#include <stdio.h>
#include <string.h>
#include <openssl/x509.h>
#include <openssl/evp.h>
#include <openssl/hmac.h>

int main(int argc, char *argv[])
{
	unsigned char pass[1024];      // passphrase read from stdin
	unsigned char salt[1024];      // salt
	int salt_len;                  // salt length
	int ic;                        // iteration
	unsigned char result[1024];    // result
	FILE *fp_salt;

	if ( argc != 3 ) {
		fprintf(stderr, "usage: %s salt_file iteration < passwd_file > binary_key_file \n", argv[0]);
		exit(1);
	}

	ic = atoi(argv[2]);

	fp_salt = fopen(argv[1], "r");
	if(!fp_salt) {
		fprintf(stderr, "error opening salt file: %s\n", argv[1]);
		exit(2);
	}

	salt_len=0;
	int ch;
	while((ch = fgetc(fp_salt)) != EOF) {
		salt[salt_len++] = (unsigned char)ch;
	}

    fclose(fp_salt);

    fgets(pass, 1024, stdin);
    if ( pass[strlen(pass)-1] == '\n' )
		pass[strlen(pass)-1] = '\0';

	PKCS5_PBKDF2_HMAC_SHA1(pass, strlen(pass), salt, salt_len, ic, 16, result);

	fwrite(result, 1, 16, stdout);

	return(0);
}