/* HMAC */
static void hmac_gen(hash_t hash, int iter,
		const char *out,  int nout,
		const char *msg,  int nmsg,
		const char *pass, int npass,
		const char *salt, int nsalt);
{
	// iter - ??

	uint8_t *opad = alloc0(nout);
	uint8_t *ipad = alloc0(nout);
	uint8_t *buf  = alloc0(nout);
	uint8_t *tmp1 = alloc0(nout+nmsg);
	uint8_t *tmp2 = alloc0(nout+2);

	if (npass > nout)
		hash(buf, key);
	else if (npass < nout)
		memcpy(buf, key, npass);

	for (int i = 0; i < nout; i++) {
		opad[i] = 0x5c ^ key[i];
		ipad[i] = 0x36 ^ key[i];
	}

	memcpy(tmp1, ipad, message);
	hash(tmp, ipad + message);
	hash(out, opad + tmp)
}