--- 1/draft-ietf-emu-rfc5448bis-01.txt 2018-09-17 06:13:08.065280850 -0700 +++ 2/draft-ietf-emu-rfc5448bis-02.txt 2018-09-17 06:13:08.157283052 -0700 @@ -1,56 +1,55 @@ Network Working Group J. Arkko Internet-Draft V. Lehtovirta Obsoletes: 5448 (if approved) V. Torvinen Updates: 4187 (if approved) Ericsson Intended status: Informational P. Eronen -Expires: January 3, 2019 Nokia - July 2, 2018 +Expires: March 21, 2019 Nokia + September 17, 2018 Improved Extensible Authentication Protocol Method for 3rd Generation Authentication and Key Agreement (EAP-AKA') - draft-ietf-emu-rfc5448bis-01 + draft-ietf-emu-rfc5448bis-02 Abstract This specification defines a new EAP method, EAP-AKA', a small revision of the EAP-AKA method. The change is a new key derivation function that binds the keys derived within the method to the name of the access network. The new key derivation mechanism has been defined in the 3rd Generation Partnership Project (3GPP). This specification allows its use in EAP in an interoperable manner. In addition, EAP-AKA' employs SHA-256 instead of SHA-1. This specification also updates RFC 4187 EAP-AKA to prevent bidding down attacks from EAP-AKA'. - This version of the EAP-AKA' specification updates a reference to - constructing one field in the protocol, so that EAP-AKA' becomes - compatible with 5G deployments as well. + This version of the EAP-AKA' specification provides updates to + specify the protocol behaviour for 5G deployments as well. Status of This Memo 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 January 3, 2019. + This Internet-Draft will expire on March 21, 2019. Copyright Notice Copyright (c) 2018 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 (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents @@ -58,49 +57,57 @@ to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 5 3. EAP-AKA' . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 3.1. AT_KDF_INPUT . . . . . . . . . . . . . . . . . . . . . . 7 - 3.2. AT_KDF . . . . . . . . . . . . . . . . . . . . . . . . . 10 - 3.3. Key Generation . . . . . . . . . . . . . . . . . . . . . 12 - 3.4. Hash Functions . . . . . . . . . . . . . . . . . . . . . 14 - 3.4.1. PRF' . . . . . . . . . . . . . . . . . . . . . . . . 14 - 3.4.2. AT_MAC . . . . . . . . . . . . . . . . . . . . . . . 14 - 3.4.3. AT_CHECKCODE . . . . . . . . . . . . . . . . . . . . 14 - 4. Bidding Down Prevention for EAP-AKA . . . . . . . . . . . . . 15 - 5. Identifier Usage in 5G . . . . . . . . . . . . . . . . . . . 16 - 5.1. Key Derivation . . . . . . . . . . . . . . . . . . . . . 17 - 5.2. EAP Identity Response and EAP-AKA' AT_IDENTITY Attribute 18 - 6. Exported Parameters . . . . . . . . . . . . . . . . . . . . . 19 - 7. Security Considerations . . . . . . . . . . . . . . . . . . . 19 - 7.1. Security Properties of Binding Network Names . . . . . . 22 - 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23 - 8.1. Type Value . . . . . . . . . . . . . . . . . . . . . . . 23 - 8.2. Attribute Type Values . . . . . . . . . . . . . . . . . . 23 - 8.3. Key Derivation Function Namespace . . . . . . . . . . . . 23 - 9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 24 - 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 24 - 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 24 - 11.1. Normative References . . . . . . . . . . . . . . . . . . 24 - 11.2. Informative References . . . . . . . . . . . . . . . . . 26 - Appendix A. Changes from RFC 5448 . . . . . . . . . . . . . . . 27 - Appendix B. Changes from RFC 4187 to RFC 5448 . . . . . . . . . 27 - Appendix C. Changes from Previous Version of This Draft . . . . 28 - Appendix D. Importance of Explicit Negotiation . . . . . . . . . 28 - Appendix E. Test Vectors . . . . . . . . . . . . . . . . . . . . 29 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 33 + 3.1. AT_KDF_INPUT . . . . . . . . . . . . . . . . . . . . . . 8 + 3.2. AT_KDF . . . . . . . . . . . . . . . . . . . . . . . . . 11 + 3.3. Key Generation . . . . . . . . . . . . . . . . . . . . . 13 + 3.4. Hash Functions . . . . . . . . . . . . . . . . . . . . . 15 + 3.4.1. PRF' . . . . . . . . . . . . . . . . . . . . . . . . 15 + 3.4.2. AT_MAC . . . . . . . . . . . . . . . . . . . . . . . 15 + 3.4.3. AT_CHECKCODE . . . . . . . . . . . . . . . . . . . . 15 + 4. Bidding Down Prevention for EAP-AKA . . . . . . . . . . . . . 16 + 5. Peer Identities . . . . . . . . . . . . . . . . . . . . . . . 17 + 5.1. Username Types in EAP-AKA' Identities . . . . . . . . . . 18 + 5.2. Generating Pseudonyms and Fast Re-Authentication + Identities . . . . . . . . . . . . . . . . . . . . . . . 18 + 5.3. Identifier Usage in 5G . . . . . . . . . . . . . . . . . 19 + 5.3.1. Key Derivation . . . . . . . . . . . . . . . . . . . 20 + 5.3.2. EAP Identity Response and EAP-AKA' AT_IDENTITY + Attribute . . . . . . . . . . . . . . . . . . . . . . 21 + 6. Exported Parameters . . . . . . . . . . . . . . . . . . . . . 23 + 7. Security Considerations . . . . . . . . . . . . . . . . . . . 24 + 7.1. Privacy . . . . . . . . . . . . . . . . . . . . . . . . . 26 + 7.2. Discovered Vulnerabilities . . . . . . . . . . . . . . . 28 + 7.3. Pervasive Monitoring . . . . . . . . . . . . . . . . . . 30 + 7.4. Security Properties of Binding Network Names . . . . . . 31 + 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 32 + 8.1. Type Value . . . . . . . . . . . . . . . . . . . . . . . 32 + 8.2. Attribute Type Values . . . . . . . . . . . . . . . . . . 32 + 8.3. Key Derivation Function Namespace . . . . . . . . . . . . 32 + 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 33 + 9.1. Normative References . . . . . . . . . . . . . . . . . . 33 + 9.2. Informative References . . . . . . . . . . . . . . . . . 34 + Appendix A. Changes from RFC 5448 . . . . . . . . . . . . . . . 37 + Appendix B. Changes from RFC 4187 to RFC 5448 . . . . . . . . . 38 + Appendix C. Changes from Previous Version of This Draft . . . . 38 + Appendix D. Importance of Explicit Negotiation . . . . . . . . . 38 + Appendix E. Test Vectors . . . . . . . . . . . . . . . . . . . . 39 + Appendix F. Contributors . . . . . . . . . . . . . . . . . . . . 43 + Appendix G. Acknowledgments . . . . . . . . . . . . . . . . . . 44 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 44 1. Introduction This specification defines a new Extensible Authentication Protocol (EAP)[RFC3748] method, EAP-AKA', a small revision of the EAP-AKA method originally defined in [RFC4187]. What is new in EAP-AKA' is that it has a new key derivation function, specified in [TS-3GPP.33.402]. This function binds the keys derived within the method to the name of the access network. This limits the effects of compromised access network nodes and keys. This specification @@ -128,76 +135,81 @@ function to SHA-256 [FIPS.180-4]. But it is otherwise equivalent to RFC 4187. Given that a different EAP method type value is used for EAP-AKA and EAP-AKA', a mutually supported method may be negotiated using the standard mechanisms in EAP [RFC3748]. Note: Appendix D explains why it is important to be explicit about the change of semantics for the keys, and why other approaches would lead to severe interoperability problems. This version of the EAP-AKA' specification obsoletes RFC 5448. The - changes consist of three things: + changes are as follows: o Update the reference on how the Network Name field is constructed - in the protocol. The update helps ensure that EAP-AKA' becomes - compatible with 5G deployments as well. RFC 5448 referred to the - Release 8 version of [TS-3GPP.24.302] and this update points to - the first 5G version, Release 15. + in the protocol. The update ensures that EAP-AKA' is compatible + with 5G deployments. RFC 5448 referred to the Release 8 version + of [TS-3GPP.24.302] and this update points to the first 5G + version, Release 15. - o Specify how EAP and EAP-AKA' use identifiers in 5G, as additional - identifiers are introduced, and for interoperability, it is - important that implementations use the right ones. + o Specify how EAP and EAP-AKA' use identifiers in 5G. Additional + identifiers are introduced in 5G, and for interoperability, it is + necessary that the right identifiers are used as inputs in the key + generation. In addition, for identity privacy it is important + that when privacy-friendly identifiers in 5G are used, no + trackable, permanent identifiers are passed in EAP-AKA' either. o Specify session identifiers and other exported parameters, as those were not specified in [RFC5448] despite requirements set forward in [RFC5247] to do so. Also, while [RFC5247] specified session identifiers for EAP-AKA, it only did so for the full authentication case, not for the case of fast re-authentication. - Arguably, the updates are small. For the first update, the 3GPP - specification number for the updated calculation has not changed, + o Update the requirements on generating pseudonym usernames and fast + re-authentication identities to ensure identity privacy. + + o Describe what has been learned about any vulnerabilities in AKA or + EAP-AKA'. + + o Describe the privacy and pervasive monitoring considerations + related to EAP-AKA'. + + Some of the updates are small. For instance, for the first update, + the reference update does not change the 3GPP specification number, only the version. But this reference is crucial in correct calculation of the keys resulting from running the EAP-AKA' method, so an update of the RFC with the newest version pointer may be - warranted. As always, feedback is welcome on that point as well as - on any other topic within this document. - - Note: It is an open issue whether this update should refer to only - the 5G version of the definition, or be explicit that any further - update of that specification is something that EAP-AKA' - implementations should take into account. Note that one should - keep in mind that specification being automatically updated is - different from implementations taking notice of new things. - - The second update is needed to ensure that implementations use the - correct identifiers in the context of 5G, as it introduces additional - privacy-protected identifiers, and it is no longer clear which - identifiers are used in EAP-AKA'. + warranted. - The third update is necessary in order to fix a problem in previous - RFCs. + Note: This specification refers only to the 5G specifications. + Any further update that affects, for instance, key generation is + something that EAP-AKA' implementations should take into account. + Upon such updates there will be a need to both update the + specification and the implementations. It is an explicit non-goal of this draft to include any other technical modifications, addition of new features or other changes. The EAP-AKA' base protocol is stable and needs to stay that way. If there are any extensions or variants, those need to be proposed as standalone extensions or even as different authentication methods. The rest of this specification is structured as follows. Section 3 defines the EAP-AKA' method. Section 4 adds support to EAP-AKA to - prevent bidding down attacks from EAP-AKA'. Section 7 explains the - security differences between EAP-AKA and EAP-AKA'. Section 8 - describes the IANA considerations and Appendix A and Appendix B - explains what updates to RFC 5448 AKA' and RFC 4187 EAP-AKA have been - made in this specification. Appendix D explains some of the design - rationale for creating EAP-AKA' Finally, Appendix E provides test - vectors. + prevent bidding down attacks from EAP-AKA'. Section 5 specifies + requirements regarding the use of peer identities, including how how + EAP-AKA' identifiers are used in 5G context. Section 6 specifies + what parameters EAP-AKA' exports out of the method. Section 7 + explains the security differences between EAP-AKA and EAP-AKA'. + Section 8 describes the IANA considerations and Appendix A and + Appendix B explains what updates to RFC 5448 EAP-AKA' and RFC 4187 + EAP-AKA have been made in this specification. Appendix D explains + some of the design rationale for creating EAP-AKA' Finally, + Appendix E provides test vectors. Editor's Note: The publication of this RFC depends on its normative references [TS-3GPP.24.302] and [TS-3GPP.33.501] reaching a stable status for Release 15, as indicated by 3GPP. This is expected to happen shortly. The RFC Editor should check with the 3GPP liaisons that this has happened. RFC Editor: Please delete this note upon publication of this specification as an RFC. 2. Requirements Language @@ -264,25 +276,25 @@ | the network name from AT_KDF_INPUT attribute is | | | used in running the AKA' algorithms, verifying AUTN | | | from AT_AUTN and MAC from AT_MAC attributes. The | | | peer then generates RES. The peer also derives | | | session keys from CK'/IK'. The AT_RES and AT_MAC | | | attributes are constructed. | | +------------------------------------------------------+ | | EAP-Response/AKA'-Challenge | | (AT_RES, AT_MAC) | |------------------------------------------------------->| - | +-------------------------------------------------+ + | +--------------------------------------------------+ | | Server checks the RES and MAC values received | | | in AT_RES and AT_MAC, respectively. Success | | | requires both to be found correct. | - | +-------------------------------------------------+ + | +--------------------------------------------------+ | EAP-Success | |<-------------------------------------------------------| Figure 1: EAP-AKA' Authentication Process EAP-AKA' can operate on the same credentials as EAP-AKA and employ the same identities. However, EAP-AKA' employs different leading characters than EAP-AKA for the conventions given in Section 4.1.1 of [RFC4187] for International Mobile Subscriber Identifier (IMSI) based usernames. EAP-AKA' MUST use the leading character "6" (ASCII 36 @@ -348,21 +360,21 @@ the peer over EAP-AKA'. The value of the AT_KDF_INPUT attribute from the server MUST be non-empty. If it is empty, the peer behaves as if AUTN had been incorrect and authentication fails. See Section 3 and Figure 3 of [RFC4187] for an overview of how authentication failures are handled. Note: Currently, [TS-3GPP.24.302] or [TS-3GPP.33.501] specify separate values. The former specifies what is called "Access Network ID" and the latter specifies what is called "Serving Network Name". However, from an EAP-AKA' perspective both occupy - the same field, and need to be distinghuishable from each other. + the same field, and need to be distinguishable from each other. Currently specified values are distinguishable, but it would be useful that this be specified explicitly in the 3GPP specifications. In addition, the peer MAY check the received value against its own understanding of the network name. Upon detecting a discrepancy, the peer either warns the user and continues, or fails the authentication process. More specifically, the peer SHOULD have a configurable policy that it can follow under these circumstances. If the policy indicates that it can continue, the peer SHOULD log a warning message @@ -718,54 +730,139 @@ authentication (see Figure 3 of [RFC4187]). A peer not supporting EAP-AKA' will simply ignore this attribute. In all cases, the attribute is protected by the integrity mechanisms of EAP-AKA, so it cannot be removed by a man-in-the-middle attacker. Note that we assume (Section 7) that EAP-AKA' is always stronger than EAP-AKA. As a result, there is no need to prevent bidding "down" attacks in the other direction, i.e., attackers forcing the endpoints to use EAP-AKA'. -5. Identifier Usage in 5G +5. Peer Identities + + EAP-AKA' peer identities are as specified in [RFC4187] Section 4.1, + with the addition of some requirements specified in this section. + + EAP-AKA' includes optional identity privacy support that can be used + to hide the cleartext permanent identity and thereby make the + subscriber's EAP exchanges untraceable to eavesdroppers. EAP-AKA' + can also use the privacy friendly identifiers specified for 5G + networks. + + The permanent identity is usually based on the IMSI, which may + further help the tracking, because the same identifier may be used in + other contexts as well. Identity privacy is based on temporary + usernames, or pseudonym usernames. These are similar to but separate + from the Temporary Mobile Subscriber Identities (TMSI) that are used + on cellular networks. + +5.1. Username Types in EAP-AKA' Identities + + Section 4.1.1.3 of [RFC4187] specified that there are three types of + usernames: permanent, pseudonym, and fast re-authentication + usernames. This specification extends this definition as follows. + There are four types of usernames: + + (1) Regular usernames. These are external names given to EAP- + AKA'. The regular usernames are further subdivided into to + categories: + + (a) Permanent usernames, for instance IMSI-based usernames. + + (b) Privacy-friendly temporary usernames, for instance 5G + privacy identifiers (see Section 5.3.2 and Section 5.3.2.1. + + (2) EAP-AKA' pseudonym usernames. For example, + 2s7ah6n9q@example.com might be a valid pseudonym identity. In + this example, 2s7ah6n9q is the pseudonym username. + + (3) EAP-AKA' fast re-authentication usernames. For example, + 43953754@example.com might be a valid fast re-authentication + identity and 43953754 the fast re-authentication username. + + The permanent, privacy-friendly temporary, and pseudonym usernames + are only used on full authentication, and fast re-authentication + usernames only on fast re-authentication. Unlike permanent usernames + and pseudonym usernames, privacy friendly temporary usernames and + fast re-authentication usernames are one-time identifiers, which are + not re-used across EAP exchanges. + +5.2. Generating Pseudonyms and Fast Re-Authentication Identities + + As specified by [RFC4187] Section 4.1.1.7, pseudonym usernames and + fast re-authentication identities are generated by the EAP server, in + an implementation-dependent manner. RFC 4187 provides some general + requirements on how these identities are transported, how they map to + the NAI syntax, how they are distinguished from each other, and so + on. + + However, to ensure privacy some additional requirements need to be + applied. + + The pseudonym usernames and fast re-authentication identities MUST be + generated in a cryptographically secure way so that that it is + computationally infeasible for at attacker to differentiate two + identities belonging to the same user from two identities belonging + to different users. This can be achieved, for instance, by using + random or pseudo-random identifiers such as random byte strings or + ciphertexts. + + Note that the pseudonym and fast re-authentication usernames also + MUST NOT include substrings that can be used to relate the username + to a particular entity or a particular permanent identity. For + instance, the usernames can not include any subscriber-identifying + part of an IMSI or other permanent identifier. Similarly, no part of + the username can be formed by a fixed mapping that stays the same + across multiple different pseudonyms or fast re-authentication + identities for the same subscriber. + + When the identifier used to identify a subscriber in an EAP-AKA' + authentication exchange is a privacy-friendly identifier that is used + only once, the EAP-AKA' peer MUST NOT use a pseudonym provided in + that authentication exchange in subsequent exchanges more than once. + To ensure that this does not happen, EAP-AKA' server MAY decline to + provide a pseudonym in such authentication exchanges. An important + case where such privacy-friendly identifiers are used is in 5G + networks (see Section 5.3) + +5.3. Identifier Usage in 5G In EAP-AKA', the peer identity may be communicated to the server in one of three ways: o As a part of link layer establishment procedures, externally to EAP. o With the EAP-Response/Identity message in the beginning of the EAP exchange, but before the selection of EAP-AKA'. o Transmitted from the peer to the server using EAP-AKA messages instead of EAP-Response/Identity. In this case, the server includes an identity requesting attribute (AT_ANY_ID_REQ, AT_FULLAUTH_ID_REQ or AT_PERMANENT_ID_REQ) in the EAP-Request/AKA- Identity message; and the peer includes the AT_IDENTITY attribute, which contains the peer's identity, in the EAP-Response/AKA- Identity message. - The identity carried above may be a permanent identity or a pseudonym - identity or fast re-authentication identity as defined in this RFC. + The identity carried above may be a permanent identity, privacy + friendly identity, pseudonym identity, or fast re-authentication + identity as defined in this RFC. - In networks where EAP is the only part handling such pseudonym or - fast re-authentication identities, this usage is clear. However, 5G - supports the concept of pseudonym or privacy identifiers, and it is - important for interoperability that the right type of identifiers are - used in the right place. + 5G supports the concept of privacy identifiers, and it is important + for interoperability that the right type of identifier is used. 5G defines the SUbscription Permanent Identifier (SUPI) and SUbscription Concealed Identifier (SUCI) [TS-3GPP.23.501] - [TS-3GPP.33.501]. SUPI is globally unique and allocated to each - subscriber. However, it is only used internally in the 5G network, - and is privacy sensitive. The SUCI is a privacy preserving - identifier containing the concealed SUPI, using public key + [TS-3GPP.33.501] [TS-3GPP.23.003]. SUPI is globally unique and + allocated to each subscriber. However, it is only used internally in + the 5G network, and is privacy sensitive. The SUCI is a privacy + preserving identifier containing the concealed SUPI, using public key cryptography to encrypt the SUPI. Given the choice between these two types of identifiers, two areas need further specification in EAP-AKA' to ensure that different implementations understand each other and stay interoperable: o Where identifiers are used within EAP-AKA' -- such as key derivation -- specify what values exactly should be used, to avoid ambiguity. @@ -775,71 +872,162 @@ In 5G, the normal mode of operation is that identifiers are only transmitted outside EAP. However, in a system involving terminals from many generations and several connectivity options via 5G and other mechanisms, implementations and the EAP-AKA' specification need to prepare for many different situations, including sometimes having to communicate identities within EAP. The following sections clarify which identifiers are used and how. -5.1. Key Derivation +5.3.1. Key Derivation In EAP-AKA', the peer identity is used in the Section 3.3 key derivation formula. If the AT_KDF_INPUT parameter contains the prefix "5G:", the AT_KDF parameter has the value 1, and this authentication is not a fast re- authentication, then the peer identity used in the key derivation MUST be the 5G SUPI for the peer. This rule applies to all full EAP- AKA' authentication processes, even if the peer sent some other identifier at a lower layer or as a response to an EAP Identity Request or if no identity was sent. + The identity MUST also be represented in the exact correct format for + the key derivation formula to produce correct results. For the SUPI, + this format is as defined Section 5.3.1.1. + In all other cases, the following applies: The identity used in the key derivation formula MUST be exactly the one sent in EAP-AKA' AT_IDENTITY attribute, if one was sent, regardless of the kind of identity that it may have been. If no AT_IDENTITY was sent, the identity MUST be the exactly the one sent in the generic EAP Identity exchange, if one was made. Again, the identity MUST be used exactly as sent. If no identity was communicated inside EAP, then the identity is the one communicated outside EAP in link layer messaging. In this case, the used identity MUST be the identity most recently communicated by the peer to the network, again regardless of what type of identity it may have been. -5.2. EAP Identity Response and EAP-AKA' AT_IDENTITY Attribute +5.3.1.1. Format of the SUPI + + A SUPI is either an IMSI or a Network Access Identifier [RFC4282]. + + The NAI string MUST be directly used in key derivation, and for IMSI, + the following string MUST be used: + + o Three ASCII digits to represent the Mobile Country Code (MCC). + + o Three ASCII digits to represent the Mobile Network Code (MNC). If + there are only 2 significant digits in the MNC, one "0" digit + shall be inserted at the left side to fill the 3 digits coding of + MNC. + + o ASCII digits to represent the rest of the IMSI. + + The component values are specified in more detail in + [TS-3GPP.23.003]. Note that no prefix ("0" or "6") in front of the + entire IMSI is used in the IMSI when used in the key derivation + function in 5G. + +5.3.2. EAP Identity Response and EAP-AKA' AT_IDENTITY Attribute The EAP authentication option is only available in 5G when the new 5G core network is also in use. However, in other networks an EAP-AKA' peer may be connecting to other types of networks and existing equipment. When the EAP peer is connecting to a 5G access network and uses the - 5G core network signalling mechanisms, it can assume that the EAP - server is in a 5G network. The EAP level identity exchanges are not - generally used in this case, but if there is, the EAP peer SHOULD - employ only the privacy preserving SUCI identifier within EAP (either - in EAP Identity Response or EAP-AKA' AT_IDENTITY attribute). + 5G Non-Access Stratum (NAS) protocol [TS-3GPP.24.501], the EAP server + is in a 5G network. The EAP identity exchanges are generally not + used in this case, as the identity is already made available on + previous link layer exchanges. - Similarly, if the peer is explicitly communicating through mechanisms - developed for 5G to connect to 5G networks over WLAN, it MUST assume - that the EAP server is in a 5G network, and again employ the SUCI - within EAP. + In this situation, the EAP server SHOULD NOT request an additional + identity from the peer. If the peer for some reason receives EAP- + Request/Identity or EAP-Request/AKA-Identity messages, the peer + should behave as follows. + + Receive EAP-Request/Identity + + In this case, the peer SHOULD respond with a EAP-Response/Identity + containing the privacy-friendly 5G identifier, the SUCI. The SUCI + SHOULD be represented as specified in Section 5.3.2.1. + + EAP-Request/AKA-Identity with AT_PERMANENT_REQ + + For privacy reasons, the peer should follow a "conservative" + policy and terminate the authentication exchange rather than risk + revaling its permanent identity. + + The peer SHOULD respond with EAP-Response/AKA-Client-Error with + the client error code 0, "unable to process packet". + + EAP-Request/AKA-Identity with AT_FULLAUTH_REQ + + In this case, the peer SHOULD respond with a EAP-Response/AKA- + Identity containing the SUCI. The SUCI SHOULD be represented as + specified in Section 5.3.2.1. + + EAP-Request/AKA-Identity with AT_ANY_ID_REQ + + If the peer supports fast re-authentication and has a fast re- + authentication identity available, the peer SHOULD respond with + EAP-Response/AKA-Identity containing the fast re-authentication + identity. Otherwise the peer SHOULD respond with a EAP-Response/ + AKA-Identity containing the SUCI, and SHOULD represent the SUCI as + specified in Section 5.3.2.1. + + Similarly, if the peer is communicating over a non-3GPP network but + carrying EAP inside 5G NAS protocol, it MUST assume that the EAP + server is in a 5G network, and again employ the SUCI within EAP. Otherwise, the peer SHOULD employ IMSI, SUPI, or a NAI as it is configured to use. +5.3.2.1. Format of the SUCI + + The SUCI format extends the format specified in [RFC4187] + Section 4.1.1.6 for IMSIs. + + A SUCI SHOULD be represented by an ASCII string containing the + following components in sequence: + + o A leading "6" + + o Three ASCII digits to represent the Mobile Country Code (MCC). + + o Three ASCII digits to represent the Mobile Network Code (MNC). If + there are only 2 significant digits in the MNC, one "0" digit + shall be inserted at the left side to fill the 3 digits coding of + MNC. + + o Four ASCII digits to represent a routing indicator. + + o One hex character ("0" through "9" and "a" through "f") to + represent the protection profile. + + o Hex characters representing Home Network Public Key Identifier + (HNPKI). The number of hex characters needed for this depends on + the protection profile. + + o Hex characters representing the encrypted identity. The number of + hex characters depends on the protection profile and identity + being encrypted. + + The component values are specified in more detail in + [TS-3GPP.23.003]. + 6. Exported Parameters The EAP-AKA' Session-Id is the concatenation of the EAP Type Code (50, one octet) with the contents of the RAND field from the AT_RAND attribute, followed by the contents of the AUTN field in the AT_AUTN attribute: Session-Id = 50 || RAND || AUTN When using fast re-authentication, the EAP-AKA' Session-Id is the @@ -847,22 +1035,27 @@ NONCE_S field from the AT_NONCE_S attribute, followed by the contents of the MAC field from the AT_MAC attribute from EAP-Request/AKA- Reauthentication: Session-Id = 50 || NONCE_S || MAC The Peer-Id is the contents of the Identity field from the AT_IDENTITY attribute, using only the Actual Identity Length octets from the beginning. Note that the contents are used as they are transmitted, regardless of whether the transmitted identity was a - permanent, pseudonym, or fast EAP re-authentication identity. The - Server-Id is the null string (zero length). + permanent, pseudonym, or fast EAP re-authentication identity. If no + AT_IDENTITY attribute was exchanged, the exported Peer-Id is the + identity provided from the EAP Identity Response packet. If no EAP + Identity Response was provided either, the exported Peer-Id is null + string (zero length). + + The Server-Id is the null string (zero length). 7. Security Considerations A summary of the security properties of EAP-AKA' follows. These properties are very similar to those in EAP-AKA. We assume that SHA-256 is at least as secure as SHA-1. This is called the SHA-256 assumption in the remainder of this section. Under this assumption, EAP-AKA' is at least as secure as EAP-AKA. If the AT_KDF attribute has value 1, then the security properties of @@ -919,21 +1112,21 @@ K_aut, K_re), the MSK, and the EMSK are cryptographically separate. If we make the assumption that SHA-256 behaves as a pseudo-random function, an attacker is incapable of deriving any non-trivial information about any of these keys based on the other keys. An attacker also cannot calculate the pre-shared secret from IK, CK, IK', CK', K_encr, K_aut, K_re, MSK, or EMSK by any practically feasible means. EAP-AKA' adds an additional layer of key derivation functions within itself to protect against the use of compromised keys. - This is discussed further in Section 7.1. + This is discussed further in Section 7.4. EAP-AKA' uses a pseudo-random function modeled after the one used in IKEv2 [RFC4306] together with SHA-256. Key strength See above. Dictionary attack resistance @@ -976,23 +1168,214 @@ EAP-AKA', like EAP-AKA, does not provide channel bindings as they're defined in [RFC3748] and [RFC5247]. New skippable attributes can be used to add channel binding support in the future, if required. However, including the Network Name field in the AKA' algorithms (which are also used for other purposes than EAP-AKA') provides a form of cryptographic separation between different network names, which resembles channel bindings. However, the network name does not typically identify the EAP (pass-through) authenticator. See - the following section for more discussion. + Section 7.4 for more discussion. -7.1. Security Properties of Binding Network Names +7.1. Privacy + + [RFC6973] suggests that the privacy considerations of IETF protocols + be documented. + + The confidentiality properties of EAP-AKA' itself have been discussed + above under "Confidentiality". + + EAP-AKA' uses several different types of identifiers to identify the + authenticating peer. It is strongly RECOMMENDED to use the privacy- + friendly temporary or hidden identifiers, i.e., the 5G SUCI, + pseudonym usernames, and fast re-authentication usernames. The use + of permanent identifiers such as the IMSI or SUPI may lead to an + ability to track the peer and/or user associated with the peer. The + use of permanent identifiers such as the IMSI or SUPI is strongly NOT + RECOMMENDED. + + As discussed in Section 5.3, when authenticating to a 5G network, + only the 5G SUCI identifier should be used. The use of pseudonyms in + this situation is at best limited. In fact, the re-use of the same + pseudonym multiple times will result in a tracking opportunity for + observers that see the pseudonym pass by. To avoid this, the peer + and server need to follow the guidelines given in Section 5.2. + + When authenticating to a 5G network, per Section 5.3.1, both the EAP- + AKA' peer and server need employ permanent identifier, SUPI, as an + input to key generation. However, this use of the SUPI is only + internal and the SUPI need not be communicated in EAP messages. SUCI + MUST NOT be communicated in EAP-AKA' when authenticating to a 5G + network. + + While the use of SUCI in 5G networks generally provides identity + privacy, this is not true if the null-scheme encryption is used to + construct the SUCI (see [TS-3GPP.23.501] Annex C). The use of this + scheme turns the use of SUCI equivalent to the use of SUPI or IMSI. + The use of the null scheme is NOT RECOMMENDED where identity privacy + is important. + + The use of fast re-authentication identities when authenticating to a + 5G network does not have the same problems as the use of pseudonyms, + as long as the 5G authentication server generates the fast re- + authentication identifiers in a proper manner specified in + Section 5.2. + + Outside 5G, there is a full choice to use permanent, pseudonym, or + fast re-authentication identifiers: + + o A peer that has not yet performed any EAP-AKA' exchanges does not + typically have a pseudonym available. If the peer does not have a + pseudonym available, then the privacy mechanism cannot be used, + and the permanent identity will have to be sent in the clear. + + The terminal SHOULD store the pseudonym in non-volatile memory so + that it can be maintained across reboots. An active attacker that + impersonates the network may use the AT_PERMANENT_ID_REQ attribute + ([RFC4187] Section 4.1.2) to learn the subscriber's IMSI. + However, as discussed in [RFC4187] Section 4.1.2, the terminal can + refuse to send the cleartext permanent identity if it believes + that the network should be able to recognize the pseudonym. + + o When pseudonyms and fast re-authentication identities are used, + the peer relies on the properly created identifiers by the server. + + It is essential that an attacker cannot link a privacy-friendly + identifier to the user in any way or determine that two + identifiers belong to the same user as outlined in Section 5.2. + The pseudonym usernames and fast re-authentication identities MUST + also not be used for other purposes (e.g. in other protocols). + + If the peer and server cannot guarantee that 5G SUCI can be used or + pseudonyms will available, generated properly, and maintained + reliably, and identity privacy is required then additional protection + from an external security mechanism such as tunneled EAP methods may + be used. The benefits and the security considerations of using an + external security mechanism with EAP-AKA are beyond the scope of this + document. + + Finally, as with other EAP methods, even when privacy-friendly + identifiers or EAP tunneling is used, typically the domain part of an + identifier (e.g., the home operator) is visible to external parties. + +7.2. Discovered Vulnerabilities + + There have been no published attacks that violate the primary secrecy + or authentication properties defined for the anticipated + Authentication and Key Agreement (AKA) under the originally assumed + trust model. The same is true of EAP-AKA'. + + However, there have been attacks when a different trust model is in + use, with characteristics not originally provided by the design, or + when participants in the protocol leak information to outsiders on + purpose, and there has been some privacy-related attacks. + + For instance, the original AKA protocol does not prevent supplying + keys by an insider to a third party as done in, e.g., by Mjolsnes and + Tsay in [MT2012] where a serving network lets an authentication run + succeed, but then misuses the session keys to send traffic on the + authenticated user's behalf. This particular attack is not different + from any on-path entity (such as a router) pretending to send + traffic, but the general issue of insider attacks can be a problem, + particularly in a large group of collaborating operators. + + Another class of attacks is the use of tunneling of traffic from one + place to another, e.g., as done by Zhang and Fang in [ZF2005] to + leverage security policy differences between different operator + networks, for instance. To gain something in such an attack, the + attacker needs to trick the user into believing it is in another + location where, for instance, it is not required to encrypt all + payload traffic after encryption. As an authentication mechanism, + EAP-AKA' is not directly affected by most such attacks. EAP-AKA' + network name binding can also help alleviate some of the attacks. In + any case, it is RECOMMENDED that EAP-AKA' configuration not be + dependent on the location of where a request comes from. + + Zhang and Fang also looked at Denial-of-Service attacks [ZF2005]. A + serving network may request large numbers of authentication runs for + a particular subscriber from a home network. While resynchronization + process can help recover from this, eventually it is possible to + exhaust the sequence number space and render the subscriber's card + unusable. This attack is possible for both native AKA and EAP-AKA'. + However, it requires the collaboration of a serving network in an + attack. It is recommended that EAP-AKA' implementations provide + means to track, detect, and limit excessive authentication attempts + to combat this problem. + + There has also been attacks related to the use of AKA without the + generated session keys (e.g., [BT2013]). Some of those attacks + relate to the use of originally man-in-the-middle vulnerable HTTP + Digest AKAv1 [RFC3310]. This has since then been corrected in + [RFC4169]. The EAP-AKA' protocol uses session keys and provides + channel binding, and as such, is resistant to the above attacks + except where the protocol participants leak information to outsiders. + + Basin et al [Basin2018] have performed formal analysis and concluded + that the AKA protocol would have benefited from additional security + requirements, such as key confirmation. + + In the context of pervasive monitoring revelations, there were also + reports of compromised long term pre-shared keys used in SIM and AKA + [Heist2015]. While no protocol can survive the theft of key material + associated with its credentials, there are some things that alleviate + the impacts in such situations. These are discussed further in + Section 7.3. + + Arapinis et al ([Arapinis2012]) describe an attack that uses the AKA + resynchronization protocol to attempt to detect whether a particular + subscriber is on a given area. This attack depends on the ability of + the attacker to have a false base station on the given area, and the + subscriber performing at least one authentication between the time + the attack is set up and run. + + Finally, while this is not a problem with the protocol itself, bad + implementations may not produce pseudonym usernames or fast re- + authentication identities in a manner that is sufficiently secure. + Recommendations from Section 5.2 need to be followed to avoid this. + +7.3. Pervasive Monitoring + + As required by [RFC7258], work on IETF protocols needs to consider + the effects of pervasive monitoring and mitigate them when possible. + + As described Section 7.2, after the publication of RFC 5448, new + information has come to light regarding the use of pervasive + monitoring techniques against many security technologies, including + AKA-based authentication. + + For AKA, these attacks relate to theft of the long-term shared secret + key material stored on the cards. Such attacks are conceivable, for + instance, during the manufacturing process of cards, through coercion + of the card manufacturers, or during the transfer of cards and + associated information to an operator. Since the publication of + reports about such attacks, manufacturing and provisioning processes + have gained much scrutiny and have improved. + + In particular, it is crucial that manufacturers limit access to the + secret information and the cards only to necessary systems and + personnel. It is also crucial that secure mechanisms be used to + communicate the secrets between the manufacturer and the operator + that adopts those cards for their customers. + + Beyond these operational considerations, there are also technical + means to improve resistance to these attacks. One approach is to + provide Perfect Forwards Secrecy (PFS). This would prevent any + passive attacks merely based on the long-term secrets and observation + of traffic. Such a mechanism can be defined as an backwards- + compatible extension of EAP-AKA', and is pursued separately from this + specification [I-D.arkko-eap-aka-pfs]. Alternatively, EAP-AKA' + authentication can be run inside a PFS-capable tunneled + authentication method. In any case, the use of some PFS-capable + mechanism is RECOMMENDED. + +7.4. Security Properties of Binding Network Names The ability of EAP-AKA' to bind the network name into the used keys provides some additional protection against key leakage to inappropriate parties. The keys used in the protocol are specific to a particular network name. If key leakage occurs due to an accident, access node compromise, or another attack, the leaked keys are only useful when providing access with that name. For instance, a malicious access point cannot claim to be network Y if it has stolen keys from network X. Obviously, if an access point is compromised, the malicious node can still represent the compromised node. As a @@ -1066,60 +1449,56 @@ 8.3. Key Derivation Function Namespace IANA has also created a new namespace for EAP-AKA' AT_KDF Key Derivation Function Values. This namespace exists under the EAP-AKA and EAP-SIM Parameters registry. The initial contents of this namespace are given below; new values can be created through the Specification Required policy [RFC8126]. Value Description Reference - --------- ---------------------- --------------- - 0 Reserved [RFC 5448] - 1 EAP-AKA' with CK'/IK' [RFC 5448] + --------- ---------------------- ------------------------------- + 0 Reserved [RFC Editor: Refer to this RFC] + 1 EAP-AKA' with CK'/IK' [RFC Editor: Refer to this RFC] 2-65535 Unassigned -9. Contributors - - The test vectors in Appendix C were provided by Yogendra Pal and - Jouni Malinen, based on two independent implementations of this - specification. - - Jouni Malinen provided suggested text for Section 6. - -10. Acknowledgments - - The authors would like to thank Guenther Horn, Joe Salowey, Mats - Naslund, Adrian Escott, Brian Rosenberg, Laksminath Dondeti, Ahmad - Muhanna, Stefan Rommer, Miguel Garcia, Jan Kall, Ankur Agarwal, Jouni - Malinen, Brian Weis, Russ Housley, Alfred Hoenes, Vesa Torvinen, - Anand Palanigounder, and Mohit Sethi for their in-depth reviews and - interesting discussions in this problem space. +9. References -11. References +9.1. Normative References -11.1. Normative References + [TS-3GPP.23.003] + 3GPP, "3rd Generation Partnership Project; Technical + Specification Group Core Network and Terminals; Numbering, + addressing and identification (Release 15)", 3GPP Draft + Technical Specification 23.003, June 2018. [TS-3GPP.23.501] 3GPP, "3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; 3G Security; Security architecture and procedures for 5G System; (Release 15)", 3GPP Technical Specification 23.501, December 2017. [TS-3GPP.24.302] 3GPP, "3rd Generation Partnership Project; Technical Specification Group Core Network and Terminals; Access to the 3GPP Evolved Packet Core (EPC) via non-3GPP access networks; Stage 3; (Release 15)", 3GPP Draft Technical Specification 24.302, June 2018. + [TS-3GPP.24.501] + 3GPP, "3rd Generation Partnership Project; Technical + Specification Group Core Network and Terminals; Access to + the 3GPP Evolved Packet Core (EPC) via non-3GPP access + networks; Stage 3; (Release 15)", 3GPP Draft Technical + Specification 24.501, June 2018. + [TS-3GPP.33.102] 3GPP, "3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; 3G Security; Security architecture (Release 15)", 3GPP Draft Technical Specification 33.102, June 2018. [TS-3GPP.33.402] 3GPP, "3GPP System Architecture Evolution (SAE); Security aspects of non-3GPP accesses (Release 15)", 3GPP Draft Technical Specification 33.402, June 2018. @@ -1150,36 +1529,35 @@ [RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H. Levkowetz, Ed., "Extensible Authentication Protocol (EAP)", RFC 3748, DOI 10.17487/RFC3748, June 2004, . [RFC4187] Arkko, J. and H. Haverinen, "Extensible Authentication Protocol Method for 3rd Generation Authentication and Key Agreement (EAP-AKA)", RFC 4187, DOI 10.17487/RFC4187, January 2006, . + [RFC4282] Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The + Network Access Identifier", RFC 4282, + DOI 10.17487/RFC4282, December 2005, . + [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, June 2017, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . -11.2. Informative References - - [TS-3GPP.23.003] - 3GPP, "3rd Generation Partnership Project; Technical - Specification Group Core Network and Terminals; Numbering, - addressing and identification (Release 15)", 3GPP Draft - Technical Specification 23.003, June 2018. +9.2. Informative References [TS-3GPP.35.208] 3GPP, "3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; 3G Security; Specification of the MILENAGE Algorithm Set: An example algorithm set for the 3GPP authentication and key generation functions f1, f1*, f2, f3, f4, f5 and f5*; Document 4: Design Conformance Test Data (Release 14)", 3GPP Technical Specification 35.208, March 2017. @@ -1187,20 +1565,31 @@ National Institute of Standards and Technology, "Secure Hash Standard", FIPS PUB 180-1, April 1995, . [FIPS.180-2] National Institute of Standards and Technology, "Secure Hash Standard", FIPS PUB 180-2, August 2002, . + [RFC3310] Niemi, A., Arkko, J., and V. Torvinen, "Hypertext Transfer + Protocol (HTTP) Digest Authentication Using Authentication + and Key Agreement (AKA)", RFC 3310, DOI 10.17487/RFC3310, + September 2002, . + + [RFC4169] Torvinen, V., Arkko, J., and M. Naslund, "Hypertext + Transfer Protocol (HTTP) Digest Authentication Using + Authentication and Key Agreement (AKA) Version-2", + RFC 4169, DOI 10.17487/RFC4169, November 2005, + . + [RFC4186] Haverinen, H., Ed. and J. Salowey, Ed., "Extensible Authentication Protocol Method for Global System for Mobile Communications (GSM) Subscriber Identity Modules (EAP-SIM)", RFC 4186, DOI 10.17487/RFC4186, January 2006, . [RFC4284] Adrangi, F., Lortz, V., Bari, F., and P. Eronen, "Identity Selection Hints for the Extensible Authentication Protocol (EAP)", RFC 4284, DOI 10.17487/RFC4284, January 2006, . @@ -1223,33 +1612,88 @@ Authentication Protocol (EAP) Key Management Framework", RFC 5247, DOI 10.17487/RFC5247, August 2008, . [RFC5448] Arkko, J., Lehtovirta, V., and P. Eronen, "Improved Extensible Authentication Protocol Method for 3rd Generation Authentication and Key Agreement (EAP-AKA')", RFC 5448, DOI 10.17487/RFC5448, May 2009, . + [RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J., + Morris, J., Hansen, M., and R. Smith, "Privacy + Considerations for Internet Protocols", RFC 6973, + DOI 10.17487/RFC6973, July 2013, . + + [RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an + Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May + 2014, . + + [I-D.arkko-eap-aka-pfs] + Arkko, J., Norrman, K., and V. Torvinen, "Perfect-Forward + Secrecy for the Extensible Authentication Protocol Method + for Authentication and Key Agreement (EAP-AKA' PFS)", + draft-arkko-eap-aka-pfs-02 (work in progress), July 2018. + + [Heist2015] + Scahill, J. and J. Begley, "The great SIM heist", February + 2015, in https://firstlook.org/theintercept/2015/02/19/ + great-sim-heist/ . + + [MT2012] Mjolsnes, S. and J-K. Tsay, "A vulnerability in the UMTS + and LTE authentication and key agreement protocols", + October 2012, in Proceedings of the 6th international + conference on Mathematical Methods, Models and + Architectures for Computer Network Security: computer + network security. + + [BT2013] Beekman, J. and C. Thompson, "Breaking Cell Phone + Authentication: Vulnerabilities in AKA, IMS and Android", + August 2013, in 7th USENIX Workshop on Offensive + Technologies, WOOT '13. + + [ZF2005] Zhang, M. and Y. Fang, "Breaking Cell Phone + Authentication: Vulnerabilities in AKA, IMS and Android", + March 2005, IEEE Transactions on Wireless Communications, + Vol. 4, No. 2. + + [Basin2018] + Basin, D., Dreier, J., Hirsch, L., Radomirovic, S., Sasse, + R., and V. Stettle, "A Formal Analysis of 5G + Authentication", August 2018, arXiv:1806.10360. + + [Arapinis2012] + Arapinis, M., Mancini, L., Ritter, E., Ryan, M., Golde, + N., and R. Borgaonkar, "New Privacy Issues in Mobile + Telephony: Fix and Verification", October 2012, CCS'12, + Raleigh, North Carolina, USA. + Appendix A. Changes from RFC 5448 The changes consist first of all, referring to a newer version of [TS-3GPP.24.302]. The new version includes an updated definition of the Network Name field, to include 5G. - Secondly, identifier usage for 5G has been specified in Section 5. + Secondly, identifier usage for 5G has been specified in Section 5.3. + Also, the requirements on generating pseudonym usernames and fast re- + authentication identities have been updated from the original + definition in RFC 5448, which referenced RFC 4187. See Section 5. Thirdly, exported parameters for EAP-AKA' have been defined in Section 6, as required by [RFC5247], including the definition of those parameters for both full authentication and fast re- authentication. + The security, privacy, and pervasive monitoring considerations have + been updated or added. See Section 7. + Finally, the references to [RFC2119], [RFC5226], [FIPS.180-1] and [FIPS.180-2] have been updated to their most recent versions and language in this document changed accordingly. Similarly, references to all 3GPP technical specifications have been updated to their 5G (Release 15) versions or otherwise most recent version when there has not been a 5G-related update. Appendix B. Changes from RFC 4187 to RFC 5448 The changes to RFC 4187 relate only to the bidding down prevention @@ -1258,28 +1702,40 @@ and IK, not CK' and IK'); neither is any processing of the AMF bit added to RFC 4187. Appendix C. Changes from Previous Version of This Draft RFC Editor: Please delete this section at the time of publication. The -00 version of the working group draft is merely a republication of an earlier individual draft. - The -01 version of the working group clarifies updates relationship - to RFC 4187, clarifies language relating to obsoleting RFC 5448, - clarifies when the 3GPP references are expected to be stable, updates - several past references to their more recently published versions, - specifies what identifiers should be used in key derivation formula - for 5G, specifies how to construct the network name in manner that is - compatible with both 5G and previous versions, and has some minor - editorial changes. + The -01 version of the working group draft clarifies updates + relationship to RFC 4187, clarifies language relating to obsoleting + RFC 5448, clarifies when the 3GPP references are expected to be + stable, updates several past references to their more recently + published versions, specifies what identifiers should be used in key + derivation formula for 5G, specifies how to construct the network + name in manner that is compatible with both 5G and previous versions, + and has some minor editorial changes. + + The -02 version of the working group draft added specification of + peer identity usage in EAP-AKA', added requirements on the generation + of pseudonym and fast re-authentication identifiers, specified the + format of 5G-identifiers when they are used within EAP-AKA', defined + privacy and pervasive surveillance considerations, clarified when 5G- + related procedures apply, specified what Peer-Id value is exported + when no AT_IDENTITY is exchanged within EAP-AKA', and made a number + of other clarifications and editorial improvements. The security + considerations section also includes a summary of vulnerabilities + brought up in the context of AKA or EAP-AKA', and discusses their + applicability and impacts in EAP-AKA'. Appendix D. Importance of Explicit Negotiation Choosing between the traditional and revised AKA key derivation functions is easy when their use is unambiguously tied to a particular radio access network, e.g., Long Term Evolution (LTE) as defined by 3GPP or evolved High Rate Packet Data (eHRPD) as defined by 3GPP2. There is no possibility for interoperability problems if this radio access network is always used in conjunction with new protocols that cannot be mixed with the old ones; clients will always @@ -1311,21 +1767,21 @@ provide all features of the current release. And obviously, there are many EAP and even some EAP-AKA implementations that are not bundled with the 3GPP network offerings. In general, these approaches are expected to lead to hard-to-diagnose problems and increased support calls. Appendix E. Test Vectors Test vectors are provided below for four different cases. The test vectors may be useful for testing implementations. In the first two - cases, we employ the Milenage algorithm and the algorithm + cases, we employ the MILENAGE algorithm and the algorithm configuration parameters (the subscriber key K and operator algorithm variant configuration value OP) from test set 19 in [TS-3GPP.35.208]. The last two cases use artificial values as the output of AKA, and is useful only for testing the computation of values within EAP-AKA', not AKA itself. Case 1 The parameters for the AKA run are as follows: @@ -1487,21 +1943,41 @@ MSK: c6d3 a6e0 ceea 951e b20d 74f3 2c30 61d0 680a 04b0 b086 ee87 00ac e3e0 b95f a026 83c2 87be ee44 4322 94ff 98af 26d2 cc78 3bac e75c 4b0a f7fd feb5 511b a8e4 cbd0 EMSK: 7fb5 6813 838a dafa 99d1 40c2 f198 f6da cebf b6af ee44 4961 1054 02b5 08c7 f363 352c b291 9644 b504 63e6 a693 5415 0147 ae09 cbc5 4b8a 651d 8787 a689 3ed8 536d +Appendix F. Contributors + + The test vectors in Appendix C were provided by Yogendra Pal and + Jouni Malinen, based on two independent implementations of this + specification. + + Jouni Malinen provided suggested text for Section 6. John Mattsson + provided much of the text for Section 7.1. Karl Norrman was the + source of much of the information in Section 7.2. + +Appendix G. Acknowledgments + + The authors would like to thank Guenther Horn, Joe Salowey, Mats + Naslund, Adrian Escott, Brian Rosenberg, Laksminath Dondeti, Ahmad + Muhanna, Stefan Rommer, Miguel Garcia, Jan Kall, Ankur Agarwal, Jouni + Malinen, John Mattsson, Brian Weis, Russ Housley, Alfred Hoenes, + Anand Palanigounder, and Mohit Sethi for their in-depth reviews and + interesting discussions in this problem space. + Authors' Addresses + Jari Arkko Ericsson Jorvas 02420 Finland Email: jari.arkko@piuha.net Vesa Lehtovirta Ericsson Jorvas 02420