Create setting that disables password stores

components/os_crypt/key_storage_util_linux.cc

 // Copyright 2016 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 "components/os_crypt/key_storage_util_linux.h"
 
+#include "base/files/file_path.h"
+#include "base/files/file_util.h"
 #include "base/logging.h"
 
+namespace {
+
+// OSCrypt has a setting that determines whether a backend will be used.
+// The presense of this file in the file system means that the backend
+// should be ignored. It's absence means we should use the backend.
+constexpr const char kPreferenceFileName[] = "Disable Local Encryption";
+
+bool ReadBackendUse(const base::FilePath& user_data_dir, bool* use) {
+  if (user_data_dir.empty())
+    return false;
+  base::FilePath pref_path = user_data_dir.Append(kPreferenceFileName);
+  *use = !base::PathExists(pref_path);
+  return true;
+}
+
+}  // namespace
+
 namespace os_crypt {
 
 SelectedLinuxBackend SelectBackend(const std::string& type,
+                                   bool use_backend,
                                    base::nix::DesktopEnvironment desktop_env) {
+  // Explicitly requesting a store overrides other production logic.
   if (type == "kwallet")
     return SelectedLinuxBackend::KWALLET;
   if (type == "kwallet5")
     return SelectedLinuxBackend::KWALLET5;
   if (type == "gnome")
     return SelectedLinuxBackend::GNOME_ANY;
   if (type == "gnome-keyring")
     return SelectedLinuxBackend::GNOME_KEYRING;
   if (type == "gnome-libsecret")
     return SelectedLinuxBackend::GNOME_LIBSECRET;
   if (type == "basic")
     return SelectedLinuxBackend::BASIC_TEXT;
 
+  // Ignore the backends if requested to.
+  if (!use_backend)
+    return SelectedLinuxBackend::BASIC_TEXT;
+
+  // Detect the store to use automatically.
   const char* name = base::nix::GetDesktopEnvironmentName(desktop_env);
   VLOG(1) << "Password storage detected desktop environment: "
           << (name ? name : "(unknown)");
-
-  // Detect the store to use automatically.
   switch (desktop_env) {
     case base::nix::DESKTOP_ENVIRONMENT_KDE4:
       return SelectedLinuxBackend::KWALLET;
     case base::nix::DESKTOP_ENVIRONMENT_KDE5:
       return SelectedLinuxBackend::KWALLET5;
     case base::nix::DESKTOP_ENVIRONMENT_GNOME:
     case base::nix::DESKTOP_ENVIRONMENT_UNITY:
     case base::nix::DESKTOP_ENVIRONMENT_XFCE:
       return SelectedLinuxBackend::GNOME_ANY;
     // KDE3 didn't use DBus, which our KWallet store uses.
     case base::nix::DESKTOP_ENVIRONMENT_KDE3:
     case base::nix::DESKTOP_ENVIRONMENT_OTHER:
       return SelectedLinuxBackend::BASIC_TEXT;
   }
 
   NOTREACHED();
   return SelectedLinuxBackend::BASIC_TEXT;
 }
 
+bool WriteBackendUse(const base::FilePath& user_data_dir, bool use) {
+  if (user_data_dir.empty())
+    return false;
+  base::FilePath pref_path = user_data_dir.Append(kPreferenceFileName);
+  if (use)
+    return base::DeleteFile(pref_path, false);
+  FILE* f = base::OpenFile(pref_path, "w");
+  return f != nullptr && base::CloseFile(f);
+}
+
+bool GetBackendUse(const base::FilePath& user_data_dir) {
+  bool setting;
+  if (ReadBackendUse(user_data_dir, &setting))
+    return setting;
+  return true;
+}
+
 }  // namespace os_crypt