Implementing gRPC Authentication

Server server = ServerBuilder.forPort(9090)
  .useTransportSecurity(new File("server.crt"), new File("server.key"))
  .addService(new MyService())
  .build();

Metadata md = new Metadata();
md.put(Metadata.Key.of("authorization", ASCII_STRING_MARSHALLER), "Bearer " + jwt);
MyServiceGrpc.newBlockingStub(channel)
  .withCallCredentials(MoreCallCredentials.from(googleCreds))
  .myMethod(req);

public class AuthInterceptor implements ServerInterceptor {
  public <Req, Resp> Listener<Req> interceptCall(ServerCall<Req,Resp> call, Metadata headers, ServerCallHandler<Req,Resp> next) {
    String auth = headers.get(AUTH_KEY);
    if (auth == null || !auth.startsWith("Bearer ")) {
      call.close(Status.UNAUTHENTICATED, new Metadata()); return new NoopListener<>();
    }
    Context ctx = Context.current().withValue(USER_CTX, verify(auth.substring(7)));
    return Contexts.interceptCall(ctx, call, headers, next);
  }
}