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