Initial skeletal implementation of the PrincipalService. Also, use the Login()/GetUserBlessing()

examples/echo/echo_server.cc

Index: examples/echo/echo_server.cc
diff --git a/examples/echo/echo_server.cc b/examples/echo/echo_server.cc
index 6ff79a68826c38f04029bd8db85b2ddab5eb4a79..520f7b351eb668c45d6b0ea45901de085b27ce04 100644
--- a/examples/echo/echo_server.cc
+++ b/examples/echo/echo_server.cc
@@ -7,9 +7,12 @@
 #include "mojo/public/c/system/main.h"
 #include "mojo/public/cpp/application/application_connection.h"
 #include "mojo/public/cpp/application/application_delegate.h"
+#include "mojo/public/cpp/application/application_impl.h"
 #include "mojo/public/cpp/application/application_runner.h"
 #include "mojo/public/cpp/application/interface_factory.h"
 #include "mojo/public/cpp/bindings/strong_binding.h"
+#include "mojo/public/cpp/utility/run_loop.h"
+#include "mojo/services/vanadium/security/public/interfaces/principal.mojom.h"
 
 namespace mojo {
 namespace examples {
@@ -48,15 +51,30 @@ class StrongBindingEchoImpl : public EchoImpl {
   mojo::StrongBinding<Echo> strong_binding_;
 };
 
+class GetBlessingResponse {
+ public:
+  void Run(const BlessingPtr& b) const {
+    // EchoClient user identity is available as b.get()->chain
+    RunLoop::current()->Quit();
+  }
+};
+
 // MultiServer creates a new object to handle each message pipe.
 class MultiServer : public mojo::ApplicationDelegate,
                     public mojo::InterfaceFactory<Echo> {
  public:
   MultiServer() {}
 
+  void Initialize(ApplicationImpl* app) override {
+    app->ConnectToService("mojo:go_principal_service", &login_service_);
+  }
+
   // From ApplicationDelegate
   bool ConfigureIncomingConnection(
       mojo::ApplicationConnection* connection) override {
+    AppInstanceNamePtr app(AppInstanceName::New());
+    app->url = connection->GetRemoteApplicationURL();
+    login_service_->GetUserBlessing(app.Pass(), GetBlessingResponse());
     connection->AddService<Echo>(this);
     return true;
   }
@@ -68,6 +86,9 @@ class MultiServer : public mojo::ApplicationDelegate,
     // StrongBinding<> for the declaration of |strong_binding_|.
     new StrongBindingEchoImpl(request.Pass());
   }
+
+ private:
+  PrincipalServicePtr login_service_;
 };
 
 // SingletonServer uses the same object to handle all message pipes. Useful