Policy implementation for encryptfs to ext4 migration strategy

chrome/browser/chromeos/arc/arc_util.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 "chrome/browser/chromeos/arc/arc_util.h"
 
 #include <linux/magic.h>
 #include <sys/statfs.h>
 
 #include "base/callback.h"
+#include "base/command_line.h"
 #include "base/files/file_path.h"
 #include "base/logging.h"
 #include "base/sys_info.h"
 #include "base/task_scheduler/post_task.h"
 #include "base/threading/thread_restrictions.h"
+#include "chrome/browser/browser_process.h"
 #include "chrome/browser/chromeos/arc/arc_session_manager.h"
 #include "chrome/browser/chromeos/login/user_flow.h"
 #include "chrome/browser/chromeos/login/users/chrome_user_manager.h"
+#include "chrome/browser/chromeos/policy/browser_policy_connector_chromeos.h"
+#include "chrome/browser/chromeos/policy/proto/chrome_device_policy.pb.h"
 #include "chrome/browser/chromeos/profiles/profile_helper.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/common/pref_names.h"
+#include "chromeos/chromeos_switches.h"
 #include "components/arc/arc_util.h"
 #include "components/prefs/pref_service.h"
 #include "components/user_manager/known_user.h"
 #include "components/user_manager/user.h"
 #include "components/user_manager/user_manager.h"
 
 namespace arc {
 
 namespace {
 
 constexpr char kLsbReleaseArcVersionKey[] = "CHROMEOS_ARC_ANDROID_SDK_VERSION";
 constexpr char kAndroidMSdkVersion[] = "23";
 
 // Let IsAllowedForProfile() return "false" for any profile.
 bool g_disallow_for_testing = false;
 
 // Let IsArcBlockedDueToIncompatibleFileSystem() return the specified value
 // during test runs.
 bool g_arc_blocked_due_to_incomaptible_filesystem_for_testing = false;
 
+// This flag is set only in case the command line flag is set to mark the device
+// as requiring the migration. The value is set the first time the policy fetch
+// is done, and remains unchanged after that.
+// TODO(igorcov): Remove this after migration. crbug.com/725493
+ArcAvailabilityPolicyStatus g_arc_availability_policy_status =
+    ArcAvailabilityPolicyStatus::UNKNOWN;
+
 // Returns whether ARC can run on the filesystem mounted at |path|.
 // This function should run only on threads where IO operations are allowed.
 bool IsArcCompatibleFilesystem(const base::FilePath& path) {
   base::ThreadRestrictions::AssertIOAllowed();
 
   // If it can be verified it is not on ecryptfs, then it is ok.
   struct statfs statfs_buf;
   if (statfs(path.value().c_str(), &statfs_buf) < 0)
     return false;
   return statfs_buf.f_type != ECRYPTFS_SUPER_MAGIC;
@@ skipping 13 matching lines @@
 }
 
 FileSystemCompatibilityState GetFileSystemCompatibilityPref(
     const AccountId& account_id) {
   int pref_value = kFileSystemIncompatible;
   user_manager::known_user::GetIntegerPref(
       account_id, prefs::kArcCompatibleFilesystemChosen, &pref_value);
   return static_cast<FileSystemCompatibilityState>(pref_value);
 }
 
+// Returns if the migration from ecryptfs to ext4 is allowed. It is true if it
+// is known that the device is consumer owned, or if the device policy is
+// present and has the value |kAllowMigration|. The response is cached the first
+// time the function is used, and the policy update won't change the return
+// value after that.
+bool IsMigrationAllowed() {
+  if (g_arc_availability_policy_status ==

[hidehiko, 2017/06/07 12:22:20]

nit/optional: How about using base::Optional<bool> ? Something like;

namespace {

base::Optional<bool> g_is_arc_migration_allowed;

bool IsArcMigrationAllowedInternal() {
  if (... if not enterprise managed ...)
    return true;
  return pref->GetValue()->GetInt == ALLOW_MIGRATION;
}

}  // namespace

bool IsArcMigrationAllowed() {
  if (!g_is_arc_migration_allowed.has_value())
    g_is_arc_migration_allowed = IsArcMigrationAllowedInternal();
  return g_is_arc_migration_allowed.value();
}

[igorcov, 2017/06/08 10:42:25]

Done.

+      ArcAvailabilityPolicyStatus::UNKNOWN) {
+    // If the device is not managed, then the migration allowed.
+    if (!g_browser_process->platform_part()
+             ->browser_policy_connector_chromeos()
+             ->IsEnterpriseManaged()) {
+      g_arc_availability_policy_status = ArcAvailabilityPolicyStatus::AVAILABLE;
+      return true;
+    }
+
+    const PrefService* pref_service =
+        user_manager::UserManager::Get()->GetLocalState();
+    const PrefService::Preference* pref =
+        pref_service->FindPreference(prefs::kDeviceEcryptfsMigrationStrategy);
+
+    if (pref && pref->GetValue() &&
+        pref->GetValue()->GetInt() ==
+            enterprise_management::DeviceEcryptfsMigrationStrategyProto::
+                ALLOW_MIGRATION)
+      g_arc_availability_policy_status = ArcAvailabilityPolicyStatus::AVAILABLE;
+    else
+      g_arc_availability_policy_status = ArcAvailabilityPolicyStatus::DISABLED;
+  }
+
+  return g_arc_availability_policy_status ==
+         ArcAvailabilityPolicyStatus::AVAILABLE;
+}
+
 }  // namespace
 
 bool IsArcAllowedForProfile(const Profile* profile) {
   if (g_disallow_for_testing) {
     VLOG(1) << "ARC is disallowed for testing.";
     return false;
   }
 
   // ARC Kiosk can be enabled even if ARC is not yet supported on the device.
   // In that case IsArcKioskMode() should return true as profile is already
@@ skipping 29 matching lines @@
   // users do this through GAIA, but Kiosk and Active Directory users use
   // different application install mechanism. ARC is not allowed otherwise
   // (e.g. in public sessions). cf) crbug.com/605545
   const user_manager::User* user =
       chromeos::ProfileHelper::Get()->GetUserByProfile(profile);
   if (!IsArcAllowedForUser(user)) {
     VLOG(1) << "ARC is not allowed for the user.";
     return false;
   }
 
+  const auto* command_line = base::CommandLine::ForCurrentProcess();
+  // In the case the initial encryption was ecryptfs, the user data require
+  // migration to ext4 in order to have ARC available. The migration is
+  // forbidden if the device is managed and the policy is set to disable
+  // migration. This makes the ARC unavailable too.
+  // TODO(igorcov): Remove this after migration. crbug.com/725493
+  if (command_line->HasSwitch(chromeos::switches::kInitialEncryptionEcryptfs) &&

[hidehiko, 2017/06/07 12:22:20]

IIUC, This won't work as expected if;
- FS is currently ecryptfs, but
- ARC is still M.

right?
You'd need to check ARC version and/or FS encryption, too?

[igorcov, 2017/06/07 13:45:18]

Do you mean the case when user had ARC M, had ecryptfs and now is not allowed to
migrate? In this case according to design doc, ARC will disappear. We just need
to make sure the ARC data is not deleted. Or is it other case and I'm missing
something?

+      !IsMigrationAllowed()) {
+    VLOG(1) << "ARC requires migration, but is not allowed by the policy.";
+    return false;
+  }
+
   // Do not run ARC instance when supervised user is being created.
   // Otherwise noisy notification may be displayed.
   chromeos::UserFlow* user_flow =
       chromeos::ChromeUserManager::Get()->GetUserFlow(user->GetAccountId());
   if (!user_flow || !user_flow->CanStartArc()) {
     VLOG(1) << "ARC is not allowed in the current user flow.";
     return false;
   }
 
   return true;
@@ skipping 120 matching lines @@
 
   // Otherwise, check the underlying filesystem.
   base::PostTaskWithTraitsAndReplyWithResult(
       FROM_HERE,
       {base::MayBlock(), base::TaskPriority::USER_BLOCKING,
        base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN},
       base::Bind(&IsArcCompatibleFilesystem, profile_path),
       base::Bind(&StoreCompatibilityCheckResult, account_id, callback));
 }
 
+ArcAvailabilityPolicyStatus GetArcAvailabilityPolicyStatus() {
+  return g_arc_availability_policy_status;
+}
+
+void ResetGlobalDataForTesting() {
+  g_arc_availability_policy_status = ArcAvailabilityPolicyStatus::UNKNOWN;
+}
+
 }  // namespace arc