--- 1/draft-ietf-emu-rfc5448bis-04.txt 2019-07-08 13:14:27.123077469 -0700 +++ 2/draft-ietf-emu-rfc5448bis-05.txt 2019-07-08 13:14:27.231080182 -0700 @@ -1,59 +1,62 @@ 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: July 21, 2019 Independent - January 17, 2019 +Expires: January 9, 2020 Independent + July 8, 2019 - Improved Extensible Authentication Protocol Method for 3rd Generation - Authentication and Key Agreement (EAP-AKA') - draft-ietf-emu-rfc5448bis-04 + Improved Extensible Authentication Protocol Method for 3GPP Mobile + Network Authentication and Key Agreement (EAP-AKA') + draft-ietf-emu-rfc5448bis-05 Abstract - The 3rd Generation Authentication and Key Agreement (AKA) is the + The 3GPP Mobile Network Authentication and Key Agreement (AKA) is the primary authentication mechanism for devices wishing to access mobile networks. RFC 4187 (EAP-AKA) made the use of this mechanism possible within the Extensible Authentication Protocol (EAP) framework. RFC 5448 (EAP-AKA') was an improved version of EAP-AKA. - This memo is an update of the specification for EAP-AKA'. This - version obsoletes RFC 5448. + This memo replaces the specification of EAP-AKA'. EAP-AKA' was + defined in RFC 5448 and updated EAP-AKA RFC 4187. As such this + document obsoletes RFC 5448 and updates RFC 4187. EAP-AKA' differs from EAP-AKA by providing a key derivation function that binds the keys derived within the method to the name of the access network. The key derivation function has been defined in the 3rd Generation Partnership Project (3GPP). EAP-AKA' allows its use in EAP in an interoperable manner. EAP-AKA' is also an algorithm - update, as it employs SHA-256 instead of SHA-1 as in EAP-AKA. + update, as it employs SHA-256 / HMAC-SHA-256 instead of SHA-1 / HMAC- + SHA-1 as in EAP-AKA. This version of EAP-AKA' specification specifies 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 July 21, 2019. + + This Internet-Draft will expire on January 9, 2020. Copyright Notice Copyright (c) 2019 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 @@ -68,81 +71,84 @@ 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 5 3. EAP-AKA' . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.1. AT_KDF_INPUT . . . . . . . . . . . . . . . . . . . . . . 8 3.2. AT_KDF . . . . . . . . . . . . . . . . . . . . . . . . . 11 3.3. Key Derivation . . . . . . . . . . . . . . . . . . . . . 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 + 3.5. Summary of Attributes for EAP-AKA' . . . . . . . . . . . 16 + 4. Bidding Down Prevention for EAP-AKA . . . . . . . . . . . . . 18 + 4.1. Summary of Attributes for EAP-AKA . . . . . . . . . . . . 19 + 5. Peer Identities . . . . . . . . . . . . . . . . . . . . . . . 20 + 5.1. Username Types in EAP-AKA' Identities . . . . . . . . . . 20 5.2. Generating Pseudonyms and Fast Re-Authentication - Identities . . . . . . . . . . . . . . . . . . . . . . . 18 - 5.3. Identifier Usage in 5G . . . . . . . . . . . . . . . . . 19 - 5.3.1. Key Derivation . . . . . . . . . . . . . . . . . . . 20 + Identities . . . . . . . . . . . . . . . . . . . . . . . 21 + 5.3. Identifier Usage in 5G . . . . . . . . . . . . . . . . . 22 + 5.3.1. Key Derivation . . . . . . . . . . . . . . . . . . . 23 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 . . . . . . 30 - 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 31 - 8.1. Type Value . . . . . . . . . . . . . . . . . . . . . . . 32 - 8.2. Attribute Type Values . . . . . . . . . . . . . . . . . . 32 - 8.3. Key Derivation Function Namespace . . . . . . . . . . . . 32 - - 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 32 - 9.1. Normative References . . . . . . . . . . . . . . . . . . 32 - 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 . . . . . . . . . 39 - Appendix E. Test Vectors . . . . . . . . . . . . . . . . . . . . 40 - Appendix F. Contributors . . . . . . . . . . . . . . . . . . . . 44 - Appendix G. Acknowledgments . . . . . . . . . . . . . . . . . . 45 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 45 + Attribute . . . . . . . . . . . . . . . . . . . . . . 24 + 6. Exported Parameters . . . . . . . . . . . . . . . . . . . . . 25 + 7. Security Considerations . . . . . . . . . . . . . . . . . . . 26 + 7.1. Privacy . . . . . . . . . . . . . . . . . . . . . . . . . 29 + 7.2. Discovered Vulnerabilities . . . . . . . . . . . . . . . 30 + 7.3. Pervasive Monitoring . . . . . . . . . . . . . . . . . . 33 + 7.4. Security Properties of Binding Network Names . . . . . . 33 + 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 34 + 8.1. Type Value . . . . . . . . . . . . . . . . . . . . . . . 35 + 8.2. Attribute Type Values . . . . . . . . . . . . . . . . . . 35 + 8.3. Key Derivation Function Namespace . . . . . . . . . . . . 35 + 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 35 + 9.1. Normative References . . . . . . . . . . . . . . . . . . 35 + 9.2. Informative References . . . . . . . . . . . . . . . . . 37 + Appendix A. Changes from RFC 5448 . . . . . . . . . . . . . . . 41 + Appendix B. Changes from RFC 4187 to RFC 5448 . . . . . . . . . 41 + Appendix C. Changes from Previous Version of This Draft . . . . 42 + Appendix D. Importance of Explicit Negotiation . . . . . . . . . 43 + Appendix E. Test Vectors . . . . . . . . . . . . . . . . . . . . 44 + Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 48 + Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 49 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 49 1. Introduction - The 3rd Generation Authentication and Key Agreement (AKA) is the + The 3GPP Mobile Network Authentication and Key Agreement (AKA) is the primary authentication mechanism for devices wishing to access mobile networks. [RFC4187] (EAP-AKA) made the use of this mechanism possible within the Extensible Authentication Protocol (EAP) framework [RFC3748]. [RFC5448] (EAP-AKA') was an improved version of EAP-AKA. This memo - is an update of the specification for EAP-AKA'. This version - obsoletes RFC 5448. + replaces the specification of EAP-AKA'. EAP-AKA' was defined in RFC + 5448 and updated EAP-AKA RFC 4187. As such this document obsoletes + RFC 5448 and updates RFC 4187. - EAP-AKA' is commonly implemented in smart phones and network + EAP-AKA' is commonly implemented in mobile phones and network equipment. It can be used for authentication to gain network access via Wireless LAN networks and, with 5G, also directly to mobile networks. EAP-AKA' differs from EAP-AKA by providing a different key derivation function. 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. EAP-AKA' is also an algorithm update for the used hash functions. The EAP-AKA' method employs the derived keys CK' and IK' from the 3GPP specification [TS-3GPP.33.402] and updates the used hash - function to SHA-256 [FIPS.180-4]. Otherwise, EAP-AKA' is equivalent - to EAP-AKA. 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]. + function to SHA-256 [FIPS.180-4] and HMAC to HMAC-SHA-256. + Otherwise, EAP-AKA' is equivalent to EAP-AKA. 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 that any change of the key derivation must be unambiguous to both sides in the protocol. That is, it must not be possible to accidentally connect old equipment to new equipment and get the key derivation wrong or attempt to use wrong keys without getting a proper error message. See Appendix D for further information. Note also that choices in authentication protocols should be secure against bidding down attacks that attempt to force the participants to use the least secure function. See Section 4 for @@ -200,56 +206,58 @@ 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 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, + 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. + normative references to 3GPP Technical Specifications reaching a + stable status for Release 15, as indicated by 3GPP. The RFC + Editor should check with the 3GPP liaisons that a stable version + from Release 15 is available and refer to that version. RFC + Editor: Please delete this note upon publication of this + specification as an RFC. 2. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 3. EAP-AKA' EAP-AKA' is an EAP method that follows the EAP-AKA specification [RFC4187] in all respects except the following: - o It uses the Type code 50, not 23 (which is used by EAP-AKA). + o It uses the Type code 0x32, not 0x17 (which is used by EAP-AKA). o It carries the AT_KDF_INPUT attribute, as defined in Section 3.1, to ensure that both the peer and server know the name of the access network. o It supports key derivation function negotiation via the AT_KDF attribute (Section 3.2) to allow for future extensions. o It calculates keys as defined in Section 3.3, not as defined in EAP-AKA. - o It employs SHA-256, not SHA-1 [FIPS.180-4] (Section 3.4). + o It employs SHA-256 / HMAC-SHA-256, not SHA-1 / HMAC-SHA-1 + [FIPS.180-4] (Section 3.4 [RFC2104]). Figure 1 shows an example of the authentication process. Each message AKA'-Challenge and so on represents the corresponding message from EAP-AKA, but with EAP-AKA' Type code. The definition of these messages, along with the definition of attributes AT_RAND, AT_AUTN, AT_MAC, and AT_RES can be found in [RFC4187]. Peer Server | EAP-Request/Identity | |<-------------------------------------------------------| @@ -297,32 +305,34 @@ | 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 - hexadecimal) instead of "0" for IMSI-based permanent usernames. All - other usage and processing of the leading characters, usernames, and - identities is as defined by EAP-AKA [RFC4187]. For instance, the - pseudonym and fast re-authentication usernames need to be constructed - so that the server can recognize them. As an example, a pseudonym - could begin with a leading "7" character (ASCII 37 hexadecimal) and a - fast re-authentication username could begin with "8" (ASCII 38 - hexadecimal). Note that a server that implements only EAP-AKA may - not recognize these leading characters. According to Section 4.1.4 - of [RFC4187], such a server will re-request the identity via the EAP- - Request/AKA-Identity message, making obvious to the peer that EAP-AKA - and associated identity are expected. + hexadecimal) instead of "0" for IMSI-based permanent usernames, or + 5G-specific identifiers in 5G networks. Identifier usage in 5G is + specified in Section 5.3. All other usage and processing of the + leading characters, usernames, and identities is as defined by EAP- + AKA [RFC4187]. For instance, the pseudonym and fast re- + authentication usernames need to be constructed so that the server + can recognize them. As an example, a pseudonym could begin with a + leading "7" character (ASCII 37 hexadecimal) and a fast re- + authentication username could begin with "8" (ASCII 38 hexadecimal). + Note that a server that implements only EAP-AKA may not recognize + these leading characters. According to Section 4.1.4 of [RFC4187], + such a server will re-request the identity via the EAP- Request/AKA- + Identity message, making obvious to the peer that EAP-AKA and + associated identity are expected. 3.1. AT_KDF_INPUT The format of the AT_KDF_INPUT attribute is shown below. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | AT_KDF_INPUT | Length | Actual Network Name Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ @@ -457,21 +467,22 @@ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The fields are as follows: AT_KDF This is set to 24. Length - The length of the attribute, MUST be set to 1. + The length of the attribute, calculated as defined in [RFC4187], + Section 8.1. For AT_KDF, the Length field MUST be set to 1. Key Derivation Function An enumerated value representing the key derivation function that the server (or peer) wishes to use. Value 1 represents the default key derivation function for EAP-AKA', i.e., employing CK' and IK' as defined in Section 3.3. Servers MUST send one or more AT_KDF attributes in the EAP-Request/ AKA'-Challenge message. These attributes represent the desired @@ -489,21 +500,22 @@ alternative, the peer behaves as if AUTN had been incorrect and authentication fails (see Figure 3 of [RFC4187]). The peer fails the authentication also if there are any duplicate values within the list of AT_KDF attributes (except where the duplication is due to a request to change the key derivation function; see below for further information). Upon receiving an EAP-Response/AKA'-Challenge with AT_KDF from the peer, the server checks that the suggested AT_KDF value was one of the alternatives in its offer. The first AT_KDF value in the message - from the server is not a valid alternative. If the peer has replied + from the server is not a valid alternative since the peer should have + accepted it without further negotiation. If the peer has replied with the first AT_KDF value, the server behaves as if AT_MAC of the response had been incorrect and fails the authentication. For an overview of the failed authentication process in the server side, see Section 3 and Figure 2 of [RFC4187]. Otherwise, the server re-sends the EAP-Response/AKA'-Challenge message, but adds the selected alternative to the beginning of the list of AT_KDF attributes and retains the entire list following it. Note that this means that the selected alternative appears twice in the set of AT_KDF values. Responding to the peer's request to change the key derivation function is the only legal situation where such duplication may @@ -514,23 +526,29 @@ occurred in the list of AT_KDF attributes. If so, it continues with processing the received EAP-Request/AKA'-Challenge as specified in [RFC4187] and Section 3.1 of this document. If not, it behaves as if AT_MAC had been incorrect and fails the authentication. If the peer receives multiple EAP-Request/AKA'-Challenge messages with differing AT_KDF attributes without having requested negotiation, the peer MUST behave as if AT_MAC had been incorrect and fail the authentication. Note that the peer may also request sequence number resynchronization [RFC4187]. This happens after AT_KDF negotiation has already - completed. An AKA'-Synchronization-Failure message is sent as a - response to the newly received EAP-Request/AKA'-Challenge (the last - message of the AT_KDF negotiation). The AKA'-Synchronization-Failure + completed. That is, the EAP-Request/AKA'-Challenge and, possibly, + the EAP-Response/AKA'-Challenge message are exchanged first to come + up with a mutually acceptable key derivation function, and only then + the possible AKA'-Synchronization-Failure message is sent. The AKA'- + Synchronization-Failure message is sent as a response to the newly + received EAP-Request/AKA'-Challenge which is the last message of the + AT_KDF negotiation. Note that if the first proposed KDF is + acceptable, then last message is at the same time the first EAP- + Request/AKA'-Challenge message. The AKA'-Synchronization-Failure message MUST contain the AUTS parameter as specified in [RFC4187] and a copy the AT_KDF attributes as they appeared in the last message of the AT_KDF negotiation. If the AT_KDF attributes are found to differ from their earlier values, the peer and server MUST behave as if AT_MAC had been incorrect and fail the authentication. 3.3. Key Derivation Both the peer and server MUST derive the keys as follows. @@ -538,30 +556,30 @@ In this case, MK is derived and used as follows: MK = PRF'(IK'|CK',"EAP-AKA'"|Identity) K_encr = MK[0..127] K_aut = MK[128..383] K_re = MK[384..639] MSK = MK[640..1151] EMSK = MK[1152..1663] - Here [n..m] denotes the substring from bit n to m. PRF' is a new - pseudo-random function specified in Section 3.4. The first 1664 - bits from its output are used for K_encr (encryption key, 128 - bits), K_aut (authentication key, 256 bits), K_re (re- - authentication key, 256 bits), MSK (Master Session Key, 512 bits), - and EMSK (Extended Master Session Key, 512 bits). These keys are - used by the subsequent EAP-AKA' process. K_encr is used by the - AT_ENCR_DATA attribute, and K_aut by the AT_MAC attribute. K_re - is used later in this section. MSK and EMSK are outputs from a - successful EAP method run [RFC3748]. + Here [n..m] denotes the substring from bit n to m, including bits + n and m. PRF' is a new pseudo-random function specified in + Section 3.4. The first 1664 bits from its output are used for + K_encr (encryption key, 128 bits), K_aut (authentication key, 256 + bits), K_re (re-authentication key, 256 bits), MSK (Master Session + Key, 512 bits), and EMSK (Extended Master Session Key, 512 bits). + These keys are used by the subsequent EAP-AKA' process. K_encr is + used by the AT_ENCR_DATA attribute, and K_aut by the AT_MAC + attribute. K_re is used later in this section. MSK and EMSK are + outputs from a successful EAP method run [RFC3748]. IK' and CK' are derived as specified in [TS-3GPP.33.402]. The functions that derive IK' and CK' take the following parameters: CK and IK produced by the AKA algorithm, and value of the Network Name field comes from the AT_KDF_INPUT attribute (without length or padding) . The value "EAP-AKA'" is an eight-characters-long ASCII string. It is used as is, without any trailing NUL characters. @@ -618,29 +636,30 @@ The peer behaves as if the AUTN had been incorrect and MUST fail the authentication. If the peer supports a given key derivation function but is unwilling to perform it for policy reasons, it refuses to calculate the keys and behaves as explained in Section 3.2. 3.4. Hash Functions - EAP-AKA' uses SHA-256, not SHA-1 (see [FIPS.180-4]) as in EAP-AKA. - This requires a change to the pseudo-random function (PRF) as well as - the AT_MAC and AT_CHECKCODE attributes. + EAP-AKA' uses SHA-256 / HMAC-SHA-256, not SHA-1 / HMAC-SHA-1 (see + [FIPS.180-4] [RFC2104]) as in EAP-AKA. This requires a change to the + pseudo-random function (PRF) as well as the AT_MAC and AT_CHECKCODE + attributes. 3.4.1. PRF' The PRF' construction is the same one IKEv2 uses (see Section 2.13 of [RFC4306]). The function takes two arguments. K is a 256-bit value - and S is an byte string of arbitrary length. PRF' is defined as + and S is a byte string of arbitrary length. PRF' is defined as follows: PRF'(K,S) = T1 | T2 | T3 | T4 | ... where: T1 = HMAC-SHA-256 (K, S | 0x01) T2 = HMAC-SHA-256 (K, T1 | S | 0x02) T3 = HMAC-SHA-256 (K, T2 | S | 0x03) T4 = HMAC-SHA-256 (K, T3 | S | 0x04) ... @@ -673,40 +692,124 @@ | | | Checkcode (0 or 32 bytes) | | | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Second, the checkcode is a hash value, calculated with SHA-256 [FIPS.180-4], over the data specified in Section 10.13 of [RFC4187]. +3.5. Summary of Attributes for EAP-AKA' + + The following table provides a guide to which attributes may be found + in which kinds of messages, and in what quantity. + + Messages are denoted with numbers in parentheses as follows: + + (1) EAP-Request/AKA-Identity, + + (2) EAP-Response/AKA-Identity, + + (3) EAP-Request/AKA-Challenge, + + (4) EAP-Response/AKA-Challenge, + + (5) EAP-Request/AKA-Notification, + + (6) EAP-Response/AKA-Notification, + + (7) EAP-Response/AKA-Client-Error + + (8) EAP-Request/AKA-Reauthentication, + + (9) EAP-Response/AKA-Reauthentication, + + (10) EAP-Response/AKA-Authentication-Reject, and + + (11) EAP-Response/AKA-Synchronization-Failure. + + The column denoted with "E" indicates whether the attribute is a + nested attribute that MUST be included within AT_ENCR_DATA. + + In addition: + + "0" indicates that the attribute MUST NOT be included in the + message, + + "1" indicates that the attribute MUST be included in the message, + + "0-1" indicates that the attribute is sometimes included in the + message, + + "0+" indicates that zero or more copies of the attribute MAY be + included in the message, + + "1+" indicates that there MUST be at least one attribute in the + message but more than one MAY be included in the message, and + + "0*" indicates that the attribute is not included in the message + in cases specified in this document, but MAY be included in the + future versions of the protocol. + + The attribute table is shown below. The table is largely the same as + in the EAP-AKA attribute table ([RFC4187] Section 10.1), but changes + how many times AT_MAC may appear in EAP-Response/AKA'-Challenge + message as it does not appear there when AT_KDF has to be sent from + the peer to the server. The table also adds the AT_KDF and + AT_KDF_INPUT attributes. + + Attribute (1) (2) (3) (4) (5) (6) (7) (8) (9) (10)(11) E + AT_PERMANENT_ID_REQ 0-1 0 0 0 0 0 0 0 0 0 0 N + AT_ANY_ID_REQ 0-1 0 0 0 0 0 0 0 0 0 0 N + AT_FULLAUTH_ID_REQ 0-1 0 0 0 0 0 0 0 0 0 0 N + AT_IDENTITY 0 0-1 0 0 0 0 0 0 0 0 0 N + AT_RAND 0 0 1 0 0 0 0 0 0 0 0 N + AT_AUTN 0 0 1 0 0 0 0 0 0 0 0 N + AT_RES 0 0 0 1 0 0 0 0 0 0 0 N + AT_AUTS 0 0 0 0 0 0 0 0 0 0 1 N + AT_NEXT_PSEUDONYM 0 0 0-1 0 0 0 0 0 0 0 0 Y + AT_NEXT_REAUTH_ID 0 0 0-1 0 0 0 0 0-1 0 0 0 Y + AT_IV 0 0 0-1 0* 0-1 0-1 0 1 1 0 0 N + AT_ENCR_DATA 0 0 0-1 0* 0-1 0-1 0 1 1 0 0 N + AT_PADDING 0 0 0-1 0* 0-1 0-1 0 0-1 0-1 0 0 Y + AT_CHECKCODE 0 0 0-1 0-1 0 0 0 0-1 0-1 0 0 N + AT_RESULT_IND 0 0 0-1 0-1 0 0 0 0-1 0-1 0 0 N + AT_MAC 0 0 1 0-1 0-1 0-1 0 1 1 0 0 N + AT_COUNTER 0 0 0 0 0-1 0-1 0 1 1 0 0 Y + AT_COUNTER_TOO_SMALL 0 0 0 0 0 0 0 0 0-1 0 0 Y + AT_NONCE_S 0 0 0 0 0 0 0 1 0 0 0 Y + AT_NOTIFICATION 0 0 0 0 1 0 0 0 0 0 0 N + AT_CLIENT_ERROR_CODE 0 0 0 0 0 0 1 0 0 0 0 N + AT_KDF 0 0 1+ 0+ 0 0 0 0 0 0 1+ N + AT_KDF_INPUT 0 0 1 0 0 0 0 0 0 0 0 N + 4. Bidding Down Prevention for EAP-AKA As discussed in [RFC3748], negotiation of methods within EAP is insecure. That is, a man-in-the-middle attacker may force the endpoints to use a method that is not the strongest that they both support. This is a problem, as we expect EAP-AKA and EAP-AKA' to be negotiated via EAP. In order to prevent such attacks, this RFC specifies a new mechanism for EAP-AKA that allows the endpoints to securely discover the capabilities of each other. This mechanism comes in the form of the AT_BIDDING attribute. This allows both endpoints to communicate their desire and support for EAP-AKA' when exchanging EAP-AKA - messages. This attribute is not included in EAP-AKA' messages as - defined in this RFC. It is only included in EAP-AKA messages. This - is based on the assumption that EAP-AKA' is always preferable (see - Section 7). If during the EAP-AKA authentication process it is - discovered that both endpoints would have been able to use EAP-AKA', - the authentication process SHOULD be aborted, as a bidding down - attack may have happened. + messages. This attribute is not included in EAP-AKA' messages. It + is only included in EAP-AKA messages. (Those messages are protected + with the AT_MAC attribute.) This approach is based on the assumption + that EAP-AKA' is always preferable (see Section 7). If during the + EAP-AKA authentication process it is discovered that both endpoints + would have been able to use EAP-AKA', the authentication process + SHOULD be aborted, as a bidding down attack may have happened. The format of the AT_BIDDING attribute is shown below. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | AT_BIDDING | Length |D| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The fields are as follows: @@ -705,25 +808,27 @@ 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | AT_BIDDING | Length |D| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The fields are as follows: AT_BIDDING + This is set to 136. Length - The length of the attribute, MUST be set to 1. + The length of the attribute, calculated as defined in [RFC4187], + Section 8.1. For AT_BIDDING, the Length MUST be set to 1. D This bit is set to 1 if the sender supports EAP-AKA', is willing to use it, and prefers it over EAP-AKA. Otherwise, it should be set to zero. Reserved This field MUST be set to zero when sent and ignored on receipt. @@ -736,20 +841,28 @@ 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'. +4.1. Summary of Attributes for EAP-AKA + + The appearance of the AT_BIDDING attribute in EAP-AKA exchanges is + shown below, using the notation from Section 3.5: + + Attribute (1) (2) (3) (4) (5) (6) (7) (8) (9) (10)(11) E + AT_BIDDING 0 0 1 0 0 0 0 0 0 0 0 N + 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. @@ -895,22 +1008,23 @@ 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. + the key derivation formula to produce correct results. In 5G, this + identifier is the SUPI. The SUPI 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. @@ -920,21 +1034,21 @@ 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. 5.3.1.1. Format of the SUPI A SUPI is either an IMSI or a Network Access Identifier [RFC4282]. When used in EAP-AKA', the format of the SUPI MUST be as specified in [TS-3GPP.23.003] Section 28.7.2, with the semantics defined in - [TS-3GPP.23.003] Section 2.2B. Also, in contrast to [RFC5448], in 5G + [TS-3GPP.23.003] Section 2.2A. Also, in contrast to [RFC5448], in 5G EAP-AKA' does not use the "0" or "6" prefix in front of the entire IMSI. For instance, if the IMSI is 234150999999999 (MCC = 234, MNC = 15), the NAI format for the SUPI takes the form: 234150999999999@nai.5gc.mnc015.mcc234.3gppnetwork.org 5.3.2. EAP Identity Response and EAP-AKA' AT_IDENTITY Attribute @@ -945,50 +1059,49 @@ When the EAP peer is connecting to a 5G access network and uses the 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. 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. + behaves as follows. Receive EAP-Request/Identity - In this case, the peer SHOULD respond with a EAP-Response/Identity + In this case, the peer MUST 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. + MUST 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 + For privacy reasons, the peer MUST follow a "conservative" policy + and terminate the authentication exchange rather than risk revealing its permanent identity. - The peer SHOULD respond with EAP-Response/AKA-Client-Error with - the client error code 0, "unable to process packet". + The peer MUST 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 + In this case, the peer MUST respond with a EAP-Response/AKA- + Identity containing the SUCI. The SUCI MUST 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 + identity. Otherwise the peer MUST respond with a EAP-Response/ + AKA-Identity containing the SUCI, and MUST 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 @@ -1011,33 +1124,33 @@ For the Profile protection scheme: type0.rid678.schid1.hnkey27.ecckey. cip.mac@nai.5gc. mnc015.mcc234.3gppnetwork.org 6. Exported Parameters The EAP-AKA' Session-Id is the concatenation of the EAP Type Code - (50, one byte) with the contents of the RAND field from the AT_RAND + (0x32, one byte) 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 + Session-Id = 0x32 || RAND || AUTN When using fast re-authentication, the EAP-AKA' Session-Id is the - concatenation of the EAP Type Code (50) with the contents of the + concatenation of the EAP Type Code (0x32) with the contents of the 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 + Session-Id = 0x32 || NONCE_S || MAC The Peer-Id is the contents of the Identity field from the AT_IDENTITY attribute, using only the Actual Identity Length bytes 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. 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). @@ -1064,40 +1177,40 @@ The negotiation mechanism allows changing the offered key derivation function, but the change is visible in the final EAP- Request/AKA'-Challenge message that the server sends to the peer. This message is authenticated via the AT_MAC attribute, and carries both the chosen alternative and the initially offered list. The peer refuses to accept a change it did not initiate. As a result, both parties are aware that a change is being made and what the original offer was. Mutual authentication - Under the SHA-256 assumption, the properties of EAP-AKA' are at least as good as those of EAP-AKA in this respect. Refer to [RFC4187], Section 12 for further details. Integrity protection Under the SHA-256 assumption, the properties of EAP-AKA' are at least as good (most likely better) as those of EAP-AKA in this respect. Refer to [RFC4187], Section 12 for further details. The - only difference is that a stronger hash algorithm, SHA-256, is - used instead of SHA-1. + only difference is that a stronger hash algorithm and keyed MAC, + SHA-256 / HMAC-SHA-256, is used instead of SHA-1 / HMAC-SHA-1. Replay protection Under the SHA-256 assumption, the properties of EAP-AKA' are at least as good as those of EAP-AKA in this respect. Refer to [RFC4187], Section 12 for further details. Confidentiality + The properties of EAP-AKA' are exactly the same as those of EAP- AKA in this respect. Refer to [RFC4187], Section 12 for further details. Key derivation EAP-AKA' supports key derivation with an effective key strength against brute force attacks equal to the minimum of the length of the derived keys and the length of the AKA base key, i.e., 128 bits or more. The key hierarchy is specified in Section 3.3. @@ -1189,25 +1302,25 @@ 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 derivation. 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. + AKA' peer and server need to employ the permanent identifier, SUPI, + as an input to key derivation. However, this use of the SUPI is only + internal. As such, the SUPI need not be communicated in EAP + messages. Therefore, SUPI 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, @@ -1317,24 +1431,52 @@ 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. + Borgaonkar et al discovered that the AKA resynchronization protocol + may also be used to predict the authentication frequency of a + subscribers if non-time-based SQN generation scheme is used + [Borgaonkar2018]. The attacker can force the re-use of the keystream + that is used to protect the SQN in the AKA resynchronization + protocol. The attacker then guesses the authentication frequency + based on the lowest bits of two XORed SQNs. The researchers' concern + was that the authentication frequency would reveal some information + about the phone usage behavior, e.g., number of phone calls made or + number of SMS messages sent. However, phone calls and SMS messages + are just some of the many potential triggers for authentication. For + instance, various mobility events and the amount of mobile data sent + or received can also trigger authentication. As a result, while some + amount of information may be derived about the activity level on a + particular phone in some cases, the linkage to specific activities is + not direct. The impact of the attack is also different depending on + whether time or non-time-based SQN generation scheme is used. + + Similar attacks are possible outside AKA in the cellular paging + protocols where the attacker can simply send application layer data, + short messages or make phone calls to the intended victim and observe + the air-interface (e.g., [Kune2012] and [Shaik2016]). Hussain et. + al. demonstrated a slightly more sophisticated version of the attack + that exploits the fact that 4G paging protocol uses the IMSI to + calculate the paging timeslot [Hussain2019]. As this attack is + outside AKA, it does not impact EAP-AKA'. + + Finally, bad implementations of EAP-AKA' may not produce pseudonym + usernames or fast re-authentication identities in a manner that is + sufficiently secure. While it is not a problem with the protocol + itself, 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. @@ -1420,21 +1562,21 @@ domains or devices using the same technology. 8. IANA Considerations IANA should update the Extensible Authentication Protocol (EAP) Registry and the EAP-AKA and EAP-SIM Parameters so that entries pointing to RFC 5448 will point to this RFC instead. 8.1. Type Value - EAP-AKA' has the EAP Type value 50 in the Extensible Authentication + EAP-AKA' has the EAP Type value 0x32 in the Extensible Authentication Protocol (EAP) Registry under Method Types. Per Section 6.2 of [RFC3748], this allocation can be made with Designated Expert and Specification Required. 8.2. Attribute Type Values EAP-AKA' shares its attribute space and subtypes with EAP-SIM [RFC4186] and EAP-AKA [RFC4187]. No new registries are needed. However, a new Attribute Type value (23) in the non-skippable range @@ -1458,64 +1600,67 @@ Value Description Reference --------- ---------------------- ------------------------------- 0 Reserved [RFC Editor: Refer to this RFC] 1 EAP-AKA' with CK'/IK' [RFC Editor: Refer to this RFC] 2-65535 Unassigned 9. References 9.1. Normative References + [Note] Editors, "All 3GPP references should be updated to the + latest Release 15 version before publishing.". + [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, September 2018. + Technical Specification 23.003, June 2019. [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, September 2018. + 23.501, June 2019. [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, September 2018. + Specification 24.302, June 2019. [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, September 2018. + Specification 24.501, June 2019. [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. + Technical Specification 33.102, December 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. [TS-3GPP.33.501] 3GPP, "3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; 3G Security; Security architecture and procedures for 5G System (Release 15)", 3GPP Draft Technical Specification - 33.501, September 2018. + 33.501, June 2019. [FIPS.180-4] National Institute of Standards and Technology, "Secure Hash Standard", FIPS PUB 180-4, August 2015, . [RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed- Hashing for Message Authentication", RFC 2104, DOI 10.17487/RFC2104, February 1997, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . 9.2. Informative References + [NoteAlso] + Editors, "All 3GPP references should be updated to the + latest Release 15 version before publishing.". + [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. + 3GPP Technical Specification 35.208, October 2018. [FIPS.180-1] 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, . [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-03 (work in progress), October - 2018. + draft-arkko-eap-aka-pfs-04 (work in progress), January + 2019. [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 @@ -1672,20 +1821,44 @@ 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. + [Borgaonkar2018] + Borgaonkar, R., Hirschi, L., Park, S., and A. Shaik, "New + Privacy Threat on 3G, 4G, and Upcoming 5G AKA Protocols", + 2018 in IACR Cryptology ePrint Archive. + + [Kune2012] + Kune, D., Koelndorfer, J., and Y. Kim, "Location leaks on + the GSM air interface", 2012 in the proceedings of NDSS + '12 held 5-8 February, 2012 in San Diego, California. + + [Shaik2016] + Shaik, A., Seifert, J., Borgaonkar, R., Asokan, N., and V. + Niemi, "Practical attacks against privacy and availability + in 4G/LTE mobile communication systems", 2012 in the + proceedings of NDSS '16 held 21-24 February, 2016 in San + Diego, California. + + [Hussain2019] + Hussain, S., Echeverria, M., Chowdhury, O., Li, N., and E. + Bertino, "Privacy Attacks to the 4G and 5G Cellular Paging + Protocols Using Side Channel Information", in the + Proceedings of NDSS '19, held 24-27 February, 2019, in San + Diego, California. + 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 5.3. 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. @@ -1698,21 +1871,22 @@ The security, privacy, and pervasive monitoring considerations have been updated or added. See Section 7. 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. - Finally, a number of editorial clarifications have been made. + Finally, a number of clarifications have been made, including a + summary of where attributes may appear. Appendix B. Changes from RFC 4187 to RFC 5448 The changes to RFC 4187 relate only to the bidding down prevention support defined in Section 4. In particular, this document does not change how the Master Key (MK) is calculated in RFC 4187 (it uses CK 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 @@ -1756,20 +1930,57 @@ when referring to AT_KDF values vs. AT_KDF attribute number, provided guidance on random number generation, clarified the dangers relating to the use of permanent user identities such as IMSIs, aligned the key derivation function/mechanism terminology, aligned the key derivation/generation terminology, aligned the octet/byte terminology, clarified the text regarding strength of SHA-256, added some cross references between sections, instructed IANA to change registries to point to this RFC rather than RFC 5448, and changed Pasi's listed affiliation. + The -05 version of the draft corrected the Section 7.1 statement that + SUCI must not be communicated in EAP-AKA'; this statement was meant + to say SUPI must not be communicated. That was a major bug, but + hopefully one that previous readers understood was a mistake! + + The -05 version also changed keyword strengths for identifier + requests in different cases in a 5G network, to match the 3GPP + specifications (see Section 5.3.2. + + Tables of where attributes may appear has been added to the -05 + version of the document, see Section 3.5 and Section 4.1. The tables + are based on the original table in RFC 4187. + + Other changes in the -05 version included the following: + + o The attribute appearance table entry for AT_MAC in EAP-Response/ + AKA-Challenge has been specified to be 0-1 because it does not + appear when AT_KDF has to be sent; this was based on implementor + feedback. + + o Added information about attacks against the re-synchronization + protocol and other attacks recently discussed in academic + conferences. + + o Clarified length field calculations and the AT_KDF negotiation + procedure. + + o The treatment of AT_KDF attribute copy in the EAP-Response/AKA'- + Synchronization-Failure message was clarified in Section 3.2. + + o Updated and added several references + + o Switched to use of hexadecimal for EAP Type Values for consistency + with other documents. + + o Made editorial clarifications to a number places in the document. + 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 know whether they are connecting to the old or new system. @@ -1976,38 +2187,39 @@ 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 +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 +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, Jesus De Gregorio, Brian Weis, Russ Housley, - Alfred Hoenes, Anand Palanigounder, and Mohit Sethi for their in- - depth reviews and interesting discussions in this problem space. + Alfred Hoenes, Anand Palanigounder, Michael Richardsson, Marcus Wong, + Kalle Jarvinen, Daniel Migault, 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