hmac_memory.c

/* LibTomCrypt, modular cryptographic library -- Tom St Denis
 *
 * LibTomCrypt is a library that provides various cryptographic
 * algorithms in a highly modular and flexible manner.
 *
 * The library is free for all purposes without any express
 * guarantee it works.
 *
 * Tom St Denis, tomstdenis@iahu.ca, http://libtomcrypt.org
 */
/* Submited by Dobes Vandermeer  (dobes@smartt.com) */

#include "mycrypt.h"

/*
    (1) append zeros to the end of K to create a B byte string
        (e.g., if K is of length 20 bytes and B=64, then K will be
         appended with 44 zero bytes 0x00)
    (2) XOR (bitwise exclusive-OR) the B byte string computed in step
        (1) with ipad (ipad = the byte 0x36 repeated B times)
    (3) append the stream of data 'text' to the B byte string resulting
        from step (2)
    (4) apply H to the stream generated in step (3)
    (5) XOR (bitwise exclusive-OR) the B byte string computed in
        step (1) with opad (opad = the byte 0x5C repeated B times.)
    (6) append the H result from step (4) to the B byte string
        resulting from step (5)
    (7) apply H to the stream generated in step (6) and output
        the result
*/

#ifdef HMAC

#define HMAC_BLOCKSIZE hash_descriptor[hash].blocksize

int hmac_memory(int hash, const unsigned char *key, unsigned long keylen,
                const unsigned char *data, unsigned long len, 
                unsigned char *dst, unsigned long *dstlen)
{
    hmac_state hmac;
    int err;

    _ARGCHK(key    != NULL);
    _ARGCHK(data   != NULL);
    _ARGCHK(dst    != NULL); 
    _ARGCHK(dstlen != NULL);
    
    if((err = hash_is_valid(hash)) != CRYPT_OK) {
        return err;
    }

    if ((err = hmac_init(&hmac, hash, key, keylen)) != CRYPT_OK) {
        return err;
    }

    if ((err = hmac_process(&hmac, data, len)) != CRYPT_OK) {
       return err;
    }

    if ((err = hmac_done(&hmac, dst, dstlen)) != CRYPT_OK) {
       return err;
    }
    return CRYPT_OK;
}

#endif