[Chromoting] Factor out common code for pin hashing.

remoting/host/pin_hash.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 "remoting/host/pin_hash.h"
+
+#include "base/base64.h"
+#include "base/logging.h"
+#include "remoting/protocol/authentication_method.h"
+
+namespace remoting {
+
+// Hashes a host ID and a PIN.
+std::string GetPinHash(const std::string& host_id, const std::string& pin) {
+  std::string hash = protocol::AuthenticationMethod::ApplyHashFunction(
+      protocol::AuthenticationMethod::HMAC_SHA256, host_id, pin);
+  std::string hash_base64;
+  bool base64_result = base::Base64Encode(hash, &hash_base64);

[Wez, 2012/04/30 23:13:57]

nit: Test base::Base64Encode()'s result directly rather than saving into a local
variable.

[simonmorris, 2012/05/01 00:25:55]

Done.

+  if (!base64_result) {
+    LOG(FATAL) << "Base64Encode failed";
+  }
+  return "hmac:" + hash_base64;
+}
+
+}  // namespace remoting