1/* hmac-md5.c -- hashed message authentication codes
2 Copyright (C) 2005-2006, 2009-2012 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, see <http://www.gnu.org/licenses/>. */
16
17/* Written by Simon Josefsson. */
18
19#include <config.h>
20
21#include "hmac.h"
22
23#include "memxor.h"
24#include "md5.h"
25
26#include <string.h>
27
28#define IPAD 0x36
29#define OPAD 0x5c
30
31int
32hmac_md5 (const void *key, size_t keylen,
33 const void *in, size_t inlen, void *resbuf)
34{
35 struct md5_ctx inner;
36 struct md5_ctx outer;
37 char optkeybuf[16];
38 char block[64];
39 char innerhash[16];
40
41 /* Reduce the key's size, so that it becomes <= 64 bytes large. */
42
43 if (keylen > 64)
44 {
45 struct md5_ctx keyhash;
46
47 md5_init_ctx (&keyhash);
48 md5_process_bytes (key, keylen, &keyhash);
49 md5_finish_ctx (&keyhash, optkeybuf);
50
51 key = optkeybuf;
52 keylen = 16;
53 }
54
55 /* Compute INNERHASH from KEY and IN. */
56
57 md5_init_ctx (&inner);
58
59 memset (block, IPAD, sizeof (block));
60 memxor (block, key, keylen);
61
62 md5_process_block (block, 64, &inner);
63 md5_process_bytes (in, inlen, &inner);
64
65 md5_finish_ctx (&inner, innerhash);
66
67 /* Compute result from KEY and INNERHASH. */
68
69 md5_init_ctx (&outer);
70
71 memset (block, OPAD, sizeof (block));
72 memxor (block, key, keylen);
73
74 md5_process_block (block, 64, &outer);
75 md5_process_bytes (innerhash, 16, &outer);
76
77 md5_finish_ctx (&outer, resbuf);
78
79 return 0;
80}
81