[Pidgin] #48: Make SIP/SIMPLE work with Microsoft Live Communication Server

[Pidgin]

#48: Make SIP/SIMPLE work with Microsoft Live Communication Server
--------------------------+-------------------------------------------------
  Reporter:  MarkDoliner  |       Owner:  shulman      
      Type:  patch        |      Status:  new          
  Priority:  minor        |   Milestone:  2.3.0        
 Component:  libpurple    |     Version:  2.0          
Resolution:               |    Keywords:  MS LCS SIMPLE
   Pending:  0            |  
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Comment (by shulman):

 I am realizing that I may not have much time to work on this so I have
 posted the code and information I have. Hope this helps. I'll hop back on
 the task if I get some time. Cheers!

 First to generate an NTLM datagram session key (an arc4 implementation is
 needed. One is available at: http://xyssl.org/code/source/arc4/):

 static void generate_datagram_session_key(char *lm_hash, char
 *lm_response, char *session_key, char *encrypted_session_key) {
   /*Input:      LM hash (unsigned char *, 21 bytes?)
    *            LM Response (unsigned char *, 24 bytes?)
    *            Session Key Buffer (8-bytes for weakend?)
    *            Encrypted Session Key Buffer (16-byte)
    *Postcondition: Session Key & Encrypted Session Key are populated
 correctly
    *
    *Datagram Session Security
    *http://davenport.sourceforge.net/ntlm.html
    */
   char des_source_1[7];
   char des_source_2[7];
   char des_key_1[8];
   char des_key_2[8];
   char lan_manager_session_key[16];
   char full_session_key[16];
   int i;

   //1. The 16-byte LM hash (calculated previously) is truncated to 8
 bytes.
   //2. This is padded to 14 bytes with the value "0xbdbdbdbdbdbd".
   //   Is it the string value or the hex value? Hex is right size.
   //3. This value is split into two 7-byte halves.
   memcpy(des_source_1, lm_hash, 7);
   memcpy(des_source_2, lm_hash+7, 1);
   for(i=1; i<7; i++) {
     des_source_2[i] = (char) 0xbd;
   }

   //4. These values are used to create two DES keys (one from each 7-byte
 half).
   setup_des_key(des_source_1, des_key_1);
   setup_des_key(des_source_2, des_key_2);

   //5. Each of these keys is used to DES-encrypt the first 8 bytes of the
 LM
   //   response (resulting in two 8-byte ciphertext values).
   //6. These two ciphertext values are concatenated to form a 16-byte
 value -
   //   the Lan Manager Session Key.
   des_ecb_encrypt(lm_response, (char*)(lan_manager_session_key),
 des_key_1);
   des_ecb_encrypt(lm_response, (char*)(lan_manager_session_key+8),
 des_key_2);

   //7. The client selects a random 16-byte key that will be used as the
 basis
   //   for signing and sealing.  This is RC4 encrypted using the Lan
 Manager
   //   Session key, and the encrypted value is sent to the server in the
 Type
   //   3 message (the session key field).
   gensesskey(full_session_key, NULL);
   arc4_encrypt(full_session_key, encrypted_session_key,
 lan_manager_session_key);
   //8. The 16-byte key from the previous step is weakened to 40 bits - the
 first
   //   5 bytes are retained, then padded to 8 bytes with 0xe538b0.
   for(i=0; i<5; i++) {
     session_key[i]=full_session_key[i];
   }
   session_key[5]=(char)0xe5;
   session_key[6]=(char)0x38;
   session_key[7]=(char)0xb0;
 }

 Some Excerpts from an earlier email from Anibal regarding computing of
 signature:
 The signature is computed using the
 session key across following fields:

 -  The From header URI
 -  The To header URI
 -  The From header tag
 -  The To header tag
 - The "crand" parameter in the Proxy-Authorization or the "srand"
 parameter in the Proxy-Authentication-Info header
 - The Expires value in the SIP message Expires header.

 The message body of the SIP message is not included in the signature.
 A proxy-authorization header contains either the gssapi-data parameter
 or the response (signature) parameter."

-- 
Ticket URL: <http://developer.pidgin.im/ticket/48#comment:71>
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