hmac.c

/* 
 libpwsafe - a portable implementation of the passwordsafe format
 Copyright © 2011 Noa Resare 
 
 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.
 
 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.
 
 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <string.h>

#include "sph_sha2.h"
#include "hmac.h"

#ifdef TEST
#include <stdio.h>
#endif

/* block size in bytes of SHA256 */
#define BLOCK_SIZE 64

/* hash output size in bytes for SHA256 */
#define HASH_SIZE 32

/**
 * Initialize the HMAC state stucture 
 */
void hmac_init(hmac_state *state, unsigned char *key, int key_length)
{
    unsigned char tmp[BLOCK_SIZE] = {0};
    int i;
    sph_sha256_context c;

    if (key_length > BLOCK_SIZE) {
        sph_sha256_init(&c);
        sph_sha256(&c, key, key_length);
        sph_sha256_close(&c, tmp);
    } else {
        memcpy(tmp, key, key_length);
    }        

    sph_sha256_init(&state->inner);
    sph_sha256_init(&state->outer);

    for (i = 0; i < BLOCK_SIZE; i++) {
        tmp[i] = tmp[i] ^ 0x36;
        
    }
    sph_sha256(&state->inner, tmp, BLOCK_SIZE);
    for (i = 0; i < BLOCK_SIZE; i++) {
        tmp[i] = tmp[i] ^ (0x36 ^ 0x5c);

    }
    sph_sha256(&state->outer, tmp, BLOCK_SIZE);
}

void hmac_update(hmac_state *state, unsigned char *data, int count)
{
    sph_sha256(&state->inner, data, count);
}

void hmac_result(hmac_state *state, unsigned char *result)
{
    unsigned char tmp[32];
    sph_sha256_close(&state->inner, tmp);
    sph_sha256(&state->outer, tmp, 32);
    sph_sha256_close(&state->outer, result);
}

#ifdef TEST

static void print_hex(unsigned char *data, int len)
{
    int i;
    for (i = 0; i < len; i++) {
      printf("%02hhx ", data[i]);
    }
    printf("\n");
}


int main(int argc, char **argv)
{
    unsigned char result[32];
    hmac_state state;
    char *key = "key";  
    char *data = "The quick brown fox jumps over the lazy dog";  
    
    hmac_init(&state, (unsigned char*)key, strlen(key));
    hmac_update(&state, (unsigned char*)data, strlen(data));
    hmac_result(&state, result);
    
    print_hex(result, 32);
    return 0;    
}

#endif