lgl/hmac-md5.c

   1 /* hmac-md5.c -- hashed message authentication codes
   2    Copyright (C) 2005, 2006 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU Lesser General Public License as published by
   6    the Free Software Foundation; either version 2.1, or (at your option)
   7    any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public License
  15    along with this program; if not, write to the Free Software Foundation,
  16    Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
  17
  18 /* Written by Simon Josefsson.  */
  19
  20 #include <config.h>
  21
  22 #include "hmac.h"
  23
  24 #include "memxor.h"
  25 #include "md5.h"
  26
  27 #include <string.h>
  28
  29 #define IPAD 0x36
  30 #define OPAD 0x5c
  31
  32 int
  33 hmac_md5 (const void *key, size_t keylen,
  34           const void *in, size_t inlen, void *resbuf)
  35 {
  36   struct md5_ctx inner;
  37   struct md5_ctx outer;
  38   char optkeybuf[16];
  39   char block[64];
  40   char innerhash[16];
  41
  42   /* Reduce the key's size, so that it becomes <= 64 bytes large.  */
  43
  44   if (keylen > 64)
  45     {
  46       struct md5_ctx keyhash;
  47
  48       md5_init_ctx (&keyhash);
  49       md5_process_bytes (key, keylen, &keyhash);
  50       md5_finish_ctx (&keyhash, optkeybuf);
  51
  52       key = optkeybuf;
  53       keylen = 16;
  54     }
  55
  56   /* Compute INNERHASH from KEY and IN.  */
  57
  58   md5_init_ctx (&inner);
  59
  60   memset (block, IPAD, sizeof (block));
  61   memxor (block, key, keylen);
  62
  63   md5_process_block (block, 64, &inner);
  64   md5_process_bytes (in, inlen, &inner);
  65
  66   md5_finish_ctx (&inner, innerhash);
  67
  68   /* Compute result from KEY and INNERHASH.  */
  69
  70   md5_init_ctx (&outer);
  71
  72   memset (block, OPAD, sizeof (block));
  73   memxor (block, key, keylen);
  74
  75   md5_process_block (block, 64, &outer);
  76   md5_process_bytes (innerhash, 16, &outer);
  77
  78   md5_finish_ctx (&outer, resbuf);
  79
  80   return 0;
  81 }