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

components/os_crypt/os_crypt.h

 // 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 COMPONENTS_OS_CRYPT_OS_CRYPT_H_
 #define COMPONENTS_OS_CRYPT_OS_CRYPT_H_
 
 #include <string>
 
 #include "base/macros.h"
 #include "base/strings/string16.h"
 #include "build/build_config.h"
+#if defined(USE_LIBSECRET)

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

Add a blank line separator

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

Done.

+#include "components/os_crypt/key_storage_linux.h"
+#include "components/os_crypt/key_storage_mock.h"
+#endif
 
 // The OSCrypt class gives access to simple encryption and decryption of
 // strings. Note that on Mac, access to the system Keychain is required and
 // these calls can block the current thread to collect user input.
 class OSCrypt {
  public:
   // Encrypt a string16. The output (second argument) is really an array of
   // bytes, but we're passing it back as a std::string.
   static bool EncryptString16(const base::string16& plaintext,
                               std::string* ciphertext);
@@ skipping 13 matching lines @@
   // get your (binary) data into a string.
   static bool DecryptString(const std::string& ciphertext,
                             std::string* plaintext);
 
 #if defined(OS_MACOSX)
   // For unit testing purposes we instruct the Encryptor to use a mock Keychain
   // on the Mac. The default is to use the real Keychain.
   static void UseMockKeychain(bool use_mock);
 #endif
 
+#if defined(USE_LIBSECRET)
+  // For unit testing purposes, use a mocked |KeyStorage| service.

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

Refer to variables as |var_name|, not classes.

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

Acknowledged.

+  // A reference is to the |KeyStorageMock| is returned, so that the test can
+  // manipulate the service.
+  static KeyStorageMock* UseMockKeyStorage(bool use_mock);

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

This sounds confusing. What does UseMock...(use_mock = false) mean?

UseMockKeychain() above is slightly better but still a bit vague. That and
nobody ever calls UseMockKeychain(false).

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

I changed it so that a pointer is no longer returned. I assume that was what
made it worse than UseMockKeychain()?

(use_mock = false) means to stop mocking and restore behaviour to whatever is
intended for real use. I think such a cleanup is necessary, since the
configuration is static and doesn't go away when a test is destroyed. With that
argument, UseMockKeychain(false) should also be used, but this CL is focused on
Linux stuff

+#endif
+
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(OSCrypt);
 };
 
 #endif  // COMPONENTS_OS_CRYPT_OS_CRYPT_H_