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	hmac_sha1.c - pubsubhubbubblub - pubsubhubbub client implementation
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	hmac_sha1.c (1696B)
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	1 /* Adapted from RFC2104 hmac_md5, some code-style changes and data strea…
	2
	3 #include <string.h>
	4 #include <stdio.h>
	5
	6 #include "hmac_sha1.h"
	7
	8 void
	9 hmac_sha1_init(SHA_CTX ctx, const unsigned char key, size_t key_len,
	10 unsigned char *k_opad, size_t k_opadlen)
	11 {
	12 SHA_CTX tctx;
	13 unsigned char k_ipad[65]; /* inner padding - key XORd with ipad …
	14 unsigned char tk[20];
	15 int i;
	16
	17 /* if key is longer than 64 bytes reset it to key=SHA1(key) */
	18 if (key_len > 64) {
	19 SHA1_Init(&tctx);
	20 SHA1_Update(&tctx, key, key_len);
	21 SHA1_Final(tk, &tctx);
	22
	23 key = tk;
	24 key_len = 20;
	25 }
	26
	27 /*
	28 * the HMAC_SHA1 transform looks like:
	29 *
	30 * SHA1(K XOR opad, SHA1(K XOR ipad, text))
	31 *
	32 * where K is an n byte key
	33 * ipad is the byte 0x36 repeated 64 times
	34 * opad is the byte 0x5c repeated 64 times
	35 * and text is the data being protected
	36 */
	37
	38 /* start out by storing key in pads */
	39 memset(k_ipad, 0, sizeof(k_ipad));
	40 memset(k_opad, 0, k_opadlen);
	41 memcpy(k_ipad, key, key_len);
	42 memcpy(k_opad, key, key_len);
	43
	44 /* XOR key with ipad and opad values */
	45 for (i = 0; i < 64; i++) {
	46 k_ipad[i] ^= 0x36;
	47 k_opad[i] ^= 0x5c;
	48 }
	49 /* perform inner SHA1 */
	50 SHA1_Init(ctx); /* init context for 1st pass */
	51 SHA1_Update(ctx, k_ipad, 64); /* start with inner pad */
	52 }
	53
	54 void
	55 hmac_sha1_final(SHA_CTX ctx, const unsigned char k_opad, unsigned char…
	56 {
	57 SHA1_Final(digest, ctx); /* finish up 1st pass */
	58 /* perform outer SHA1 */
	59 SHA1_Init(ctx); /* init context for 2nd pass */
	60 SHA1_Update(ctx, k_opad, 64); /* start with outer pad */
	61 SHA1_Update(ctx, digest, 20); /* then results of 1st hash */
	62 SHA1_Final(digest, ctx); /* finish up 2nd pass */
	63 }