remove port suffix from JWT audience

src/php/lib/Grpc/BaseStub.php

@@ -199,6 +199,13 @@ class BaseStub
      */
     private function _get_jwt_aud_uri($method)
     {
+        // TODO(jtattermusch): This is not the correct implementation
+        // of extracting JWT "aud" claim. We should rely on
+        // grpc_metadata_credentials_plugin which
+        // also provides the correct value of "aud" claim
+        // in the grpc_auth_metadata_context.service_url field.
+        // Trying to do the construction of "aud" field ourselves
+        // is bad.
         $last_slash_idx = strrpos($method, '/');
         if ($last_slash_idx === false) {
             throw new \InvalidArgumentException(
@@ -213,6 +220,12 @@ class BaseStub
             $hostname = $this->hostname;
         }
 
+        // Remove the port if it is 443
+        // See https://github.com/grpc/grpc/blob/07c9f7a36b2a0d34fcffebc85649cf3b8c339b5d/src/core/lib/security/transport/client_auth_filter.cc#L205
+        if ((strlen($hostname) > 4) && (substr($hostname, -4) === ":443")) {
+            $hostname = substr($hostname, 0, -4);
+        }
+
         return 'https://'.$hostname.$service_name;
     }