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

examples/bank_app/bank.cc

Index: examples/bank_app/bank.cc
diff --git a/examples/bank_app/bank.cc b/examples/bank_app/bank.cc
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index 0000000000000000000000000000000000000000..d94bc1e8a2703975699986aac64e2a0f20698ae0
--- /dev/null
+++ b/examples/bank_app/bank.cc
@@ -0,0 +1,98 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "examples/bank_app/bank.mojom.h"
+#include "mojo/common/binding_set.h"
+#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 {

[jamesr, 2015/08/19 05:30:54]

drop the 'mojo::' part

[gautham, 2015/08/19 17:45:51]

Done.

+namespace examples {
+
+using namespace vanadium;

[jamesr, 2015/08/19 05:30:54]

google's C++ style guide (which we use) bans using-directives:
https://google-styleguide.googlecode.com/svn/trunk/cppguide.html#Namespaces. 
you can use using statements to pull specific types into the namespace

[gautham, 2015/08/19 17:45:51]

Done.

+
+class BankImpl : public Bank {
+ public:
+  BankImpl() : balance_(0) {}
+  void Deposit(int32_t usd) override { balance_ += usd; }
+  void Withdraw(int32_t usd) override { balance_ -= usd; }
+  void GetBalance(const GetBalanceCallback& callback) override {
+    callback.Run(balance_);
+  }
+ private:
+  int32_t balance_;
+};
+
+class BankUser {
+ public:
+  explicit BankUser(std::string* user) : user_(user) { }
+  void Run(const BlessingPtr& b) const {
+    user_->clear();
+    if (b) {
+      for (size_t i = 0; i < b->chain.size(); i++) {
+        user_->append("/");

[ashankar, 2015/08/19 05:50:38]

Should this separator "/" be defined as a mojom constant?
https://docs.google.com/document/d/1r7yCseBktlDEN9CKp_JWD0ZYxMi4GCsLXMvSN5sI0...

[gautham, 2015/08/19 17:45:50]

Done.

+        user_->append(b->chain[i]->extension);
+      }
+    }
+  }
+ private:
+  std::string *user_;
+};
+
+class BankApp : public mojo::ApplicationDelegate,
+                public mojo::InterfaceFactory<Bank> {
+ public:
+  BankApp() {
+  }
+  void Initialize(ApplicationImpl* app) override {
+    app->ConnectToService("mojo:principal_service", &login_service_);
+  }
+
+  // From ApplicationDelegate
+  bool ConfigureIncomingConnection(
+      mojo::ApplicationConnection* connection) override {
+    std::string url = connection->GetRemoteApplicationURL();
+    if (url.length() > 0) {
+      AppInstanceNamePtr app(AppInstanceName::New());
+      app->url = url;
+      std::string user;
+      login_service_->GetUserBlessing(app.Pass(), BankUser(&user));
+      login_service_.WaitForIncomingResponse();

[jamesr, 2015/08/19 05:30:54]

hmm - our c++ bindings let you choose whether to register services on a
connection at any time (i.e. you could curry the |connection| param along into a
callback and decide to call AddService<> based on that) but not a clean way to
close down a connection later.  we should probably fix that.

at a minimum you should check the return value of WaitForIncomingResponse(). if
it's false, that means the pipe closed before a reply was read which you should
treat as a failure to get a blessing (checking for an empty string is too
indirect imo)

[gautham, 2015/08/19 17:45:50]

Checked the return value and logged a failure for now. 

+      // Record user access to the bank and reject customers that
+      // don't have a user identity.
+      if (user.empty()) {
+        MOJO_LOG(INFO) << "Rejecting customer without a user identity";
+        return false;

[ashankar, 2015/08/19 05:50:38]

When would url.length be 0, and in that case why is it okay to connect to the
service unauthenticated?

(It might all be fine - my mojo mojo just isn't up to snuff to know that)

[gautham, 2015/08/19 17:45:50]

This happens I launch both mojo:customer and mojo:bank from the command line and
the shell connects to the bank? ie: the shell has an empty application url.

+      }
+      MOJO_LOG(INFO) << "Customer " << user << " accessing bank";
+    }
+    connection->AddService<Bank>(this);

[jamesr, 2015/08/19 05:30:54]

nit: i don't think you need the <Bank> part of this call, the template parameter
should be unambiguously deduced in this context

[gautham, 2015/08/19 17:45:51]

Done.

+    return true;
+  }
+
+  void Create(mojo::ApplicationConnection* connection,
+              mojo::InterfaceRequest<Bank> request) override {
+    bindings_.AddBinding(&bank_impl_, request.Pass());
+  }
+
+ private:
+  BankImpl bank_impl_;
+  mojo::BindingSet<Bank> bindings_;
+  PrincipalServicePtr login_service_;
+};
+
+}  // namespace examples
+}  // namespace mojo
+
+MojoResult MojoMain(MojoHandle application_request) {
+  mojo::ApplicationRunner runner(new mojo::examples::BankApp());
+  return runner.Run(application_request);
+}