Maybe anybody can help with algorithm of calculation AT_MAC parameter for EAP-AKA authentication ? I need to answer out with 3 parameters: AT_RAND, AT_AUTN, AT_MAC. It's clear how to generate AT_RAND and AT_AUTN. I have such input options: 3GPP-SIP-Authorization Confidentiality-Key Integrity-Key Identity 3GPP-SIP-Authenticate When i tried to calculate it like this (RFC 4187), it's not working: 10.15. AT_MAC The AT_MAC attribute is used for EAP-AKA message authentication. Section 9 specifies in which messages AT_MAC MUST be included. The value field of the AT_MAC attribute contains two reserved bytes followed by a keyed message authentication code (MAC). The MAC is calculated over the whole EAP packet and concatenated with optional message-specific data, with the exception that the value field of the MAC attribute is set to zero when calculating the MAC. The EAP packet includes the EAP header that begins with the Code field, the EAP-AKA header that begins with the Subtype field, and all the attributes, as specified in Section 8.1. The reserved bytes in AT_MAC are set to zero when sending and ignored on reception. The contents of the message-specific data that may be included in the MAC calculation are specified separately for each EAP-AKA message in Section 9. The format of the AT_MAC 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_MAC | Length = 5 | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | MAC | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The MAC algorithm is HMAC-SHA1-128 [RFC2104] keyed hash value. (The HMAC-SHA1-128 value is obtained from the 20-byte HMAC-SHA1 value by truncating the output to 16 bytes. Hence, the length of the MAC is 16 bytes.) The derivation of the authentication key (K_aut) used in the calculation of the MAC is specified in Section 7. When the AT_MAC attribute is included in an EAP-AKA message, the recipient MUST process the AT_MAC attribute before looking at any other attributes, except when processing EAP-Request/AKA-Challenge. The processing of EAP-Request/AKA-Challenge is specified in Arkko & Haverinen Informational [Page 63] RFC 4187 EAP-AKA Authentication January 2006 Section 9.3. If the message authentication code is invalid, then the recipient MUST ignore all other attributes in the message and operate as specified in Section 6.3. Здесь еще есть отсылка на секцию 7 где описывается алгоритм генерации ключа для расчета MAC 7. Key Generation This section specifies how keying material is generated. On EAP-AKA full authentication, a Master Key (MK) is derived from the underlying AKA values (CK and IK keys), and the identity, as follows. MK = SHA1(Identity|IK|CK) In the formula above, the "|" character denotes concatenation. Identity denotes the peer identity string without any terminating null characters. It is the identity from the last AT_IDENTITY attribute sent by the peer in this exchange, or, if AT_IDENTITY was Specification is clear but the result is different with working system. If anybody can share working script on python or any other language it will be grate. Continue reading...
