INTERNET DRAFT T. Polk Intended Status: Informational NIST R. Housley Vigil Security Expires: 19 April 2010 19 October 2009 Routing Authentication Using A Database of Long-Lived Cryptographic Keys draft-polk-saag-rtg-auth-keytable-00.txt Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. 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/1id-abstracts.html The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html Abstract This document describes the application of a database of long-lived cryptographic keys to establish session-specific cryptographic keys to support authentication services in routing protocols. Keys may be established between two peers for pair-wise communications, or between groups of peers for multicast traffic. Polk & Housley Expires 19 April 2010 [Page 1] INTERNET DRAFT 19 October 2009 Table of Contents 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 2 2 Architecture and Design . . . . . . . . . . . . . . . . . . . . . 2 3 Pair-wise Application . . . . . . . . . . . . . . . . . . . . . . 3 4 Identifier Mapping . . . . . . . . . . . . . . . . . . . . . . . 5 4.1 Selected Range Reservation . . . . . . . . . . . . . . . . . 5 4.2 Protocol Specific Mapping Tables . . . . . . . . . . . . . . 6 5 Worked Example: TCP-AO . . . . . . . . . . . . . . . . . . . . . 6 6 Security Considerations . . . . . . . . . . . . . . . . . . . . 7 6 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7 7 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 7.1 Normative References . . . . . . . . . . . . . . . . . . . 7 7.2 Informative References . . . . . . . . . . . . . . . . . . 7 Author's Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7 Full Copyright Statement . . . . . . . . . . . . . . . . . . . . . 8 1 Introduction This document describes the application of a database of long-lived cryptographic keys, as defined in [KEYTAB], to establish session- specific cryptographic keys to provide authentication services in routing protocols. Keys may be established between two peers for pair-wise communications, or between groups of peers for multicast traffic. 1.1 Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. 2 Architecture and Design Polk & Housley Expires 19 April 2010 [Page 2] INTERNET DRAFT 19 October 2009 Figure 1 illustrates the establishment and use of cryptographic keys for authentication in routing protocols. Long-lived cryptographic keys are inserted in a database manually. In the future, we anticipate an automated key management protocol to insert these keys in the database. In this future environment, we do not anticipate an environment where the automated key management protocol will be used to create short-lived cryptographic session keys. The structure of the database of long-lived cryptographic keys is described in [KEYTAB]. The cryptographic keying material for individual sessions is derived from the keying material stored in the database of long-lived cryptographic keys. A key derivation function (KDF) and its inputs are named in the database of long-lived cryptographic keys; session specific values based on the routing protocol are input the the KDF. Protocol specific key identifiers may be assigned to the cryptographic keying material for individual sessions if needed. +--------------+ +----------------+ | | | | | Manual Key | | Automated Key | | Installation | | Mgmt. Protocol | | | | | +------+-------+ +--+----------+--+ | | | | | | V V |<== Not expected for security +------------------------+ | of routing protocols, but | | | often used in other | Long-lived Crypto Keys | | protocol environments | | | like IPsec and TLS. +------------+-----------+ | | | | | V V +---------------------------------+ | | | Short-lived Crypto Session Keys | | | +---------------------------------+ Figure 1. Cryptographic key establishment and use. 3 Pair-wise Application Figure 2 illustrates how the long-lived cryptographic keys are accessed and employed when an entity wishes to establish a protected session with a peer. As one step in the initiation process, the Polk & Housley Expires 19 April 2010 [Page 3] INTERNET DRAFT 19 October 2009 intitator requests the set of long term keys associated with the peer for the particular protocol. If the set contains more than one key, the initiator selects one long-term key based on the local policy. The long-term key is provided as an input, along with session- specific information (e.g., ports or initial counters), to a key derivation function. The result is session-specific key material which is used to generate cryptographic authentication. Where the initiator is establishing a multicast session, the Peer in the key request identifies the set of systems that will receive this information. +-------------------------+ | | | Long-Lived | | Crypto Keys | | | +-+---------------------+-+ ^ | | | | V +-------+-------+ +-------+-------+ | | | | | Lookup Keys | | Select Key | | By Peer | | By Policy | | and Protocol | | | | | +-------+-------+ +-------+-------+ | ^ | | V | +-------+-------+ | | | | | Session Key | | | Derivation | | | | | +-------+-------+ | | | | +-------+-------+ V | | +-------+-------+ | Initiate | | | | Session | |Authentication | | with Peer | | Mechanism | | | | | +---------------+ +---------------+ Figure 3 illustrates how an entity that receives a session generates Polk & Housley Expires 19 April 2010 [Page 4] INTERNET DRAFT 19 October 2009 the necessary long-lived cryptographic keys to verify data when a protected session is requested. As step one in the initiation process, the receiver extracts the keyID for the long-term keyID from the received data. The receiver then requests the specified long- term key from the table. The long-term key is provided as an input, along with session-specific information (e.g., ports or initial counters), to a key derivation function. The result is session- specific key material which is used to verify the cryptographic authentication information. +-------------------------+ | | | Long-Lived | | Crypto Keys | | | +-+---------------------+-+ ^ | | | | V +-------+-------+ +-------+-------+ | | | | | Lookup Key | | Session Key | | By KeyID | | Derivation | | | | | +-------+-------+ +-------+-------+ ^ | | | | V +-------+-------+ +-------+-------+ | | | | | Receive Data | |Authentication | | From Peer | | Mechanism | | | | | +---------------+ +---------------+ 4 Identifier Mapping [KEYTAB] specifies a 16-bit identifier, but protocols already exist with key identifiers of various sizes. Where the identifiers are of different sizes, an extra mapping step may be required. Note that mapping mechanisms are local - that is, different mapping mechanisms could be employed on different peers. 4.1 Selected Range Reservation Where a protocol sues an index of less than 16 bits, a selected range Polk & Housley Expires 19 April 2010 [Page 5] INTERNET DRAFT 19 October 2009 of the local index space can be reserved for a particular protocol. For example, consider two protocols P1 and P2 that each use 8 bit key identifiers. Sharing the space {0x0000 through 0x00ff} would limit the pair pair of protocols to 256 keys in total. By reserving the ranges {0xff00 through 0xffff} and {0xfe00 through 0xfeff} for P1 and P2 respectively permits each protocol to use the full 256 key identifiers and establishes an unambiguous mapping for the protocol key identifiers and local table identifiers. When an initiator selects a key from the set in the table, the given key identifier needs to be masked or shifted to the on-the-wire range. Before requesting a specific key, the receiver would use a shim layer would need to map the on-the-wire identifier into the reserved range. 4.2 Protocol Specific Mapping Tables Each protocol can also maintain a simple mapping table with two fields: the l6 bit index and the protocol specific value KEYTAB index (16 bits) | Protocol specific index (8 bits) In this case, the host system would maintain separate mapping tables for protocols P1 and P2. 5 Worked Example: TCP-AO This section describes the way a TCP-AO implementation could use the database. [tcpao] TCP-AO protocol is an example where the key identifier is limited to 8 bits, so an identifier mapping is needed. We will assume two peers Xp and Yp. Xp employs the range reservation method for mapping and has reserved the range {0xff00 ... 0xffff} mapping to {0x00 ... 0xff}. Yp employs a protocol specific mapping table. <> Polk & Housley Expires 19 April 2010 [Page 6] INTERNET DRAFT 19 October 2009 6 Security Considerations 6 IANA Considerations This document requires no actions by IANA. 7 References 7.1 Normative References [RFC2119] S. Bradner, "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [KEYTAB] R. Housley and Polk, T. "Database of Long-Lived Cryptographic Keys", draft-housley-saag-crypto-key-table- 00.txt, September 2009. 7.2 Informative References [tcpao] J. Touch, Mankin A., and Bonica R. "The TCP Authentication Option", draft-ietf-tcpm-tcp-auth-opt-05.txt, July 2009. Author's Addresses Tim Polk National Institute of Standards and Technology 100 Bureau Drive, Mail Stop 8930 Gaithersburg, MD 20899-8930 USA EMail: tim.polk@nist.gov Russell Housley Vigil Security, LLC 918 Spring Knoll Drive Herndon, VA 20170 USA EMail: housley@vigilsec.com Polk & Housley Expires 19 April 2010 [Page 7] INTERNET DRAFT 19 October 2009 Full Copyright Statement Copyright (c) 2009 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. 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