Sign CertificateVerify messages on a background thread.

net/ssl/threaded_ssl_private_key.h

Index: net/ssl/threaded_ssl_private_key.h
diff --git a/net/ssl/threaded_ssl_private_key.h b/net/ssl/threaded_ssl_private_key.h
new file mode 100644
index 0000000000000000000000000000000000000000..2a25ddbc4589c34ac88058f7b4779ed3b8219086
--- /dev/null
+++ b/net/ssl/threaded_ssl_private_key.h
@@ -0,0 +1,76 @@
+// Copyright 2015 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 NET_SSL_THREADED_SSL_PRIVATE_KEY_H_
+#define NET_SSL_THREADED_SSL_PRIVATE_KEY_H_
+
+#include <stdint.h>
+
+#include <vector>
+
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
+#include "base/strings/string_piece.h"
+#include "net/ssl/ssl_private_key.h"
+
+namespace base {
+class TaskRunner;
+}
+
+namespace net {
+
+// An SSLPrivateKey implementation which offloads key operations to a background
+// thread.
+class ThreadedSSLPrivateKey : public SSLPrivateKey {
+ public:
+  // Interface for consumers to implement to perform the actual signing
+  // operation. All methods must be callable on any thread.
+  class Delegate {
+   public:
+    Delegate() {}
+    virtual ~Delegate() {}
+
+    virtual Type GetType() = 0;
+    virtual bool SupportsHash(Hash hash) = 0;
+    virtual size_t GetMaxSignatureLength() = 0;
+    virtual Error SignDigest(Hash hash,
+                             const base::StringPiece& input,
+                             std::vector<uint8_t>* signature) = 0;
+
+   private:
+    DISALLOW_COPY_AND_ASSIGN(Delegate);
+  };
+
+  ThreadedSSLPrivateKey(scoped_ptr<Delegate> delegate,
+                        const scoped_refptr<base::TaskRunner>& task_runner);
+  ~ThreadedSSLPrivateKey() override;
+
+  // SSLPrivateKey implementation.
+  Type GetType() override;
+  bool SupportsHash(Hash hash) override;
+  size_t GetMaxSignatureLength() override;
+  void SignDigest(Hash hash,
+                  const base::StringPiece& input,
+                  const SignCallback& callback) override;
+
+ private:
+  class Core;
+
+  // A wrapper over SignCallback to ensure the callback isn't called if the key
+  // is destroyed.
+  void DoCallback(const SignCallback& callback,
+                  std::vector<uint8_t>* signature,
+                  Error error);

[Ryan Sleevi, 2015/06/15 22:55:23]

nit: I'm still unclear why this needs to be a private member. This doesn't
access any private instance data - seems perfectly fine to keep isolated to the
.cc

You're just doing it for the WeakFactory/WeakPtr, AFAICT, and that seems fine to
express by just passing a WeakPtr<ThreadedSSLPrivateKey> as the first arg to the
static DoCallback with the check to is_valid() [or, more aptly, to bool
equivalency

DoCallback(const base::WeakPtr<ThreadedSSLPrivateKey>& private_key,
           ...) {
  if (!private_key)
    return;
  callback.Run(...);
}

[This one I'm less worried about forward declaring, but it does seem unnecessary
for the cancellation semantics, strictly speaking]

[davidben, 2015/06/17 20:47:02]

Done.

+
+  scoped_refptr<Core> core_;
+  scoped_refptr<base::TaskRunner> task_runner_;
+  base::WeakPtrFactory<ThreadedSSLPrivateKey> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(ThreadedSSLPrivateKey);
+};
+
+}  // namespace net
+
+#endif  // NET_SSL_THREADED_SSL_PRIVATE_KEY_H_