Reauthenticate the user before launching Smart Lock setup app.

The reauth is needed to acquire the user's password to add a new cryptohome
key for sign-in.

BUG=409427

Review URL: https://codereview.chromium.org/668213003

Cr-Commit-Position: refs/heads/master@{#302541}

13 files changed, 395 insertions, 16 deletions

diff --git a/chrome/app/generated_resources.grd b/chrome/app/generated_resources.grd
index 07f06be..3a3bc47 100644
--- a/chrome/app/generated_resources.grd
+++ b/chrome/app/generated_resources.grd
@@ -14889,6 +14889,9 @@ Do you accept?
     <message name="IDS_EASY_UNLOCK_SCREENLOCK_TOOLTIP_LOGIN_FAILURE" desc="Tooltip text shown on a user's lock screen when Smart Lock signin attempt fails.">
       Smart Lock couldn't verify your account. Type your password to enter.
     </message>
+    <message name="IDS_SMART_LOCK_SCREENLOCK_TOOLTIP_HARDLOCK_REAUTH_USER" desc="Tooltip text shown on a user's lock screen pod to reauthenticate the user before setting up Smart Lock. A password has to be entered to unlock the device.">
+      To set up Chrome Smart Lock, Google needs to make sure it's you--type your password to get started.
+    </message>
     <message name="IDS_EASY_UNLOCK_SCREENLOCK_USER_POD_AUTH_VALUE" desc="Message on lock screen user pod shown in place of password field when Easy Unlock is enabled and a phone that can unlock the Chromebook is detected in proximity.">
       Click to enter
     </message>
diff --git a/chrome/browser/chromeos/login/easy_unlock/easy_unlock_reauth.cc b/chrome/browser/chromeos/login/easy_unlock/easy_unlock_reauth.cc
new file mode 100644
index 0000000..a19360d
--- /dev/null
+++ b/chrome/browser/chromeos/login/easy_unlock/easy_unlock_reauth.cc
@@ -0,0 +1,130 @@
+// Copyright 2014 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 "base/bind.h"
+#include "base/message_loop/message_loop.h"
+#include "chrome/browser/chrome_notification_types.h"
+#include "chrome/browser/chromeos/login/easy_unlock/easy_unlock_reauth.h"
+#include "chrome/browser/chromeos/login/lock/screen_locker.h"
+#include "chrome/browser/signin/screenlock_bridge.h"
+#include "chrome/grit/generated_resources.h"
+#include "chromeos/dbus/dbus_thread_manager.h"
+#include "chromeos/dbus/session_manager_client.h"
+#include "chromeos/login/auth/auth_status_consumer.h"
+#include "chromeos/login/auth/user_context.h"
+#include "content/public/browser/notification_details.h"
+#include "content/public/browser/notification_observer.h"
+#include "content/public/browser/notification_registrar.h"
+#include "content/public/browser/notification_service.h"
+#include "ui/base/l10n/l10n_util.h"
+
+namespace chromeos {
+
+namespace {
+
+void EndReauthAttempt();
+
+// Performs the actual reauth flow and returns the user context it obtains.
+class ReauthHandler : public content::NotificationObserver,
+                      public chromeos::AuthStatusConsumer {
+ public:
+  explicit ReauthHandler(EasyUnlockReauth::UserContextCallback callback)
+      : callback_(callback) {}
+
+  virtual ~ReauthHandler() {}
+
+  bool Start() {
+    ScreenLocker* screen_locker = ScreenLocker::default_screen_locker();
+    if (screen_locker && screen_locker->locked()) {
+      NOTREACHED();
+      return false;
+    }
+
+    user_manager::UserManager* user_manager = user_manager::UserManager::Get();
+    if (user_manager->GetPrimaryUser() != user_manager->GetActiveUser() ||
+        user_manager->GetUnlockUsers().size() != 1) {
+      LOG(WARNING) << "Only primary users in non-multiprofile sessions are "
+                   << "currently supported for reauth.";
+      return false;
+    }
+
+    notification_registrar_.Add(this,
+                                chrome::NOTIFICATION_SCREEN_LOCK_STATE_CHANGED,
+                                content::NotificationService::AllSources());
+
+    SessionManagerClient* session_manager =
+        chromeos::DBusThreadManager::Get()->GetSessionManagerClient();
+    session_manager->RequestLockScreen();
+    return true;
+  }
+
+  // content::NotificationObserver
+  void Observe(int type,
+               const content::NotificationSource& source,
+               const content::NotificationDetails& details) override {
+    CHECK(type == chrome::NOTIFICATION_SCREEN_LOCK_STATE_CHANGED);
+    bool is_screen_locked = *content::Details<bool>(details).ptr();
+    DCHECK(is_screen_locked);
+    notification_registrar_.RemoveAll();
+
+    // TODO(tengs): Add an explicit reauth state to the locker and account
+    // picker, so we can customize the UI.
+    ScreenLocker* screen_locker = ScreenLocker::default_screen_locker();
+    screen_locker->SetLoginStatusConsumer(this);
+
+    // Show tooltip explaining reauth.
+    ScreenlockBridge::UserPodCustomIconOptions icon_options;
+    icon_options.SetIcon(ScreenlockBridge::USER_POD_CUSTOM_ICON_NONE);
+    icon_options.SetTooltip(
+        l10n_util::GetStringUTF16(
+            IDS_SMART_LOCK_SCREENLOCK_TOOLTIP_HARDLOCK_REAUTH_USER),
+        true);
+
+    const user_manager::UserList& lock_users = screen_locker->users();
+    DCHECK(lock_users.size() == 1);
+    ScreenlockBridge::Get()->lock_handler()->ShowUserPodCustomIcon(
+        lock_users[0]->email(), icon_options);
+  }
+
+  // chromeos::AuthStatusConsumer:
+  virtual void OnAuthSuccess(
+      const chromeos::UserContext& user_context) override {
+    callback_.Run(user_context);
+    // Schedule deletion.
+    base::MessageLoopForUI::current()->PostTask(FROM_HERE,
+                                                base::Bind(&EndReauthAttempt));
+  }
+
+  virtual void OnAuthFailure(const chromeos::AuthFailure& error) override {}
+
+ private:
+  content::NotificationRegistrar notification_registrar_;
+  EasyUnlockReauth::UserContextCallback callback_;
+
+  DISALLOW_COPY_AND_ASSIGN(ReauthHandler);
+};
+
+ReauthHandler* g_reauth_handler = NULL;
+
+void EndReauthAttempt() {
+  DCHECK(base::MessageLoopForUI::IsCurrent());
+  DCHECK(g_reauth_handler);
+  delete g_reauth_handler;
+  g_reauth_handler = NULL;
+}
+
+}  // namespace
+
+// static.
+bool EasyUnlockReauth::ReauthForUserContext(
+    base::Callback<void(const UserContext&)> callback) {
+  DCHECK(base::MessageLoopForUI::IsCurrent());
+  if (g_reauth_handler)
+    return false;
+
+  g_reauth_handler = new ReauthHandler(callback);
+  return g_reauth_handler->Start();
+}
+
+}  // namespace chromeos
diff --git a/chrome/browser/chromeos/login/easy_unlock/easy_unlock_reauth.h b/chrome/browser/chromeos/login/easy_unlock/easy_unlock_reauth.h
new file mode 100644
index 0000000..041dc87
--- /dev/null
+++ b/chrome/browser/chromeos/login/easy_unlock/easy_unlock_reauth.h
@@ -0,0 +1,31 @@
+// Copyright 2014 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.
+
+#ifndef CHROME_BROWSER_CHROMEOS_LOGIN_EASY_UNLOCK_EASY_UNLOCK_REAUTH_H_
+#define CHROME_BROWSER_CHROMEOS_LOGIN_EASY_UNLOCK_EASY_UNLOCK_REAUTH_H_
+
+#include "base/callback_forward.h"
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+
+namespace chromeos {
+
+class UserContext;
+
+// Responsible for locking the screen and reauthenticating the user so we can
+// create new cryptohome keys for passwordless sign-in.
+class EasyUnlockReauth {
+ public:
+  typedef base::Callback<void(const UserContext&)> UserContextCallback;
+
+  // Launches the reauth screen to get the user context. If the screen fails
+  // for some reason, then this function will return false.
+  static bool ReauthForUserContext(UserContextCallback callback);
+
+  DISALLOW_IMPLICIT_CONSTRUCTORS(EasyUnlockReauth);
+};
+
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_LOGIN_EASY_UNLOCK_EASY_UNLOCK_REAUTH_H_
diff --git a/chrome/browser/chromeos/login/easy_unlock/short_lived_user_context.cc b/chrome/browser/chromeos/login/easy_unlock/short_lived_user_context.cc
new file mode 100644
index 0000000..41283cc
--- /dev/null
+++ b/chrome/browser/chromeos/login/easy_unlock/short_lived_user_context.cc
@@ -0,0 +1,55 @@
+// Copyright 2014 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 "chrome/browser/chromeos/login/easy_unlock/short_lived_user_context.h"
+
+#include "base/bind.h"
+#include "base/location.h"
+#include "base/task_runner.h"
+#include "chrome/common/extensions/extension_constants.h"
+#include "chromeos/login/auth/user_context.h"
+
+namespace chromeos {
+
+namespace {
+
+// The number of minutes that the user context will be stored.
+const int64 kUserContextTimeToLiveMinutes = 10;
+
+}  // namespace
+
+ShortLivedUserContext::ShortLivedUserContext(
+    const UserContext& user_context,
+    apps::AppLifetimeMonitor* app_lifetime_monitor,
+    base::TaskRunner* task_runner)
+    : user_context_(new UserContext(user_context)),
+      app_lifetime_monitor_(app_lifetime_monitor),
+      weak_ptr_factory_(this) {
+  app_lifetime_monitor_->AddObserver(this);
+
+  task_runner->PostDelayedTask(
+      FROM_HERE,
+      base::Bind(&ShortLivedUserContext::Reset, weak_ptr_factory_.GetWeakPtr()),
+      base::TimeDelta::FromMinutes(kUserContextTimeToLiveMinutes));
+}
+
+ShortLivedUserContext::~ShortLivedUserContext() {
+  Reset();
+}
+
+void ShortLivedUserContext::Reset() {
+  if (user_context_.get()) {
+    user_context_->ClearSecrets();
+    user_context_.reset();
+    app_lifetime_monitor_->RemoveObserver(this);
+  }
+}
+
+void ShortLivedUserContext::OnAppDeactivated(Profile* profile,
+                                             const std::string& app_id) {
+  if (app_id == extension_misc::kEasyUnlockAppId)
+    Reset();
+}
+
+}  // namespace chromeos
diff --git a/chrome/browser/chromeos/login/easy_unlock/short_lived_user_context.h b/chrome/browser/chromeos/login/easy_unlock/short_lived_user_context.h
new file mode 100644
index 0000000..7e4bdabc
--- /dev/null
+++ b/chrome/browser/chromeos/login/easy_unlock/short_lived_user_context.h
@@ -0,0 +1,53 @@
+// Copyright 2014 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.
+
+#ifndef CHROME_BROWSER_CHROMEOS_LOGIN_EASY_UNLOCK_SHORT_LIVED_USER_CONTEXT_H_
+#define CHROME_BROWSER_CHROMEOS_LOGIN_EASY_UNLOCK_SHORT_LIVED_USER_CONTEXT_H_
+
+#include "apps/app_lifetime_monitor.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
+
+namespace base {
+class TaskRunner;
+}
+
+namespace chromeos {
+
+class UserContext;
+
+// Stores the UserContext of an authentication operation on the sign-in/lock
+// screen, which is used to generate the keys for Easy Sign-in.
+// The lifetime of the user context is bound the the setup app window. As a
+// fail-safe, the user context will also be deleted after a set period of time
+// in case the app is left open indefintely.
+class ShortLivedUserContext : public apps::AppLifetimeMonitor::Observer {
+ public:
+  ShortLivedUserContext(const UserContext& user_context,
+                        apps::AppLifetimeMonitor* app_lifetime_monitor,
+                        base::TaskRunner* task_runner);
+  virtual ~ShortLivedUserContext();
+
+  // The UserContext returned here can be NULL if its time-to-live has expired.
+  UserContext* user_context() { return user_context_.get(); }
+
+ private:
+  void Reset();
+
+  // apps::AppLifetimeMonitor::Observer:
+  virtual void OnAppDeactivated(Profile* profile,
+                                const std::string& app_id) override;
+
+  scoped_ptr<UserContext> user_context_;
+
+  apps::AppLifetimeMonitor* app_lifetime_monitor_;
+
+  base::WeakPtrFactory<ShortLivedUserContext> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(ShortLivedUserContext);
+};
+
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_LOGIN_EASY_UNLOCK_SHORT_LIVED_USER_CONTEXT_H_
diff --git a/chrome/browser/signin/easy_unlock_service.cc b/chrome/browser/signin/easy_unlock_service.cc
index cb498dd..6144119 100644
--- a/chrome/browser/signin/easy_unlock_service.cc
+++ b/chrome/browser/signin/easy_unlock_service.cc
@@ -383,7 +383,7 @@ void EasyUnlockService::CheckCryptohomeKeysAndMaybeHardlock() {
     chromeos::EasyUnlockKeyManager::RemoteDeviceListToDeviceDataList(
         *device_list, &parsed_paired);
     for (const auto& device_key_data : parsed_paired)
-      paired_devices.insert(device_key_data.public_key);
+      paired_devices.insert(device_key_data.psk);
   }
   if (paired_devices.empty()) {
     SetHardlockState(EasyUnlockScreenlockStateHandler::NO_PAIRING);
@@ -618,7 +618,7 @@ void EasyUnlockService::OnCryptohomeKeysFetchedForChecking(
 
   std::set<std::string> devices_in_cryptohome;
   for (const auto& device_key_data : key_data_list)
-    devices_in_cryptohome.insert(device_key_data.public_key);
+    devices_in_cryptohome.insert(device_key_data.psk);
 
   if (paired_devices != devices_in_cryptohome ||
       GetHardlockState() == EasyUnlockScreenlockStateHandler::NO_PAIRING) {
diff --git a/chrome/browser/signin/easy_unlock_service.h b/chrome/browser/signin/easy_unlock_service.h
index 1f256a1..ade435b 100644
--- a/chrome/browser/signin/easy_unlock_service.h
+++ b/chrome/browser/signin/easy_unlock_service.h
@@ -215,6 +215,12 @@ class EasyUnlockService : public KeyedService {
     return screenlock_state_handler_.get();
   }
 
+  // Saves hardlock state for the given user. Update UI if the currently
+  // associated user is the same.
+  void SetHardlockStateForUser(
+      const std::string& user_id,
+      EasyUnlockScreenlockStateHandler::HardlockState state);
+
  private:
   // A class to detect whether a bluetooth adapter is present.
   class BluetoothDetector;
@@ -231,12 +237,6 @@ class EasyUnlockService : public KeyedService {
   // Callback when Bluetooth adapter present state changes.
   void OnBluetoothAdapterPresentChanged();
 
-  // Saves hardlock state for the given user. Update UI if the currently
-  // associated user is the same.
-  void SetHardlockStateForUser(
-      const std::string& user_id,
-      EasyUnlockScreenlockStateHandler::HardlockState state);
-
 #if defined(OS_CHROMEOS)
   // Callback for get key operation from CheckCryptohomeKeysAndMaybeHardlock.
   void OnCryptohomeKeysFetchedForChecking(
diff --git a/chrome/browser/signin/easy_unlock_service_regular.cc b/chrome/browser/signin/easy_unlock_service_regular.cc
index 870d663..fb027f3 100644
--- a/chrome/browser/signin/easy_unlock_service_regular.cc
+++ b/chrome/browser/signin/easy_unlock_service_regular.cc
@@ -18,9 +18,15 @@
 #include "chrome/common/extensions/extension_constants.h"
 #include "chrome/common/pref_names.h"
 #include "components/pref_registry/pref_registry_syncable.h"
+#include "content/public/browser/browser_thread.h"
 #include "extensions/browser/extension_system.h"
 
 #if defined(OS_CHROMEOS)
+#include "apps/app_lifetime_monitor_factory.h"
+#include "base/thread_task_runner_handle.h"
+#include "chrome/browser/chromeos/login/easy_unlock/easy_unlock_key_manager.h"
+#include "chrome/browser/chromeos/login/easy_unlock/easy_unlock_reauth.h"
+#include "chrome/browser/chromeos/login/session/user_session_manager.h"
 #include "chrome/browser/chromeos/profiles/profile_helper.h"
 #include "components/user_manager/user_manager.h"
 #endif
@@ -40,7 +46,8 @@ const char kKeyPhoneId[] = "permitRecord.id";
 
 EasyUnlockServiceRegular::EasyUnlockServiceRegular(Profile* profile)
     : EasyUnlockService(profile),
-      turn_off_flow_status_(EasyUnlockService::IDLE) {
+      turn_off_flow_status_(EasyUnlockService::IDLE),
+      weak_ptr_factory_(this) {
 }
 
 EasyUnlockServiceRegular::~EasyUnlockServiceRegular() {
@@ -55,6 +62,52 @@ std::string EasyUnlockServiceRegular::GetUserEmail() const {
 }
 
 void EasyUnlockServiceRegular::LaunchSetup() {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+#if defined(OS_CHROMEOS)
+  // Force the user to reauthenticate by showing a modal overlay (similar to the
+  // lock screen). The password obtained from the reauth is cached for a short
+  // period of time and used to create the cryptohome keys for sign-in.
+  if (short_lived_user_context_ && short_lived_user_context_->user_context()) {
+    OpenSetupApp();
+  } else {
+    bool reauth_success = chromeos::EasyUnlockReauth::ReauthForUserContext(
+        base::Bind(&EasyUnlockServiceRegular::OnUserContextFromReauth,
+                   weak_ptr_factory_.GetWeakPtr()));
+    if (!reauth_success)
+      OpenSetupApp();
+  }
+#else
+  OpenSetupApp();
+#endif
+}
+
+#if defined(OS_CHROMEOS)
+void EasyUnlockServiceRegular::OnUserContextFromReauth(
+    const chromeos::UserContext& user_context) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  short_lived_user_context_.reset(new chromeos::ShortLivedUserContext(
+      user_context, apps::AppLifetimeMonitorFactory::GetForProfile(profile()),
+      base::ThreadTaskRunnerHandle::Get().get()));
+
+  OpenSetupApp();
+}
+
+void EasyUnlockServiceRegular::OnKeysRefreshedForSetDevices(bool success) {
+  // If the keys were refreshed successfully, the hardlock state should be
+  // cleared, so Smart Lock can be used normally. Otherwise, we fall back to
+  // a hardlock state to force the user to type in their credentials again.
+  if (success) {
+    SetHardlockStateForUser(GetUserEmail(),
+                            EasyUnlockScreenlockStateHandler::NO_HARDLOCK);
+  }
+
+  // Even if the keys refresh suceeded, we still fetch the cryptohome keys as a
+  // sanity check.
+  CheckCryptohomeKeysAndMaybeHardlock();
+}
+#endif
+
+void EasyUnlockServiceRegular::OpenSetupApp() {
   ExtensionService* service =
       extensions::ExtensionSystem::Get(profile())->extension_service();
   const extensions::Extension* extension =
@@ -103,7 +156,29 @@ void EasyUnlockServiceRegular::SetRemoteDevices(
   DictionaryPrefUpdate pairing_update(profile()->GetPrefs(),
                                       prefs::kEasyUnlockPairing);
   pairing_update->SetWithoutPathExpansion(kKeyDevices, devices.DeepCopy());
+
+#if defined(OS_CHROMEOS)
+  // TODO(tengs): Investigate if we can determine if the remote devices were set
+  // from sync or from the setup app.
+  if (short_lived_user_context_ && short_lived_user_context_->user_context() &&
+      !devices.empty()) {
+    // We may already have the password cached, so proceed to create the
+    // cryptohome keys for sign-in or the system will be hardlocked.
+    chromeos::UserContext* user_context =
+        short_lived_user_context_->user_context();
+    chromeos::EasyUnlockKeyManager* key_manager =
+        chromeos::UserSessionManager::GetInstance()->GetEasyUnlockKeyManager();
+
+    key_manager->RefreshKeys(
+        *user_context, devices,
+        base::Bind(&EasyUnlockServiceRegular::OnKeysRefreshedForSetDevices,
+                   weak_ptr_factory_.GetWeakPtr()));
+  } else {
+    CheckCryptohomeKeysAndMaybeHardlock();
+  }
+#else
   CheckCryptohomeKeysAndMaybeHardlock();
+#endif
 }
 
 void EasyUnlockServiceRegular::ClearRemoteDevices() {
@@ -184,6 +259,10 @@ void EasyUnlockServiceRegular::InitializeInternal() {
 }
 
 void EasyUnlockServiceRegular::ShutdownInternal() {
+#if defined(OS_CHROMEOS)
+  short_lived_user_context_.reset();
+#endif
+
   turn_off_flow_.reset();
   turn_off_flow_status_ = EasyUnlockService::IDLE;
   registrar_.RemoveAll();
diff --git a/chrome/browser/signin/easy_unlock_service_regular.h b/chrome/browser/signin/easy_unlock_service_regular.h
index 749b583..3a48585 100644
--- a/chrome/browser/signin/easy_unlock_service_regular.h
+++ b/chrome/browser/signin/easy_unlock_service_regular.h
@@ -12,6 +12,10 @@
 #include "base/prefs/pref_change_registrar.h"
 #include "chrome/browser/signin/easy_unlock_service.h"
 
+#if defined(OS_CHROMEOS)
+#include "chrome/browser/chromeos/login/easy_unlock/short_lived_user_context.h"
+#endif
+
 namespace base {
 class DictionaryValue;
 class ListValue;
@@ -50,6 +54,9 @@ class EasyUnlockServiceRegular : public EasyUnlockService {
   void ShutdownInternal() override;
   bool IsAllowedInternal() override;
 
+  // Opens the component packaged app responsible for setting up Smart Lock.
+  void OpenSetupApp();
+
   // Callback when the controlling pref changes.
   void OnPrefsChanged();
 
@@ -59,11 +66,20 @@ class EasyUnlockServiceRegular : public EasyUnlockService {
   // Callback invoked when turn off flow has finished.
   void OnTurnOffFlowFinished(bool success);
 
+#if defined(OS_CHROMEOS)
+  void OnUserContextFromReauth(const chromeos::UserContext& user_context);
+  void OnKeysRefreshedForSetDevices(bool success);
+
+  scoped_ptr<chromeos::ShortLivedUserContext> short_lived_user_context_;
+#endif
+
   PrefChangeRegistrar registrar_;
 
   TurnOffFlowStatus turn_off_flow_status_;
   scoped_ptr<EasyUnlockToggleFlow> turn_off_flow_;
 
+  base::WeakPtrFactory<EasyUnlockServiceRegular> weak_ptr_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(EasyUnlockServiceRegular);
 };
 
diff --git a/chrome/browser/signin/screenlock_bridge.cc b/chrome/browser/signin/screenlock_bridge.cc
index 5fb5192..c2d7224 100644
--- a/chrome/browser/signin/screenlock_bridge.cc
+++ b/chrome/browser/signin/screenlock_bridge.cc
@@ -62,9 +62,6 @@ scoped_ptr<base::DictionaryValue>
 ScreenlockBridge::UserPodCustomIconOptions::ToDictionaryValue() const {
   scoped_ptr<base::DictionaryValue> result(new base::DictionaryValue());
   std::string icon_id = GetIdForIcon(icon_);
-  if (icon_id.empty())
-    return result.Pass();
-
   result->SetString("id", icon_id);
 
   if (!tooltip_.empty()) {
diff --git a/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc b/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc
index 6c5f84b..2cfb24d 100644
--- a/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc
+++ b/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc
@@ -1242,10 +1242,10 @@ void SigninScreenHandler::HandleAccountPickerReady() {
   is_account_picker_showing_first_time_ = true;
   gaia_screen_handler_->MaybePreloadAuthExtension();
 
+  ScreenlockBridge::Get()->SetLockHandler(this);
   if (ScreenLocker::default_screen_locker()) {
     ScreenLocker::default_screen_locker()->delegate()->OnLockWebUIReady();
   }
-  ScreenlockBridge::Get()->SetLockHandler(this);
 
   if (delegate_)
     delegate_->OnSigninScreenReady();
diff --git a/chrome/chrome_browser_chromeos.gypi b/chrome/chrome_browser_chromeos.gypi
index b7bbae8..65b6ee1 100644
--- a/chrome/chrome_browser_chromeos.gypi
+++ b/chrome/chrome_browser_chromeos.gypi
@@ -429,10 +429,14 @@
         'browser/chromeos/login/easy_unlock/easy_unlock_key_manager.h',
         'browser/chromeos/login/easy_unlock/easy_unlock_metrics.cc',
         'browser/chromeos/login/easy_unlock/easy_unlock_metrics.h',
+        'browser/chromeos/login/easy_unlock/easy_unlock_reauth.cc',
+        'browser/chromeos/login/easy_unlock/easy_unlock_reauth.h',
         'browser/chromeos/login/easy_unlock/easy_unlock_remove_keys_operation.cc',
         'browser/chromeos/login/easy_unlock/easy_unlock_remove_keys_operation.h',
         'browser/chromeos/login/easy_unlock/easy_unlock_types.cc',
         'browser/chromeos/login/easy_unlock/easy_unlock_types.h',
+        'browser/chromeos/login/easy_unlock/short_lived_user_context.cc',
+        'browser/chromeos/login/easy_unlock/short_lived_user_context.h',
         'browser/chromeos/login/easy_unlock/easy_unlock_user_login_flow.cc',
         'browser/chromeos/login/easy_unlock/easy_unlock_user_login_flow.h',
         'browser/chromeos/login/enrollment/auto_enrollment_check_screen.cc',
diff --git a/ui/login/account_picker/user_pod_row.js b/ui/login/account_picker/user_pod_row.js
index 5526f91..fd3778d 100644
--- a/ui/login/account_picker/user_pod_row.js
+++ b/ui/login/account_picker/user_pod_row.js
@@ -200,6 +200,13 @@ cr.define('login', function() {
     __proto__: HTMLDivElement.prototype,
 
     /**
+     * The id of the icon being shown.
+     * @type {string}
+     * @private
+     */
+    iconId_: '',
+
+    /**
      * Tooltip to be shown when the user hovers over the icon. The icon
      * properties may be set so the tooltip is shown automatically when the icon
      * is updated. The tooltip is shown in a bubble attached to the icon
@@ -286,6 +293,7 @@ cr.define('login', function() {
      *    one of the ids listed in {@code UserPodCustomIcon.ICONS}.
      */
     setIcon: function(id) {
+      this.iconId_ = id;
       UserPodCustomIcon.ICONS.forEach(function(icon) {
         this.iconElement.classList.toggle(icon.class, id == icon.id);
       }, this);
@@ -477,7 +485,9 @@ cr.define('login', function() {
       bubbleContent.textContent = this.tooltip_;
 
       /** @const */ var BUBBLE_OFFSET = CUSTOM_ICON_CONTAINER_SIZE / 2;
-      /** @const */ var BUBBLE_PADDING = 8;
+      // TODO(tengs): Introduce a special reauth state for the account picker,
+      // instead of showing the tooltip bubble here (crbug.com/409427).
+      /** @const */ var BUBBLE_PADDING = 8 + (this.iconId_ ? 0 : 23);
       $('bubble').showContentForElement(this,
                                         cr.ui.Bubble.Attachment.RIGHT,
                                         bubbleContent,
@@ -2265,10 +2275,11 @@ cr.define('login', function() {
         return;
       }
 
-      if (!icon.id)
+      if (!icon.id && !icon.tooltip)
         return;
 
-      pod.customIconElement.setIcon(icon.id);
+      if (icon.id)
+        pod.customIconElement.setIcon(icon.id);
 
       if (icon.hardlockOnClick) {
         pod.customIconElement.setInteractive(