<?php

namespace Friendica\Security\OAuth1;

use Friendica\Security\OAuth1\OAuthRequest;

/**
 * The RSA-SHA1 signature method uses the RSASSA-PKCS1-v1_5 signature algorithm as defined in
 * [RFC3447] section 8.2 (more simply known as PKCS#1), using SHA-1 as the hash function for
 * EMSA-PKCS1-v1_5. It is assumed that the Consumer has provided its RSA public key in a
 * verified way to the Service Provider, in a manner which is beyond the scope of this
 * specification.
 *   - Chapter 9.3 ("RSA-SHA1")
 */
abstract class OAuthSignatureMethod_RSA_SHA1 extends OAuthSignatureMethod
{
	public function get_name()
	{
		return "RSA-SHA1";
	}

	// Up to the SP to implement this lookup of keys. Possible ideas are:
	// (1) do a lookup in a table of trusted certs keyed off of consumer
	// (2) fetch via http using a url provided by the requester
	// (3) some sort of specific discovery code based on request
	//
	// Either way should return a string representation of the certificate
	protected abstract function fetch_public_cert(&$request);

	// Up to the SP to implement this lookup of keys. Possible ideas are:
	// (1) do a lookup in a table of trusted certs keyed off of consumer
	//
	// Either way should return a string representation of the certificate
	protected abstract function fetch_private_cert(&$request);

	public function build_signature(OAuthRequest $request, \Friendica\Security\OAuth1\OAuthConsumer $consumer, \Friendica\Security\OAuth1\OAuthToken $token = null)
	{
		$base_string          = $request->get_signature_base_string();
		$request->base_string = $base_string;

		// Fetch the private key cert based on the request
		$cert = $this->fetch_private_cert($request);

		// Pull the private key ID from the certificate
		$privatekeyid = openssl_get_privatekey($cert);

		// Sign using the key
		openssl_sign($base_string, $signature, $privatekeyid);

		// Release the key resource
		openssl_free_key($privatekeyid);

		return base64_encode($signature);
	}

	public function check_signature(OAuthRequest $request, \Friendica\Security\OAuth1\OAuthConsumer $consumer, $signature, \Friendica\Security\OAuth1\OAuthToken $token = null)
	{
		$decoded_sig = base64_decode($signature);

		$base_string = $request->get_signature_base_string();

		// Fetch the public key cert based on the request
		$cert = $this->fetch_public_cert($request);

		// Pull the public key ID from the certificate
		$publickeyid = openssl_get_publickey($cert);

		// Check the computed signature against the one passed in the query
		$ok = openssl_verify($base_string, $decoded_sig, $publickeyid);

		// Release the key resource
		openssl_free_key($publickeyid);

		return $ok == 1;
	}
}