PBKDF2 based on OpenSSL implementation

gistfile1.m

static int PKCS5_PBKDF2_HMAC(CCHmacAlgorithm algorithm, int digestLength, const char *pass, int passlen,
						   const unsigned char *salt, int saltlen, int iter,
						   int keylen, unsigned char *out)
{
	unsigned char digtmp[digestLength], *p, itmp[4];
	int cplen, j, k, tkeylen;
	unsigned long i = 1;
	
	
	CCHmacContext ctx;

	p = out;
	tkeylen = keylen;
	if (!pass) passlen = 0;
	else if (passlen == -1) passlen = strlen(pass);
	
	while (tkeylen) {
		if(tkeylen > digestLength) cplen = digestLength;
		else cplen = tkeylen;
		/* We are unlikely to ever use more than 256 blocks (5120 bits!)
		 * but just in case...
		 */
		itmp[0] = (unsigned char)((i >> 24) & 0xff);
		itmp[1] = (unsigned char)((i >> 16) & 0xff);
		itmp[2] = (unsigned char)((i >> 8) & 0xff);
		itmp[3] = (unsigned char)(i & 0xff);

		CCHmacInit(&ctx, algorithm, pass, passlen);
		CCHmacUpdate(&ctx, salt, saltlen);
		CCHmacUpdate(&ctx, itmp, 4);
		CCHmacFinal(&ctx, digtmp);

		memcpy(p, digtmp, cplen);
		for(j = 1; j < iter; j++) {
			CCHmac(algorithm, pass, passlen, digtmp, digestLength, digtmp);
			for(k = 0; k < cplen; k++) p[k] ^= digtmp[k];
		}
		tkeylen -= cplen;
		i++;
		p += cplen;
	}

	return 1;
}