mojo/system/transport_data.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 "mojo/system/transport_data.h"
   6
   7 #include <string.h>
   8
   9 #include "base/compiler_specific.h"
  10 #include "base/logging.h"
  11 #include "mojo/system/channel.h"
  12 #include "mojo/system/constants.h"
  13 #include "mojo/system/message_in_transit.h"
  14
  15 namespace mojo {
  16 namespace system {
  17
  18 // The maximum amount of space needed per platform handle.
  19 // (|{Channel,RawChannel}::GetSerializedPlatformHandleSize()| should always
  20 // return a value which is at most this. This is only used to calculate
  21 // |TransportData::kMaxBufferSize|. This value should be a multiple of the
  22 // alignment in order to simplify calculations, even though the actual amount of
  23 // space needed need not be a multiple of the alignment.
  24 const size_t kMaxSizePerPlatformHandle = 8;
  25 COMPILE_ASSERT(kMaxSizePerPlatformHandle %
  26                    MessageInTransit::kMessageAlignment == 0,
  27                kMaxSizePerPlatformHandle_not_a_multiple_of_alignment);
  28
  29 STATIC_CONST_MEMBER_DEFINITION const size_t
  30     TransportData::kMaxSerializedDispatcherSize;
  31 STATIC_CONST_MEMBER_DEFINITION const size_t
  32     TransportData::kMaxSerializedDispatcherPlatformHandles;
  33
  34 // static
  35 const size_t TransportData::kMaxPlatformHandles =
  36     kMaxMessageNumHandles * kMaxSerializedDispatcherPlatformHandles;
  37
  38 // In additional to the header, for each attached (Mojo) handle there'll be a
  39 // handle table entry and serialized dispatcher data.
  40 // Note: This definition must follow the one for |kMaxPlatformHandles|;
  41 // otherwise, we get a static initializer with gcc (but not clang).
  42 // static
  43 const size_t TransportData::kMaxBufferSize =
  44     sizeof(Header) +
  45     kMaxMessageNumHandles * (sizeof(HandleTableEntry) +
  46                                  kMaxSerializedDispatcherSize) +
  47     kMaxPlatformHandles * kMaxSizePerPlatformHandle;
  48
  49 struct TransportData::PrivateStructForCompileAsserts {
  50   // The size of |Header| must be a multiple of the alignment.
  51   COMPILE_ASSERT(sizeof(Header) % MessageInTransit::kMessageAlignment == 0,
  52                  sizeof_MessageInTransit_Header_invalid);
  53
  54   // The maximum serialized dispatcher size must be a multiple of the alignment.
  55   COMPILE_ASSERT(kMaxSerializedDispatcherSize %
  56                      MessageInTransit::kMessageAlignment == 0,
  57                  kMaxSerializedDispatcherSize_not_a_multiple_of_alignment);
  58
  59   // The size of |HandleTableEntry| must be a multiple of the alignment.
  60   COMPILE_ASSERT(sizeof(HandleTableEntry) %
  61                      MessageInTransit::kMessageAlignment == 0,
  62                  sizeof_MessageInTransit_HandleTableEntry_invalid);
  63 };
  64
  65 TransportData::TransportData(scoped_ptr<DispatcherVector> dispatchers,
  66                              Channel* channel) {
  67   DCHECK(dispatchers);
  68   DCHECK(channel);
  69
  70   const size_t num_handles = dispatchers->size();
  71   DCHECK_GT(num_handles, 0u);
  72
  73   // The offset to the start of the (Mojo) handle table.
  74   const size_t handle_table_start_offset = sizeof(Header);
  75   // The offset to the start of the serialized dispatcher data.
  76   const size_t serialized_dispatcher_start_offset =
  77       handle_table_start_offset + num_handles * sizeof(HandleTableEntry);
  78   // The estimated size of the secondary buffer. We compute this estimate below.
  79   // It must be at least as big as the (eventual) actual size.
  80   size_t estimated_size = serialized_dispatcher_start_offset;
  81   size_t estimated_num_platform_handles = 0;
  82 #if DCHECK_IS_ON
  83   std::vector<size_t> all_max_sizes(num_handles);
  84   std::vector<size_t> all_max_platform_handles(num_handles);
  85 #endif
  86   for (size_t i = 0; i < num_handles; i++) {
  87     if (Dispatcher* dispatcher = (*dispatchers)[i].get()) {
  88       size_t max_size = 0;
  89       size_t max_platform_handles = 0;
  90       Dispatcher::TransportDataAccess::StartSerialize(
  91               dispatcher, channel, &max_size, &max_platform_handles);
  92
  93       DCHECK_LE(max_size, kMaxSerializedDispatcherSize);
  94       estimated_size += MessageInTransit::RoundUpMessageAlignment(max_size);
  95       DCHECK_LE(estimated_size, kMaxBufferSize);
  96
  97       DCHECK_LE(max_platform_handles,
  98                 kMaxSerializedDispatcherPlatformHandles);
  99       estimated_num_platform_handles += max_platform_handles;
 100       DCHECK_LE(estimated_num_platform_handles, kMaxPlatformHandles);
 101
 102 #if DCHECK_IS_ON
 103       all_max_sizes[i] = max_size;
 104       all_max_platform_handles[i] = max_platform_handles;
 105 #endif
 106     }
 107   }
 108
 109   size_t size_per_platform_handle = 0;
 110   if (estimated_num_platform_handles > 0) {
 111     size_per_platform_handle = channel->GetSerializedPlatformHandleSize();
 112     DCHECK_LE(size_per_platform_handle, kMaxSizePerPlatformHandle);
 113     estimated_size += estimated_num_platform_handles * size_per_platform_handle;
 114     estimated_size = MessageInTransit::RoundUpMessageAlignment(estimated_size);
 115     DCHECK_LE(estimated_size, kMaxBufferSize);
 116   }
 117
 118   buffer_.reset(static_cast<char*>(
 119       base::AlignedAlloc(estimated_size, MessageInTransit::kMessageAlignment)));
 120   // Entirely clear out the secondary buffer, since then we won't have to worry
 121   // about clearing padding or unused space (e.g., if a dispatcher fails to
 122   // serialize).
 123   memset(buffer_.get(), 0, estimated_size);
 124
 125   if (estimated_num_platform_handles > 0) {
 126     DCHECK(!platform_handles_);
 127     platform_handles_.reset(new embedder::PlatformHandleVector());
 128   }
 129
 130   Header* header = reinterpret_cast<Header*>(buffer_.get());
 131   header->num_handles = static_cast<uint32_t>(num_handles);
 132   // (Okay to leave |platform_handle_table_offset|, |num_platform_handles|, and
 133   // |unused| be zero; we'll set the former two later if necessary.)
 134
 135   HandleTableEntry* handle_table = reinterpret_cast<HandleTableEntry*>(
 136       buffer_.get() + handle_table_start_offset);
 137   size_t current_offset = serialized_dispatcher_start_offset;
 138   for (size_t i = 0; i < num_handles; i++) {
 139     Dispatcher* dispatcher = (*dispatchers)[i].get();
 140     if (!dispatcher) {
 141       COMPILE_ASSERT(Dispatcher::kTypeUnknown == 0,
 142                      value_of_Dispatcher_kTypeUnknown_must_be_zero);
 143       continue;
 144     }
 145
 146 #if DCHECK_IS_ON
 147     size_t old_platform_handles_size =
 148         platform_handles_ ? platform_handles_->size() : 0;
 149 #endif
 150
 151     void* destination = buffer_.get() + current_offset;
 152     size_t actual_size = 0;
 153     if (Dispatcher::TransportDataAccess::EndSerializeAndClose(
 154             dispatcher, channel, destination, &actual_size,
 155             platform_handles_.get())) {
 156       handle_table[i].type = static_cast<int32_t>(dispatcher->GetType());
 157       handle_table[i].offset = static_cast<uint32_t>(current_offset);
 158       handle_table[i].size = static_cast<uint32_t>(actual_size);
 159       // (Okay to not set |unused| since we cleared the entire buffer.)
 160
 161 #if DCHECK_IS_ON
 162       DCHECK_LE(actual_size, all_max_sizes[i]);
 163       DCHECK_LE(platform_handles_ ? (platform_handles_->size() -
 164                                          old_platform_handles_size) : 0,
 165                 all_max_platform_handles[i]);
 166 #endif
 167     } else {
 168       // Nothing to do on failure, since |buffer_| was cleared, and
 169       // |kTypeUnknown| is zero. The handle was simply closed.
 170       LOG(ERROR) << "Failed to serialize handle to remote message pipe";
 171     }
 172
 173     current_offset += MessageInTransit::RoundUpMessageAlignment(actual_size);
 174     DCHECK_LE(current_offset, estimated_size);
 175     DCHECK_LE(platform_handles_ ? platform_handles_->size() : 0,
 176               estimated_num_platform_handles);
 177   }
 178
 179   if (platform_handles_ && platform_handles_->size() > 0) {
 180     header->platform_handle_table_offset =
 181         static_cast<uint32_t>(current_offset);
 182     header->num_platform_handles =
 183         static_cast<uint32_t>(platform_handles_->size());
 184     current_offset += platform_handles_->size() * size_per_platform_handle;
 185     current_offset = MessageInTransit::RoundUpMessageAlignment(current_offset);
 186   }
 187
 188   // There's no aligned realloc, so it's no good way to release unused space (if
 189   // we overshot our estimated space requirements).
 190   buffer_size_ = current_offset;
 191
 192   // |dispatchers_| will be destroyed as it goes out of scope.
 193 }
 194
 195 #if defined(OS_POSIX)
 196 TransportData::TransportData(
 197     embedder::ScopedPlatformHandleVectorPtr platform_handles)
 198     : buffer_size_(sizeof(Header)),
 199       platform_handles_(platform_handles.Pass()) {
 200   buffer_.reset(static_cast<char*>(
 201       base::AlignedAlloc(buffer_size_, MessageInTransit::kMessageAlignment)));
 202   memset(buffer_.get(), 0, buffer_size_);
 203 }
 204 #endif  // defined(OS_POSIX)
 205
 206 TransportData::~TransportData() {
 207 }
 208
 209 // static
 210 const char* TransportData::ValidateBuffer(
 211     size_t serialized_platform_handle_size,
 212     const void* buffer,
 213     size_t buffer_size) {
 214   DCHECK(buffer);
 215   DCHECK_GT(buffer_size, 0u);
 216
 217   // Always make sure that the buffer size is sane; if it's not, someone's
 218   // messing with us.
 219   if (buffer_size < sizeof(Header) || buffer_size > kMaxBufferSize ||
 220       buffer_size % MessageInTransit::kMessageAlignment != 0)
 221     return "Invalid message secondary buffer size";
 222
 223   const Header* header = static_cast<const Header*>(buffer);
 224   const size_t num_handles = header->num_handles;
 225
 226 #if !defined(OS_POSIX)
 227   // On POSIX, we send control messages with platform handles (but no handles)
 228   // attached (see the comments for
 229   // |TransportData(embedder::ScopedPlatformHandleVectorPtr)|. (This check isn't
 230   // important security-wise anyway.)
 231   if (num_handles == 0)
 232     return "Message has no handles attached, but secondary buffer present";
 233 #endif
 234
 235   // Sanity-check |num_handles| (before multiplying it against anything).
 236   if (num_handles > kMaxMessageNumHandles)
 237     return "Message handle payload too large";
 238
 239   if (buffer_size < sizeof(Header) + num_handles * sizeof(HandleTableEntry))
 240     return "Message secondary buffer too small";
 241
 242   if (header->num_platform_handles == 0) {
 243     // Then |platform_handle_table_offset| should also be zero.
 244     if (header->platform_handle_table_offset != 0) {
 245       return
 246           "Message has no handles attached, but platform handle table present";
 247     }
 248   } else {
 249     // |num_handles| has already been validated, so the multiplication is okay.
 250     if (header->num_platform_handles >
 251             num_handles * kMaxSerializedDispatcherPlatformHandles)
 252       return "Message has too many platform handles attached";
 253
 254     static const char kInvalidPlatformHandleTableOffset[] =
 255         "Message has invalid platform handle table offset";
 256     // This doesn't check that the platform handle table doesn't alias other
 257     // stuff, but it doesn't matter, since it's all read-only.
 258     if (header->platform_handle_table_offset %
 259             MessageInTransit::kMessageAlignment != 0)
 260       return kInvalidPlatformHandleTableOffset;
 261
 262     // ">" instead of ">=" since the size per handle may be zero.
 263     if (header->platform_handle_table_offset > buffer_size)
 264       return kInvalidPlatformHandleTableOffset;
 265
 266     // We already checked |platform_handle_table_offset| and
 267     // |num_platform_handles|, so the addition and multiplication are okay.
 268     if (header->platform_handle_table_offset +
 269             header->num_platform_handles * serialized_platform_handle_size >
 270             buffer_size)
 271       return kInvalidPlatformHandleTableOffset;
 272   }
 273
 274   const HandleTableEntry* handle_table =
 275       reinterpret_cast<const HandleTableEntry*>(
 276           static_cast<const char*>(buffer) + sizeof(Header));
 277   static const char kInvalidSerializedDispatcher[] =
 278       "Message contains invalid serialized dispatcher";
 279   for (size_t i = 0; i < num_handles; i++) {
 280     size_t offset = handle_table[i].offset;
 281     if (offset % MessageInTransit::kMessageAlignment != 0)
 282       return kInvalidSerializedDispatcher;
 283
 284     size_t size = handle_table[i].size;
 285     if (size > kMaxSerializedDispatcherSize || size > buffer_size)
 286       return kInvalidSerializedDispatcher;
 287
 288     // Note: This is an overflow-safe check for |offset + size > buffer_size|
 289     // (we know that |size <= buffer_size| from the previous check).
 290     if (offset > buffer_size - size)
 291       return kInvalidSerializedDispatcher;
 292   }
 293
 294   return NULL;
 295 }
 296
 297 // static
 298 void TransportData::GetPlatformHandleTable(const void* transport_data_buffer,
 299                                            size_t* num_platform_handles,
 300                                            const void** platform_handle_table) {
 301   DCHECK(transport_data_buffer);
 302   DCHECK(num_platform_handles);
 303   DCHECK(platform_handle_table);
 304
 305   const Header* header = static_cast<const Header*>(transport_data_buffer);
 306   *num_platform_handles = header->num_platform_handles;
 307   *platform_handle_table = static_cast<const char*>(transport_data_buffer) +
 308       header->platform_handle_table_offset;
 309 }
 310
 311 // static
 312 scoped_ptr<DispatcherVector> TransportData::DeserializeDispatchers(
 313     const void* buffer,
 314     size_t buffer_size,
 315     embedder::ScopedPlatformHandleVectorPtr platform_handles,
 316     Channel* channel) {
 317   DCHECK(buffer);
 318   DCHECK_GT(buffer_size, 0u);
 319   DCHECK(channel);
 320
 321   const Header* header = static_cast<const Header*>(buffer);
 322   const size_t num_handles = header->num_handles;
 323   scoped_ptr<DispatcherVector> dispatchers(new DispatcherVector(num_handles));
 324
 325   const HandleTableEntry* handle_table =
 326       reinterpret_cast<const HandleTableEntry*>(
 327           static_cast<const char*>(buffer) + sizeof(Header));
 328   for (size_t i = 0; i < num_handles; i++) {
 329     size_t offset = handle_table[i].offset;
 330     size_t size = handle_table[i].size;
 331     // Should already have been checked by |ValidateBuffer()|:
 332     DCHECK_EQ(offset % MessageInTransit::kMessageAlignment, 0u);
 333     DCHECK_LE(offset, buffer_size);
 334     DCHECK_LE(offset + size, buffer_size);
 335
 336     const void* source = static_cast<const char*>(buffer) + offset;
 337     (*dispatchers)[i] = Dispatcher::TransportDataAccess::Deserialize(
 338         channel, handle_table[i].type, source, size, platform_handles.get());
 339   }
 340
 341   return dispatchers.Pass();
 342 }
 343
 344 }  // namespace system
 345 }  // namespace mojo