net/server/web_socket_encoder.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 "net/server/web_socket_encoder.h"
   6
   7 #include "base/logging.h"
   8 #include "base/strings/string_number_conversions.h"
   9 #include "base/strings/stringprintf.h"
  10 #include "net/base/io_buffer.h"
  11 #include "net/websockets/websocket_extension_parser.h"
  12
  13 namespace net {
  14
  15 const char WebSocketEncoder::kClientExtensions[] =
  16     "Sec-WebSocket-Extensions: permessage-deflate; client_max_window_bits";
  17
  18 namespace {
  19
  20 const int kInflaterChunkSize = 16 * 1024;
  21
  22 // Constants for hybi-10 frame format.
  23
  24 typedef int OpCode;
  25
  26 const OpCode kOpCodeContinuation = 0x0;
  27 const OpCode kOpCodeText = 0x1;
  28 const OpCode kOpCodeBinary = 0x2;
  29 const OpCode kOpCodeClose = 0x8;
  30 const OpCode kOpCodePing = 0x9;
  31 const OpCode kOpCodePong = 0xA;
  32
  33 const unsigned char kFinalBit = 0x80;
  34 const unsigned char kReserved1Bit = 0x40;
  35 const unsigned char kReserved2Bit = 0x20;
  36 const unsigned char kReserved3Bit = 0x10;
  37 const unsigned char kOpCodeMask = 0xF;
  38 const unsigned char kMaskBit = 0x80;
  39 const unsigned char kPayloadLengthMask = 0x7F;
  40
  41 const size_t kMaxSingleBytePayloadLength = 125;
  42 const size_t kTwoBytePayloadLengthField = 126;
  43 const size_t kEightBytePayloadLengthField = 127;
  44 const size_t kMaskingKeyWidthInBytes = 4;
  45
  46 WebSocket::ParseResult DecodeFrameHybi17(const base::StringPiece& frame,
  47                                          bool client_frame,
  48                                          int* bytes_consumed,
  49                                          std::string* output,
  50                                          bool* compressed) {
  51   size_t data_length = frame.length();
  52   if (data_length < 2)
  53     return WebSocket::FRAME_INCOMPLETE;
  54
  55   const char* buffer_begin = const_cast<char*>(frame.data());
  56   const char* p = buffer_begin;
  57   const char* buffer_end = p + data_length;
  58
  59   unsigned char first_byte = *p++;
  60   unsigned char second_byte = *p++;
  61
  62   bool final = (first_byte & kFinalBit) != 0;
  63   bool reserved1 = (first_byte & kReserved1Bit) != 0;
  64   bool reserved2 = (first_byte & kReserved2Bit) != 0;
  65   bool reserved3 = (first_byte & kReserved3Bit) != 0;
  66   int op_code = first_byte & kOpCodeMask;
  67   bool masked = (second_byte & kMaskBit) != 0;
  68   *compressed = reserved1;
  69   if (!final || reserved2 || reserved3)
  70     return WebSocket::FRAME_ERROR;  // Only compression extension is supported.
  71
  72   bool closed = false;
  73   switch (op_code) {
  74     case kOpCodeClose:
  75       closed = true;
  76       break;
  77     case kOpCodeText:
  78       break;
  79     case kOpCodeBinary:        // We don't support binary frames yet.
  80     case kOpCodeContinuation:  // We don't support binary frames yet.
  81     case kOpCodePing:          // We don't support binary frames yet.
  82     case kOpCodePong:          // We don't support binary frames yet.
  83     default:
  84       return WebSocket::FRAME_ERROR;
  85   }
  86
  87   if (client_frame && !masked)  // In Hybi-17 spec client MUST mask its frame.
  88     return WebSocket::FRAME_ERROR;
  89
  90   uint64 payload_length64 = second_byte & kPayloadLengthMask;
  91   if (payload_length64 > kMaxSingleBytePayloadLength) {
  92     int extended_payload_length_size;
  93     if (payload_length64 == kTwoBytePayloadLengthField)
  94       extended_payload_length_size = 2;
  95     else {
  96       DCHECK(payload_length64 == kEightBytePayloadLengthField);
  97       extended_payload_length_size = 8;
  98     }
  99     if (buffer_end - p < extended_payload_length_size)
 100       return WebSocket::FRAME_INCOMPLETE;
 101     payload_length64 = 0;
 102     for (int i = 0; i < extended_payload_length_size; ++i) {
 103       payload_length64 <<= 8;
 104       payload_length64 |= static_cast<unsigned char>(*p++);
 105     }
 106   }
 107
 108   size_t actual_masking_key_length = masked ? kMaskingKeyWidthInBytes : 0;
 109   static const uint64 max_payload_length = 0x7FFFFFFFFFFFFFFFull;
 110   static size_t max_length = std::numeric_limits<size_t>::max();
 111   if (payload_length64 > max_payload_length ||
 112       payload_length64 + actual_masking_key_length > max_length) {
 113     // WebSocket frame length too large.
 114     return WebSocket::FRAME_ERROR;
 115   }
 116   size_t payload_length = static_cast<size_t>(payload_length64);
 117
 118   size_t total_length = actual_masking_key_length + payload_length;
 119   if (static_cast<size_t>(buffer_end - p) < total_length)
 120     return WebSocket::FRAME_INCOMPLETE;
 121
 122   if (masked) {
 123     output->resize(payload_length);
 124     const char* masking_key = p;
 125     char* payload = const_cast<char*>(p + kMaskingKeyWidthInBytes);
 126     for (size_t i = 0; i < payload_length; ++i)  // Unmask the payload.
 127       (*output)[i] = payload[i] ^ masking_key[i % kMaskingKeyWidthInBytes];
 128   } else {
 129     output->assign(p, p + payload_length);
 130   }
 131
 132   size_t pos = p + actual_masking_key_length + payload_length - buffer_begin;
 133   *bytes_consumed = pos;
 134   return closed ? WebSocket::FRAME_CLOSE : WebSocket::FRAME_OK;
 135 }
 136
 137 void EncodeFrameHybi17(const std::string& message,
 138                        int masking_key,
 139                        bool compressed,
 140                        std::string* output) {
 141   std::vector<char> frame;
 142   OpCode op_code = kOpCodeText;
 143   size_t data_length = message.length();
 144
 145   int reserved1 = compressed ? kReserved1Bit : 0;
 146   frame.push_back(kFinalBit | op_code | reserved1);
 147   char mask_key_bit = masking_key != 0 ? kMaskBit : 0;
 148   if (data_length <= kMaxSingleBytePayloadLength)
 149     frame.push_back(data_length | mask_key_bit);
 150   else if (data_length <= 0xFFFF) {
 151     frame.push_back(kTwoBytePayloadLengthField | mask_key_bit);
 152     frame.push_back((data_length & 0xFF00) >> 8);
 153     frame.push_back(data_length & 0xFF);
 154   } else {
 155     frame.push_back(kEightBytePayloadLengthField | mask_key_bit);
 156     char extended_payload_length[8];
 157     size_t remaining = data_length;
 158     // Fill the length into extended_payload_length in the network byte order.
 159     for (int i = 0; i < 8; ++i) {
 160       extended_payload_length[7 - i] = remaining & 0xFF;
 161       remaining >>= 8;
 162     }
 163     frame.insert(frame.end(), extended_payload_length,
 164                  extended_payload_length + 8);
 165     DCHECK(!remaining);
 166   }
 167
 168   const char* data = const_cast<char*>(message.data());
 169   if (masking_key != 0) {
 170     const char* mask_bytes = reinterpret_cast<char*>(&masking_key);
 171     frame.insert(frame.end(), mask_bytes, mask_bytes + 4);
 172     for (size_t i = 0; i < data_length; ++i)  // Mask the payload.
 173       frame.push_back(data[i] ^ mask_bytes[i % kMaskingKeyWidthInBytes]);
 174   } else {
 175     frame.insert(frame.end(), data, data + data_length);
 176   }
 177   *output = std::string(&frame[0], frame.size());
 178 }
 179
 180 }  // anonymous namespace
 181
 182 // static
 183 WebSocketEncoder* WebSocketEncoder::CreateServer(
 184     const std::string& request_extensions,
 185     std::string* response_extensions) {
 186   bool deflate;
 187   bool has_client_window_bits;
 188   int client_window_bits;
 189   int server_window_bits;
 190   bool client_no_context_takeover;
 191   bool server_no_context_takeover;
 192   ParseExtensions(request_extensions, &deflate, &has_client_window_bits,
 193                   &client_window_bits, &server_window_bits,
 194                   &client_no_context_takeover, &server_no_context_takeover);
 195
 196   if (deflate) {
 197     *response_extensions = base::StringPrintf(
 198         "permessage-deflate; server_max_window_bits=%d%s", server_window_bits,
 199         server_no_context_takeover ? "; server_no_context_takeover" : "");
 200     if (has_client_window_bits) {
 201       base::StringAppendF(response_extensions, "; client_max_window_bits=%d",
 202                           client_window_bits);
 203     } else {
 204       DCHECK_EQ(client_window_bits, 15);
 205     }
 206     return new WebSocketEncoder(true /* is_server */, server_window_bits,
 207                                 client_window_bits, server_no_context_takeover);
 208   } else {
 209     *response_extensions = std::string();
 210     return new WebSocketEncoder(true /* is_server */);
 211   }
 212 }
 213
 214 // static
 215 WebSocketEncoder* WebSocketEncoder::CreateClient(
 216     const std::string& response_extensions) {
 217   bool deflate;
 218   bool has_client_window_bits;
 219   int client_window_bits;
 220   int server_window_bits;
 221   bool client_no_context_takeover;
 222   bool server_no_context_takeover;
 223   ParseExtensions(response_extensions, &deflate, &has_client_window_bits,
 224                   &client_window_bits, &server_window_bits,
 225                   &client_no_context_takeover, &server_no_context_takeover);
 226
 227   if (deflate) {
 228     return new WebSocketEncoder(false /* is_server */, client_window_bits,
 229                                 server_window_bits, client_no_context_takeover);
 230   } else {
 231     return new WebSocketEncoder(false /* is_server */);
 232   }
 233 }
 234
 235 // static
 236 void WebSocketEncoder::ParseExtensions(const std::string& header_value,
 237                                        bool* deflate,
 238                                        bool* has_client_window_bits,
 239                                        int* client_window_bits,
 240                                        int* server_window_bits,
 241                                        bool* client_no_context_takeover,
 242                                        bool* server_no_context_takeover) {
 243   *deflate = false;
 244   *has_client_window_bits = false;
 245   *client_window_bits = 15;
 246   *server_window_bits = 15;
 247   *client_no_context_takeover = false;
 248   *server_no_context_takeover = false;
 249
 250   if (header_value.empty())
 251     return;
 252
 253   WebSocketExtensionParser parser;
 254   if (!parser.Parse(header_value))
 255     return;
 256   const std::vector<WebSocketExtension>& extensions = parser.extensions();
 257   // TODO(tyoshino): Fail if this method is used for parsing a response and
 258   // there are multiple permessage-deflate extensions or there are any unknown
 259   // extensions.
 260   for (const auto& extension : extensions) {
 261     if (extension.name() != "permessage-deflate") {
 262       continue;
 263     }
 264
 265     const std::vector<WebSocketExtension::Parameter>& parameters =
 266         extension.parameters();
 267     for (const auto& param : parameters) {
 268       const std::string& name = param.name();
 269       // TODO(tyoshino): Fail the connection when an invalid value is given.
 270       if (name == "client_max_window_bits") {
 271         *has_client_window_bits = true;
 272         if (param.HasValue()) {
 273           int bits = 0;
 274           if (base::StringToInt(param.value(), &bits) && bits >= 8 &&
 275               bits <= 15) {
 276             *client_window_bits = bits;
 277           }
 278         }
 279       }
 280       if (name == "server_max_window_bits" && param.HasValue()) {
 281         int bits = 0;
 282         if (base::StringToInt(param.value(), &bits) && bits >= 8 && bits <= 15)
 283           *server_window_bits = bits;
 284       }
 285       if (name == "client_no_context_takeover")
 286         *client_no_context_takeover = true;
 287       if (name == "server_no_context_takeover")
 288         *server_no_context_takeover = true;
 289     }
 290     *deflate = true;
 291
 292     break;
 293   }
 294 }
 295
 296 WebSocketEncoder::WebSocketEncoder(bool is_server) : is_server_(is_server) {
 297 }
 298
 299 WebSocketEncoder::WebSocketEncoder(bool is_server,
 300                                    int deflate_bits,
 301                                    int inflate_bits,
 302                                    bool no_context_takeover)
 303     : is_server_(is_server) {
 304   deflater_.reset(new WebSocketDeflater(
 305       no_context_takeover ? WebSocketDeflater::DO_NOT_TAKE_OVER_CONTEXT
 306                           : WebSocketDeflater::TAKE_OVER_CONTEXT));
 307   inflater_.reset(
 308       new WebSocketInflater(kInflaterChunkSize, kInflaterChunkSize));
 309
 310   if (!deflater_->Initialize(deflate_bits) ||
 311       !inflater_->Initialize(inflate_bits)) {
 312     // Disable deflate support.
 313     deflater_.reset();
 314     inflater_.reset();
 315   }
 316 }
 317
 318 WebSocketEncoder::~WebSocketEncoder() {
 319 }
 320
 321 WebSocket::ParseResult WebSocketEncoder::DecodeFrame(
 322     const base::StringPiece& frame,
 323     int* bytes_consumed,
 324     std::string* output) {
 325   bool compressed;
 326   WebSocket::ParseResult result =
 327       DecodeFrameHybi17(frame, is_server_, bytes_consumed, output, &compressed);
 328   if (result == WebSocket::FRAME_OK && compressed) {
 329     if (!Inflate(output))
 330       result = WebSocket::FRAME_ERROR;
 331   }
 332   return result;
 333 }
 334
 335 void WebSocketEncoder::EncodeFrame(const std::string& frame,
 336                                    int masking_key,
 337                                    std::string* output) {
 338   std::string compressed;
 339   if (Deflate(frame, &compressed))
 340     EncodeFrameHybi17(compressed, masking_key, true, output);
 341   else
 342     EncodeFrameHybi17(frame, masking_key, false, output);
 343 }
 344
 345 bool WebSocketEncoder::Inflate(std::string* message) {
 346   if (!inflater_)
 347     return false;
 348   if (!inflater_->AddBytes(message->data(), message->length()))
 349     return false;
 350   if (!inflater_->Finish())
 351     return false;
 352
 353   std::vector<char> output;
 354   while (inflater_->CurrentOutputSize() > 0) {
 355     scoped_refptr<IOBufferWithSize> chunk =
 356         inflater_->GetOutput(inflater_->CurrentOutputSize());
 357     if (!chunk.get())
 358       return false;
 359     output.insert(output.end(), chunk->data(), chunk->data() + chunk->size());
 360   }
 361
 362   *message =
 363       output.size() ? std::string(&output[0], output.size()) : std::string();
 364   return true;
 365 }
 366
 367 bool WebSocketEncoder::Deflate(const std::string& message,
 368                                std::string* output) {
 369   if (!deflater_)
 370     return false;
 371   if (!deflater_->AddBytes(message.data(), message.length())) {
 372     deflater_->Finish();
 373     return false;
 374   }
 375   if (!deflater_->Finish())
 376     return false;
 377   scoped_refptr<IOBufferWithSize> buffer =
 378       deflater_->GetOutput(deflater_->CurrentOutputSize());
 379   if (!buffer.get())
 380     return false;
 381   *output = std::string(buffer->data(), buffer->size());
 382   return true;
 383 }
 384
 385 }  // namespace net