How can I allow only authorized user to access gRPC service?

The Authorize([Authorize]) attribute is used to allow only authorized user to access the service. 

[Authorize]
public class ExampleService
{
    
}

Please refer to the documentation for more details: https://learn.microsoft.com/en-us/aspnet/core/grpc/authn-and-authz?view=aspnetcore-7.0#authorize-users-to-access-services-and-service-methods