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<?php
namespace PayPal\Auth\Oauth;
/**
 * 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 OAuthSignatureMethodRsaSha1 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($request, $consumer, $token) {
                $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
                $ok = openssl_sign($base_string, $signature, $privatekeyid);

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

                return base64_encode($signature);
        }

        public function check_signature($request, $consumer, $token, $signature) {
                $decoded_sig = base64_decode($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;
        }
}