media_device_id.cc revision a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7 
1// Copyright 2013 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4#include "content/public/browser/media_device_id.h"
5
6#include "base/logging.h"
7#include "base/strings/string_number_conversions.h"
8#include "base/strings/string_util.h"
9#include "content/public/browser/resource_context.h"
10#include "crypto/hmac.h"
11
12namespace content {
13
14std::string GetHMACForMediaDeviceID(ResourceContext* rc,
15                                    const GURL& security_origin,
16                                    const std::string& raw_unique_id) {
17  DCHECK(security_origin.is_valid());
18  DCHECK(!raw_unique_id.empty());
19  crypto::HMAC hmac(crypto::HMAC::SHA256);
20  const size_t digest_length = hmac.DigestLength();
21  std::vector<uint8> digest(digest_length);
22  std::string salt = rc->GetMediaDeviceIDSalt();
23  bool result = hmac.Init(security_origin.spec()) &&
24      hmac.Sign(raw_unique_id + salt, &digest[0], digest.size());
25  DCHECK(result);
26  return StringToLowerASCII(base::HexEncode(&digest[0], digest.size()));
27}
28
29bool DoesMediaDeviceIDMatchHMAC(ResourceContext* rc,
30                                const GURL& security_origin,
31                                const std::string& device_guid,
32                                const std::string& raw_unique_id) {
33  DCHECK(security_origin.is_valid());
34  DCHECK(!raw_unique_id.empty());
35  std::string guid_from_raw_device_id =
36      GetHMACForMediaDeviceID(rc, security_origin, raw_unique_id);
37  return guid_from_raw_device_id == device_guid;
38}
39
40}  // namespace content
41