112 lines
3.1 KiB
C
112 lines
3.1 KiB
C
/* LibTomCrypt, modular cryptographic library -- Tom St Denis
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*
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* LibTomCrypt is a library that provides various cryptographic
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* algorithms in a highly modular and flexible manner.
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*
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* The library is free for all purposes without any express
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* guarantee it works.
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*
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* Tom St Denis, tomstdenis@iahu.ca, http://libtomcrypt.org
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*/
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/* Submited by Dobes Vandermeer (dobes@smartt.com) */
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#include "mycrypt.h"
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/*
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(1) append zeros to the end of K to create a B byte string
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(e.g., if K is of length 20 bytes and B=64, then K will be
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appended with 44 zero bytes 0x00)
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(2) XOR (bitwise exclusive-OR) the B byte string computed in step
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(1) with ipad (ipad = the byte 0x36 repeated B times)
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(3) append the stream of data 'text' to the B byte string resulting
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from step (2)
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(4) apply H to the stream generated in step (3)
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(5) XOR (bitwise exclusive-OR) the B byte string computed in
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step (1) with opad (opad = the byte 0x5C repeated B times.)
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(6) append the H result from step (4) to the B byte string
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resulting from step (5)
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(7) apply H to the stream generated in step (6) and output
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the result
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*/
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#ifdef HMAC
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#define HMAC_BLOCKSIZE hash_descriptor[hash].blocksize
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int hmac_init(hmac_state *hmac, int hash, const unsigned char *key, unsigned long keylen)
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{
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unsigned char *buf;
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unsigned long hashsize;
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unsigned long i, z;
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int err;
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_ARGCHK(hmac != NULL);
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_ARGCHK(key != NULL);
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/* valid hash? */
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if ((err = hash_is_valid(hash)) != CRYPT_OK) {
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return err;
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}
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hmac->hash = hash;
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hashsize = hash_descriptor[hash].hashsize;
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/* valid key length? */
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if (keylen == 0) {
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return CRYPT_INVALID_KEYSIZE;
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}
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/* allocate ram for buf */
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buf = XMALLOC(HMAC_BLOCKSIZE);
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if (buf == NULL) {
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return CRYPT_MEM;
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}
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/* allocate memory for key */
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hmac->key = XMALLOC(HMAC_BLOCKSIZE);
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if (hmac->key == NULL) {
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XFREE(buf);
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return CRYPT_MEM;
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}
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/* (1) make sure we have a large enough key */
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if(keylen > HMAC_BLOCKSIZE) {
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z = HMAC_BLOCKSIZE;
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if ((err = hash_memory(hash, key, keylen, hmac->key, &z)) != CRYPT_OK) {
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goto __ERR;
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}
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if(hashsize < HMAC_BLOCKSIZE) {
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zeromem((hmac->key) + hashsize, (size_t)(HMAC_BLOCKSIZE - hashsize));
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}
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keylen = hashsize;
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} else {
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XMEMCPY(hmac->key, key, (size_t)keylen);
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if(keylen < HMAC_BLOCKSIZE) {
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zeromem((hmac->key) + keylen, (size_t)(HMAC_BLOCKSIZE - keylen));
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}
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}
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/* Create the initial vector for step (3) */
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for(i=0; i < HMAC_BLOCKSIZE; i++) {
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buf[i] = hmac->key[i] ^ 0x36;
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}
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/* Pre-pend that to the hash data */
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hash_descriptor[hash].init(&hmac->md);
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if ((err = hash_descriptor[hash].process(&hmac->md, buf, HMAC_BLOCKSIZE)) != CRYPT_OK) {
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goto __ERR;
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}
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goto done;
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__ERR:
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/* free the key since we failed */
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XFREE(hmac->key);
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done:
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#ifdef CLEAN_STACK
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zeromem(buf, HMAC_BLOCKSIZE);
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#endif
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XFREE(buf);
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return err;
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}
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#endif
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