available, the Nonce payloads MUST be included in the message for freshness. If present, the nonce values transmitted MUST be the GC/KSs generated Nonce_R value and the combined Nonce_C value which was generated by using the GC/KSs Nonce_R value and the Nonce_I value received from the GM in the RTD. This Nonce_C value MUST be saved relative to this departing GMs ID. The GM MUST be able to process the Departure_Response message. The following checks SHOULD be performed in the order presented. The GM MUST verify that the message header is properly formed and confirm that this message is for this group by checking the value of the GroupID. If the header checks pass, the GM MUST confirm that this message was intended for itself by comparing the Member ID in the Identification payload to Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 42] INTERNET-DRAFT GSAKMP June 2004 its identity. After identification confirmation, the freshness values are checked. If using Nonces, the GM MUST use its saved Nonce_I value, extract the received GC/KS Nonce_R value, compute the combined Nonce_C value, and compare it to the received Nonce_C value. If not using Nonces, the GM MUST check the timestamp in the signature payload to determine if the message is new. After freshness is confirmed, confirmation of the identity of the signer of the DR message is the GMs authorized GC/KS is performed. Then the signature MUST be verified to ensure its authenticity, The GM MUST use verified and trusted authentication material from a known root. If the message signature verifies, then the GM MUST verify that the Notification is of Type Departure_Accepted or Request_to_Depart_Error. If the processing is successful, and the Notification payload is of type Departure_Accepted, the member MUST form the Departure_ACK message as defined in section 5.3.2.3.3. If the processing is successful, and the Notification payload is of type Request_to_Depart_Error, the member MUST remove all state associated with the de-registration session. If the member still desires to De-Register from the group, the member MUST restart the De-Registration process. If the processing of the message fails the de-registration session MUST be terminated and all state associated with this session is removed. If the GM is operating in Terse Mode, then a Departure_Ack Message with Notification Payload of type NACK is sent to the GC/KS. If the GM is operating in Verbose Mode, then the GM sends a Departure_Ack Message with a Notification Payload of the appropriate failure type. 5.3.2.3.3 Departure_ACK - The Exchange Type for a Departure_ACK Message is fifteen (15). The components of the Departure_ACK Message are shown in Table 10: Table 10: Departure_ACK (DA) Message Definition Message Name : Departure_ACK (DA) Dissection : {HDR-GrpID, [Nonce_C], Notif_Ack, [VendorID]}SigM Payload Types : GSAKMP Header, [Nonce], Notification, [Vendor ID], Signature SigM : Signature of Group Member {}SigX :Indicates fields used in Signature In response to a properly processed Departure_Response message, the GM MUST create and send the Departure_ACK message. As defined in the dissection of the message, this message MUST contain payloads to hold the following information: Notification payload of type Acknowledgment (ACK) and signature information. If synchronization time is not available, the Nonce payload MUST be present for freshness, and the nonce value transmitted MUST be the GMs generated Nonce_C value. Upon receipt of the Departure_ACK, the GC/KS MUST perform the following Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 43] INTERNET-DRAFT GSAKMP June 2004 checks. These checks SHOULD be performed in the order presented. In this procedure, the GC/KS MUST verify that the message header is properly formed and confirm that this message is for this group by checking the value of the GroupID. If the header checks pass, the GC/KS MUST check the message for freshness. If using Nonces, the GC/KS MUST use its saved Nonce_C value, and compare it to the received Nonce_C value. If not using Nonces, the GC/KS MUST check the timestamp in the signature payload to determine if the message is new. After freshness is confirmed, the signature MUST be verified to ensure its authenticity, The GC/KS MUST use verified and trusted authentication material from a known root. If the message signature verifies, the GC/KS processes the Notification payload. If the notification type is of type ACK, this is considered a successful processing of this message. If the processing of the message is successful, the GC/KS MUST remove the member from the group. This MAY involve initiating a Rekey Event for the group. If the processing of the message fails or if no Departure_Ack is received, the GC/KS MAY issue a LOA message. 6 Security Suite The Security Definition Suite 1 MUST be supported. Other security suite definitions MAY be defined in other Internet specifications. 6.1 Assumptions All potential GMs will have enough information available to them to use the correct Security Suite to join the group. This can be accomplished by a well known default suite 'Security Suite 1' or by announcing/posting another suite. 6.2 Definition Suite 1 GSAKMP implementations MUST support the following suite of algorithms and configurations. The following definition of Suite 1 borrows heavily from IKE's Oakley group 2 definition and Oakley itself. The GSAKMP Suite 1 definition defines all the algorithm and cryptographic definitions required to process group establishment messages. It is important to note that GSAKMP does not negotiate these cryptographic mechanisms. This definition is set by the Group Owner via the Policy Token Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 44] INTERNET-DRAFT GSAKMP June 2004 (passed during the GSAKMP exchange for member verification purposes). The GSAKMP Suite 1 definition is Key download and Policy Token encryption algorithm definition: Algorithm: 3DES Mode: CBC64 Key Length: 192 bits Policy Token digital signature algorithm is: DSS-ASN1-DER Hash algorithm is: SHA-1 Nonce Hash algorithm is: SHA-1 The Key Creation definition is: Algorithm type is Diffie Hellman MODP group definition g: 2 p: "FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1" "29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD" "EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245" "E485B576 625E7EC6 F44C42E9 A637ED6B 0BFF5CB6 F406B7ED" "EE386BFB 5A899FA5 AE9F2411 7C4B1FE6 49286651 ECE65381" "FFFFFFFF FFFFFFFF" NOTE: The p and g values comes from IKE [RFC 2409], section 6.2 Second Oakley Group, and p is 1024 bits long. The digital signature algorithm is: DSS-SHA1-ASN1-DER The digital signature ID type is: ID-U-NAME 7 GSAKMP Payload Structure A GSAKMP Message is composed of a GSAKMP Header (Section 7.1) followed by at least one GSAKMP Payload. All GSAKMP Payloads are composed of the Generic Payload Header (Section 7.2) followed by the specific payload data. The message is chained by a preceeding payload defining its succeeding payload. Payloads are not required to be in the exact order shown in the message dissection in Sections 5 provided that all required payloads are present. Unless it is explicitly stated in a dissection that multiple payloads of a single type may be present, no more than one payload of each Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 45] INTERNET-DRAFT GSAKMP June 2004 type allowed by the message may appear. The final payload in a message will point to no succeeding payload. All fields of type integer in the Header and Payload structure that are larger than one octet, MUST be converted into Network Byte Order prior to data transmission. Padding of fields MUST NOT be done as this leads to processing errors. When a message contains a Vendor ID payload, the processing of the payloads of that message are modified as defined in Section 7.10. 7.1 GSAKMP Header 7.1.1 GSAKMP Header Structure The GSAKMP Header fields are shown in Figure 3 and defined as: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! GroupID Type ! GroupID Length! Group ID Value ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ! Next Payload ! Version ! Exchange Type ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Sequence ID ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: GSAKMP Header Format Group Identification Type (1 octet) - Table 11 presents the group identification types. This field is treated as an unsigned value. Group Identification Length (1 octet) - Length of the Group ID field in octets. This value MUST NOT be zero (0). This field is treated as an unsigned value. Group Identification Value (variable length) - Indicates the name/title of the group. All GroupID types should provide unique naming across groups. GroupID types SHOULD provide this capability by including a random element generated by the creator (owner) of the group of at least Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 46] INTERNET-DRAFT GSAKMP June 2004 Table 11: Group Identification Types Grp ID Type Value Description _______________________________________________________________________________ Reserved 0 UTF-8 1 This format is defined in Section 7.1.1.1.1. Octet String 2 This type MUST be implemented. This format is defined in Section 7.1.1.1.2. IPv4 3 This format is defined in Section 7.1.1.1.3. IPv6 4 This format is defined in Section 7.1.1.1.4. Reserved to IANA 5 - 192 Private Use 193 - 255 eight (8) octets, providing extremely low probability of collision in group names. The GroupID value is static throughout the life of the group. Next Payload (1 octet) - Indicates the type of the next payload in the message. The format for each payload is defined in the following sections. Table 12 presents the payload types. This field is treated as an unsigned value. Table 12: Payload Types Next_Payload_Type Value ___________________________________ None 0 Policy Token 1 Key Download Packet 2 Rekey event 3 Identification 4 Reserved 5 Certificate 6 Reserved 7 Signature 8 Notification 9 Vendor ID 10 Key Creation 11 Nonce 12 Reserved to IANA 13 - 192 Private Use 193 -- 255 Version (1 octet) - Indicates the version of the GSAKMP protocol in use. The current value is one (1). This field is treated as an unsigned value. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 47] INTERNET-DRAFT GSAKMP June 2004 Exchange Type (1 octet) - Indicates the type of exchange (also known as the message type). Table 13 presents the exchange type values. This field is treated as an unsigned value. Table 13: Exchange Types Exchange_Type Value ________________________________________ Reserved 0 - 3 Key Download Ack/Failure 4 Rekey Event 5 Reserved 6 - 7 Request to Join 8 Key Download 9 Cookie Download 10 Request to Join Error 11 Lack of Ack 12 Request to Depart 13 Departure Response 14 Departure Ack 15 Reserved to IANA 16 - 192 Private Use 193 -- 255 Sequence ID (4 octets) - The Sequence ID is used for replay protection of group management messages. If the message is not a group management message, this value MUST be set to zero (0). The first value used by a (S-)GC/KS MUST be one (1). For each distinct group management message that this (S-)GC/KS transmits, this value MUST be incremented by one (1). Receivers of this group management message MUST confirm that the value received is greater that the value of the sequence ID received with the last group management message from this (S-)GC/KS. Group Components (e.g., GMs, S-GC/KSs) MUST terminate processing upon receipt of an authenticated group management message containing a Sequence ID of 0xFFFFFFFF. This field is treated as an unsigned integer in network byte order. Length (4 octets) - Length of total message (header + payloads) in octets. This field is treated as an unsigned integer in network byte order. 7.1.1.1 GroupID Structure This section defines the formats for the defined GroupID types. 7.1.1.1.1 UTF-8 - The format for type UTF-8 [RFC 3629] is shown in Figure 4. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 48] INTERNET-DRAFT GSAKMP June 2004 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Random Value ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! UTF-8 String ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: GroupID UTF-8 Format Random Value (16 octets) - For the UTF-8 GroupID type, the Random Value is represented as a string of exactly 16 hexadecimal digits converted from its octet values in network-byte order. The leading zero hexadecimal digits and the trailing zero hexadecimal digits are always included in the string, rather than being truncated. UTF-8 String (variable length) - This field contains the human readable portion of the GroupID in UTF-8 format. Its length is calculated as the GroupID Length - 16 for the Random Value field. The minimum length for this field is one (1) octet. 7.1.1.1.2 Octet String The format for type Octet String is shown in Figure 5. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Random Value ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Octet String ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5: GroupID Octet String Format Random Value (8 octets) - The 8 octet unsigned random value in network Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 49] INTERNET-DRAFT GSAKMP June 2004 byte order format. Octet String (variable length) - This field contains the Octet String portion of the GroupID. Its length is calculated as the GroupID Length - 16 for the Random Value field. The minimum length for this field is one (1) octet. 7.1.1.1.3 IPv4 Group Identifier The format for type IPv4 Group Identifier is shown in Figure 6. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Random Value ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! IPv4 Value ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 6: GroupID IPv4 Format Random Value (8 octets) - The 8 octet unsigned random value in network byte order format. IPv4 Value (4 octets) - The IPv4 value in network byte order format. This value MAY contain the multicast address of the group. 7.1.1.1.4 IPv6 Group Identifier The format for type IPv6 Group Identifier is shown in Figure 7. Random Value (8 octets) - The 8 octet unsigned random value in network byte order format. IPv6 Value (16 octets) - The IPv6 value in network byte order format. This value MAY contain the multicast address of the group. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 50] INTERNET-DRAFT GSAKMP June 2004 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Random Value ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! IPv6 Value ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 7: GroupID IPv6 Format 7.1.2 GSAKMP Header Processing When processing the GSAKMP Header, the following fields MUST be checked for correct values: 1. Group ID Type - The Group ID Type value MUST be checked to be a valid group identification payload type as defined by Table 11. If the value is not valid, then an error is logged and if in Verbose mode an appropriate message containing notification value Payload-Malformed will be sent. 2. GroupID - The GroupID of the received message MUST be checked against the valid GroupIDs of the Group Component. If no match is found, then an error is logged and if in Verbose mode an appropriate message containing notification value Invalid-Group-ID will be sent. 3. Next Payload - The Next Payload value MUST be checked to be a valid payload type as defined by Table 12. If the value is not valid, then an error is logged and if in Verbose mode an appropriate message containing notification value Invalid-Payload-Type will be sent. 4. Version - The GSAKMP version number MUST be checked that its value is one (1). For other values, see below for processing. The GSAKMP version number MUST be checked that it is consistent with the group's policy as specified in its Policy Token. If the version is not supported or authorized, then an error is logged and if in Verbose mode an appropriate message containing notification value Invalid-Version will be sent. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 51] INTERNET-DRAFT GSAKMP June 2004 5. Exchange Type - The Exchange Type MUST be checked to be a valid exchange type as defined by Table 13 and MUST be of the type expected to be received by the GSAKMP state machine. If the exchange type is not valid, then an error is logged and if in Verbose mode an appropriate message containing notification value Invalid-Exchange-Type will be sent. 6. Sequence ID - The Sequence ID value MUST be checked for correctness. For negotiation messages this value MUST be zero (0). For group management messages, this value MUST be greater than the last sequence ID received from this (S-)GC/KS. Receipt of incorrect Sequence ID on group management messages MUST NOT cause a reply message to be generated. Receipt of incorrect Sequence ID on non-group management messages, then an error is logged and if in Verbose mode an appropriate message containing notification value Invalid-Sequence-ID to be sent. The length fields in the GSAKMP Header (Group ID Length and Length) are used to help process the message. If any field is found to be incorrect, then an error is logged and if in Verbose mode an appropriate message containing notification value Payload-Malformed will be sent. In order to allow a GSAKMP version one (1) (v1) implementation to interoperate with future versions of the protocol, some ideas will be discussed here to this affect. A (S)-GC/KS that is operating in a multi-versioned group as defined by the Policy Token can take many approaches on how to interact with the GMs in this group for a Rekey Message. One possible solution is for the (S)-GC/KS to send out multiple Rekey Messages, one per version level that it supports. Then each GM would only process the message that has the version at which it is operating. An alternative approach which all GM v1 implementations MUST support is the embedding of a v1 message inside a version two (2) (v2) message. If a GM running at v1 receives a GSAKMP message that has a version value greater than one (1), the GM will attempt to process the information immediately after the Group Header as a Group Header for v1 of the protocol. If this is in fact a v1 Group Header, then the remainder of this v1 message will be processed in place. After processing this v1 embedded message, the data following the v1 message should be the payload as identified by the Next Payload field in the original header of the message and will be ignored by the v1 member. However, if the payload following the initial header is not a v1 Group Header, then the GM will gracefully handle the unrecognized message. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 52] INTERNET-DRAFT GSAKMP June 2004 7.2 Generic Payload Header 7.2.1 Generic Payload Header Structure Each GSAKMP payload defined in the following sections begins with a generic header, shown in Figure 8, which provides a payload ``chaining`` capability and clearly defines the boundaries of a payload. The Generic Payload Header fields are defined as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Next Payload ! RESERVED ! Payload Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 8: Generic Payload Header Next Payload (1 octet) - Identifier for the payload type of the next payload in the message. If the current payload is the last in the message, then this field will be 0. This field provides the ``chaining`` capability. Table 12 identifies the payload types. This field is treated as an unsigned value. RESERVED (1 octet) - Unused, set to 0. Payload Length (2 octets) - Length in octets of the current payload, including the generic payload header. This field is treated as an unsigned integer in network byte order format. 7.2.2 Generic Payload Header Processing When processing the Generic Payload Header, the following fields MUST be checked for correct values: 1. Next Payload - The Next Payload value MUST be checked to be a valid payload type as defined by Table 12. If the payload type is not valid, then an error is logged and if in Verbose mode an appropriate message containing notification value Invalid-Payload-Type will be sent. 2. RESERVED - This field MUST contain the value zero (0). If the value of this field is not zero (0), then an error is logged and if in Verbose mode an appropriate message containing notification value Payload-Malformed will be sent. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 53] INTERNET-DRAFT GSAKMP June 2004 The length field in the Generic Payload Header is used to process the remainder of the payload. If this field is found to be incorrect, then an error is logged and if in Verbose mode an appropriate message containing notification value Payload-Malformed will be sent. 7.3 Policy Token Payload 7.3.1 Policy Token Payload Structure The Policy Token Payload contains authenticatable group specific information that describes the group security relevant behaviors, access control parameters, and security mechanisms. Figure 9 shows the format of the payload. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Next Payload ! RESERVED ! Payload Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Policy Token Type ! Policy Token Data ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 9: Policy Token Payload Format The Policy Token Payload fields are defined as follows: Next Payload (1 octet) - Identifier for the payload type of the next payload in the message. If the current payload is the last in the message, then this field will be 0. This field provides the ``chaining`` capability. Table 12 identifies the payload types. This field is treated as an unsigned value. RESERVED (1 octet) - Unused, set to 0. Payload Length (2 octets) - Length in octets of the current payload, including the generic payload header. This field is treated as an unsigned integer in network byte order format. Policy Token Type (2 octets) - Specifies the type of Policy Token being used. Table 14 identifies the types of policy tokens. This field is treated as an unsigned integer in network byte order format. Policy Token Data (variable length) - Contains Policy Token information. The values for this field are token specific and the format is specified by the PT Type field. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 54] INTERNET-DRAFT GSAKMP June 2004 Table 14: Policy Token Types Policy_Token_Type Value Definition _____________________________________________________________________________ GSAKMP_PT_V1 0 The format for this Policy Token is specified in [HCLM00]. GSAKMP_ASN.1_PT_V1 1 All implementations of GSAKMP MUST support this Policy Token format. This format is specified in TBD. Reserved to IANA 2 - 49152 Private Use 49153 - 65535 If this payload is encrypted, only the Policy Token Data field is encrypted. The payload type for the Policy Token Payload is one (1). 7.3.2 Policy Token Payload Processing When processing the Policy Token Payload, the following fields MUST be checked for correct values: 1. Next Payload, RESERVED, Payload Length - These fields are processed as defined in Section 7.2.2, Generic Payload Header Processing. 2. Policy Token Type - The Policy Token Type value MUST be checked to be a valid policy token type as defined by Table 14. If the value is not valid, then an error is logged and if in Verbose mode an appropriate message containing notification value Payload-Malformed will be sent. 3. Policy Token Data - This Policy Token Data MUST be processed according to the Policy Token Type specified. The type will define the format of the data. 7.4 Key Download Payload Refer to the terminology section for the different terms relating to keys used within this section. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 55] INTERNET-DRAFT GSAKMP June 2004 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Next Payload ! RESERVED ! Payload Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Number of Items ! Key Download Data Items ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 10: Key Download Payload Format 7.4.1 Key Download Payload Structure The Key Download Payload contains group keys (e.g., group keys, initial rekey keys, etc.). These key download payloads can have several security attributes applied to them based upon the security policy of the group. Figure 10 shows the format of the payload. The security policy of the group dictates that the key download payload MUST be encrypted with a key encryption key (KEK). The encryption mechanism used is specified in the Policy Token. The group members MUST create the KEK using the key creation method identified in the Key Creation Payload. The Key Download Payload fields are defined as follows: Next Payload (1 octet) - Identifier for the payload type of the next payload in the message. If the current payload is the last in the message, then this field will be 0. This field provides the ``chaining`` capability. Table 12 identifies the payload types. This field is treated as an unsigned value. RESERVED (1 octet) - Unused, set to 0. Payload Length (2 octets) - Length in octets of the current payload, including the generic payload header. This field is treated as an unsigned integer in network byte order format. Number of Items (2 octets) -- Contains the total number of traffic protection keys and Rekey Arrays being passed in this data block. This field is treated as an unsigned integer in network byte order format. Key Download Data Items (variable length) - Contains Key Download information. The Key Download Data is a sequence of Type/Length/Data of the Number of Items. The format for each item is defined in figure 11. For each Key Download Data Item, the data format is as follows: Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 56] INTERNET-DRAFT GSAKMP June 2004 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! KDD Item Type ! Key Download Data Item Length! ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Data for Key Download Data Item (Key Datum/Rekey Array) ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 11: Key Download Data Item Format Key Download Data (KDD) Item Type (1 octet) -- Identifier for the type of data contained in this Key Download Data Item. See Table 15 for the possible values of this field. This field is treated as an unsigned value. Table 15: Key Download Data Item Types Key Download Data Value Definition Item Type __________________________________________________________________ GTPK 0 This type MUST be implemented. This type identifies that the data contains group traffic protection key information. Rekey - LKH 1 Reserved to IANA 2 - 192 Private Use 193 - 255 Key Download Data Item Length (2 octets) -- Length in octets of the Data for the Key Download Data Item following this field. This field is treated as an unsigned integer in network byte order format. Data for Key Download Data Item (variable length) -- Contains Keys and related information. The format of this field is specific depending on the value of the Key Download Data Item Type field. For KDD Item Type of GTPK, this field will contain a Key Datum as defined in Section 7.4.1.1 . For KDD Item Type Rekey - LKH, this field will contain a Rekey Array as defined in Section 7.4.1.2 . The encryption of this payload only covers the data subsequent to the Generic Payload header (Number of Items and Key Download Data Items fields). The payload type for the Key Download Packet is two (2). Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 57] INTERNET-DRAFT GSAKMP June 2004 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Key Type ! Key ID ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ! Key Handle ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ! Key Creation Date ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! ! Key Expiration Date ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ! ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Key Data ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 12: Key Datum Format 7.4.1.1 Key Datum Structure A Key Datum contains all the information for a key. Figure 12 shows the format for this structure. Key Type (2 octets) -- This is the cryptographic algorithm for which this key data is to be used. This value is specified in the Policy Token. See Table 16 for the possible values of this field. This field is treated as an unsigned value. Key ID (4 octets) -- This is the permanent ID of all versions of the key. This value MAY be defined by the Policy Token. This field is treated as an octet string. Key Handle (4 octets) -- This is the value to uniquely identify a version (particular instance) of a key. This field is treated as an octet string. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 58] INTERNET-DRAFT GSAKMP June 2004 Table 16: Cryptographic Key Types Cryptographic_Key_Types Value Description _________________________________________________________________________ Reserved 0 - 2 3DES_CBC64_192 3 This type MUST be supported. Reserved 4 - 11 AES_CBC 12 AES_CTR 13 Reserved to IANA 14 - 49152 Private Use 49153 - 65535 Key Creation Date (15 octets) -- This is the time value of when this key data was originally generated. This field contains the timestamp in UTF-8 format YYYYMMDDHHMMSSZ, where YYYY is the year (0000 - 9999), MM is the numerical value of the month (01 - 12), DD is the day of the month (01 - 31), HH is the hour of the day (00 - 23), MM is the minute within the hour (00 - 59), SS is the seconds within the minute (00 - 59), and followed by the letter Z to indicate that this is Zulu time. This format is loosely based on [RFC 3161]. Key Expiration Date (15 octets) -- This is the time value of when this key is no longer valid for use. This field contains the timestamp in UTF-8 format YYYYMMDDHHMMSSZ, where YYYY is the year (0000 - 9999), MM is the numerical value of the month (01 - 12), DD is the day of the month (01 - 31), HH is the hour of the day (00 - 23), MM is the minute within the hour (00 - 59), SS is the seconds within the minute (00 - 59), and followed by the letter Z to indicate that this is Zulu time. This format is loosely based on [RFC 3161]. Key Data (variable length) -- This is the actual key data, which is dependent on the Key Type algorithm for its format. NOTE: The combination of the Key ID and the Key Handle MUST be unique within the group. This combination will be used to uniquely identify a key. 7.4.1.2 Rekey Array Structure A Rekey Array contains the information for the set of KEKs that is associated with a Group Member. Figure 13 shows the format for this structure. Rekey Version (1 octet) -- Contains the version of the Rekey protocol in which the data is formatted. For Key Download Data Item Type of Rekey Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 59] INTERNET-DRAFT GSAKMP June 2004 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Rekey Version#! Member ID ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ! Number of KEK Keys ! ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Key Datum(s) ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 13: Rekey Array Structure Format - LKH, refer to Section A.2 for a description of this value. This field is treated as an unsigned value. Member ID (4 octets) -- This is the Member ID of the Rekey sequence contained in this Rekey Array. This field is treated as an octet string. For Key Download Data Item Type of Rekey - LKH, refer to Section A.2 for a description of this value. Number of KEK Keys (2 octets) -- This value is the number of distinct KEK keys in this sequence. This value is treated as an unsigned integer in network byte order format. Key Datum(s) (variable length) -- The sequence of KEKs in Key Datum format. The format for each Key Datum in this sequence is defined in section 7.4.1.1. Key ID - For Key ID within the Rekey - LKH space, refer to Section A.2 for a description of this value. 7.4.2 Key Download Payload Processing Prior to processing its data, the payload contents MUST be decrypted. When processing the Key Download Payload, the following fields MUST be checked for correct values: 1. Next Payload, RESERVED, Payload Length - These fields are processed as defined in Section 7.2.2, Generic Payload Header Processing. 2. KDD Item Type - All KDD Item Type fields MUST be checked to be a valid Key Download Data Item type as defined by Table 15. If the value is not valid, then an error is logged and if in Verbose mode an appropriate Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 60] INTERNET-DRAFT GSAKMP June 2004 message containing notification value Payload-Malformed will be sent. 3. Key Type - All Key Type fields MUST be checked to be a valid encryption type as defined by table 16. If the value is not valid, then an error is logged and if in Verbose mode an appropriate message containing notification value Invalid-Key-Information will be sent. 4. Key Expiration Date - All Key Expiration Date fields MUST be checked confirm that their values represent a future and not a past time value. If the value is not valid, then an error is logged and if in Verbose mode an appropriate message containing notification value Invalid-Key-Information will be sent. The length and counter fields in the payload are used to help process the payload. If any field is found to be incorrect, then an error is logged and if in Verbose mode an appropriate message containing notification value Payload-Malformed will be sent. 7.5 Rekey Event Payload Refer to the terminology section for the different terms relating to keys used within this section. 7.5.1 Rekey Event Payload Structure The Rekey Event Payload MAY contain multiple keys encrypted in Wrapping KEKs. Figure 14 shows the format of the payload. If the data to be contained within a Rekey Event Payload is too large for the payload, the sequence can be split across multiple Rekey Event Payloads at a Rekey Event Data boundary. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Next Payload ! RESERVED ! Payload Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! RekeyEvnt Type! Rekey Event Header ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Rekey Event Data(s) ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 14: Rekey Event Payload Format The Rekey Event Payload fields are defined as follows: Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 61] INTERNET-DRAFT GSAKMP June 2004 Next Payload (1 octet) - Identifier for the payload type of the next payload in the message. If the current payload is the last in the message, then this field will be 0. This field provides the ``chaining`` capability. Table 12 identifies the payload types. This field is treated as an unsigned value. RESERVED (1 octet) - Unused, set to 0. Payload Length (2 octets) - Length in octets of the current payload, including the generic payload header. This field is treated as an unsigned integer in network byte order format. Rekey Event Type (1 octet) - Specifies the type of Rekey Event being used. Table 17 presents the types of Rekey events. This field is treated as an unsigned value. Table 17: Rekey Event Types Rekey_Event_Type Value Definition _______________________________________________________________________________ None 0 This type MUST be implemented. In this case, the size of the Rekey Event Data field will be zero bytes long. The purpose of a Rekey Event Payload with type None is when it is necessary to send out a new token with no rekey information. GSAKMP Rekey Msg requires a Rekey Event Payload, and in this instance it would have rekey data of type None. GSAKMP_LKH 1 The rekey data will be of type LKH formatted according to GSAKMP. The format for this field is defined in Section 7.5.1.2. Reserved to IANA 2 - 192 Private Use 193 - 255 Rekey Event Header (variable length) - This is the header information for the Rekey Event. The format for this is defined in Section 7.5.1.1, Rekey Event Header Structure. Rekey Event Data(s) (variable length) - This is the rekey information for the Rekey Event. The format for this is defined in Section 7.5.1.2, Rekey Event Data(s) Structure. The Rekey Event payload type is three (3). Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 62] INTERNET-DRAFT GSAKMP June 2004 7.5.1.1 Rekey Event Header Structure The format for the Rekey Event Header is shown in Figure 15. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Group ID Value ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Group ID Value ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Time/Date Stamp ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ! RekeyEnt Type ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Algorithm Ver ! # of Rekey Event Data(s) ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 15: Rekey Event Header Format Group Identification Value (variable length) - Indicates the name/title of the group to be rekeyed. This is the same format, length and value as the Group Identification Value in Section 7.1 GSAKMP Message Header. Time/Date Stamp (15 octets) -- This is the time value when the Rekey Event Data was generated. This field contains the timestamp in UTF-8 format YYYYMMDDHHMMSSZ, where YYYY is the year (0000 - 9999), MM is the numerical value of the month (01 - 12), DD is the day of the month (01 - 31), HH is the hour of the day (00 - 23), MM is the minute within the hour (00 - 59), SS is the seconds within the minute (00 - 59), and followed by the letter Z to indicate that this is Zulu time. This format is loosely based on [RFC 3161]. Rekey Event Type (1 octet) - This is the Rekey algorithm being used for this group. The values for this field can be found in Table 17. This field is treated as an unsigned value. Algorithm Version (1 octet) - Indicates the version of the Rekey Type being used. For Rekey Event Type of GSAKMP_LKH, refer to Section A.2 for a description of this value. This field is treated as an unsigned value. # of Rekey Event Data(s) (2 octets) - The number of Rekey Event Data(s) contained in the Rekey Data. This value is treated as an unsigned Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 63] INTERNET-DRAFT GSAKMP June 2004 integer in network byte order. 7.5.1.2 Rekey Event Data Structure As defined in the Rekey Event Header, # of Rekey Data(s) field, multiple pieces of information are sent in a Rekey Event Data. Each end user, will be interested in only one Rekey Event Data among all of the information sent. Each Rekey Event Data, will contain all the Key Packages that a user requires. For each Rekey Event Data, the data following the Wrapping fields is encrypted with the key identified in the Wrapping Header. Figure 16 shows the format of each Rekey Event Data. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Packet Length ! Wrapping KeyID ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ! Wrapping Key Handle ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ! # of Key Packages ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Key Packages(s) ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 16: Rekey Event Data Format Packet Length (2 octets) - Length in octets of the Rekey Event Data, which consists of the # of Key Packages and the Key Packages(s). This value is treated as an unsigned integer in network byte order. Wrapping KeyID (4 octets) - This is the Key ID of the KEK that is being used for encryption/decryption of the new (rekeyed) keys. For Rekey Event Type of Rekey - LKH, refer to Section A.2 for a description of this value. Wrapping Key Handle (4 octets) - This is a Key Handle of the KEK that is being used for encryption/decryption of the new (rekeyed) keys. Refer to Section 7.4.1.1 for the values of this field. # of Key Packages (2 octets) - The number of key packages contained in this Rekey Event Data. This value is treated as an unsigned integer in network byte order. Key Package(s) (variable length) - The type/length/value format of a Key Datum. The format for this is defined in Section 7.5.1.2.1. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 64] INTERNET-DRAFT GSAKMP June 2004 7.5.1.2.1 Key Package Structure Each Key Package contains all the information about the key. Figure 17 shows the format for a Key Package. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! KeyPkg Type ! Key Package Length ! Key Datum ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 17: Key Package Format Key Package Type (1 octet) - The type of key in this key package. Legal values for this field are defined in Table 15, Key Download Data Types. This field is treated as an unsigned value. Key Package Length (2 octets) - The length of the Key Datum. This field is treated as an unsigned integer in network byte order format. Key Datum (variable length) - The actual data of the key. The format for this field is defined in Section 7.4.1.1, Key Datum. 7.5.2 Rekey Event Payload Processing When processing the Rekey Event Payload, the following fields MUST be checked for correct values: 1. Next Payload, RESERVED, Payload Length - These fields are processed as defined in Section 7.2.2, Generic Payload Header Processing. 2. Rekey Event Type field within "Rekey Event" payload header - The Rekey Event Type MUST be checked to be a valid rekey event type as defined by Table 17. If the Rekey Event Type is not valid, then regardless of mode (e.g., Terse or Verbose) an error is logged. No response error message is generated for receipt of a Group Management Message. 3. Group ID Value - The Group ID value of the Rekey Event Header received message MUST be checked against the GroupID of the Group Component. If no match is found, the payload is discarded, then regardless of mode (e.g., Terse or Verbose) an error is logged. No response error message is generated for receipt of a Group Management Message. 4. Date/Time Stamp - The Date/Time Stamp value of the Rekey Event Header MAY be checked to determine if the Rekey Event generation time is recent Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 65] INTERNET-DRAFT GSAKMP June 2004 relative to network delay and processing times. If the TimeStamp is judged not to be recent, an error is logged. No response error message is generated for receipt of a Group Management Message. 5. Rekey Event Type field within the "Rekey Event Header" - The Rekey Event Type of the Rekey Event Header received message MUST be checked to be a valid rekey event type as defined by Table 17 and the same value of the Rekey Event Type earlier in this payload. If the Rekey Event Type is not valid or not equal to the previous value of the Rekey Event Type, then regardless of mode (e.g., Terse or Verbose) an error is logged. No response error message is generated for receipt of a Group Management Message. 6. Algorithm Version - The Rekey Algorithm Version number MUST be checked that it is supported. If the version is not supported, then regardless of mode (e.g., Terse or Verbose) an error is logged. No response error message is generated for receipt of a Group Management Message. The length and counter fields are used to help process the message. If any field is found to be incorrect, then termination processing MUST be initiated. A GM MUST process all the Rekey Event Datas as based on the Rekey method used there is a potential that multiple Rekey Event Datas are for this GM. The Rekey Event Datas are processed in order until all Rekey Event Datas are consumed. 1. Wrapping KeyID - The Wrapping KeyID MUST be checked against the list of stored KEKs that this GM holds. If a match is found, then continue processing this Rekey Event Data. Otherwise, skip to the next Rekey Event Data. 2. Wrapping Handle - If a matching Wrapping KeyID was found, then the Wrapping Handle MUST be checked against the handle of the KEK for which the KeyID was a match. If the handles match, then the GM will process the Key Packages associated with this Rekey Event Data. Otherwise, skip to the next Rekey Event Data. If a GM has found a matching Wrapping KeyID and Wrapping Handle, the GM decrypts the remaining data in this Rekey Event Data according to policy using the KEK defined by the Wrapping KeyID and Handle. After decrypting the data, the GM extracts the # of Key Packages field to help process the subsequent Key Packages. The Key Packages are processed as follows: 1. Key Package Type - The Key Package Type MUST be checked to be a valid key package type as defined by Table 15. If the Key Package Type is not valid, then regardless of mode (e.g., Terse or Verbose) an error is Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 66] INTERNET-DRAFT GSAKMP June 2004 logged. No response error message is generated for receipt of a Group Management Message. 2. Key Package Length - The Key Package Length is used to process the subsequent Key Datum information. 3. Key Type - The Key Type MUST be checked to be a valid key type as defined by Table 16. If the Key Package Type is not valid, then regardless of mode (e.g., Terse or Verbose) an error is logged. No response error message is generated for receipt of a Group Management Message. 4. Key ID - The Key ID MUST be checked against the set of Key IDs that this user maintains for this Key Type. If no match is found, then regardless of mode (e.g., Terse or Verbose) an error is logged. No response error message is generated for receipt of a Group Management Message. 5. Key Handle - The Key Handle is extracted as is and is used to be the new Key Handle for the Key currently associated with the Key Package's Key ID. 6. Key Creation Date - The Key Creation Date MUST be checked that it is subsequent to the Key Creation Date for the currently held key. If this date is prior to the currently held key, then regardless of mode (e.g., Terse or Verbose) an error is logged. No response error message is generated for receipt of a Group Management Message. 7. Key Expiration Date - The Key Expiration Date MUST be checked that it is subsequent to the Key Creation Date just received and that the time rules conform with policy. If the expiration date is not subsequent to the creation date or does not conform with policy, then regardless of mode (e.g., Terse or Verbose) an error is logged. No response error message is generated for receipt of a Group Management Message. 8. Key Data - The Key Data is extracted based on the length information in the key package. If there were no errors when processing the Key Package, the key represented by the KeyID will have all of its data updated based upon the received information. 7.6 Identification Payload 7.6.1 Identification Payload Structure The Identification Payload contains entity-specific data used to exchange identification information. This information is used to verify the Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 67] INTERNET-DRAFT GSAKMP June 2004 identities of members. Figure 18 shows the format of the Identification Payload. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Next Payload ! RESERVED ! Payload Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! ID Classif ! ID Type ! Identification Data ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 18: Identification Payload Format The Identification Payload fields are defined as follows: Next Payload (1 octet) - Identifier for the payload type of the next payload in the message. If the current payload is the last in the message, then this field will be 0. This field provides the ``chaining`` capability. Table 12 identifies the payload types. This field is treated as an unsigned value. RESERVED (1 octet) - Unused, set to 0. Payload Length (2 octets) - Length in octets of the current payload, including the generic payload header. This field is treated as an unsigned integer in network byte order format. Identification (ID) Classification (1 octet) - Classifies the ownership of the Identification Data. Table 18 identifies possible values for this field. This field is treated as an unsigned value. Table 18: Identification Classification ID_Classification Value _______________________________ Sender 0 Receiver 1 Third Party 2 Reserved to IANA 3 - 192 Private Use 193 - 255 Identification (ID) Type (1 octet) - Specifies the type of Identification being used. Table 19 identifies possible values for this type. This field is treated as an unsigned value. All defined types are OPTIONAL unless otherwise stated. Identification Data (variable length) - Contains identity information. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 68] INTERNET-DRAFT GSAKMP June 2004 Table 19: Identification Types ID_Type Value PKIX Cert Description Field _______________________________________________________________________________ Reserved 0 ID_IPV4_ADDR 1 SubjAltName See [IKEv2] sec 3.5. iPAddress ID_FQDN 2 SubjAltName See [IKEv2] sec 3.5. dNSName ID_RFC822_ADDR 3 SubjAltName See [IKEv2] sec 3.5. rfc822Name Reserved 4 ID_IPV6_ADDR 5 SubjAltName See [IKEv2] sec 3.5. iPAddress Reserved 6 - 8 ID_DER_ASN1_DN 9 Entire Subject, See [IKEv2] sec 3.5. bitwise Compare Reserved 10 ID_KEY_ID 11 N/A See [IKEv2] sec 3.5. Reserved 12 - 29 Unencoded Name 30 Subject This type MUST be (ID_U_NAME) implemented. The format for this type is defined in Section 7.6.1.1. Reserved to IANA 31 - 192 Private Use 193 - 255 The values for this field are group-specific and the format is specified by the ID Type field. The format for this field is stated in conjunction with the type in Table 19. The payload type for the Identification Payload is four (4). 7.6.1.1 ID_U_NAME Structure The format for type Unencoded Name (ID_U_NAME) is shown in Figure 19. Serial Number (20 octets) -- The certificate serial number. This field is treated as an unsigned integer in network byte order format. Length (4 octets) -- Length in octets of the DN Data field. This field is treated as an unsigned integer in network byte order format. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 69] INTERNET-DRAFT GSAKMP June 2004 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Serial Number ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! DN Data ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 19: Unencoded Name (ID-U-NAME) Format DN Data (variable length) -- The actual UTF-8 DN value (Subject field) using the slash (/) character for field delimiters. (e.g., "/C=US/ST=MD/L=Somewhere/O=ACME, Inc./OU=DIV1/CN=user1/Email=user1@acme.com" without the surrounding quotes) 7.6.2 Identification Payload Processing When processing the Identification Payload, the following fields MUST be checked for correct values: 1. Next Payload, RESERVED, Payload Length - These fields are processed as defined in Section 7.2.2, Generic Payload Header Processing. 2. Identification Classification - The Identification Classification value MUST be checked to be a valid identification classification type as defined by Table 18. If the value is not valid, then an error is logged and if in Verbose mode an appropriate message containing notification value Payload-Malformed will be sent. 3. Identification Type - The Identification Type value MUST be checked to be a valid identification type as defined by Table 19. If the value is not valid, then an error is logged and if in Verbose mode an appropriate message containing notification value Payload-Malformed will be sent. 4. Identification Data - This Identification Data MUST be processed Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 70] INTERNET-DRAFT GSAKMP June 2004 according to the identification type specified. The type will define the format of the data. If the identification data is being used to find a match and no match is found, then an error is logged and if in Verbose mode an appropriate message containing notification value Invalid-ID-Information will be sent. 7.6.2.1 ID_U_NAME Processing When processing the Identification Data of type ID_U_NAME, the following fields MUST be checked for correct values: 1. Serial Number - The serial number MUST be a greater than or equal to one (1) to be a valid serial number from a conforming CA [RFC 3280]. If the value is not valid, then an error is logged and if in Verbose mode an appropriate message containing notification value Payload-Malformed will be sent. 2. DN Data - The DN data is processed as a UTF-8 string. 3. The CA MUST be a valid trust anchor as defined by the Policy Token. These 2 pieces of information, Serial Number and DN Data, in conjunction will then be used for party identification. These values are also used to help identify the certificate when necessary. 7.7 Certificate Payload 7.7.1 Certificate Payload Structure The Certificate Payload provides a means to transport certificates or other certificate-related information via GSAKMP and can appear in any GSAKMP message. Certificate payloads SHOULD be included in an exchange whenever an appropriate directory service (e.g. Secure DNS [DNSSEC]) is not available to distribute certificates. Multiple certificate payloads MAY be sent to enable verification of certificate chains. Conversely, zero (0) certificate payloads may be sent and the receiving GSAKMP MUST rely on some other mechanism to retrieve certificates for verification purposes. Figure 20 shows the format of the Certificate Payload. The Certificate Payload fields are defined as follows: Next Payload (1 octet) - Identifier for the payload type of the next Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 71] INTERNET-DRAFT GSAKMP June 2004 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Next Payload ! RESERVED ! Payload Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Cert Type ! Certificate Data ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 20: Certificate Payload Format payload in the message. If the current payload is the last in the message, then this field will be 0. This field provides the ``chaining`` capability. Table 12 identifies the payload types. This field is treated as an unsigned value. RESERVED (1 octet) - Unused, set to 0. Payload Length (2 octets) - Length in octets of the current payload, including the generic payload header. This field is treated as an unsigned integer in network byte order format. Certificate Type (2 octets) - This field indicates the type of certificate or certificate-related information contained in the Certificate Data field. Table 20 presents the types of certificate payloads. This field is treated as an unsigned integer in network byte order format. Certificate Data (variable length) - Actual encoding of certificate data. The type of certificate is indicated by the Certificate Type/Encoding field. The payload type for the Certificate Payload is six (6). 7.7.2 Certificate Payload Processing When processing the Certificate Payload, the following fields MUST be checked for correct values: 1. Next Payload, RESERVED, Payload Length - These fields are processed as defined in Section 7.2.2, Generic Payload Header Processing. 2. Certificate Type - The Certificate Type value MUST be checked to be a valid certificate type as defined by Table 20. If the value is not valid, then an error is logged and if in Verbose mode an appropriate message containing notification value Cert-Type-Unsupported will be Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 72] INTERNET-DRAFT GSAKMP June 2004 Table 20: Certificate Payload Types Certificate_Type Value Description _______________________________________________________________________________ None 0 Reserved 1 - 3 X.509v3 Certificate 4 This type MUST be -- Signature implemented. Contains a DER -- DER Encoding encoded X.509 certificate. Reserved 5 - 6 Certificate Revocation List 7 Contains a BER encoded (CRL) X.509 CRL. Reserved 8 - 9 X.509 Certificate 10 See [IKEv2] section 3.6. -- Attribute Raw RSA Key 11 See [IKEv2] section 3.6. Hash and URL of X.509 12 See [IKEv2] section 3.6. Certificate Hash and URL of X.509 13 See [IKEv2] section 3.6. bundle Reserved to IANA 14 -- 49152 Private Use 49153 -- 65535 sent. 3. Certificate Data - This Certificate Data MUST be processed according to the certificate type specified. The type will define the format of the data. Receipt of a root trust anchor CA certificate in a Certificate payload causes the payload to be discarded. This received certificate MUST NOT be used to verify the message. The root trust anchor CA certificate MUST be retrieved by other means. 7.8 Signature Payload 7.8.1 Signature Payload Structure The Signature Payload contains data generated by the digital signature function. The digital signature, as defined by the dissection of each message, covers the message from the GSAKMP Message Header through the Signature Payload up to but not including the Signature Data Length. Figure 21 shows the format of the Signature Payload. The Signature Payload fields are defined as follows: Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 73] INTERNET-DRAFT GSAKMP June 2004 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Next Payload ! RESERVED ! Payload Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Signature Type ! Sig ID Type ! ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Signature Timestamp ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ! Signer ID Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Signer ID Data ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Signature Length ! Signature Data ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 21: Signature Payload Format Next Payload (1 octet) - Identifier for the payload type of the next payload in the message. If the current payload is the last in the message, then this field will be 0. This field provides the ``chaining`` capability. Table 12 identifies the payload types. This field is treated as an unsigned value. RESERVED (1 octet) - Unused, set to 0. Payload Length (2 octets) - Length in octets of the current payload, including the generic payload header. This field is treated as an unsigned integer in network byte order format. Signature Type (2 octets) -- Indicates the type of signature. Table 21 presents the allowable signature types. This field is treated as an unsigned integer in network byte order format. Signature ID Type (1 octet) -- Indicates the format for the Signature ID Data. These values are the same as those defined for the Identification Payload Identification types which can be found in Table 19. This field is treated as an unsigned value. Signature Timestamp (15 octets) -- This is the time value when the digital signature was applied. This field contains the timestamp in UTF-8 format YYYYMMDDHHMMSSZ, where YYYY is the year (0000 - 9999), MM is Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 74] INTERNET-DRAFT GSAKMP June 2004 Table 21: Signature Types Signature Type Value Description ________________________________________________________________________ DSS/SHA1 with ASN.1/DER encoding 0 This type MUST be (DSS-SHA1-ASN1-DER) supported. RSA1024-MD5 1 See [RFC 3447]. ECDSA-P384-SHA3 2 See [FIPS 186-2]. Reserved to IANA 3 - 41952 Private Use 41953 - 65536 the numerical value of the month (01 - 12), DD is the day of the month (01 - 31), HH is the hour of the day (00 - 23), MM is the minute within the hour (00 - 59), SS is the seconds within the minute (00 - 59), and followed by the letter Z to indicate that this is Zulu time. This format is loosely based on [RFC 3161]. Signer ID Length (2 octets) - Length in octets of the Signer' ID. This field is treated as an unsigned integer in network byte order format. Signer ID Data (variable length) -- Data identifying the Signer's ID (e.g., DN). The format for this field is based on the Signature ID Type field and is shown where that type is defined. The contents of this field MUST be checked against the Policy Token to determine the authority and access of the Signer within the context of the group. Signature Length (2 octets) -- Length in octets of the Signature Data. This field is treated as an unsigned integer in network byte order format. Signature Data (variable length) - Data that results from applying the digital signature function to the GSAKMP message and/or payload. The payload type for the Signature Payload is eight (8). 7.8.2 Signature Payload Processing When processing the Signature Payload, the following fields MUST be checked for correct values: 1. Next Payload, RESERVED, Payload Length - These fields are processed as defined in Section 7.2.2, Generic Payload Header Processing. 2. Signature Type - The Signature Type value MUST be checked to be a valid Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 75] INTERNET-DRAFT GSAKMP June 2004 signature type as defined by Table 21. If the value is not valid, then an error is logged and if in Verbose mode an appropriate message containing notification value Payload-Malformed will be sent. 3. Signature ID Type - The Signature ID Type value MUST be checked to be a valid signature ID type as defined by Table 19. If the value is not valid, then an error is logged and if in Verbose mode an appropriate message containing notification value Payload-Malformed will be sent. 4. Signature Timestamp - This field MAY be checked to determine if the transaction signing time is fresh relative to expected network delays. Such a check is appropriate for systems in which archived sequences of events is desired. NOTE: The maximum acceptable age of a signature timestamp relative to the local system clock is a locally configured parameter that can be tuned by its GSAKMP management interface. 5. Signature ID Data - This field will be used to identify the sending party. This information MUST then be used to confirm that the correct party sent this information. This field is also used to retrieve the appropriate public key of the certificate to verify the message. 6. Signature Data - This value MUST be compared to the recomputed signature to verify the message. Information on how to verify certificates used to ascertain the validity of the signature can be found in [RFC 3280]. Only after the certificate identified by the Signature ID Data is verified can the signature be computed to compare to the signature data for signature verification. A potential error that can occur during signature verification is Authentication-Failed. Potential errors that can occur while processing certificates for signature verification are: Invalid-Certificate, Invalid-Cert-Authority, Cert-Type-Unsupported, and Certificate-Unavailable. The length fields in the Signature Payload are used to process the remainder of the payload. If any field is found to be incorrect, then termination processing MUST be initiated. 7.9 Notification Payload 7.9.1 Notification Payload Structure The Notification Payload can contain both GSAKMP and group specific data and is used to transmit informational data, such as error conditions, to a GSAKMP peer. It is possible to send multiple independent Notification payloads in a single GSAKMP message. Figure 22 shows the format of the Notification Payload. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 76] INTERNET-DRAFT GSAKMP June 2004 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Next Payload ! RESERVED ! Payload Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Notification Type ! Notification Data ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 22: Notification Payload Format The Notification Payload fields are defined as follows: Next Payload (1 octet) - Identifier for the payload type of the next payload in the message. If the current payload is the last in the message, then this field will be 0. This field provides the ``chaining`` capability. Table 12 identifies the payload types. This field is treated as an unsigned value. RESERVED (1 octet) - Unused, set to 0. Payload Length (2 octets) - Length in octets of the current payload, including the generic payload header. This field is treated as an unsigned integer in network byte order format. Notification Type (2 octets) - Specifies the type of notification message. Table 22 presents the Notify Payload Types. This field is treated as an unsigned integer in network byte order format. Notification Data (variable length) - Informational or error data transmitted in addition to the Notify Payload Type. Values for this field are Domain of Interpretation (DOI)-specific. The payload type for the Notification Payload is nine (9). Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 77] INTERNET-DRAFT GSAKMP June 2004 Table 22: Notification Types Notification Type Value __________________________________________________________ None 0 Invalid-Payload-Type 1 Reserved 2 - 3 Invalid-Version 4 Invalid-Group-ID 5 Invalid-Sequence-ID 6 Payload-Malformed 7 Invalid-Key-Information 8 Invalid-ID-Information 9 Reserved 10 - 11 Cert-Type-Unsupported 12 Invalid-Cert-Authority 13 Authentication-Failed 14 Reserved 15 - 16 Certificate-Unavailable 17 Reserved 18 Unauthorized-Request 19 Reserved 20 - 22 Acknowledgment 23 Reserved 24 - 25 Nack 26 Cookie-Required 27 Cookie 28 Mechanism Choices 29 Leave Group 30 Departure Accepted 31 Request to Depart Error 32 Invalid Exchange Type 33 IPv4 Value 34 IPv6 Value 35 Prohibited by Group Policy 36 Prohibited by Locally Configured Policy 37 Reserved to IANA 38 - 49152 Private Use 49153 -- 65535 Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 78] INTERNET-DRAFT GSAKMP June 2004 7.9.1.1 Notification Data - Acknowledgment (ACK) Payload Type The data portion of the Notification payload of type ACK serves either for confirmation of correct receipt of the Key Download message, or, when needed, can provide other receipt information when included in a signed message. Figure 23 shows the format of the Notification Data - Acknowledge Payload Type. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Ack Type ! Acknowledgment Data ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 23: Notification Data - Acknowledge Payload Type Format The Notification Data - Acknowledgment Payload Type data fields are defined as follows: Ack Type (1 octet) - Specifies the type of acknowledgment. Table 23 presents the Notify Acknowledgment Payload Types. This field is treated as an unsigned value. Table 23: Acknowledgment Types ACK_Type Value Definition _____________________________________________________ Simple 0 Data portion null. Reserved to IANA 1 - 192 Private Use 193 - 255 7.9.1.2 Notification Data - Cookie_Required and Cookie Payload Type The data portion of the Notification payload of types Cookie_Required and Cookie contain the Cookie value. The value for this field will have been computed by the responder GC/KS and sent to the GM. The GM will take the value received and copy it into the Notification payload Notification Data field of type Cookie that is transmitted in the "Request to Join with Cookie Info" back to the GC/KS. The cookie value MUST NOT be modified. The format for this is already described in the discussion on cookies in section 5.2.2. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 79] INTERNET-DRAFT GSAKMP June 2004 7.9.1.3 Notification Data - Mechanism Choices Payload Type The data portion of the Notification payload of types Mechanism Choices contains the mechanisms the GM is requesting to use for the negotiation with the GC/KS. This information will be supplied by the GM in a RTJ message. Figure 24 shows the format of the Notification Data - Mechanism Choices Payload Type. Multiple type|length|data choices are strung together in one notification payload to allow a user to transmit all relevant information within one Notification Payload. The length of the payload will control the parsing of the Notification Data Mechanism Choices field. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Mech Type ! Mechanism Choice Data ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... Figure 24: Notification Data - Mechanism Choices Payload Type Format The Notification Data - Mechanism Choices Payload Type data fields are defined as follows: Mechanism Type (1 octet) - Specifies the type of mechanism. Table 24 presents the Notify Mechanism Choices Mechanism Types. This field is treated as an unsigned value. Table 24: Mechanism Types Mechanism_Type Value Mechanism Choice Data Value Table Reference ___________________________________________________________________ Key Creation Algorithm 0 Table 26 Encryption Algorithm 1 Table 16 Nonce Hash Algorithm 2 Table 25 Reserved to IANA 3 - 192 Private Use 193 - 255 Mechanism Choice Data (2 octets) - The data value for the mechanism type being selected. The values are specific to each Mechanism Type defined. All tables necessary to define the values that are not defined elsewhere (in this specification or others) are defined here. This field is treated as an unsigned integer in network byte order format. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 80] INTERNET-DRAFT GSAKMP June 2004 Table 25: Nonce Hash Types Nonce_Hash_Type Value Description ___________________________________________________________________ Reserved 0 SHA-1 1 This type MUST be supported. Reserved to IANA 2 - 49152 Private Use 49153 - 65535 7.9.1.4 Notification Data - IPv4 and IPv6 Value Payload Types The data portion of the Notification payload of type IPv4 and IPv6 value contains the appropriate IP value in network byte order. This value will be set by the creator of the message for consumption by the receiver of the message. 7.9.2 Notification Payload Processing When processing the Notification Payload, the following fields MUST be checked for correct values: 1. Next Payload, RESERVED, Payload Length - These fields are processed as defined in Section 7.2.2, Generic Payload Header Processing. 2. Notification Type - The Notification type value MUST be checked to be a notification type as defined by Table 22. If the value is not valid, then an error is logged and if in Verbose mode an appropriate message containing notification value Payload-Malformed will be sent. 3. Notification Data - This Notification Data MUST be processed according to the notification type specified. The type will define the format of the data. When processing this data, any type field MUST be checked against the appropriate table for correct values. If the contents of the Notification Data are not valid, then an error is logged and if in Verbose mode an appropriate message containing notification value Payload-Malformed will be sent. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 81] INTERNET-DRAFT GSAKMP June 2004 7.10 Vendor ID Payload 7.10.1 Vendor ID Payload Structure The Vendor ID Payload contains a vendor defined constant. The constant is used by vendors to identify and recognize remote instances of their implementations. This mechanism allows a vendor to experiment with new features while maintaining backwards compatibility. Figure 25 shows the format of the payload. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Next Payload ! RESERVED ! Payload Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Vendor ID (VID) ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 25: Vendor ID Payload Format A Vendor ID payload MAY announce that the sender is capable to accepting certain extensions to the protocol, or it MAY simply identify the implementation as an aid in debugging. A Vendor ID payload MUST NOT change the interpretation of any information defined in this specification. Multiple Vendor ID payloads MAY be sent. An implementation is NOT REQUIRED to send any Vendor ID payload at all. A Vendor ID payload may be sent as part of any message. Reception of a familiar Vendor ID payload allows an implementation to make use of Private Use numbers described throughout this specification -- private payloads, private exchanges, private notifications, etc. This implies that all the processing rules defined for all the payloads are now modified to recognize all values defined by this Vendor ID for all fields of all payloads. Unfamiliar Vendor IDs MUST be ignored. Writers of Internet-Drafts who wish to extend this protocol MUST define a Vendor ID payload to announce the ability to implement the extension in the Internet-Draft. It is expected that Internet-Drafts which gain acceptance and are standardized will be given assigned values out of the Reserved to IANA range and the requirement to use a Vendor ID payload will go away. The VendorID Payload fields are defined as follows: Next Payload (1 octet) - Identifier for the payload type of the next payload in the message. If the current payload is the last in the message, then this field will be 0. This field provides the Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 82] INTERNET-DRAFT GSAKMP June 2004 ``chaining`` capability. Table 12 identifies the payload types. This field is treated as an unsigned value. RESERVED (1 octet) - Unused, set to 0. Payload Length (2 octets) - Length in octets of the current payload, including the generic payload header. This field is treated as an unsigned integer in network byte order format. Vendor ID (variable length) - The Vendor ID value. The minimum length for this field is four (4) octets. It is the responsibility of the person choosing the Vendor ID to assure its uniqueness in spite of the absence of any central registry for IDs. Good practice is to include a company name, a person name or similar type data. A message digest of a long unique string is preferable to the long unique string itself. The payload type for the Vendor ID Payload is ten (10). 7.10.2 Vendor ID Payload Processing When processing the Vendor ID Payload, the following fields MUST be checked for correct values: 1. Next Payload, RESERVED, Payload Length - These fields are processed as defined in Section 7.2.2, Generic Payload Header Processing. 2. Vendor ID - The Vendor ID Data MUST be processed to determine if the Vendor ID value is recognized by the implementation. If the Vendor ID value is not recognized, then regardless of mode (e.g., Terse or Verbose) this information is logged. Processing of the message MUST continue regardless of recognition of this value. It is recommended that implementations that want to use Vendor ID specific information attempt to process the Vendor ID payloads of an incoming message prior to the remainder of the message processing. This will allow the implementation to recognize that when processing other payloads that it can use the larger set of values for payload fields (Private Use values, etc.) as defined by the recognized Vendor IDs. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 83] INTERNET-DRAFT GSAKMP June 2004 7.11 Key Creation Payload 7.11.1 Key Creation Payload Structure The Key Creation Payload contains information used to create key encryption keys. The security attributes for this payload are provided in the Policy Token. Figure 26 shows the format of the payload. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Next Payload ! RESERVED ! Payload Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Key Creation Type ! Key Creation Data ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 26: Key Creation Payload Format The Key Creation Payload fields are defined as follows: Next Payload (1 octet) - Identifier for the payload type of the next payload in the message. If the current payload is the last in the message, then this field will be 0. This field provides the ``chaining`` capability. Table 12 identifies the payload types. This field is treated as an unsigned value. RESERVED (1 octet) - Unused, set to 0. Payload Length (2 octets) - Length in octets of the current payload, including the generic payload header. This field is treated as an unsigned integer in network byte order format. Key Creation Type (2 octets) - Specifies the type of Key Creation being used. Table 26 identifies the types of key creation information. This field is treated as an unsigned integer in network byte order format. Key Creation Data (variable length) - Contains Key Creation information. The values for this field are group specific and the format is specified by the key creation type field. The payload type for the Key Creation Packet is eleven (11). Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 84] INTERNET-DRAFT GSAKMP June 2004 Table 26: Types Of Key Creation Information Key Creation Type Value Definition _________________________________________________________________________ Reserved 0 - 1 Diffie-Hellman 2 This type MUST be supported. 1024-bit MODP Group This is defined in IKEv2 B.2. Truncated If the output of the process is longer than needed for the defined mechanism, use the first X low order bits, and truncate the remainder. Reserved 3 - 13 Diffie-Hellman 14 This is defined in RFC 3526. 2048-bit MODP Group If the output of the process Truncated is longer than needed for the defined mechanism, use the first X low order bits, and truncate the remainder. Reserved to IANA 15 - 49152 Private Use 49153 - 65535 7.11.2 Key Creation Payload Processing The specifics of the Key Creation Payload are defined in section 7.11. When processing the Key Creation Payload, the following fields MUST be checked for correct values: 1. Next Payload, RESERVED, Payload Length - These fields are processed as defined in Section 7.2.2, Generic Payload Header Processing. 2. Key Creation Type - The Key Creation Type value MUST be checked to be a valid key creation type as defined by Table 26. If the value is not valid, then an error is logged and if in Verbose mode an appropriate message containing notification value Payload-Malformed will be sent. 3. Key Creation Data - This Key Creation Data MUST be processed according to the key creation type specified to generate the KEK to protect the information to be sent in the appropriate message. The type will define the format of the data. Implementations that want to derive other keys from the initial Key Creation keying material, for example, DH Secret keying material, MUST define a Key Creation Type other than one of those shown in Table 26. The new Key Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 85] INTERNET-DRAFT GSAKMP June 2004 Creation Type must specify that derivation's algorithm, for which the KEK MAY be one of the keys derived. 7.12 Nonce Payload 7.12.1 Nonce Payload Structure The Nonce Payload contains random data used to guarantee freshness during an exchange and protect against replay attacks. Figure 27 shows the format of the Nonce Payload. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Next Payload ! RESERVED ! Payload Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Nonce Type ! Nonce Data ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 27: Nonce Payload Format The Nonce Payload fields are defined as follows: Next Payload (1 octet) - Identifier for the payload type of the next payload in the message. If the current payload is the last in the message, then this field will be 0. This field provides the ``chaining`` capability. Table 12 identifies the payload types. This field is treated as an unsigned value. RESERVED (1 octet) - Unused, set to 0. Payload Length (2 octets) - Length in octets of the current payload, including the generic payload header. This field is treated as an unsigned integer in network byte order format. Nonce Type (1 octet) - Specifies the type of Nonce being used. Table 27 identifies the types of nonces. This field is treated as an unsigned value. Nonce Data (variable length) - Contains the nonce information. The values for this field are group-specific and the format is specified by the Nonce Type field. If no group-specific information is provided, the minimum length for this field is 4 bytes. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 86] INTERNET-DRAFT GSAKMP June 2004 Table 27: Nonce Types Nonce_Type Value Definition _____________________________________________________________________________ None 0 Initiator (Nonce_I) 1 Responder (Nonce_R) 2 Combined (Nonce_C) 3 Hash (Append(Initiator_Value,Responder_Value)) The hash type comes from the Policy (e.g., Security Suite Definition or Policy Token). Reserved to IANA 4 - 192 Private Use 192 - 255 The payload type for the Nonce Payload is twelve (12). 7.12.2 Nonce Payload Processing When processing the Nonce Payload, the following fields MUST be checked for correct values: 1. Next Payload, RESERVED, Payload Length - These fields are processed as defined in Section 7.2.2, Generic Payload Header Processing. 2. Nonce Type - The Nonce Type value MUST be checked to be a valid nonce type as defined by Table 27. If the value is not valid, then an error is logged and if in Verbose mode an appropriate message containing notification value Payload-Malformed will be sent. 3. Nonce Data - This is the nonce data and it must be checked according to its content. The size of this field is defined in Nonce Payload section 7.12. Refer to the Message Processing Group Establishment section (Section 5.2) for interpretation of this field. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 87] INTERNET-DRAFT GSAKMP June 2004 8 GSAKMP State Diagram Figure 28 presents the states encountered in the use of this protocol. Table 28 defines the states. Table 29 defines the transitions. !-----------------> ( ) ! !-------------> ( Idle ) <------------------! ! ! ( ) ! ! ! ! ! ! ! ! ! ! ! ! ! (1a) (1) ! ! ! ! ! ! ! ! ! ! ! ! ! V V ! ! !---(5a)--- (Wait for ) (Wait for ) ----(5)-----! ! (Group ) (GC/KS Event) <--- ! (Membership) ^ ! \ \ ! ! ! ! \ \ ! ! ! ! \--(2)---\ ! (2a) (4)(3) ! ! ! ! ! ! ! ! ! V ! V !-------(4a)--- (Wait for ) (Wait for ) (Group ) (Response ) (Membership) (from Key ) /--> (Event ) (Download ) / / / / /--(3a)---/ Figure 28: GSAKMP State Diagram Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 88] INTERNET-DRAFT GSAKMP June 2004 Table 28: GSAKMP States ___________________________________________________________________________ Idle : GSAKMP Application waiting for input _____________________:_____________________________________________________ : Wait for GC/KS Event : GC/KS up and running, waiting for events _____________________:_____________________________________________________ : Wait for Response : GC/KS has sent Key Download, from Key Download : waiting for response from GM _____________________:_____________________________________________________ : Wait for Group : GM in process of joining group Membership : _____________________:_____________________________________________________ : Wait for Group : GM has group key, waiting for Membership Event : group management messages. : ___________________________________________________________________________ Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 89] INTERNET-DRAFT GSAKMP June 2004 Table 29: State Transition Events ____________________________________________________________________ Transition 1 : Create group command _______________:____________________________________________________ : Transition 2 : Receive bad RTJ : Receive valid command to change group membership : Send Compromise message x times : Member Deregistration _______________:____________________________________________________ : Transition 3 : Receive valid RTJ _______________:____________________________________________________ : Transition 4 : Timeout : Receive Ack : Receive Nack _______________:____________________________________________________ : Transition 5 : Delete group command _______________:____________________________________________________ : Transition 1a : Join group command _______________:____________________________________________________ : Transition 2a : Send Ack _______________:____________________________________________________ : Transition 3a : Receipt of group management messages _______________:____________________________________________________ : Transition 4a : Delete group command : Deregistration command _______________:____________________________________________________ : Transition 5a : Time out : Msg failure : errors : ____________________________________________________________________ Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 90] INTERNET-DRAFT GSAKMP June 2004 9 IANA Considerations 9.1 IANA Port Number Assignment IANA has provided GSAKMP port number 3761 in both the UDP and TCP spaces. All implementations MUST use this port assignment in the appropriate manner. 9.2 Initial IANA Registry Contents The following registry entries should be created: GSAKMP Group Identification Types GSAKMP Payload Types GSAKMP Exchange Types GSAKMP Policy Token Types GSAKMP Key Download Data Item Types GSAKMP Cryptographic Key Types GSAKMP Rekey Event Types GSAKMP Identification Classification GSAKMP Identification Types GSAKMP Certificate Types GSAKMP Signature Types GSAKMP Notification Types GSAKMP Acknowledgment Types GSAKMP Mechanism Types GSAKMP Nonce Hash Types GSAKMP Key Creation Types GSAKMP Nonce Types 9.2.1 GSAKMP Group Identification Types The Group Identification occurs in the GSAKMP header. Group ID Type Value ========================================= Reserved 0 UTF-8 1 Octet String 2 IPv4 3 IPv6 4 Reserved to IANA 5 - 192 Private Use 193 - 255 Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 91] INTERNET-DRAFT GSAKMP June 2004 9.2.1.1 Amending formula for GSAKMP Group Identification Types GSAKMP Group Identification Types may be allocated by Specification Required. 9.2.2 GSAKMP Payload Types Next Payload Type Value ================================== None 0 Policy Token 1 Key Download Packet 2 Rekey event 3 Identification 4 Reserved 5 Certificate 6 Reserved 7 Signature 8 Notification 9 Reserved 10 Key Creation 11 Nonce 12 Reserved to IANA 13 - 192 Private Use 193 -- 255 9.2.2.1 Amending formula for GSAKMP Payload Types GSAKMP Payload Types may be allocated by Specification Required. 9.2.3 GSAKMP Exchange Types The Exchange Type occurs in the GSAKMP header. Exchange`Type Value ======================================= Reserved 0 - 3 Key Download Ack/Failure 4 Rekey Event 5 Reserved 6 - 7 Request to Join 8 Key Download 9 Cookie Download 10 Request to Join Error 11 Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 92] INTERNET-DRAFT GSAKMP June 2004 Lack of Ack 12 Request to Depart 13 Departure Response 14 Departure Ack 15 Reserved to IANA 16 - 192 Private Use 193 -- 255 9.2.3.1 Amending formula for GSAKMP Exchange Types GSAKMP Exchange Types may be allocated by Specification Required. 9.2.4 GSAKMP Policy Token Types Policy Token Type Value Defined In =================================================== GSAKMP`PT`V1 0 (HCLM00) GSAKMP`ASN.1`PT`V1 1 (TBD) Reserved to IANA 2 - 49152 Private Use 49153 - 65535 9.2.4.1 Amending formula for GSAKMP Policy Token Types GSAKMP Policy Token Types may be allocated by Specification Required. 9.2.5 GSAKMP Key Download Data Item Types The Key Download Data Item Type occurs in the Key Download Payload. Key Download Data Item Type Value ======================================== GTPK 0 Rekey - LKH 1 Reserved to IANA 2 - 192 Private Use 193 - 255 9.2.5.1 Amending formula for GSAKMP Key Download Data Item Types GSAKMP Key Download Data Item Types may be allocated by Specification Required. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 93] INTERNET-DRAFT GSAKMP June 2004 9.2.6 GSAKMP Cryptographic Key Types The Cryptographic Key Type occurs in the Key Type field of the Key Datum. Cryptographic Key Types Value Defined In ====================================================== Reserved 0 - 2 3DES`CBC64`192 3 (RFC2451) Reserved 4 - 11 AES`CBC 12 (IKEv2) AES`CTR 13 (IKEv2) Reserved to IANA 14 - 49152 Private Use 49153 - 65535 9.2.6.1 Amending formula for GSAKMP Cryptographic Key Types GSAKMP Cryptographic Key Types may be allocated by Specification Required. 9.2.7 GSAKMP Rekey Event Types Rekey`Event`Type Value =========================== None 0 GSAKMP`LKH 1 Reserved to IANA 2 - 192 Private Use 193 - 255 9.2.7.1 Amending formula for GSAKMP Rekey Event Types GSAKMP Rekey Event Types may be allocated by Specification Required. 9.2.8 GSAKMP Identification Classification Identification Classification Value ======================================= Sender 0 Receiver 1 Third Party 2 Reserved to IANA 3 - 192 Private Use 193 - 255 Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 94] INTERNET-DRAFT GSAKMP June 2004 9.2.8.1 Amending formula for GSAKMP Identification Classification GSAKMP Identification Classification may be allocated by Specification Required. 9.2.9 GSAKMP Identification Types Identification Type Value Defined In ============================================== Reserved 0 ID`IPV4`ADDR 1 (IKEv2, sec 3.5) ID`FQDN 2 (IKEv2, sec 3.5) ID`RFC822`ADDR 3 (IKEv2, sec 3.5) Reserved 4 ID`IPV6`ADDR 5 (IKEv2, sec 3.5) Reserved 6 - 8 ID`DER`ASN1`DN 9 (IKEv2, sec 3.5) Reserved 10 ID`KEY`ID 11 (IKEv2, sec 3.5) Reserved 12 - 29 ID`U`NAME 30 Reserved to IANA 32 - 192 Private Use 193 - 255 9.2.9.1 Amending formula for GSAKMP Identification Types GSAKMP Identification Types may be allocated by Specification Required. 9.2.10 GSAKMP Certificate Types Certificate Type Value Defined In ================================================================ None 0 Reserved 1 - 3 X.509v3 Certificate 4 -- Signature - DER Encoding Reserved 5 - 6 Certificate Revocation List 7 Reserved 8 - 9 X.509 Certificate 10 (IKEv2, sec 3.6) -- Attribute Raw RSA Key 11 (IKEv2, sec 3.6) Hash and URL of X.509 12 (IKEv2, sec 3.6) Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 95] INTERNET-DRAFT GSAKMP June 2004 Certificate Hash and URL of X.509 bundle 13 (IKEv2, sec 3.6) Reserved to IANA 5 -- 49152 Private Use 49153 -- 65535 9.2.10.1 Amending formula for GSAKMP Certificate Types GSAKMP Certificate Types may be allocated by Specification Required. 9.2.11 GSAKMP Signature Types Signature Type Value Defined In ============================================= DSS-SHA1-ASN1-DER 0 RSA1024-MD5 1 (RFC 3447) ECDSA-P384-SHA3 2 (FIPS 186-2) Reserved to IANA 3 - 41952 Private Use 41953 - 65536 9.2.11.1 Amending formula for GSAKMP Signature Types GSAKMP Signature Types may be allocated by Specification Required. 9.2.12 GSAKMP Notification Types Notification Type Value =============================================== None 0 Invalid-Payload-Type 1 Reserved 2 - 3 Invalid-Version 4 Invalid-Group-ID 5 Invalid-Sequence-ID 6 Payload-Malformed 7 Invalid-Key-Information 8 Invalid-ID-Information 9 Reserved 10 - 11 Cert-Type-Unsupported 12 Invalid-Cert-Authority 13 Authentication-Failed 14 Reserved 15 - 16 Certificate-Unavailable 17 Unequal-Payload-Lengths 18 Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 96] INTERNET-DRAFT GSAKMP June 2004 Unauthorized-Request 19 Reserved 20 - 22 Acknowledgment 23 Reserved 24 - 25 Nack 26 Cookie-Required 27 Cookie 28 Mechanism Choices 29 Leave Group 30 Departure Accepted 31 Request to Depart Error 32 Invalid Exchange Type 33 IPv4 Value 34 IPv6 Value 35 Prohibited by Group Policy 36 Prohibited by Locally Configured Policy 37 Reserved to IANA 38 - 49152 Private Use 49153 -- 65535 9.2.12.1 Amending formula for GSAKMP Notification Types GSAKMP Notification Types may be allocated by Specification Required. 9.2.13 GSAKMP Acknowledgment Types The Acknowledgment Type occurs in the Notification Payload of type Acknowledgment. ACK Type Value =============================== Simple 0 Reserved to IANA 1 - 192 Private Use 193 - 255 9.2.13.1 Amending formula for GSAKMP Acknowledgment Types GSAKMP Acknowledgment Types may be allocated by Specification Required. 9.2.14 GSAKMP Mechanism Types The Mechanism Type occurs in the Notification Payload of type Mechanism Choices. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 97] INTERNET-DRAFT GSAKMP June 2004 Mechanism Type Value =================================== Key Creation Algorithm 0 Encryption Algorithm 1 Nonce Hash Algorithm 2 Reserved to IANA 3 - 192 Private Use 193 - 255 9.2.14.1 Amending formula for GSAKMP Mechanism Types GSAKMP Mechanism Types may be allocated by Specification Required. 9.2.15 GSAKMP Nonce Hash Types The Nonce Hash Type occurs in the Notification Payload of type Mechanism Choices of type Nonce Hash Algorithm. Nonce Hash Type Value =============================== Reserved 0 SHA-1 1 Reserved to IANA 2 - 49152 Private Use 49153 - 65535 9.2.15.1 Amending formula for GSAKMP Nonce Hash Types GSAKMP Nonce Hash Types may be allocated by Specification Required. 9.2.16 GSAKMP Key Creation Types Key Creation Type Value Defined In ============================================== Reserved 0 - 1 Diffie-Hellman 2 (IKEv2 B.2) 1024-bit MODP Group Reserved 3 - 13 Diffie-Hellman 14 (RFC3526) 2048-bit MODP Group Reserved 15 - 49152 Private Use 49153 - 65535 Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 98] INTERNET-DRAFT GSAKMP June 2004 9.2.16.1 Amending formula for GSAKMP Key Creation Types GSAKMP Key Creation Types may be allocated by Specification Required. 9.2.17 GSAKMP Nonce Types Nonce Type Value ================================ None 0 Initiator (Nonce`I) 1 Responder (Nonce`R) 2 Combined (Nonce`C) 3 Reserved to IANA 4 - 192 Private Use 192 - 255 9.2.17.1 Amending formula for GSAKMP Nonce Types GSAKMP Nonce Types may be allocated by Specification Required. 10 Acknowledgments This document is the collaborative effort of many individuals. If there were no limit to the number of authors that could appear on an RFC, the following, in alphabetical order would have been listed: Haitham S. Cruickshank of University of Surrey, Sunil Iyengar of University Of Surrey Gavin Kenny of LogicaCMG, Patrick McDaniel of AT&T Labs Research, and Angela Schuett of NSA. The following individuals deserve recognition and thanks for their contributions which have greatly improved this protocol: Eric Harder is an author to the Tunneled-GSAKMP, whose concepts are found in GSAKMP as well. Rod Fleischer, also a Tunneled-GSAKMP author, and Peter Lough were both instrumental in coding a prototype of the GSAKMP software and helped define many areas of the protocol that were vague at best. Andrew McFarland and Gregory Bergren provided critical analysis of early versions of the specification. Ran Canetti analyzed the security of the protocol and provided denial of service suggestions leading to optional "cookie protection". Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 99] INTERNET-DRAFT GSAKMP June 2004 11 References The following references were used in the preparation of this document. 11.1 Normative References [DH77] Diffie, W., and M. Hellman, ``New Directions in Cryptography'', IEEE Transactions on Information Theory, June 1977. [FIPS 186-2] NIST, "Digital Signature Standard", FIPS PUB 186-2, National Institute of Standards and Technology, U.S. Department of Commerce, January 2000. [FIPS 196] ``Entity Authentication Using Public Key Cryptography,'' Federal Information Processing Standards Publication 196, NIST, February 1997. [HCLM00] H. Harney, A. Colegrove, P. Lough, U. Meth, ``GSAKMP Token Specification'', draft-ietf-msec-tokenspec-sec-00.txt [RFC 2119] Bradner, S., "Key Words for use in RFCs to indicate Requirement Levels", BCP 14, March 1997. [RFC 2409] Harkins D. and Carrel D., ``The Internet Key Exchange (IKE)'', RFC 2409, Proposed Standard, November 1998. [RFC 2412] Orman H. K., ``The OAKLEY Key Determination Protocol'', RFC 2412, Informational, November 1998. [RFC 2627] D. Wallner, E. Harder, R. Agee, Kay Management for Multicast: Issues and Architectures, June 1999 [RFC 3280] R. Housley, W. Polk, W. Ford, D. Solo, Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile, April 2002 [RFC 3629] F. Yergeau, UTF-8, a transformation format of ISO 10646, November 2003 [IKEv2] C. Kaufman, ``Internet Key Exchange (IKEv2) Protocol'', draft-ietf-ipsec-ikev2-12.txt, January 2004 11.2 Informative References [BMS] Balenson D., McGrew D., Sherman A., ``Key Management for Large Dynamic Groups: One-Way Function Trees and Amortized Initialization'', Internet Draft, February 1999. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 100] INTERNET-DRAFT GSAKMP June 2004 [HCM] H. Harney, A. Colegrove, P. McDaniel, "Principles of Policy in Secure Groups", Proceedings of Network and Distributed Systems Security 2001 Internet Society, San Diego, CA, February 2001 [HHMCD01] Thomas Hardjono, Hugh Harney, Pat McDaniel, Andrea Colgrove, Pete Dinsmore, Group Security Policy Token: Definition and Payloads', draft-ietf-msec-gspt-00.txt, Work in progress. [HW05] Hardjono T., Weis B., ``he Multicast Group Security Architecture'', draft-ietf-msec-arch-05.txt, January 2004. [MSST98] Maughan, D., Schertler, M., Schneider, M., and J. Turner, ``Internet Security Association and Key Management Protocol (ISAKMP)'', RFC 2408, November 1998. [WHA98] Wallner, D., Harder E., and Agee R., ``Key Management for Multicast: Issues and Architectures'', Internet Draft, Informational, September 1998. [RFC 2093] Harney H., Muckenhirn C., and Rivers T., ``Group Key, Management Protocol Specification'', RFC 2093, Experimental, July 1997. [RFC 2094] Harney H., Muckenhirn C., and Rivers T., ``Group Key Management Protocol Architecture'', RFC 2094, Experimental, July 1997. [RFC 2104] Krawczyk H., Bellare M., and Canetti R., ``HMAC: Keyed-Hashing for Message Authentication'', RFC 2104, Informational, February [RFC 2401] Kent S. and Atkinson, R., ``Security Architecture for the Internet Protocol'', RFC 2401, November 1998, Proposed Standard. [RFC 2402] Kent S. and Atkinson, R., ``IP Authentication Header'', RFC 2402, November 1998, Proposed Standard.1997. [RFC 2406] Kent S. and Atkinson, R., ``IP Encapsulating Security Payload (ESP)'', RFC 2406, November 1998, Proposed Standard. [RFC 2408] Maughan D., Schertler M., Schneider M., and Turner J., ``Internet Security Association and Key Management Protocol (ISAKMP)'', RFC 2408, Proposed Standard, November 1998. [RFC 2543] M. Handley, H. Schulzrinne, E. Schooler, J. Rosenberg, SIP: Session Initiation Protocol, March 99 [RFC 2974] M. Handley, C. Perkins, E. Whelan, Session Announcement Protocol, Oct 2000. [RFC 3161] C. Adams, P. Cain, D. Pinkas, R. Zuccherato, Internet X.509 Public Key Infrastructure Time-Stamp Protocol (TSP), August 2001 [RFC 3447] J. Jonsson, B. Kaliski, Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1, February 2003 Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 101] INTERNET-DRAFT GSAKMP June 2004 A APPENDIX A -- LKH Information This appendix will give an overview of LKH, define the values for fields within GSAKMP messages that are specific to LKH, and give an example of a Rekey Event Message using the LKH scheme. A.1 LKH Overview LKH provides a topology for handling key distribution for a group rekey. It rekeys a group based upon a tree structure and subgroup keys. In the LKH tree shown in Figure 29, members are represented by the leaf nodes on the tree, while intermediate tree nodes represent abstract key groups. A member will possess multiple keys: the group traffic protection key (GTPK), subgroup keys for every node on its path to the root of the tree, and a personal key. For example, the member labeled as #3 will have the GTPK, Key A, Key D, and Key 3. root / \ / \ A B / \ / \ / \ / \ C D E F / \ / \ / \ / \ / \ / \ / \ / \ 1 2 3 4 5 6 7 8 Figure 29: A. 1: LKH Tree This keying topology provides for a rapid rekey to all but a compromised member of the group. If member 3 were to be compromised, the new GTPK (GTPK') would need to be distributed to the group under a key not possessed by member 3. Additionally, new Keys A and D (Key A' and Key D') would also need to be securely distributed to the other members of those subtrees. Encrypting the GTPK' with Key B would securely distribute that key to members 5, 6, 7, and 8. Key C can be used to encrypt both the GTPK' and Key A' for members 1 and 2. Member 3's nearest neighbor, Member 4 can obtain GTPK', Key D', and Key A' encrypted under its personal key, Key 4. At the end of this process, the group is securely rekeyed with Member 3 fully excluded. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 102] INTERNET-DRAFT GSAKMP June 2004 A.2 LKH and GSAKMP When using LKH with GSAKMP the following issues require attention: 1. Rekey Version # - The Rekey Version # in the Rekey Array of the Key Download Payload MUST contain the value one (1). 2. Algorithm Version - The Algorithm Version in the Rekey Event Payload MUST contain the value one (1). 3. Degree of Tree - The LKH tree used can be of any degree, it need not be binary. 4. Node Identification - Each node in the tree is treated as a KEK. A KEK is just a special key. As the rule stated for all keys in GSAKMP, the set of the KeyID and the KeyHandle MUST be unique. A suggestion on how to do this will be given in this section. 5. Wrapping KeyID and Handle - This is the KeyID and Handle of the LKH node used to wrap/encrypt the data in a Rekey Event Data. For the following discussion, refer to Figure 30. Key: o: a node in the LKH tree N: this line contains the KeyID node number L: this line contains the MemberID number for all leaves ONLY LEVEL ---- root o N: / 1 \ / \ 1 o o N: / 2 \ / 3 \ / \ / \ 2 o o o o N: /4\ /5\ /6\ /7\ / \ / \ / \ / \ 3 o o o o o o o o N: 8 9 10 11 12 13 14 15 L: 1 2 3 4 5 6 7 8 Figure 30: A. 2: GSAKMP LKH Tree Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 103] INTERNET-DRAFT GSAKMP June 2004 To guarantee uniqueness of KeyID, the Rekey Controller SHOULD build a virtual tree and label the KeyID of each node doing a breadth first search of a fully populated tree regardless of whether or not the tree is actually full. For simplicity of this example, the root of the tree was given KeyID value of one (1). These KeyID values will be static throughout the life of this tree. Additionally, the rekey arrays distributed to GMs requires a MemberID value associated with them to be distributed with the KeyDownload Payload. These MemberID values MUST be unique. Therefore, the set associated with each leaf node (the nodes from that leaf back to the root) are given a MemberID. In this example, the leftmost leaf node is given MemberID value of one (1). These 2 sets of values, the KeyIDs (represented on lines N) and the MemberIDs (represented on line L) will give sufficient information in the KeyDownload and RekeyEvent Payloads to disseminate information. The KeyHandle associated with these keys is regenerated each time the key is replace in the tree due to compromise. A.3 LKH Examples Definition of values: 0xLLLL - length value 0xHHHHHHH# - handle value YYYYMMDDHHMMSSZ - Time Value A.3.1 LKH Key Download Example This section will give an example of the data for the Key Download payload. The GM will be given MemberID 1 and its associated keys. The data shown will be subsequent to the Generic Payload Header. | GTPK | MemberID 1 | KeyID 2 | KeyID 4 | KeyID 8 Number of Items - 0x0002 Item #1: Key Download Data Item Type - 0x00 (GTPK) Key Download Data Item Length - 0xLLLL Key Type - 0x03 (3DES`CBC64`192) Key ID - KEY1 Key Handle - 0xHHHHHHH0 Key Creation Date - YYYYMMDDHHMMSSZ Key Expiration Date - YYYYMMDDHHMMSSZ Key Data - variable, based on key definition Item #2: Key Download Data Item Type - 0x01 (Rekey - LKH) Key Download Data Item Length - 0xLLLL Rekey Version Number - 0x01 Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 104] INTERNET-DRAFT GSAKMP June 2004 Member ID - 0x00000001 Number of KEK Keys - 0x0003 KEK #1: Key Type - 0x03 (3DES`CBC64`192) Key ID - 0x00000002 Key Handle - 0xHHHHHHH2 Key Creation Date - YYYYMMDDHHMMSSZ Key Expiration Date - YYYYMMDDHHMMSSZ Key Data - variable, based on key definition KEK #2: Key Type - 0x03 (3DES`CBC64`192) Key ID - 0x00000004 Key Handle - 0xHHHHHHH4 Key Creation Date - YYYYMMDDHHMMSSZ Key Expiration Date - YYYYMMDDHHMMSSZ Key Data - variable, based on key definition KEK #3: Key Type - 0x03 (3DES`CBC64`192) Key ID - 0x00000008 Key Handle - 0xHHHHHHH8 Key Creation Date - YYYYMMDDHHMMSSZ Key Expiration Date - YYYYMMDDHHMMSSZ Key Data - variable, based on key definition A.3.2 LKH Rekey Event Example This section will give an example of the data for the Rekey Event payload. The GM with MemberID 6 will be keyed out of the group. The data shown will be subsequent to the Generic Payload Header. | Rekey Event Type | GroupID | Date/Time | Rekey Type | Algorithm Ver | # of Packets| { (GTPK)2, (GTPK, 3', 6')12, (GTPK, 3')7 } This data shows that three packets are being transmitted. Read each packet as: a) GTPK wrapped in LKH KeyID 2 b) GTPK, LKH KeyIDs 3' & 6', all wrapped in LKH KeyID 12 c) GTPK and LKH KeyID 3', all wrapped in LKH KeyID 7 NOTE: Although in this example multiple keys are encrypted under one key, alternative pairings are legal (e.g., (GTPK)2, (GTPK)3', (3')6', (3')7', (6')12). We will show format for all header data, and packet (b). Rekey Event Type - 0x01 (GSAKMP`LKH) GroupID - 0xAABBCCDD 0x12345678 Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 105] INTERNET-DRAFT GSAKMP June 2004 Time/Date Stamp - YYYYMMDDHHMMSSZ Rekey Event Type - 0x01 (GSAKMP`LKH) Algorithm Vers - 0x01 # of RkyEvt Pkts - 0x0003 For Packet (b): Packet Length - 0xLLLL Wrapping KeyID - 0x000C Wrapping Key Handle - 0xHHHHHHHD # of Key Packages - 0x0003 Key Package 1: Key Pkg Type - 0x00 (GTPK) Pack Length - 0xLLLL Key Type - 0x03 (3DES`CBC64`192) Key ID - KEY1 Key Handle - 0xHHHHHHH0 Key Creation Date - YYYYMMDDHHMMSSZ Key Expiration Date - YYYYMMDDHHMMSSZ Key Data - variable, based on key definition Key Package 2: Key Pkg Type - 0x01 (Rekey - LKH) Pack Length - 0xLLLL Key Type - 0x03 (3DES`CBC64`192) Key ID - 0x00000003 Key Handle - 0xHHHHHHH3 Key Creation Date - YYYYMMDDHHMMSSZ Key Expiration Date - YYYYMMDDHHMMSSZ Key Data - variable, based on key definition Key Package 3: Key Pkg Type - 0x01 (Rekey - LKH) Pack Length - 0xLLLL Key Type - 0x03 (3DES`CBC64`192) Key ID - 0x00000006 Key Handle - 0xHHHHHHH6 Key Creation Date - YYYYMMDDHHMMSSZ Key Expiration Date - YYYYMMDDHHMMSSZ Key Data - variable, based on key definition B APPENDIX B -- Change History (To Be Removed from RFC) B.1 Changes from GSAKMP-00 to GSAKMP-01 February 2003 This specification was based on two earlier versions of GSAKMP drafts, referred to to GSAKMP and GSAKMP-Light. These two specifications were merged to incorporate all information necessary to allow the original GSAKMP-Light specification to stand on its own. The original GSAKMP protocol no longer exists as a standard, it has been subsumed by GSAKMP-Light. GSAKMP-Light is now called GSAKMP. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 106] INTERNET-DRAFT GSAKMP June 2004 Major modifications to the specification are Removed Payloads: Authorization, Certificate Request, Vendor ID, and Hash. Removed Messages: Group Removal/Destruction. Signature Processing: The signature processing has been modified. B.2 Changes from GSAKMP-01 to GSAKMP-02 June 2003 1. The specification was modified to confirm that key words are used as defined by RFC2119. 2. The Protocol Considerations section for IANA port number was added. 3. The Cookie section for mitigation of DoS attacks was added. 4. The Protocol State Diagram was added. B.3 Changes from GSAKMP-02 to GSAKMP-03 August 2003 1. Clarified Nonce value in Request to Join With Cookie msg. 2. Added Signature ID Type to Security Suite 1 definition. 3. Clarified format of Identification information used in Signature and Identification Payloads. 4. Split Signature Type field into it's two appropriate fields. This was not a change in the payload, just cleaning up the definition. B.4 Changes from GSAKMP-03 to GSAKMP-04 October 2003 1. Terminology Section (a) Rekey definition was made more verbose. 2. Security Considerations Section Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 107] INTERNET-DRAFT GSAKMP June 2004 (a) ISAKMP Section i. Corrected GSAKMPs relationship definition to ISAKMP. (b) Rekey Availability Section i. Added this new section. 3. Architecture Section (a) This section in its entirety was added for this revision of the specification. 4. Group Life Cycle Section (a) Group Establishment Section i. Introduced Verbose and Terse concept. (b) Standard Group Establishment Section i. Added messages Request to Join Error and Lack_of_Ack to ladder diagram to show verbose error messaging. ii. Modified definition of Ack message on ladder diagram to be consistent with new naming convention. iii. Reworked all section wording to convey the new message transmissions. (c) Request to Join Section i. Completely reworked to better define the process of building and processing the RTJ message by the GM and GC/KS. (d) Key Download Section Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 108] INTERNET-DRAFT GSAKMP June 2004 i. Completely reworked to better define the process of building and processing the KeyDL message by the GC/KS and GM. (e) Request to Join Error Section i. New section added for this new verbose message. (f) Key Download = Ack/Failure Section i. Completely reworked to better define the process of building and processing the KeyDL-A/F message by the GM and GC/KS. (g) Lack_of_Ack Section i. New section added for this new verbose message. (h) Added the following new Sub-sections to this section. i. Leaving Group ii. Eviction iii. Voluntary Departure without Notice iv. De-registration v. Request to Depart Message vi. Departure Response Message vii. Departure Ack Message 5. GSAKMP Payload Structure Section (a) Added note that all all integer fields larger than one octet MUST be converted to Network Byte Order prior to transmission. (b) GSAKMP Header Section i. Existing section became the Structure subsection. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 109] INTERNET-DRAFT GSAKMP June 2004 ii. Added the Processing subsection. iii. GroupID Type was modified to GroupID Length with the appropriate definitions. iv. New Exchange Types added for verbose mode. v. Sequence ID definition was modified for: A. New initial value. B. Rollover handling responsibility. (c) GSAKMP Payload Header Section i. Existing section became the Structure subsection. ii. Added the Processing subsection. (d) Policy Token Payload Section i. The header paragraph was corrected to not levy any requirements from GSAKMP on the Policy Token. ii. The PT Type field was expanded from one (1) to two (2) octets. iii. The values of the PT Types were modified and defined to reflect the true purpose. (e) Rekey Event Payload Section i. Renamed Type field to be unique within specification. ii. The values of the Rekey Type field were modified and defined to reflect their true purpose. (f) Signature Payload Section i. Existing section became the Structure subsection. ii. Added the Processing subsection. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 110] INTERNET-DRAFT GSAKMP June 2004 iii. Removed the one (1) octet field Signature ID Role from the payload, it contained irrelevant data. iv. Expanded the definition of Singer ID Data to inform the user how to interpret this field. (g) Notification Payload Section i. Removed the one (1) octet Status Type field from the payload. It was irrelevant information. Additionally, all references to Status Type were removed from the payload definition. ii. Added new Notification Payload Type "Mechanism Choices". iii. Added section "Notification Data - Mechanism Choices Payload Type" to define the format of a Notification Payload of type Mechanism Choices. (h) Key Creation Payload Section i. Existing section became the Structure subsection. ii. Added the Processing subsection. iii. Renamed Type field to be unique within specification. (i) Nonce Payload Section i. Existing section became the Structure subsection. ii. Added the Processing subsection. B.5 Changes from GSAKMP-04 to GSAKMP-05 February 2004 B.5.1 Major Modification/Reorganization of Specification B.5.1.1 Key Terms and Payloads Modified In the previous version of the specification, there was a lot of confusion with respect to the terminology used for anything to do with keys and rekey. Therefore, all the terminology has been modified to make this more Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 111] INTERNET-DRAFT GSAKMP June 2004 comprehensible. Additionally, all key information that was found in the appendices was generalized and incorporated into the main sections of the specification. Following is a list of old terms mapped to new terms: - LKH ID - Key ID, this field is now also in a GTPK, was not there previously. - Key Pack - Key Datum - Key Pack Data - Key Package - Rekey Event Packet Data - Rekey Event Data To accommodate all these changes, the Key Download Payload, Rekey Event Payload, and LKH Appendix sections were completely reworked to reflect these changes. Other major changes in these sections with respect to bits on the wire: - KeyID - All keys now have a 4 octet ID field. This was not so before. Also, this field is now 4 octets long, it was previously 2 octets. - Date Fields - These fields are now 15 bytes long and ascii format. THEREFORE, look closely at the Key Download Payload and Rekey Event Payload as the formats for these payloads have both changed dramatically the bits on the wire. B.5.2 Modification By Section 1. Protocol Considerations Section - Moved to new section entitled IANA Considerations Section. 2. Terminology Section (a) Modified the following terms: GTEK became GTPK (b) Added the following terms: Key Datum, KEK, Key Handle, Key ID, Key Package, Rekey Array, Rekey Key, Wrapping KeyID, Wrapping Key Handle Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 112] INTERNET-DRAFT GSAKMP June 2004 3. Security Considerations Section (a) Security Assumptions Section i. Added an assumption with respect to system clock. (b) Rekey Availability Section i. Stated retransmission of rekey messages required for implementations. 4. Group Establishment Section (a) Added phrase concerning error message always indicates first error found. (b) Key Download Section i. Fixed second paragraph. (c) Rekey Events Section - Made as subsection under new section Group Management. 5. GSAKMP Payload Structure Section (a) Added verbiage that no padding in any payloads. (b) All processing sections updated to indicate error processing. 6. Split following sections into Structure and Processing subsections: (a) Policy Token Payload (b) Key Download Payload (c) Rekey Event Payload (d) Identification Payload Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 113] INTERNET-DRAFT GSAKMP June 2004 (e) Certificate Payload 7. GSAKMP Header Section (a) Group ID Length and Sequence ID - Fixed definitions. (b) Updated values in tables. (c) Reworded processing section to be more precise. 8. Policy Token Payload Section (a) PT Type field in diagram was updated to reflect that this is really a 2 octet field and not a 1 octet field. (b) Updated tables. 9. Key Download and Rekey Event Payload Sections (a) Completely reworked sections. Refer to Section B.5.1.1 above for the modifications to these sections. (b) Basically, reread these sections closely as a lot has changed. 10. Identification Payload Section (a) U-NAME Definition was incorporated directly into this section. (b) Updated tables. 11. Certificate Payload Section (a) Added words to structure section about zero or multiple certificate payloads within a GSAKMP message. (b) Updated tables. 12. Signature Payload Section Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 114] INTERNET-DRAFT GSAKMP June 2004 (a) Updated Tables. (b) Signature Type field is now 2 octets long. (c) Signature Payload Span field has been removed, it no longer exists. (d) Signature Timestamp field is now 15 bytes long to conform to the (e) Processing section was updated. new date/time format begin used throughout the spec. 13. Notification Payload Section (a) Updated Tables. (b) Removed Length field from Notification Data Mechanism Choices Payload Types format. (c) Made field Mechanism Choice Data field to be a static length of 2 octets. 14. Key Creation Payload Section (a) Updated Tables. (b) Key Creation Type field is now 2 octets long. (c) Updated Processing subsection. 15. Nonce Payload Section (a) Updated Tables. (b) Updated Processing subsection. 16. Added new section IANA Considerations. B.6 Changes from GSAKMP-05 to GSAKMP-06 May 2004 NOTE: Minor editorial modifications are not listed here. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 115] INTERNET-DRAFT GSAKMP June 2004 1. Security Considerations Section (a) Security Assumptions Section i. Added considerations as pointed out by gmg. (b) Protocol Considerations Section i. Fixed wording between subsections to remove contradiction of how and when to use Diffie-Hellman. 2. Architecture Section (a) S-GC/KS Operations section replaced with Autonomous Distributed GSAKMP Operations Section (b) GSAKMP Interactions with NAT Traversal section removed. 3. Group Life Cycle Section (a) To all subsection, modified the message dissection and discussion for Nonces. Nonces are now an optional payload with a caveat. Systems that have synchronized time do not use Nonce payloads. Systems that do not have synchronized time MUST use Nonce payloads. (b) Added information concerning Vendor ID payload processing. (c) Added optional VendorID payload to all messages. (d) Group Establishment Section i. Added paragraph that Verbose mode is controlled by policy and how to handle it. ii. Standard Group Establishment Section A. Defined all possible error conditions. B. Verbosely identified that message identification is via the exchange type within the header. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 116] INTERNET-DRAFT GSAKMP June 2004 C. Introduced concept of synchronized time. iii. RTJ Section A. Added the NotifPL of type IPValue and explanation to this message type and discussion. iv. Key Download - Ack/Failure Section A. Added that upon successful registration all state information should be removed. v. Cookie Section A. Added information for calculation of cookie value in a NATted environment. (e) Group Maintenance Section i. Group Management Section A. Added sections Policy Update and Group Destruction. ii. Leaving a Group Section A. De-Registration Section - Added the GM SHOULD support and GC/KS MUST support. B. De-Registration Section - Fixed with respect to Terse/Verbose mode processing. 4. GSAKMP Payload Structure Section (a) Added pointed to VendorID section on how to process messages that contain this payload. (b) GSAKMP Header Section Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 117] INTERNET-DRAFT GSAKMP June 2004 i. GSAKMP Header Structure Section A. Updated GroupID Types table and added subsections to define the format for each type. B. Added VendorID value to Payload Types table. ii. GSAKMP Header Processing Section A. Updated processing rule for GroupID and Version. B. Added discussion for interoperability with future versions. (c) Key Download Payload Section i. Key Datum Structure Section A. Fixed Key Type to be a 2 byte field as indicated by the table which shows its values. B. Updated structure definition for Key ID, Key Handle, Key Creation Date, and Key Expiration Date. (d) Rekey Event Payload Section i. Rekey Event Payload Structure Section A. Defined how to break up the data across multiple payloads. B. Rekey Event Header Structure Section - Update structure definition of Time/Date Stamp. C. Rekey Event Data Structure Section - Clarified information of which/how many Rekey Event Datas each user is interested in. i. Rekey Event Payload Processing Section A. Updated Date/Time Stamp processing rules. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 118] INTERNET-DRAFT GSAKMP June 2004 (e) Identification Payload Section i. Added ID Classification octet to payload, associated table, and associated processing information. ii. Updated Identification Types table. iii. ID-U-NAME Structure Section A. Updated DN Data definition for UTF-8. iv. ID-U-NAME Processing Section A. Updated Serial Number and DN Data processing rules. B. Added a new rule for CA being a trust anchor. (f) Certificate Payload Section i. Certificate Payload Structure Section A. Updated Certificate Type values. (g) Signature Payload Section i. Signature Payload Structure Section A. Updated Signature Timestamp definition for UTF-8 and how to deal with time differential from local. B. Updated Signature Type table values. C. Signature ID type is now aligned with IdentificationPL ID Type. ii. Signature Payload Processing Section A. Updated processing instructions for Signature Timestamp, Signature ID Data, and Signature Data. Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 119] INTERNET-DRAFT GSAKMP June 2004 (h) Notification Payload Section i. Notification Payload Structure Section A. Updated Notification Types table. (i) Vendor ID Payload Section i. This whole section was added. (j) Key Creation Payload Section i. Key Creation Payload Structure Section A. Updated Key Creation Type table. ii. Key Creation Payload Processing Section A. Updated Key Creation Data processing instructions. 5. GSAKMP State Diagram Section (a) Updated State Transition Events table. 6. IANA Considerations Section (a) Updated all types sections for new values. Authors Addresses Hugh Harney (point-of-contact) SPARTA, Inc. 7075 Samuel Morse Drive Columbia, MD 21046 (410) 872-1515 ext 203 FAX (410) 872-8079 hh@sparta.com Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 120] INTERNET-DRAFT GSAKMP June 2004 Uri Meth SPARTA, Inc. 7075 Samuel Morse Drive Columbia, MD 21046 (410) 872-1515 ext 233 FAX (410) 872-8079 umeth@sparta.com Andrea Colegrove SPARTA, Inc. 7075 Samuel Morse Drive Columbia, MD 21046 (410) 872-1515 ext 232 FAX (410) 872-8079 acc@sparta.com George Gross IdentAware Security 82 Old Mountain Road Lebanon, NJ 08833 (908) 268 - 1629 gmgross@identaware.com Full Copyright Statement Copyright (C) The Internet Society (2004). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Document expiration: December 1, 2004 Harney, Meth, Colegrove, Gross draft-ietf-msec-gsakmp-sec-06.txt [Page 121]