[Downloads] Rework how hashes are calculated for download files.

crypto/secure_hash_default.cc

 // Copyright (c) 2012 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 "crypto/secure_hash.h"
 
 #include <stddef.h>
 
 #include "base/logging.h"
 #include "base/pickle.h"
 #include "crypto/third_party/nss/chromium-blapi.h"
 #include "crypto/third_party/nss/chromium-sha256.h"
 
 namespace crypto {
 
 namespace {
 
-const char kSHA256Descriptor[] = "NSS";
-
 class SecureHashSHA256NSS : public SecureHash {
  public:
-  static const int kSecureHashVersion = 1;
-
   SecureHashSHA256NSS() {
     SHA256_Begin(&ctx_);
   }
 
+  explicit SecureHashSHA256NSS(const SecureHashSHA256NSS& other) {

[davidben, 2016/03/08 22:12:03]

Nit: Copy constructors aren't usually explicit, are they?

[asanka, 2016/03/10 16:48:08]

Yeah. I was trying to disable implicit copies. It's not needed here, so I
removed the explicit specifier.

+    SHA256_Clone(&ctx_, const_cast<SHA256Context*>(&other.ctx_));
+  }
+
   ~SecureHashSHA256NSS() override { memset(&ctx_, 0, sizeof(ctx_)); }
 
   // SecureHash implementation:
   void Update(const void* input, size_t len) override {
     SHA256_Update(&ctx_, static_cast<const unsigned char*>(input), len);
   }
 
   void Finish(void* output, size_t len) override {
     SHA256_End(&ctx_, static_cast<unsigned char*>(output), NULL,
                static_cast<unsigned int>(len));
   }
 
-  bool Serialize(base::Pickle* pickle) override;
-  bool Deserialize(base::PickleIterator* data_iterator) override;
+  SecureHash* Clone() const override { return new SecureHashSHA256NSS(*this); }
+
+  size_t GetHashLength() const override { return SHA256_LENGTH; }
 
  private:
   SHA256Context ctx_;
 };
 
-bool SecureHashSHA256NSS::Serialize(base::Pickle* pickle) {
-  if (!pickle)
-    return false;
-
-  if (!pickle->WriteInt(kSecureHashVersion) ||
-      !pickle->WriteString(kSHA256Descriptor) ||
-      !pickle->WriteBytes(&ctx_, sizeof(ctx_))) {
-    return false;
-  }
-
-  return true;
-}
-
-bool SecureHashSHA256NSS::Deserialize(base::PickleIterator* data_iterator) {
-  int version;
-  if (!data_iterator->ReadInt(&version))
-    return false;
-
-  if (version > kSecureHashVersion)
-    return false;  // We don't know how to deal with this.
-
-  std::string type;
-  if (!data_iterator->ReadString(&type))
-    return false;
-
-  if (type != kSHA256Descriptor)
-    return false;  // It's the wrong kind.
-
-  const char* data = NULL;
-  if (!data_iterator->ReadBytes(&data, sizeof(ctx_)))
-    return false;
-
-  memcpy(&ctx_, data, sizeof(ctx_));
-
-  return true;
-}
-
 }  // namespace
 
 SecureHash* SecureHash::Create(Algorithm algorithm) {
   switch (algorithm) {
     case SHA256:
       return new SecureHashSHA256NSS();
     default:
       NOTIMPLEMENTED();
       return NULL;
   }
 }
 
 }  // namespace crypto