extensions/browser/computed_hashes.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/computed_hashes.h"
   6
   7 #include "base/base64.h"
   8 #include "base/files/file_path.h"
   9 #include "base/files/file_util.h"
  10 #include "base/json/json_reader.h"
  11 #include "base/json/json_writer.h"
  12 #include "base/stl_util.h"
  13 #include "base/values.h"
  14 #include "crypto/secure_hash.h"
  15 #include "crypto/sha2.h"
  16
  17 namespace {
  18 const char kBlockHashesKey[] = "block_hashes";
  19 const char kBlockSizeKey[] = "block_size";
  20 const char kFileHashesKey[] = "file_hashes";
  21 const char kPathKey[] = "path";
  22 const char kVersionKey[] = "version";
  23 const int kVersion = 2;
  24 }  // namespace
  25
  26 namespace extensions {
  27
  28 ComputedHashes::Reader::Reader() {
  29 }
  30
  31 ComputedHashes::Reader::~Reader() {
  32 }
  33
  34 bool ComputedHashes::Reader::InitFromFile(const base::FilePath& path) {
  35   std::string contents;
  36   if (!base::ReadFileToString(path, &contents))
  37     return false;
  38
  39   base::DictionaryValue* top_dictionary = NULL;
  40   scoped_ptr<base::Value> value(base::JSONReader::Read(contents));
  41   if (!value.get() || !value->GetAsDictionary(&top_dictionary))
  42     return false;
  43
  44   // For now we don't support forwards or backwards compatability in the
  45   // format, so we return false on version mismatch.
  46   int version = 0;
  47   if (!top_dictionary->GetInteger(kVersionKey, &version) || version != kVersion)
  48     return false;
  49
  50   base::ListValue* all_hashes = NULL;
  51   if (!top_dictionary->GetList(kFileHashesKey, &all_hashes))
  52     return false;
  53
  54   for (size_t i = 0; i < all_hashes->GetSize(); i++) {
  55     base::DictionaryValue* dictionary = NULL;
  56     if (!all_hashes->GetDictionary(i, &dictionary))
  57       return false;
  58
  59     std::string relative_path_utf8;
  60     if (!dictionary->GetString(kPathKey, &relative_path_utf8))
  61       return false;
  62
  63     int block_size;
  64     if (!dictionary->GetInteger(kBlockSizeKey, &block_size))
  65       return false;
  66     if (block_size <= 0 || ((block_size % 1024) != 0)) {
  67       LOG(ERROR) << "Invalid block size: " << block_size;
  68       block_size = 0;
  69       return false;
  70     }
  71
  72     base::ListValue* hashes_list = NULL;
  73     if (!dictionary->GetList(kBlockHashesKey, &hashes_list))
  74       return false;
  75
  76     base::FilePath relative_path =
  77         base::FilePath::FromUTF8Unsafe(relative_path_utf8);
  78     relative_path = relative_path.NormalizePathSeparatorsTo('/');
  79
  80     data_[relative_path] = HashInfo(block_size, std::vector<std::string>());
  81     std::vector<std::string>* hashes = &(data_[relative_path].second);
  82
  83     for (size_t j = 0; j < hashes_list->GetSize(); j++) {
  84       std::string encoded;
  85       if (!hashes_list->GetString(j, &encoded))
  86         return false;
  87
  88       hashes->push_back(std::string());
  89       std::string* decoded = &hashes->back();
  90       if (!base::Base64Decode(encoded, decoded)) {
  91         hashes->clear();
  92         return false;
  93       }
  94     }
  95   }
  96   return true;
  97 }
  98
  99 bool ComputedHashes::Reader::GetHashes(const base::FilePath& relative_path,
 100                                        int* block_size,
 101                                        std::vector<std::string>* hashes) {
 102   base::FilePath path = relative_path.NormalizePathSeparatorsTo('/');
 103   std::map<base::FilePath, HashInfo>::iterator i = data_.find(path);
 104   if (i == data_.end()) {
 105     // If we didn't find the entry using exact match, it's possible the
 106     // developer is using a path with some letters in the incorrect case, which
 107     // happens to work on windows/osx. So try doing a linear scan to look for a
 108     // case-insensitive match. In practice most extensions don't have that big
 109     // a list of files so the performance penalty is probably not too big
 110     // here. Also for crbug.com/29941 we plan to start warning developers when
 111     // they are making this mistake, since their extension will be broken on
 112     // linux/chromeos.
 113     for (i = data_.begin(); i != data_.end(); ++i) {
 114       const base::FilePath& entry = i->first;
 115       if (base::FilePath::CompareEqualIgnoreCase(entry.value(), path.value()))
 116         break;
 117     }
 118     if (i == data_.end())
 119       return false;
 120   }
 121   HashInfo& info = i->second;
 122   *block_size = info.first;
 123   *hashes = info.second;
 124   return true;
 125 }
 126
 127 ComputedHashes::Writer::Writer() : file_list_(new base::ListValue) {
 128 }
 129
 130 ComputedHashes::Writer::~Writer() {
 131 }
 132
 133 void ComputedHashes::Writer::AddHashes(const base::FilePath& relative_path,
 134                                        int block_size,
 135                                        const std::vector<std::string>& hashes) {
 136   base::DictionaryValue* dict = new base::DictionaryValue();
 137   base::ListValue* block_hashes = new base::ListValue();
 138   file_list_->Append(dict);
 139   dict->SetString(kPathKey,
 140                   relative_path.NormalizePathSeparatorsTo('/').AsUTF8Unsafe());
 141   dict->SetInteger(kBlockSizeKey, block_size);
 142   dict->Set(kBlockHashesKey, block_hashes);
 143
 144   for (std::vector<std::string>::const_iterator i = hashes.begin();
 145        i != hashes.end();
 146        ++i) {
 147     std::string encoded;
 148     base::Base64Encode(*i, &encoded);
 149     block_hashes->AppendString(encoded);
 150   }
 151 }
 152
 153 bool ComputedHashes::Writer::WriteToFile(const base::FilePath& path) {
 154   std::string json;
 155   base::DictionaryValue top_dictionary;
 156   top_dictionary.SetInteger(kVersionKey, kVersion);
 157   top_dictionary.Set(kFileHashesKey, file_list_.release());
 158
 159   if (!base::JSONWriter::Write(top_dictionary, &json))
 160     return false;
 161   int written = base::WriteFile(path, json.data(), json.size());
 162   if (static_cast<unsigned>(written) != json.size()) {
 163     LOG(ERROR) << "Error writing " << path.AsUTF8Unsafe()
 164                << " ; write result:" << written << " expected:" << json.size();
 165     return false;
 166   }
 167   return true;
 168 }
 169
 170 void ComputedHashes::ComputeHashesForContent(const std::string& contents,
 171                                              size_t block_size,
 172                                              std::vector<std::string>* hashes) {
 173   size_t offset = 0;
 174   // Even when the contents is empty, we want to output at least one hash
 175   // block (the hash of the empty string).
 176   do {
 177     const char* block_start = contents.data() + offset;
 178     DCHECK(offset <= contents.size());
 179     size_t bytes_to_read = std::min(contents.size() - offset, block_size);
 180     scoped_ptr<crypto::SecureHash> hash(
 181         crypto::SecureHash::Create(crypto::SecureHash::SHA256));
 182     hash->Update(block_start, bytes_to_read);
 183
 184     hashes->push_back(std::string());
 185     std::string* buffer = &(hashes->back());
 186     buffer->resize(crypto::kSHA256Length);
 187     hash->Finish(string_as_array(buffer), buffer->size());
 188
 189     // If |contents| is empty, then we want to just exit here.
 190     if (bytes_to_read == 0)
 191       break;
 192
 193     offset += bytes_to_read;
 194   } while (offset < contents.size());
 195 }
 196
 197 }  // namespace extensions