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

components/os_crypt/os_crypt_unittest.cc

 // 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.
 
 #include "components/os_crypt/os_crypt.h"
 
 #include <string>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "build/build_config.h"
+#include "components/os_crypt/key_storage_mock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace {
 
 class OSCryptTest : public testing::Test {
  public:
   OSCryptTest() {}
 
+#if defined(OS_MACOSX)
+  void SetUp() override { OSCrypt::UseMockKeychain(true); }

[Lei Zhang, 2016/05/19 22:45:38]

I'd highly prefer not to have two different implementations of the same
function. Can we keep the ifdefs inside the function, like before?

[cfroussios, 2016/05/20 16:44:52]

Done.

+#endif
+
+#if defined(USE_LIBSECRET)
   void SetUp() override {
-#if defined(OS_MACOSX)
-    OSCrypt::UseMockKeychain(true);
+    key_storage_static_ = &key_storage_;
+    UseMockKeyStorageForTesting(true, &GetKeyStorage, &GetPassword);
+  }
+
+  void TearDown() override {
+    key_storage_static_ = nullptr;
+    UseMockKeyStorageForTesting(false, nullptr, nullptr);
+  }
+
+ protected:
+  KeyStorageMock key_storage_;
+
+ private:
+  // Needed, so that we can return our |key_storage_| through static methods
+  static KeyStorageMock* key_storage_static_;

[Lei Zhang, 2016/05/19 22:45:38]

Many places use s_foo_ here, like g_foo for globals.

[cfroussios, 2016/05/20 16:44:52]

Done.

+
+  static KeyStorageLinux* GetKeyStorage() { return key_storage_static_; }
+
+  static std::string* GetPassword() { return key_storage_static_->GetKeyPtr(); }
 #endif
-  }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(OSCryptTest);
 };
 
+#if defined(USE_LIBSECRET)
+KeyStorageMock* OSCryptTest::key_storage_static_ = nullptr;
+#endif
+
 TEST_F(OSCryptTest, String16EncryptionDecryption) {
   base::string16 plaintext;
   base::string16 result;
   std::string utf8_plaintext;
   std::string utf8_result;
   std::string ciphertext;
 
   // Test borderline cases (empty strings).
   EXPECT_TRUE(OSCrypt::EncryptString16(plaintext, &ciphertext));
   EXPECT_TRUE(OSCrypt::DecryptString16(ciphertext, &result));
@@ skipping 95 matching lines @@
   ASSERT_TRUE(OSCrypt::EncryptString(plaintext, &ciphertext));
   EXPECT_NE(plaintext, ciphertext);
   ASSERT_LT(4UL, ciphertext.size());
   ciphertext[3] = ciphertext[3] + 1;
   EXPECT_FALSE(OSCrypt::DecryptString(ciphertext, &result));
   EXPECT_NE(plaintext, result);
   EXPECT_TRUE(result.empty());
 }
 
 }  // namespace