components/nacl/browser/nacl_validation_cache.cc

   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
   5 #include "components/nacl/browser/nacl_validation_cache.h"
   6
   7 #include "base/pickle.h"
   8 #include "base/rand_util.h"
   9
  10 namespace nacl {
  11
  12 // For the moment, choose an arbitrary cache size.
  13 const size_t kValidationCacheCacheSize = 200;
  14 // Key size is equal to the block size (not the digest size) of SHA256.
  15 const size_t kValidationCacheKeySize = 64;
  16 // Entry size is equal to the digest size of SHA256.
  17 const size_t kValidationCacheEntrySize = 32;
  18
  19 const char kValidationCacheBeginMagic[] = "NaCl";
  20 const char kValidationCacheEndMagic[] = "Done";
  21
  22 NaClValidationCache::NaClValidationCache()
  23     : validation_cache_(kValidationCacheCacheSize) {
  24   // Make sure the cache key is unpredictable, even if the cache has not
  25   // been loaded.
  26   Reset();
  27 }
  28
  29 NaClValidationCache::~NaClValidationCache() {
  30   // Make clang's style checking happy by adding a destructor.
  31 }
  32
  33 bool NaClValidationCache::QueryKnownToValidate(const std::string& signature,
  34                                                bool reorder) {
  35   if (signature.length() == kValidationCacheEntrySize) {
  36     ValidationCacheType::iterator iter;
  37     if (reorder) {
  38       iter = validation_cache_.Get(signature);
  39     } else {
  40       iter = validation_cache_.Peek(signature);
  41     }
  42     if (iter != validation_cache_.end()) {
  43       return iter->second;
  44     }
  45   }
  46   return false;
  47 }
  48
  49 void NaClValidationCache::SetKnownToValidate(const std::string& signature) {
  50   if (signature.length() == kValidationCacheEntrySize) {
  51     validation_cache_.Put(signature, true);
  52   }
  53 }
  54
  55 void NaClValidationCache::Serialize(Pickle* pickle) const {
  56   // Mark the beginning of the data stream.
  57   pickle->WriteString(kValidationCacheBeginMagic);
  58   pickle->WriteString(validation_cache_key_);
  59   pickle->WriteInt(validation_cache_.size());
  60
  61   // Serialize the cache in reverse order so that deserializing it can easily
  62   // preserve the MRU order.  (Last item deserialized => most recently used.)
  63   ValidationCacheType::const_reverse_iterator iter;
  64   for (iter = validation_cache_.rbegin();
  65        iter != validation_cache_.rend();
  66        ++iter) {
  67     pickle->WriteString(iter->first);
  68   }
  69
  70   // Mark the end of the data stream.
  71   pickle->WriteString(kValidationCacheEndMagic);
  72 }
  73
  74 void NaClValidationCache::Reset() {
  75   validation_cache_key_ = base::RandBytesAsString(kValidationCacheKeySize);
  76   validation_cache_.Clear();
  77 }
  78
  79 bool NaClValidationCache::Deserialize(const Pickle* pickle) {
  80   bool success = DeserializeImpl(pickle);
  81   if (!success) {
  82     Reset();
  83   }
  84   return success;
  85 }
  86
  87 bool NaClValidationCache::DeserializeImpl(const Pickle* pickle) {
  88   PickleIterator iter(*pickle);
  89   std::string buffer;
  90   int count;
  91
  92   // Magic
  93   if (!iter.ReadString(&buffer))
  94     return false;
  95   if (0 != buffer.compare(kValidationCacheBeginMagic))
  96     return false;
  97
  98   // Key
  99   if (!iter.ReadString(&buffer))
 100     return false;
 101   if (buffer.size() != kValidationCacheKeySize)
 102     return false;
 103
 104   validation_cache_key_ = buffer;
 105   validation_cache_.Clear();
 106
 107   // Cache entries
 108   if (!iter.ReadInt(&count))
 109     return false;
 110   for (int i = 0; i < count; ++i) {
 111     if (!iter.ReadString(&buffer))
 112       return false;
 113     if (buffer.size() != kValidationCacheEntrySize)
 114       return false;
 115     validation_cache_.Put(buffer, true);
 116   }
 117
 118   // Magic
 119   if (!iter.ReadString(&buffer))
 120     return false;
 121   if (0 != buffer.compare(kValidationCacheEndMagic))
 122     return false;
 123
 124   // Success!
 125   return true;
 126 }
 127
 128 } // namespace nacl
 129