OSCrypt for POSIX uses libsecret to store a randomised encryption key.

components/os_crypt/os_crypt_mocker_linux.cc

Index: components/os_crypt/os_crypt_mocker_linux.cc
diff --git a/components/os_crypt/os_crypt_mocker_linux.cc b/components/os_crypt/os_crypt_mocker_linux.cc
new file mode 100644
index 0000000000000000000000000000000000000000..cedd3b048cc1f2d4cfa5af8d85108c2c104aa530
--- /dev/null
+++ b/components/os_crypt/os_crypt_mocker_linux.cc
@@ -0,0 +1,52 @@
+// 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/os_crypt_mocker_linux.h"
+
+#include "base/base64.h"
+#include "base/rand_util.h"
+#include "components/os_crypt/os_crypt.h"
+
+namespace {

[Lei Zhang, 2016/05/20 21:15:33]

Add blank line after.

[cfroussios, 2016/05/23 09:31:22]

Done.

+KeyStorageLinux* GetKeyStorage() {
+  return OSCryptMockerLinux::GetInstance();
+}
+
+std::string* GetPassword() {
+  return OSCryptMockerLinux::GetInstance()->GetKeyPtr();
+}
+}

[Lei Zhang, 2016/05/20 21:15:33]

Add blank line before, add // namespace

[cfroussios, 2016/05/23 09:31:22]

Done.

+
+std::string OSCryptMockerLinux::GetKey() {
+  if (key_.empty())
+    base::Base64Encode(base::RandBytesAsString(16), &key_);
+  return key_;
+}
+
+bool OSCryptMockerLinux::Init() {
+  return true;
+}
+
+void OSCryptMockerLinux::ResetTo(base::StringPiece new_key) {
+  key_ = new_key.as_string();
+}
+
+std::string* OSCryptMockerLinux::GetKeyPtr() {
+  return &key_;
+}
+
+// static
+OSCryptMockerLinux* OSCryptMockerLinux::GetInstance() {
+  return base::Singleton<OSCryptMockerLinux>::get();

[Lei Zhang, 2016/05/20 21:15:33]

Can we use a lazy instance instead? See comment in singleton.h.

[cfroussios, 2016/05/23 09:31:22]

Done.

+}
+
+// static
+void OSCryptMockerLinux::SetUpWithSingleton() {
+  UseMockKeyStorageForTesting(&GetKeyStorage, &GetPassword);
+}
+
+// static
+void OSCryptMockerLinux::TearDown() {
+  UseMockKeyStorageForTesting(nullptr, nullptr);
+}