mojo api for view based lockscreen

ash/login/lock_screen_controller.cc

+// Copyright 2017 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 "ash/login/lock_screen_controller.h"
+
+#include "chromeos/cryptohome/system_salt_getter.h"
+#include "chromeos/login/auth/user_context.h"
+
+namespace ash {
+
+LockScreenController::LockScreenController() {
+  chromeos::SystemSaltGetter::Get()->GetSystemSalt(base::Bind(
+      &LockScreenController::OnSaltObtained, base::Unretained(this)));
+}
+
+LockScreenController::~LockScreenController() {}
+
+void LockScreenController::BindRequest(mojom::LockScreenRequest request) {
+  bindings_.AddBinding(this, std::move(request));
+}
+
+void LockScreenController::AuthenticateUser(const AccountId& account_id,
+                                            const std::string& password,
+                                            bool authenticated_by_pin) {
+  // Hash password before sending through mojo.

[jdufault, 2017/05/13 00:57:40]

Instead of caching system_salt_ you can call through GetSystemSalt here so that
we always know system salt is available. Otherwise, it is possible this will run
before we have the system salt. This is unlikely on lock screen but we should
consider it for sign-in screen.

ie,

   chromeos::SystemSaltGetter::Get()->GetSystemSalt(
       base::Bind(&DoAuthenticateUser, account_id, password, ...));

[xiaoyinh(OOO Sep 11-29), 2017/05/15 20:13:05]

Good point, thanks! I keep the caching part with the hope to save some time of
getting the system salt for each authentication attempt.

+  chromeos::UserContext user_context(account_id);
+  chromeos::Key key(password);

[jdufault, 2017/05/13 00:57:39]

Unfortunately PIN is hashed differently. See [1]. Feel free to add a TODO.

https://cs.chromium.org/chromium/src/chrome/browser/chromeos/login/quick_unlo...

[xiaoyinh(OOO Sep 11-29), 2017/05/15 20:13:05]

Added a TODO. Thanks for the information.

+  key.Transform(chromeos::Key::KEY_TYPE_SALTED_SHA256_TOP_HALF, system_salt_);
+  if (lock_screen_client_) {
+    lock_screen_client_->AuthenticateUser(account_id, key.GetSecret(),
+                                          authenticated_by_pin);
+  }
+}
+
+void LockScreenController::SetClient(mojom::LockScreenClientPtr client) {
+  lock_screen_client_ = std::move(client);
+}
+
+void LockScreenController::ShowErrorMessage() {
+  NOTIMPLEMENTED();
+}
+
+void LockScreenController::ClearErrors() {
+  NOTIMPLEMENTED();
+}
+
+void LockScreenController::OnSaltObtained(const std::string& system_salt) {
+  system_salt_ = system_salt;
+}
+
+}  // namespace ash