meillo@0: /*
meillo@0: ** Function: hmac_md5
meillo@0: */
meillo@0: 
meillo@0: #include <string.h>
meillo@0: #include "global.h"
meillo@0: #include "md5.h"
meillo@0: #include "hmac_md5.h"
meillo@0: 
meillo@10: void
meillo@10: hmac_md5(unsigned char *text, int text_len, unsigned char *key, int key_len, unsigned char *digest)
meillo@10: 	 /* text;     pointer to data stream */
meillo@10: 	 /* text_len; length of data stream */
meillo@10: 	 /* key;      pointer to authentication key */
meillo@10: 	 /* key_len;  length of authentication key */
meillo@10: 	 /* digest;   caller digest to be filled in */
meillo@10: {
meillo@10: 	MD5_CTX context;
meillo@10: 	unsigned char k_ipad[65];  /* inner padding - key XORd with ipad */
meillo@10: 	unsigned char k_opad[65];  /* outer padding - key XORd with opad */
meillo@10: 	unsigned char tk[16];
meillo@10: 	int i;
meillo@10: 	/* if key is longer than 64 bytes reset it to key=MD5(key) */
meillo@10: 	if (key_len > 64) {
meillo@0: 
meillo@10: 		MD5_CTX tctx;
meillo@0: 
meillo@10: 		MD5Init(&tctx);
meillo@10: 		MD5Update(&tctx, key, key_len);
meillo@10: 		MD5Final(tk, &tctx);
meillo@0: 
meillo@10: 		key = tk;
meillo@10: 		key_len = 16;
meillo@10: 	}
meillo@0: 
meillo@10: 	/*
meillo@10: 	 * the HMAC_MD5 transform looks like:
meillo@10: 	 *
meillo@10: 	 * MD5(K XOR opad, MD5(K XOR ipad, text))
meillo@10: 	 *
meillo@10: 	 * where K is an n byte key
meillo@10: 	 * ipad is the byte 0x36 repeated 64 times
meillo@10: 	 * opad is the byte 0x5c repeated 64 times
meillo@10: 	 * and text is the data being protected
meillo@10: 	 */
meillo@0: 
meillo@10: 	/* start out by storing key in pads */
meillo@10: 	bzero(k_ipad, sizeof k_ipad);
meillo@10: 	bzero(k_opad, sizeof k_opad);
meillo@10: 	bcopy(key, k_ipad, key_len);
meillo@10: 	bcopy(key, k_opad, key_len);
meillo@0: 
meillo@10: 	/* XOR key with ipad and opad values */
meillo@10: 	for (i = 0; i < 64; i++) {
meillo@10: 		k_ipad[i] ^= 0x36;
meillo@10: 		k_opad[i] ^= 0x5c;
meillo@10: 	}
meillo@10: 	/*
meillo@10: 	 * perform inner MD5
meillo@10: 	 */
meillo@10: 	MD5Init(&context);  /* init context for 1st pass */
meillo@10: 	MD5Update(&context, k_ipad, 64);  /* start with inner pad */
meillo@10: 	MD5Update(&context, text, text_len);  /* then text of datagram */
meillo@10: 	MD5Final(digest, &context);  /* finish up 1st pass */
meillo@10: 	/*
meillo@10: 	 * perform outer MD5
meillo@10: 	 */
meillo@10: 	MD5Init(&context);  /* init context for 2nd pass */
meillo@10: 	MD5Update(&context, k_opad, 64);  /* start with outer pad */
meillo@10: 	MD5Update(&context, digest, 16);  /* then results of 1st hash */
meillo@10: 	MD5Final(digest, &context); /* finish up 2nd pass */
meillo@0: }