Allow identity providers which do not support the userinfo endpoint. (#100)

* Allow identity providers which do not support the userinfo endpoint.

* Fixed empty check for userinfo endpoint

.gitignore

@@ -0,0 +1,2 @@
+vendor/**/*
+composer.lock

includes/openid-connect-generic-client-wrapper.php

@@ -330,8 +330,12 @@ class OpenID_Connect_Generic_Client_Wrapper {
 			$this->error_redirect( $valid );
 		}
 		
-		// exchange the token_response for a user_claim
+		// if userinfo endpoint is set, exchange the token_response for a user_claim
+		if ( !empty( $this->settings->endpoint_userinfo ) && isset( $token_response['access_token'] )) {
 			$user_claim = $client->get_user_claim( $token_response );
+		} else {
+			$user_claim = $id_token_claim;
+		}
 		
 		if ( is_wp_error( $user_claim ) ){
 			$this->error_redirect( $user_claim );
@@ -655,7 +659,7 @@ class OpenID_Connect_Generic_Client_Wrapper {
 		}
 
 		// attempt another request for userinfo if some values are missing
-		if ( $values_missing && isset( $token_response['access_token'] ) ) {
+		if ( $values_missing && isset( $token_response['access_token'] ) && !empty( $this->settings->endpoint_userinfo) ) {
 			$user_claim_result = $this->client->request_userinfo( $token_response['access_token'] );
 
 			// make sure we didn't get an error

includes/openid-connect-generic-client.php

@@ -284,9 +284,9 @@ class OpenID_Connect_Generic_Client {
 	 * @return bool|\WP_Error
 	 */
 	function validate_token_response( $token_response ){
-		// we need to ensure 3 specific items exist with the token response in order
-		// to proceed with confidence:  id_token, access_token, and token_type == 'Bearer'
-		if ( ! isset( $token_response['id_token'] ) || ! isset( $token_response['access_token'] ) ||
+		// we need to ensure 2 specific items exist with the token response in order
+		// to proceed with confidence:  id_token and token_type == 'Bearer'
+		if ( ! isset( $token_response['id_token'] ) || 
 		     ! isset( $token_response['token_type'] ) || strcasecmp( $token_response['token_type'], 'Bearer' )
 		) {
 			return new WP_Error( 'invalid-token-response', 'Invalid token response', $token_response );