extensions/browser/content_hash_reader.cc

   1 // Copyright 2014 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
   5 #include "extensions/browser/content_hash_reader.h"
   6
   7 #include "base/base64.h"
   8 #include "base/file_util.h"
   9 #include "base/json/json_reader.h"
  10 #include "base/metrics/histogram.h"
  11 #include "base/strings/string_util.h"
  12 #include "base/timer/elapsed_timer.h"
  13 #include "base/values.h"
  14 #include "crypto/sha2.h"
  15 #include "extensions/browser/computed_hashes.h"
  16 #include "extensions/browser/content_hash_tree.h"
  17 #include "extensions/browser/verified_contents.h"
  18 #include "extensions/common/extension.h"
  19 #include "extensions/common/file_util.h"
  20
  21 using base::DictionaryValue;
  22 using base::ListValue;
  23 using base::Value;
  24
  25 namespace extensions {
  26
  27 ContentHashReader::ContentHashReader(const std::string& extension_id,
  28                                      const base::Version& extension_version,
  29                                      const base::FilePath& extension_root,
  30                                      const base::FilePath& relative_path,
  31                                      const ContentVerifierKey& key)
  32     : extension_id_(extension_id),
  33       extension_version_(extension_version.GetString()),
  34       extension_root_(extension_root),
  35       relative_path_(relative_path),
  36       key_(key),
  37       status_(NOT_INITIALIZED),
  38       content_exists_(false),
  39       have_verified_contents_(false),
  40       have_computed_hashes_(false),
  41       block_size_(0) {
  42 }
  43
  44 ContentHashReader::~ContentHashReader() {
  45 }
  46
  47 bool ContentHashReader::Init() {
  48   base::ElapsedTimer timer;
  49   DCHECK_EQ(status_, NOT_INITIALIZED);
  50   status_ = FAILURE;
  51   base::FilePath verified_contents_path =
  52       file_util::GetVerifiedContentsPath(extension_root_);
  53
  54   // Check that this is a valid resource to verify (i.e., it exists).
  55   base::FilePath content_path = extension_root_.Append(relative_path_);
  56   if (!base::PathExists(content_path))
  57     return false;
  58
  59   content_exists_ = true;
  60
  61   if (!base::PathExists(verified_contents_path))
  62     return false;
  63
  64   verified_contents_.reset(new VerifiedContents(key_.data, key_.size));
  65   if (!verified_contents_->InitFrom(verified_contents_path, false) ||
  66       !verified_contents_->valid_signature() ||
  67       !verified_contents_->version().Equals(extension_version_) ||
  68       verified_contents_->extension_id() != extension_id_)
  69     return false;
  70
  71   have_verified_contents_ = true;
  72
  73   base::FilePath computed_hashes_path =
  74       file_util::GetComputedHashesPath(extension_root_);
  75   if (!base::PathExists(computed_hashes_path))
  76     return false;
  77
  78   ComputedHashes::Reader reader;
  79   if (!reader.InitFromFile(computed_hashes_path))
  80     return false;
  81
  82   have_computed_hashes_ = true;
  83
  84   if (!reader.GetHashes(relative_path_, &block_size_, &hashes_) ||
  85       block_size_ % crypto::kSHA256Length != 0)
  86     return false;
  87
  88   const std::string* expected_root =
  89       verified_contents_->GetTreeHashRoot(relative_path_);
  90   if (!expected_root)
  91     return false;
  92
  93   std::string root =
  94       ComputeTreeHashRoot(hashes_, block_size_ / crypto::kSHA256Length);
  95   if (*expected_root != root)
  96     return false;
  97
  98   status_ = SUCCESS;
  99   UMA_HISTOGRAM_TIMES("ExtensionContentHashReader.InitLatency",
 100                       timer.Elapsed());
 101   return true;
 102 }
 103
 104 int ContentHashReader::block_count() const {
 105   DCHECK(status_ != NOT_INITIALIZED);
 106   return hashes_.size();
 107 }
 108
 109 int ContentHashReader::block_size() const {
 110   DCHECK(status_ != NOT_INITIALIZED);
 111   return block_size_;
 112 }
 113
 114 bool ContentHashReader::GetHashForBlock(int block_index,
 115                                         const std::string** result) const {
 116   if (status_ != SUCCESS)
 117     return false;
 118   DCHECK(block_index >= 0);
 119
 120   if (static_cast<unsigned>(block_index) >= hashes_.size())
 121     return false;
 122   *result = &hashes_[block_index];
 123
 124   return true;
 125 }
 126
 127 }  // namespace extensions