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

components/os_crypt/key_storage_mock.h

Index: components/os_crypt/key_storage_mock.h
diff --git a/components/os_crypt/key_storage_mock.h b/components/os_crypt/key_storage_mock.h
new file mode 100644
index 0000000000000000000000000000000000000000..b5377671bf7ab8ec614d4f791b162db173d9d656
--- /dev/null
+++ b/components/os_crypt/key_storage_mock.h
@@ -0,0 +1,38 @@
+// 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.
+
+#ifndef COMPONENTS_OS_CRYPT_KEY_STORAGE_MOCK_H_
+#define COMPONENTS_OS_CRYPT_KEY_STORAGE_MOCK_H_
+
+#include <string>
+
+#include "base/macros.h"
+
+#include "components/os_crypt/key_storage_linux.h"
+
+// Holds and serves a password from memory.
+class KeyStorageMock : public KeyStorage {
+ public:
+  KeyStorageMock() = default;

[Lei Zhang, 2016/05/18 22:38:16]

Do you need both ctors?

[cfroussios, 2016/05/19 21:18:18]

Done.

+  explicit KeyStorageMock(std::string in_key);

[Lei Zhang, 2016/05/18 22:38:15]

Parameter should be const-ref.

[cfroussios, 2016/05/19 21:18:18]

This constructor was removed for not being necessary (see comment above). I
would note, however, that capturing by value and moving has a better average
case, because it allows objects to be moved into the new instance.

+  ~KeyStorageMock() override = default;
+
+  // KeyStorage
+  std::string GetKey() override;
+  bool Init() override;
+
+  // Set the password that |KeyStorageMock| holds
+  void ResetTo(std::string new_key);
+
+  // Get a pointer to the stored password. Lives as long as this

[Lei Zhang, 2016/05/18 22:38:16]

"Lives as long ..." -> KeyStorageMock owns the returned pointer.

[cfroussios, 2016/05/19 21:18:18]

Done.

+  // |KeyStorageMock| lives
+  std::string* GetKeyPtr();
+
+ private:
+  std::string key_;
+
+  DISALLOW_COPY_AND_ASSIGN(KeyStorageMock);
+};
+
+#endif  // COMPONENTS_OS_CRYPT_KEY_STORAGE_MOCK_H_