[webcrypto] Fix a bug where generated RSA private keys couldn't be exported.

content/child/webcrypto/platform_crypto_nss.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 "content/child/webcrypto/platform_crypto.h"
 
 #include <cryptohi.h>
 #include <pk11pub.h>
 #include <secerr.h>
 #include <sechash.h>
@@ skipping 1135 matching lines @@
       break;
     case blink::WebCryptoAlgorithmIdRsaSsaPkcs1v1_5:
       operation_flags = CKF_SIGN | CKF_VERIFY;
       break;
     default:
       NOTREACHED();
       return Status::ErrorUnexpected();
   }
   const CK_FLAGS operation_flags_mask =
       CKF_ENCRYPT | CKF_DECRYPT | CKF_SIGN | CKF_VERIFY | CKF_WRAP | CKF_UNWRAP;
-  const PK11AttrFlags attribute_flags = 0;  // Default all PK11_ATTR_ flags.
+
+  // The private key must be marked as insensitive and extractable, otherwise it
+  // cannot later be exported in unencrypted form or structured-cloned.
+  const PK11AttrFlags attribute_flags =
+      PK11_ATTR_INSENSITIVE | PK11_ATTR_EXTRACTABLE;
 
   // Note: NSS does not generate an sec_public_key if the call below fails,
   // so there is no danger of a leaked sec_public_key.
   SECKEYPublicKey* sec_public_key;
   crypto::ScopedSECKEYPrivateKey scoped_sec_private_key(
       PK11_GenerateKeyPairWithOpFlags(slot.get(),
                                       CKM_RSA_PKCS_KEY_PAIR_GEN,
                                       &rsa_gen_params,
                                       &sec_public_key,
                                       attribute_flags,
@@ skipping 325 matching lines @@
                                      key_algorithm,
                                      usage_mask);
   return Status::Success();
 }
 
 }  // namespace platform
 
 }  // namespace webcrypto
 
 }  // namespace content