lib/cram-md5/digest.c

   1 /* digest.c --- Generate a CRAM-MD5 hex encoded HMAC-MD5 response string.
   2  * Copyright (C) 2002, 2003, 2004, 2005  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 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   gc_hmac_md5 (secret, secretlen ? secretlen : strlen (secret),
  67                challenge, challengelen ? challengelen : strlen (challenge),
  68                hash);
  69
  70   for (i = 0; i < GC_MD5_DIGEST_SIZE; i++)
  71     {
  72       *response++ = HEXCHAR (hash[i] >> 4);
  73       *response++ = HEXCHAR (hash[i]);
  74     }
  75 }