Implement symmetric key for openssl

base/crypto/symmetric_key.h

Index: base/crypto/symmetric_key.h
diff --git a/base/crypto/symmetric_key.h b/base/crypto/symmetric_key.h
index 3f2be76390c7188a5ec446dd1a79aa95b575f1ab..5958ec0f7ecb2a30872ff1b15c8fe093e2451e09 100644
--- a/base/crypto/symmetric_key.h
+++ b/base/crypto/symmetric_key.h
@@ -66,8 +66,9 @@ class SymmetricKey {
 
  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_;