c hmac

1. hmac.pl

#!/usr/bin/perl

use strict;
use warnings;
use Digest::SHA qw(hmac_sha1_hex);

print hmac_sha1_hex("my data", "secret key") . "\n";

2. hmac.c

#include <stdio.h>
#include <stdlib.h>
#include <strings.h>
#include <openssl/hmac.h>

int main() {

  char* key = "secret key";
  char* data = "my data";
  char tmp[3];
  unsigned int result_len, i;
  unsigned char* result = malloc(sizeof(unsigned char) * result_len);

  HMAC_CTX ctx;
  HMAC_CTX_init(&ctx);
  HMAC_Init_ex(&ctx, (unsigned char*) key, strlen(key), EVP_sha1(), NULL);
  HMAC_Update(&ctx, (unsigned char*) data, strlen(data));
  HMAC_Final(&ctx, result, &result_len);
  HMAC_CTX_cleanup(&ctx);

  char* output = malloc(sizeof(char) * result_len);
  for (i = 0; i != result_len; i++)
  {
    //printf("Got %02X at byte %d\n", result[i], i);
    sprintf(tmp, "%02x", result[i]);
    strcat(output, tmp);
  }


  printf("output  : %s\n", output);
  printf("expected: %s\n", "97a62219092f3ddab3707cc9e85e63e926f45c87");

  return 0;
}

gistfile1.sh

$ perl hmac.pl
97a62219092f3ddab3707cc9e85e63e926f45c87

$ gcc -Wall -lcrypto hmac.c -o hmac  && ./hmac
output  : 97a62219092f3ddab3707cc9e85e63e926f45c87
expected: 97a62219092f3ddab3707cc9e85e63e926f45c87