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net/server/web_socket_frame.cc

+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "net/server/web_socket_frame.h"
+
+#include "base/rand_util.h"
+#include "base/logging.h"
+
+#include <limits>
+
+namespace net {
+
+// Constants for hybi-10 frame format.
+const WebSocketFrame::OpCode WebSocketFrame::kOpCodeContinuation = 0x0;
+const WebSocketFrame::OpCode WebSocketFrame::kOpCodeText = 0x1;
+const WebSocketFrame::OpCode WebSocketFrame::kOpCodeBinary = 0x2;
+const WebSocketFrame::OpCode WebSocketFrame::kOpCodeClose = 0x8;
+const WebSocketFrame::OpCode WebSocketFrame::kOpCodePing = 0x9;
+const WebSocketFrame::OpCode WebSocketFrame::kOpCodePong = 0xA;
+
+const unsigned char WebSocketFrame::kFinalBit = 0x80;
+const unsigned char WebSocketFrame::kReserved1Bit = 0x40;
+const unsigned char WebSocketFrame::kReserved2Bit = 0x20;
+const unsigned char WebSocketFrame::kReserved3Bit = 0x10;
+const unsigned char WebSocketFrame::kOpCodeMask = 0xF;
+const unsigned char WebSocketFrame::kMaskBit = 0x80;
+const unsigned char WebSocketFrame::kPayloadLengthMask = 0x7F;
+
+const size_t WebSocketFrame::kMaxSingleBytePayloadLength = 125;
+const size_t WebSocketFrame::kTwoBytePayloadLengthField = 126;
+const size_t WebSocketFrame::kEightBytePayloadLengthField = 127;
+const size_t WebSocketFrame::kMaskingKeyWidthInBytes = 4;
+
+WebSocketFrame::ParseResult WebSocketFrame::DecodeFrame(
+    const char* data, size_t data_length) {
+  const char* p = data;
+  const char* buffer_end = data + data_length;
+
+  if (data_length < 2)
+    return FrameIncomplete;
+
+  unsigned char first_byte = *p++;
+  unsigned char second_byte = *p++;
+
+  final_ = first_byte & kFinalBit;
+  reserved1_ = first_byte & kReserved1Bit;
+  reserved2_ = first_byte & kReserved2Bit;
+  reserved3_ = first_byte & kReserved3Bit;
+  op_code_ = first_byte & kOpCodeMask;
+  masked_ = second_byte & kMaskBit;
+
+  uint64_t payload_length64 = second_byte & kPayloadLengthMask;
+  if (payload_length64 > kMaxSingleBytePayloadLength) {
+    int extended_payload_length_size;
+    if (payload_length64 == kTwoBytePayloadLengthField)
+      extended_payload_length_size = 2;
+    else {
+      DCHECK(payload_length64 == kEightBytePayloadLengthField);
+      extended_payload_length_size = 8;
+    }
+    if (buffer_end - p < extended_payload_length_size)
+      return FrameIncomplete;
+    payload_length64 = 0;
+    for (int i = 0; i < extended_payload_length_size; ++i) {
+      payload_length64 <<= 8;
+      payload_length64 |= static_cast<unsigned char>(*p++);
+    }
+  }
+
+  static const uint64_t max_payload_ength = 0x7FFFFFFFFFFFFFFFull;
+  size_t masking_key_length = masked_ ? kMaskingKeyWidthInBytes : 0;
+  static size_t max_length = std::numeric_limits<size_t>::max();
+  if (payload_length64 > max_payload_ength ||
+      payload_length64 + masking_key_length > max_length) {
+    // WebSocket frame length too large.
+    return FrameError;
+  }
+  payload_length_ = static_cast<size_t>(payload_length64);
+
+  size_t total_length = masking_key_length + payload_length_;
+  if (static_cast<size_t>(buffer_end - p) < total_length)
+    return FrameIncomplete;
+
+  if (masked_) {
+    const char* masking_key = p;
+    char* payload = const_cast<char*>(p + kMaskingKeyWidthInBytes);
+    for (size_t i = 0; i < payload_length_; ++i) // Unmask the payload.
+      payload[i] ^= masking_key[i % kMaskingKeyWidthInBytes];
+  }
+
+  payload_ = p + masking_key_length;
+  frame_end_ = p + masking_key_length + payload_length_;
+  return FrameOK;
+}
+
+std::vector<char> WebSocketFrame::EncodeFrame(
+    OpCode op_code, const char* data, size_t data_length) {
+  std::vector<char> frame;
+
+  // Checks whether "op_code" fits in the range of opCodes.
+  DCHECK(!(op_code & ~kOpCodeMask));
+  frame.push_back(kFinalBit | op_code);
+  if (data_length <= kMaxSingleBytePayloadLength)
+    frame.push_back(kMaskBit | data_length);
+  else if (data_length <= 0xFFFF) {
+    frame.push_back(kMaskBit | kTwoBytePayloadLengthField);
+    frame.push_back((data_length & 0xFF00) >> 8);
+    frame.push_back(data_length & 0xFF);
+  } else {
+    frame.push_back(kMaskBit | kEightBytePayloadLengthField);
+    char extended_payload_length[8];
+    size_t remaining = data_length;
+    // Fill the length into extended_payload_length in the network byte order.
+    for (int i = 0; i < 8; ++i) {
+      extended_payload_length[7 - i] = remaining & 0xFF;
+      remaining >>= 8;
+    }
+    frame.insert(frame.end(),
+                 extended_payload_length,
+                 extended_payload_length + 8);
+    CHECK(!remaining);
+  }
+
+  // Mask the frame.
+  size_t masking_key_start = frame.size();
+  // Add placeholder for masking key. Will be overwritten.
+  frame.resize(frame.size() + kMaskingKeyWidthInBytes);
+  size_t payload_start = frame.size();
+  frame.insert(frame.end(), data, data + data_length);
+
+  base::RandBytes(&frame[0] + masking_key_start,
+                  kMaskingKeyWidthInBytes);
+  for (size_t i = 0; i < data_length; ++i) {
+    frame[payload_start + i] ^=
+        frame[masking_key_start + i % kMaskingKeyWidthInBytes];
+  }
+
+  return frame;
+}
+
+
+}  // namespace net