Make GetEncryptionKey thread-safe

components/os_crypt/os_crypt_mac.mm

 // 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 <CommonCrypto/CommonCryptor.h>  // for kCCBlockSizeAES128
 #include <stddef.h>
 
 #include "base/command_line.h"
 #include "base/debug/leak_annotations.h"
+#include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/synchronization/lock.h"
 #include "components/os_crypt/keychain_password_mac.h"
 #include "components/os_crypt/os_crypt_switches.h"
 #include "crypto/apple_keychain.h"
 #include "crypto/encryptor.h"
 #include "crypto/mock_apple_keychain.h"
 #include "crypto/symmetric_key.h"
 
@@ skipping 11 matching lines @@
 const size_t kEncryptionIterations = 1003;
 
 // TODO(dhollowa): Refactor to allow dependency injection of Keychain.
 static bool use_mock_keychain = false;
 
 // Prefix for cypher text returned by current encryption version.  We prefix
 // the cypher text with this string so that future data migration can detect
 // this and migrate to different encryption without data loss.
 const char kEncryptionVersionPrefix[] = "v10";
 
+// This lock is used to make the GetEncrytionKey method thread-safe.
+base::LazyInstance<base::Lock>::Leaky g_lock = LAZY_INSTANCE_INITIALIZER;
+
 // Generates a newly allocated SymmetricKey object based on the password found
 // in the Keychain.  The generated key is for AES encryption.  Returns NULL key
 // in the case password access is denied or key generation error occurs.
 crypto::SymmetricKey* GetEncryptionKey() {
   static crypto::SymmetricKey* cached_encryption_key = NULL;
   static bool key_is_cached = false;
-  static base::Lock lock;
-  base::AutoLock auto_lock(lock);
+  base::AutoLock auto_lock(g_lock.Get());
 
   if (key_is_cached)
     return cached_encryption_key;
 
   static bool mock_keychain_command_line_flag =
       base::CommandLine::ForCurrentProcess()->HasSwitch(
           os_crypt::switches::kUseMockKeychain);
 
   std::string password;
   if (use_mock_keychain || mock_keychain_command_line_flag) {
@@ skipping 99 matching lines @@
   if (!encryptor.Decrypt(raw_ciphertext, plaintext))
     return false;
 
   return true;
 }
 
 void OSCrypt::UseMockKeychain(bool use_mock) {
   use_mock_keychain = use_mock;
 }