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       1                 :            : /* digest.c --- Generate a CRAM-MD5 hex encoded HMAC-MD5 response string.
       2                 :            :  * Copyright (C) 2002-2012 Simon Josefsson
       3                 :            :  *
       4                 :            :  * This file is part of GNU SASL Library.
       5                 :            :  *
       6                 :            :  * GNU SASL Library is free software; you can redistribute it and/or
       7                 :            :  * modify it under the terms of the GNU Lesser General Public License
       8                 :            :  * as published by the Free Software Foundation; either version 2.1 of
       9                 :            :  * the License, or (at your option) any later version.
      10                 :            :  *
      11                 :            :  * GNU SASL Library is distributed in the hope that it will be useful,
      12                 :            :  * but WITHOUT ANY WARRANTY; without even the implied warranty of
      13                 :            :  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      14                 :            :  * Lesser General Public License for more details.
      15                 :            :  *
      16                 :            :  * You should have received a copy of the GNU Lesser General Public
      17                 :            :  * License along with GNU SASL Library; if not, write to the Free
      18                 :            :  * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
      19                 :            :  * Boston, MA 02110-1301, USA.
      20                 :            :  *
      21                 :            :  */
      22                 :            : 
      23                 :            : #include <string.h>
      24                 :            : 
      25                 :            : /* Get prototype. */
      26                 :            : #include "digest.h"
      27                 :            : 
      28                 :            : /* Get gc_hmac_md5. */
      29                 :            : #include "gc.h"
      30                 :            : 
      31                 :            : /*
      32                 :            :  * From draft-ietf-sasl-crammd5-02.txt:
      33                 :            :  *
      34                 :            :  *   The latter is computed by applying the keyed MD5 algorithm from
      35                 :            :  *   [KEYED-MD5] where the key is a shared secret and the digested
      36                 :            :  *   text is the challenge (including angle-brackets). The client
      37                 :            :  *   MUST NOT interpret or attempt to validate the contents of the
      38                 :            :  *   challenge in any way.
      39                 :            :  *
      40                 :            :  *   This shared secret is a string known only to the client and
      41                 :            :  *   server.  The "digest" parameter itself is a 16-octet value which
      42                 :            :  *   is sent in hexadecimal format, using lower-case US-ASCII
      43                 :            :  *   characters.
      44                 :            :  * ...
      45                 :            :  *   digest     = 32(DIGIT / %x61-66)
      46                 :            :  *   ; A hexadecimal string using only lower-case
      47                 :            :  *   ; letters
      48                 :            :  *
      49                 :            :  */
      50                 :            : 
      51                 :            : #if CRAM_MD5_DIGEST_LEN != 2*GC_MD5_DIGEST_SIZE
      52                 :            : #error MD5 length mismatch
      53                 :            : #endif
      54                 :            : 
      55                 :            : #define HEXCHAR(c) ((c & 0x0F) > 9 ? 'a' + (c & 0x0F) - 10 : '0' + (c & 0x0F))
      56                 :            : 
      57                 :            : void
      58                 :         22 : cram_md5_digest (const char *challenge,
      59                 :            :                  size_t challengelen,
      60                 :            :                  const char *secret,
      61                 :            :                  size_t secretlen, char response[CRAM_MD5_DIGEST_LEN])
      62                 :            : {
      63                 :            :   char hash[GC_MD5_DIGEST_SIZE];
      64                 :            :   size_t i;
      65                 :            : 
      66 [ -  + ][ -  + ]:         22 :   gc_hmac_md5 (secret, secretlen ? secretlen : strlen (secret),
      67                 :            :                challenge, challengelen ? challengelen : strlen (challenge),
      68                 :            :                hash);
      69                 :            : 
      70         [ +  + ]:        374 :   for (i = 0; i < GC_MD5_DIGEST_SIZE; i++)
      71                 :            :     {
      72         [ +  + ]:        352 :       *response++ = HEXCHAR (hash[i] >> 4);
      73         [ +  + ]:        352 :       *response++ = HEXCHAR (hash[i]);
      74                 :            :     }
      75                 :         22 : }