Implement symmetric key for openssl

base/crypto/symmetric_key.h

 // Copyright (c) 2010 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 BASE_CRYPTO_SYMMETRIC_KEY_H_
 #define BASE_CRYPTO_SYMMETRIC_KEY_H_
 #pragma once
 
 #include <string>
 
@@ skipping 48 matching lines @@
   HCRYPTKEY key() const { return key_.get(); }
 #endif
 
   // Extracts the raw key from the platform specific data.
   // Warning: |raw_key| holds the raw key as bytes and thus must be handled
   // carefully.
   bool GetRawKey(std::string* raw_key);
 
  private:
 #if defined(USE_OPENSSL)
-  // TODO(joth): Add a constructor that accepts OpenSSL symmetric key data, and
-  // the appropriate data members to store it in.
+  // Swaps in the content of the |key|.

[wtc, 2010/11/11 23:39:15]

Just copy the key (it is <= 32 bytes), and use this
constructor for Import only.

GenerateRandomKey and DeriveKeyFromPassword are class static
methods, so they should be able to write into key_ directly.

[joth, 2010/11/12 12:15:53]

Done.

As mentioned to rsleevi, the swap() was intended to avoid making unnecessary
copies of the confidential key, not for performance gain, but as it's not not
clear I have switched the factory methods to access the key_ member directly
(including for Import, as it seems as well to keep them all  consistent).

[wtc, 2010/11/12 15:01:50]

Ah, I see.  It was not obvious that's the purpose of the
swap.
This sounds good.  Thanks!

+  explicit SymmetricKey(std::string* key);
+  std::string key_;
 #elif defined(USE_NSS)
   explicit SymmetricKey(PK11SymKey* key);
   ScopedPK11SymKey key_;
 #elif defined(OS_MACOSX)
   SymmetricKey(const void* key_data, size_t key_size_in_bits);
   std::string key_;
 #elif defined(OS_WIN)
   SymmetricKey(HCRYPTPROV provider, HCRYPTKEY key,
                const void* key_data, size_t key_size_in_bytes);
 
   ScopedHCRYPTPROV provider_;
   ScopedHCRYPTKEY key_;
 
   // Contains the raw key, if it is known during initialization and when it
   // is likely that the associated |provider_| will be unable to export the
   // |key_|. This is the case of HMAC keys when the key size exceeds 16 bytes
   // when using the default RSA provider.
   // TODO(rsleevi): See if KP_EFFECTIVE_KEYLEN is the reason why CryptExportKey
   // fails with NTE_BAD_KEY/NTE_BAD_LEN
   std::string raw_key_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(SymmetricKey);
 };
 
 }  // namespace base
 
 #endif  // BASE_CRYPTO_SYMMETRIC_KEY_H_