| Network Working Group | Z. Cao |
| Internet-Draft | H. Deng |
| Intended status: Standards Track | China Mobile |
| Expires: August 09, 2012 | Q. Wu |
| Huawei | |
| G. Zorn | |
| Network Zen | |
| February 08, 2012 |
EAP Re-authentication Protocol Extensions for Authenticated Anticipatory Keying (ERP/AAK)
draft-ietf-hokey-erp-aak-08
The Extensible Authentication Protocol (EAP) is a generic framework supporting multiple types of authentication methods.
The EAP Re-authentication Protocol (ERP) specifies extensions to EAP and the EAP keying hierarchy to support an EAP method-independent protocol for efficient re-authentication between the peer and an EAP re-authentication server through any authenticator.
Authenticated Anticipatory Keying (AAK) is a method by which cryptographic keying material may be established upon one or more candidate attachment points (CAPs) prior to handover. AAK uses the AAA infrastructure for key transport.
This document specifies the extensions necessary to enable AAK support in ERP.
This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/.
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."
This Internet-Draft will expire on August 09, 2012.
Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved.
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The Extensible Authentication Protocol (EAP) [RFC3748] is a generic framework supporting multiple types of authentication methods. In systems where EAP is used for authentication, it is desirable to not repeat the entire EAP exchange with another authenticator. The EAP Re-authentication Protocol (ERP) [RFC5296] specifies extensions to EAP and the EAP keying hierarchy to support an EAP method-independent protocol for efficient re-authentication between the peer and an EAP re-authentication server through any authenticator. The re-authentication server may be in the home network or in the local network to which the peer is connecting.
Authenticated Anticipatory Keying (AAK) [RFC5836] is a method by which cryptographic keying materials may be established prior to handover upon one or more candidate attachment points (CAPs). AAK utilizes the AAA infrastructure for key transport.
This document specifies the extensions necessary to enable AAK support in ERP.
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].
The following acronyms are used in this document; see the references for more details.
+------+ +-----+ +-----+ +-----------+ | Peer | | SAP | | CAP | | EA Server | +--+---+ +--+--+ +--+--+ +-----+-----+ | | | | a. | [EAP-Initiate/ | | | | Re-auth-start | | | | (E-flag) | | | |<---------------| | | | | | | b. | EAP-Initiate/ | | | | Re-auth | | | | (E-flag) | | | |--------------->| | | c. | | AAA(EAP-Initiate/Re-auth(E-flag))| | |--------------------------------->| | | | +---------+---------+ | | | | CA authorized & | d. | | | | and EA Keying | | | | | Distribution | | | | +---------+---------+ | | | | | | | | f. | | AAA (EAP-Finish/Re-auth(E-flag)) | | |<---------------------------------| g. | EAP-Finish/ | | | | Re-auth(E-flag)| | | |<---------------| | | | | | |
+-----------+ +---------+
| | | |
| EA Server | | CAP |
| | | |
+-----|-----+ +----|----+
| |
| |
| AAA Request(pMSK) |
e.1|------------------------->|
| |
| |
| |
| AAA Response (Success) |
e.2|<-------------------------|
| |
| |
| |
ERP/AAK is intended to allow the establishment of cryptographic keying materials on a single Candidate Attachment Points prior to the arrival of the MH at the Candidate Access Network (CAN) upon request by the peer.
In this document, ERP/AAK support for the peer is assumed. Also it is assumed that the peer has previously completed full EAP authentication and the peer or SAP knows the identities of neighboring attachment points. Note that the behavior of the peer that does not support the ERP-AAK scheme defined in this specification is out of the scope of this document.Figure 1 shows the general protocol exchange by which the keying material is established on the CAP.
In the latter case, the SAP MAY send the identity of a candidate attachment point to the peer in the EAP-Initiate/Re-auth-Start message (see a. in the figure 1). If the EAP-Initiate/ Re-auth-Start packet is not supported by the peer, it MUST be silently discarded.
If the peer initiate ERP/AAK, the peer MAY send an early-authentication request message (EAP-Initiate/ Re-auth with the 'E' flag set) containing the keyName-NAI, the CAP- Identifier, rIK and sequence number (see b. in the figure 1). The realm in the keyName-NAI field is used to locate the peer's ERP/AAK server. The CAP- Identifier is used to identify the CAP. The rIK is defined in RFC5296 and used to protect the integrity of the message. The sequence number is used for replay protection.
The SAP SHOULD verify the integrity of the message at step b. If This verifications fail, the SAP MUST send an EAP- Finish/Re-auth message with the Result flag set to '1' (Failure).In success case, the SAP SHOULD encapsulate the early-authentication message into a AAA message and send it to the peer's ERP/AAK server in the realm indicated in the keyName-NAI field (see c. in the figure 1).
Upon receiving the message, the ERP/AAK server MUST first use the keyName indicated in the keyName-NAI to look up the rIK and MUST check the integrity and freshness of the message. Then the ERP/AAK server MUST verify the identity of the peer by checking the username portion of the KeyName-NAI. If any of the checks fail, the server MUST send an early- authentication finish message (EAP-Finish/Re-auth with E-flag set) with the Result flag set to '1'. Next, the server MUST authorize the CAP specified in the CAP-Identifier TLV. In success case, the server MUST derive a pMSK from the pRK for each CAP carried in the the CAP-Identifier field using the sequence number associated with CAP-Identifier as an input to the key derivation. (see d. in the figure 1)
Then The ERP/AAK server MUST transport the pMSK to the authorized CAP via AAA Section 7 as described in figure 2 (see e.1,e.2 in the figure 2). Note that key distribution in the figure 2 is one part of step d. in the figure 1.
Finally, in response to the EAP-Initiate/Re-auth message, the ERP/AAK server SHOULD send the early-authentication finish message (EAP-Finish/ Re-auth with E-flag set) containing the identity of the authorized CAP to the peer via the SAP and associated lifetime of pMSK, OPTIONALLY, if the peer also requests the server for the rRK lifetime, the ERP/AAK server SHOULD send the rRK lifetime in the EAP- Finish/Re-auth message. (see f.,g. in the figure 1).
DSRK EMSK
| |
+---+---+---+---+
|
pRK ...
pRK
|
+--------+--------+
|
pMSK ...
As an extension of ERP, ERP/AAK uses a key hierarchy similar to that of ERP. The ERP/AAK pre-established Root Key (pRK) is derived from either EMSK or DSRK as specified in the section 4.1. In general, the pRK is derived from the EMSK in case of the peer moving in the home AAA realm and derived from the DRSK in case of the peer moving in a visited realm. The DSRK is delivered from the EAP server to the ERP/AAK server as specified in [I-D.ietf-dime-local-keytran]. If the peer has previously been authenticated by means of ERP or ERP/AAK, the DSRK SHOULD be directly re-used. Figure 4,
The rRK is derived as specified in [RFC5295].
pRK = KDF (K, S), where
The pRK Label is an IANA-assigned 8-bit ASCII string:
assigned from the "USRK key labels" name space in accordance with [RFC5295]. The KDF and algorithm agility for the KDF are as defined in [RFC5295].
The pMSK is derived as follows.
pMSK = KDF (K, S), where
The pMSK label is the 8-bit ASCII string:
The length field refers to the length of the pMSK in octets encoded as specified in [RFC5295]. SEQ is sent by either the peer or the server in the ERP/AAK message using SEQ field or Sequence number TLV and encoded as an 8-bit number specified in the section 5.2 and section 5.3.
This section describes the packet and TLV extensions for the ERP/AAK exchange.
Figure 5 shows the changed parameters contained in the EAP-Initiate/Re-auth-Start packet defined in RFC 5296 [RFC5296].
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Code | Identifier | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type |E| Reserved | 1 or more TVs or TLVs ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Flags
‘E’ – The E flag is used to indicate early-authentication. This field MUST be set to '1' if early authentication is in use and MUST be set to '0' otherwise.
The rest of the 7 bits (Reserved ) MUST be set to 0 and ignored on reception.
TVs and TLVs
CAP-Identifier: Carried in a TLV payload. The format is identical to that of a DiameterIdentity [RFC3588]. It is used by the SAP to advertise the identity of the CAP to the peer. Exactly one CAP-Identifier TLV MAY be included in the EAP-Initiate/Re-auth-Start packet if the SAP has performed CAP discovery.
If the EAP-Initiate/Re-auth-Start packet is not supported by the peer, it SHOULD be discarded silently.
Figure 6 illustrates the changed parameters contained in the EAP-Initiate/Re-auth packet defined in RFC 5296 [RFC5296].
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Code | Identifier | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type |R|x|L|E|Resved | SEQ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1 or more TVs or TLVs ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Cryptosuite | Authentication Tag ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Flags
'x' – The x flag is reserved. It MUST be set to 0.
'E’ – The E flag is used to indicate early-authentication.
The rest of the 4 bits (Resved) MUST be set to 0 and ignored on reception.
SEQ
As defined in Section 5.3.2 of [RFC5296],this field is 16-bit sequence number and used for replay protection.
TVs and TLVs
keyName-NAI: As defined in RFC 5296 [RFC5296], this is carried in a TLV payload. The Type is 1. The NAI is variable in length, not exceeding 253 octets. The username part of the NAI is the EMSKname used to identify the peer. The realm part of the NAI is the peer's home domain name if the peer communicates with the home EA server or the domain to which the peer is currently attached (i.e., local domain name) if the peer communicates with the local EA server. The SAP knows whether the KeyName-NAI carries the local domain name by comparing the domain name carried in KeyName-NAI with local domain name which is associated with the SAP and SAP has already known. Exactly one keyName-NAI attribute SHALL be present in an EAP-Initiate/Re-auth packet and The realm part of it SHOULD follows the use of internationalized domain names defined in the RFC5890 [RFC5890].
CAP-Identifier: Carried in a TLV payload.The Type is TBD (less than 128). This field is used to indicate the FQDN of a CAP. The value field MUST be encoded as specified in Section 8 of RFC 3315 [RFC3315]. There at least one instance of the CAP-Identifier TLV MUST be present in the ERP/AAK-Key TLV.
Sequence number: The Type is TBD (less than 128). The value field is a 16-bit field and used in the derivation of the pMSK for a CAP. If multiple CAP-Identifiers are carried,each CAP-Identifier in the packet MUST be associated with a unique sequence number and followed by that sequence number.
Cryptosuite
This field indicates the integrity algorithm used for ERP/AAK. Key lengths and output lengths are either indicated or obvious from the cryptosuite name, e.g., HMAC-SHA256-128 denotes HMAC computed using the SHA-256 function [RFC4868] and with the 256 bit key length and output truncated to 128 bits [RFC2104]. We specify some cryptosuites below:
HMAC-SHA256-128 is REQUIRED to implement and SHOULD be enabled in the default configuration.
Authentication Tag
This field contains the integrity checksum over the ERP/AAK packet, excluding the authentication tag field itself. The value field is calculated using the integrity algorithm indicated in the Cryptosuite field and rIK specified in [RFC5296] as the secret key. The length of the field is indicated by the Cryptosuite.
The peer uses authentication tag to determine the validity of the EAP-Finish/Re-auth message originates at a server.
If the message doesn't pass verification or authentication tag is not included in the message, the message SHOULD be discarded silently.
If the EAP-Initiate/Re-auth packet is not supported by the SAP, it SHOULD be discarded silently.
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Code | Identifier | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type |R|x|L|E|Resved | SEQ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 1 or more TVs or TLVs ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Cryptosuite | Authentication Tag ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7 shows the changed parameters contained in the EAP-Finish/Re-auth packet defined in [RFC5296].
Flags
'x' – The x flag is reserved. It MUST be set to 0.
‘E’ – The E flag is used to indicate early-authentication.
The rest of the 4 bits (Resved) MUST be set to 0 and ignored on reception.
SEQ
As defined in Section 5.3.2 of [RFC5296], this field is 16-bit sequence number and used for replay protection.
TVs and TLVs
keyName-NAI: As defined in RFC 5296 [RFC5296], this is carried in a TLV payload. The Type is 1. The NAI is variable in length, not exceeding 253 octets. Exactly one keyName-NAI attribute SHALL be present in an EAP-Finish/Re-auth packet.
ERP/AAK-Key ::=
{ sub-TLV: CAP-Identifier }
{ sub-TLV: pMSK-lifetime }
{ sub-TLV: pRK-lifetime }
{ sub-TLV: Cryptosuites }
ERP/AAK-Key: Carried in a TLV payload for the key container. The type is TBD. Exactly one ERP/AAK-key SHALL only be present in an EAP-Finish/Re-auth packet.
Cryptosuite
This field indicates the integrity algorithm and PRF used for ERP/ AAK. HMAC-SHA256-128 is mandatory to implement and should be enabled in the default configuration. Key lengths and output lengths are either indicated or obvious from the cryptosuite name.
Authentication Tag
This field contains the integrity checksum over the ERP/AAK packet, excluding the authentication tag field itself. The value field is calculated using the integrity algorithm indicated in the Cryptosuite field and rIK [RFC5296] as the integrity key. The length of the field is indicated by the corresponding Cryptosuite.
The peer uses authentication tag to determine the validity of the EAP-Finish/Re-auth message originates at a server.
If the message doesn't pass verification or authentication tag is not included in the message, the message SHOULD be discarded silently.
If the EAP-Initiate/Re-auth packet is not supported by the SAP, it is discarded silently.
With the exception of the rRK-Lifetime and rMSK-Lifetime TV payloads, the attributes specified in Section 5.3.4 of [RFC5296] also apply to this document. In this document, new attributes which may be present in the EAP-Initiate and EAP-Finish messages are defined as below:
Similar to ERP, some lower layer specifications may need to be revised to support ERP/AAK; refer to of Section 6 [RFC5296] for additional guidance.
AAA transport of ERP/AAK messages is the same as AAA transport of the ERP message [RFC5296]. In addition, the document requires AAA transport of the ERP/AAK keying materials delivered by the ERP/AAK server to the CAP. Hence, a new AAA message for ERP/AAK application should be specified to transport the keying materials.
This section provides an analysis of the protocol in accordance with the AAA key management requirements specified in RFC 4962 [RFC4962].
IANA is requested to assign four TLV type values from the registry of EAP Initiate and Finish Attributes maintained at http://www.iana.org/assignments/eap-numbers/eap-numbers.xml.
with the following assigned number:
This document reuses the crytosuites we have already created for 'Re-authentication Cryptosuites' in [RFC5296].
Further, this document instructs IANA to add a new label in the User Specific Root Keys (USRK) Key Labels of the Extended Master Session Key (EMSK) Parameters registry, as follows:
In writing this document, Yungui Wang contributed to early versions of this document and we have received reviews from many experts in the IETF, including Tom Taylor, Tena Zou, Tim Polk, Tan Zhang and Semyon Mizikovsky, Stephen Farrell,Sujing Zhou. We apologize if we miss some of those who have helped us.
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. |
| [RFC5296] | Narayanan, V. and L. Dondeti, "EAP Extensions for EAP Re-authentication Protocol (ERP)", RFC 5296, August 2008. |
| [RFC3315] | Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C. and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003. |
| [RFC5295] | Salowey, J., Dondeti, L., Narayanan, V. and M. Nakhjiri, "Specification for the Derivation of Root Keys from an Extended Master Session Key (EMSK)", August 2008. |