draft-haverinen-pppext-eap-sim-05.txt

Linux上的802.1x 的supplicant的实现。很多supplicant程序都是基于它开发的

  
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   ignored on reception. The AT_IV attribute MUST be included if and 
   only if the AT_ENCR_DATA is included. Messages that do not meet this 
   condition MUST be silently discarded.  

   The sender of the AT_IV attribute chooses the initialization vector 
   by random. The sender MUST NOT reuse the initialization vector value 
   from previous EAP SIM packets but the sender MUST choose it freshly 
   for each AT_IV attribute. The sends SHOULD use a good source of 
   randomness to generate the initialization vector. The format of 
   AT_IV 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_IV     | Length = 5    |           Reserved            | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                                                               | 
   |                 Initialization Vector                         | 
   |                                                               | 
   |                                                               | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    

   The value field of the AT_ENCR_DATA attribute consists of two 
   reserved bytes followed by bytes encrypted using the Advanced 
   Encryption Standard (AES) [5] in the Cipher Block Chaining (CBC) 
   mode of operation, using the initialization vector from the AT_IV 
   attribute. The reserved bytes are set to zero when sending and 
   ignored on reception. Please see [6] for a description of the CBC 
   mode. The format of the AT_ENCR_DATA 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_ENCR_DATA  | Length        |           Reserved            | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                                                               | 
   .                    Encrypted Data                             . 
   .                                                               . 
   |                                                               | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    

   The derivation of the encryption key (K_encr) is specified in 
   Section 15. 

   The plaintext consists of nested EAP/SIM attributes. 

8. EAP-Response/Identity 

   In the beginning of EAP authentication, the Authenticator issues the 
   EAP-Request/Identity packet to the client. The client responds with 

  
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   EAP-Response/Identity, which contains the user's identity. The 
   formats of these packets are specified in [1]. 

   GSM subscribers are identified with the International Mobile 
   Subscriber Identity (IMSI) [7]. The IMSI is composed of a three 
   digit Mobile Country Code (MCC), a two or three digit Mobile Network 
   Code (MNC) and a not more than 10 digit Mobile Subscriber 
   Identification Number (MSIN). In other words, the IMSI is a string 
   of not more than 15 digits. MCC and MNC uniquely identify the GSM 
   operator. 

   Internet AAA protocols identify users with the Network Access 
   Identifier (NAI) [8]. When used in a roaming environment, the NAI is 
   composed of a username and a realm, separated with "@" 
   (username@realm). The username portion identifies the subscriber 
   within the realm. The AAA nodes use the realm portion of the NAI to 
   route AAA requests to the correct AAA server. The realm name used in 
   this protocol MAY be chosen by the operator and it MAY a 
   configurable parameter in the EAP/SIM client implementation. In this 
   case, the client is typically configured with the NAI realm of the 
   home operator. Operators MAY reserve a specific realm name  for 
   EAP/SIM users. This convention makes it easy to recognize that the 
   NAI identifies a GSM subscriber. Such reserved NAI realm may be 
   useful as a hint as to the first authentication method to use during 
   method negotiation. 

   There are two types of NAI username portions in EAP/SIM: non-
   pseudonym permanent usernames and pseudonym usernames. When the 
   optional IMSI privacy support is not used, the non-pseudonym 
   permanent username is used. The non-pseudonym permanent username is 
   of the format "1imsi". In other words, the first character of the 
   username is the digit one (ASCII value 0x31), followed by the IMSI. 
   The IMSI is an ASCII string that consists of not more than 15 
   decimal digits (ASCII values between 0x30 and 0x39) as specified in 
   [7]. 

   The EAP server MAY use the leading "1" as a hint to try EAP/SIM as 
   the first authentication method during method negotiation, rather 
   than for example EAP/AKA. The EAP/SIM server MAY propose EAP/SIM 
   even if the leading character was not "1". 

   When the optional identity privacy support is used, the client MAY 
   use the pseudonym received as part of the previous authentication 
   sequence as the username portion of the NAI, as specified in Section 
   5. The client MUST NOT modify the pseudonym received in 
   AT_PSEUDONYM. For example, the client MUST NOT append any leading 
   characters in the pseudonym. 

   If no configured realm name is available, the client MAY derive the 
   realm name from the MCC and MNC portions of the IMSI. In this case, 
   the realm name is obtained by concatenating "mnc", the MNC digits of 
   IMSI, ".mcc", the MCC digits of IMSI and ".owlan.org". For example, 

  
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   if the IMSI is 123456789098765, and the MNC is three digits long, 
   then the derived realm name is "mnc456.mcc123.owlan.org". 

   If the client is not able to determine whether the MNC is two or 
   three digits long, the client MAY use a 3-digit MNC. If the correct 
   length of the MNC is two, then the MNC used in the realm name will 
   include the first digit of MSIN. Hence, when configuring AAA 
   networks for operators that have 2-digit MNC's, the network SHOULD 
   also be prepared for realm names with incorrect 3-digit MNC's. 

9. EAP-Request/SIM/Start 

   The first SIM specific EAP Request is of subtype Start. The format 
   of the EAP Request/SIM/Start packet 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 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |     Code      |  Identifier   |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |     Type      |    Subtype    |           Reserved            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |AT_PERM..._REQ | Length = 1    |           Reserved            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |AT_ID..._REQ   | Length = 1    |           Reserved            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Code 

      1 for Request  

   Identifier 

      See [1]. 

   Length 

      The length of the EAP packet. 

   Type 

      18 

   Subtype 

      10 

   Reserved 

      Set to zero on sending, ignored on reception 

  
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   AT_PERMANENT_IDENTITY_REQ 

      The AT_PERMANENT_IDENTITY_REQ attribute is optional and it is 
      included in the cases defined in Section 5. It MUST NOT be 
      included if AT_IDENTITY_REQ is included. The value field only 
      contains two reserved bytes, which are set to zero on sending and 
      ignored on reception. 

   AT_IDENTITY_REQ 

      The AT_IDENTITY_REQ attribute is optional and it is included in 
      the cases defined in Section 4. It MUST NOT be included if 
      AT_PERMANENT_IDENTITY_REQ is included. The value field only 
      contains two reserved bytes, which are set to zero on sending and 
      ignored on reception. 

10. EAP-Response/SIM/Start 

   The format of the EAP Response/SIM/Start packet 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 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |     Code      |  Identifier   |            Length             | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |     Type      |    Subtype    |           Reserved            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |AT_NONCE_MT    | Length = 5    |           Reserved            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                                                               | 
      |                           NONCE_MT                            | 
      |                                                               | 
      |                                                               | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      | AT_PERM...    | Length        | Actual Identity Length        | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                                                               | 
      .               Cleartext Identity (optional)                   . 
      .                                                               . 
      |                                                               | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      | AT_IDENTITY   | Length        | Actual Identity Length        | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                                                               | 
      .                 Current Identity (optional)                   . 
      .                                                               . 
      |                                                               | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    

   Code 

      2 for Response 
  
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   Identifier 

      See [1]. 

   Length 

      The length of the EAP packet. 

   Type 

      18 

   Subtype 

      10 

   Reserved 

      Set to zero when sending, ignored on reception. 

   AT_NONCE_MT 

      The AT_NONCE_MT attribute MUST be included. The value field 
      contains two reserved bytes followed by a random number generated 
      by the client (16 bytes) freshly for this EAP/SIM authentication. 
      The random number is used as a seed value for the new keying 
      material. The reserved bytes are set to zero upon sending and 
      ignored upon reception. 

   AT_PERMANENT_IDENTITY 

      The AT_PERMANENT_IDENTITY attribute is optional and it is 
      included in cases defined in Section 5. It MUST NOT be included 
      if AT_IDENTITY is included. The value field of this attribute 
      begins with 2-byte actual identity length, which specifies the 
      length of the identity in bytes. This field is followed by the 
      non-pseudonym permanent Network Access Identifier username 
      portion of the indicated actual length. The username format is 
      specified in Section 8. The username does not include any 
      terminating null characters. Because the length of the attribute 
      must be a multiple of 4 bytes, the sender pads the identity with 
      zero bytes when necessary. 

   AT_IDENTITY 

      The AT_IDENTITY attribute is optional and it is included in cases 
      defined in Section 4. It MUST NOT be included if 
      AT_PERMANENT_IDENTITY is included. The value field of this 
      attribute begins with 2-byte actual identity length, which 
      specifies the length of the identity in bytes. This field is 
      followed by the Network Access Identifier username portion of the 
      indicated actual length. The username format is specified in 
      Section 8. The username is either the non-pseudonym permanent 
  
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      username or a pseudonym username. The username does not include 
      any terminating null characters. Because the length of the 
      attribute must be a multiple of 4 bytes, the sender pads the 
      identity with zero bytes when necessary. 

11. EAP-Request/SIM/Challenge 

   The format of the EAP-Request/SIM/Challenge packet 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 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |     Code      |  Identifier   |            Length             | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |     Type      |    Subtype    |           Reserved            | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     | AT_RAND       | Length        |           Reserved            | 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     |                                                               | 
     .                            n*RAND                             . 
     .                                                               . 
     |                                                               |