EAP-SIM Using EAP-SIM for WLAN Authentication yliqiang gmail com

EAP-SIM Using EAP-SIM for WLAN Authentication yliqiang@gmail. com 2005 -9 -13 EAP-SIM 1

Definition(定义 ) • EAP-SIM is an Extensible Authentication Protocol (EAP) [RFC 3748] mechanism for authentication and session key distribution using the Global System for Mobile communications (GSM) Subscriber Identity Module (SIM). 用GSM-SIM卡作为EAP的认证和密匙分 发机制 EAP-SIM 2

EAP Introduction (简介 ) • EAP is an authentication framework which supports multiple authentication methods. 支持多种认证机制的认证框架。 • EAP typically runs directly over data link layers such as Point-to-Point Protocol (PPP) or IEEE 802 EAP 通常直接运行在数据链路层如 PPP或 IEEE 802 EAP-SIM 3

EAP Introduction (简介 ) • EAP permits the use of a backend authentication server, with the authenticator acting as a pass-through for some or all methods and peers. EAP 允许使用后台认证服务器，把认证端作为 一些或全部认证机制的转发者。 • Conceptually, EAP implementations consist of the following components: 从概念上讲，EAP的实现有下面这些组件构成。 EAP-SIM 4

IEEE 802. 1 X EAPOL Lower Layer Authenticator (认证 者) Peer(被认证者) EAP-SIM 5

IEEE 802. 1 X EAPOL Lower Layer Peer(被认证者) Radius Protocol Pass-through Authenticator (认证 者) Authentication Server (认证服务器) AAA: Authentication(认证 ）, Authorization (授权), and Accounting (记帐) EAP-SIM 6

GSM authentication(认证 ) • RAND is a 128 -bit random challenge issued from the base station to the mobile. RAND 是基站发给移动台(手机)的128比特长随机数。 • SRES is a 32 -bit response generated by A 3 issued from the mobile to the base station SRES 是移动台(手机)发给基站的32比特长响应, 由A 3生 成。 EAP-SIM 7

GSM authentication(认证 ) • Kc is a 64 -bit Cipher Key, used for A 5. Kc是 64比特长密匙，由A 8生成用于数据加密(A 5)。 • Ki is the SIM’s 128 -bit individual subscriber key. Ki是 128比特长SIM卡的密匙(拥有标识)。 • A 3/A 8 are specified by each operator rather than being fully standardized, but usually implemented together as COMP 128. A 3/A 8定义了算法的输入输出，具体实现由厂商决定， 实际上厂商都采用了COMP 128，它同时实现了A 3, A 8。 EAP-SIM 8

EAP-SIM Introduction(简介) Peer Authenticator AAA/RADIUS SS 7 Network GSM/MAP/SS 7 Gateway SIM Card GSM Authentication Center • builds on underlying GSM mechanisms 构建在GSM认证机制之上。 EAP-SIM 9

EAP-SIM Introduction(简介) • Provides mutual authentication 支持相互认证。 • several RAND challenges are used for generating several 64 -bit Kc keys, which are combined to constitute stronger keying material. 多次挑战生成多个Kc, 组合起来生成更强 的相关密匙。 EAP-SIM 10

EAP-SIM Introduction(简介) • EAP-SIM specifies optional support for protecting the privacy of subscriber identity using the same concept as GSM, which is using pseudonyms/temporary identifiers. EAP-SIM支持用户身份保密(可选)。 • It also specifies an optional fast reauthentication procedure. 支持快速重复认证(可选) EAP-SIM 11

Peer EAP-SIM Full Authentication Procedure( ) Authenticator | EAP-Request/Identity | |<-----------------------------| | EAP-Response/Identity | |----------------------------->| | EAP-Request/SIM/Start (AT_VERSION_LIST) | |<-----------------------------| | EAP-Response/SIM/Start (AT_NONCE_MT, AT_SELECTED_VERSION)| |----------------------------->| | EAP-Request/SIM/Challenge (AT_RAND, AT_MAC) | |<-----------------------------| +-------------------+ | | Peer runs GSM algorithms, verifies | | | AT_MAC and derives session keys | | +-------------------+ | | EAP-Response/SIM/Challenge (AT_MAC) | |----------------------------->| | EAP-Success | |<-----------------------------| | | EAP-SIM 完 全 认 证 过 程 12

Key Generation • • MK = SHA 1(Identity|n*Kc| NONCE_MT| Version List| Selected Version) K_aut , K_encr , MSK and EMSK are derived from MK using Pseudo-Random number Function (PRF) Request AT_MAC = HMAC-SHA 1 -128(K_aut, EAP packet| NONCE_MT) Response AT_MAC = HMAC-SHA 1 -128(K_aut, EAP packet| n*SRES) In the formula above, the "|" character denotes concatenation. Nonce A value that is used at most once or that is never repeated within the same cryptographic context. MAC Message Authentication Code EAP-SIM 13

Indication of vulnerabilities(弱点) • The security of the A 3 and A 8 algorithms is important to the security of EAP-SIM. Some A 3/A 8 algorithms have been compromised; see for example [GSM Cloning] for discussion about the security of COMP-128 version 1. Note that several revised versions of the COMP-128 A 3/A 8 algorithm have been devised after the publication of these weaknesses and that the publicly specified GSM -MILENAGE [3 GPP TS 55. 205] algorithm is not vulnerable to any known attacks. A 3/A 8算法的安全性对EAP-SIM是至关重要的。COMP 128 -v 1已经被破解( 当前市面上大部分SIM卡用的是COMP 128 -v 1), 修订过的COMP 128 v 2, v 3 以及公开标准的GSM-MILENAGE, 当前还没有方法攻破。 EAP-SIM 14

Indication of vulnerabilities(弱点) • Mutual Authentication and Triplet Exposure EAP-SIM provides mutual authentication. The peer believes that the network is authentic because the network can calculate a correct AT_MAC value in the EAP-Request/SIM/Challenge packet. To calculate the AT_MAC it is sufficient to know the RAND and Kc values from the GSM triplets (RAND, SRES, Kc) used in the authentication. Because the network selects the RAND challenges and the triplets, an attacker that knows n (2 or 3) GSM triplets for the subscriber is able to impersonate a valid network to the peer. EAP-SIM支持双向认证。被认证者相信认证者是因为认证者能计算出正 确的AT_MAC, 要计算AT_MAC知道RAND和Kc就足够了。因为是认证者 选择RAND，攻击者只需知道几个(2 -3)Kc就可以假装是一个有效的认证者。 EAP-SIM 15

Security Claims(安全声明) • Auth. mechanism: EAP-SIM is based on the GSM SIM mechanism, which is a challenge/response authentication and key agreement mechanism based on a symmetric 128 -bit pre-shared secret. EAP-SIM also makes use of a peer challenge to provide mutual authentication. 认证机理: EAP-SIM基于GSM-SIM的认证机理, 它是一种基 于挑战/响应的认证和密匙分发机制，需要一个预先共 享的128比特长对称密匙(Ki)。EAP-SIM通过被认证者 发挑战(NONCE_MT)支持双向认证。 EAP-SIM 16

Security Claims(安全声明) • • • • Ciphersuite negotiation: No Mutual authentication: Yes Integrity protection: Yes Replay protection: Yes Confidentiality: Yes, except method specific success and failure indications Key derivation: Yes Description of key hierarchy: (page 13) Dictionary attack protection: N/A Fast reconnect: Yes Cryptographic binding: N/A Session independence: Yes Fragmentation: No Channel binding: No Indication of vulnerabilities: (page 14, 15) EAP-SIM 17

Example Using EAP-SIM for WLAN Authentication EAP-SIM 18

Requirements(需求清单) • Windows XP built-in supplicant • EAP-SIM plug-in for the Windows XP built-in 802. 1 x Supplicant (http: //weap. sf. net) • PC/SC compatible smart card reader (QWY Low. Speed CCID smart card reader) • Wireless Access Point support RADIUS (TP -LINK TL-WR 541 G) • RADIUS server support EAP-SIM (Free. Radius 1. 0. 4) EAP-SIM 19

Network topological diagram ( 网络拓扑图) simtriplets. dat EAP-SIM 20

SIM Reader Installation • Download the driver from http: //agsm. sf. net • Insert the USB smart card reader in a USB port, specify the location of the driver. • Insert your sim-card into smart card reader, run agsm 2. exe to make sure you can access the sim-card. EAP-SIM 21

Configure freeradius • Download freeradius-1. 0. 4 from http: //www. freeradius. org • cd freeradius-1. 0. 4; Configure; make install; cd srcmodulesrlm_sim_files; make install. • Add the following to radiusd. conf: In modules {}, add: sim_files { simtriplets = " ${raddbdir}/simtriplets. dat " } in eap{} add sim{} In authorized {}, add: sim_files before eap. • Add the following to clients. conf client 192. 168. 1. 0/24 {secret = eap-sim shortname= eap-sim} EAP-SIM 22

• Run agsm 2. exe. simtriplets. dat #IMSI RAND SRES Kc 1460001551807128, 52632 FE 305874545 AC 9936926 D 796256, 8184 a 227, 5 F 05 b 4 a 2 CE 884400 1460001551807128, ECEB 1577 E 275414 e 9 DD 9 EF 98 B 277 E 54 A, 00 fb 682 e, B 6 c 0 de 73256 c 0400 ………… Make sure insert 1 EAP-SIM Generate simtriplets. dat • Copy IMSI, RAND, SRES, Kc to simtriplets. dat, at least 5 entries. 23

Configure AP EAP-SIM 24

EAP-SIM plug-in installation • Download w. EAP-SIM from http: //weap. sf. net • Install. • Enable tracing. Enable. Console. Tracing : set HKEY_LOCAL_MACHINESOFTWAREMICROSOFTTRACING Enable. Console. Tracing to nozero set HKEY_LOCAL_MACHINESOFTWAREMICROSOFTTRACING w. EAP-SIM Enable. Console. Tracing to nozero Enable. File. Tracing: set HKEY_LOCAL_MACHINESOFTWAREMICROSOFTTRACING w. EAP-SIM Enable. File. Tracing to nozero EAP-SIM 25

Authenticate the client EAP-SIM 26

References • http: //www. intel. com/technology/itj/2005/volume 09 issue 01/art 07_next_generation/p 05_simpl_netw ork. htm • draft-haverinen-pppext-eap-sim-16. txt • [RFC 3748] Extensible Authentication Protocol (EAP) • S 5. Brumley-comp 128. pdf • [GSM Cloning] http: //www. isaac. cs. berkeley. edu/isaac/gsm. html EAP-SIM 27

问题 & 讨论 EAP-SIM 28