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view src/md5/hmac_md5.c @ 210:e0938c511243
we need at least 32 bits, so let's take a long
Solar Designer explained to me that it was int for better performance
| author | meillo@marmaro.de |
|---|---|
| date | Sun, 18 Jul 2010 22:02:54 +0200 |
| parents | 26e34ae9a3e3 |
| children | 0f36c0a46f82 |
line source
1 /*
2 ** Function: hmac_md5
3 */
5 #include <string.h>
6 #include "md5.h"
7 #include "hmac_md5.h"
9 void
10 hmac_md5(unsigned char *text, int text_len, unsigned char *key, int key_len, unsigned char *digest)
11 /* text; pointer to data stream */
12 /* text_len; length of data stream */
13 /* key; pointer to authentication key */
14 /* key_len; length of authentication key */
15 /* digest; caller digest to be filled in */
16 {
17 MD5_CTX context;
18 unsigned char k_ipad[65]; /* inner padding - key XORd with ipad */
19 unsigned char k_opad[65]; /* outer padding - key XORd with opad */
20 unsigned char tk[16];
21 int i;
22 /* if key is longer than 64 bytes reset it to key=MD5(key) */
23 if (key_len > 64) {
25 MD5_CTX tctx;
27 MD5_Init(&tctx);
28 MD5_Update(&tctx, key, key_len);
29 MD5_Final(tk, &tctx);
31 key = tk;
32 key_len = 16;
33 }
35 /*
36 * the HMAC_MD5 transform looks like:
37 *
38 * MD5(K XOR opad, MD5(K XOR ipad, text))
39 *
40 * where K is an n byte key
41 * ipad is the byte 0x36 repeated 64 times
42 * opad is the byte 0x5c repeated 64 times
43 * and text is the data being protected
44 */
46 /* start out by storing key in pads */
47 bzero(k_ipad, sizeof k_ipad);
48 bzero(k_opad, sizeof k_opad);
49 bcopy(key, k_ipad, key_len);
50 bcopy(key, k_opad, key_len);
52 /* XOR key with ipad and opad values */
53 for (i = 0; i < 64; i++) {
54 k_ipad[i] ^= 0x36;
55 k_opad[i] ^= 0x5c;
56 }
57 /*
58 * perform inner MD5
59 */
60 MD5_Init(&context); /* init context for 1st pass */
61 MD5_Update(&context, k_ipad, 64); /* start with inner pad */
62 MD5_Update(&context, text, text_len); /* then text of datagram */
63 MD5_Final(digest, &context); /* finish up 1st pass */
64 /*
65 * perform outer MD5
66 */
67 MD5_Init(&context); /* init context for 2nd pass */
68 MD5_Update(&context, k_opad, 64); /* start with outer pad */
69 MD5_Update(&context, digest, 16); /* then results of 1st hash */
70 MD5_Final(digest, &context); /* finish up 2nd pass */
71 }