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/*
* Copyright (C) 2011 Google Inc. All rights reserved.
* Copyright (C) Research In Motion Limited 2011. All rights reserved.
* Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies)
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public License
* along with this program; see the file COPYING.LIB. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
* Boston, MA 02110-1301, USA.
*
*/
#include "config.h"
#include "WebSocketFrame.h"
#include <wtf/CryptographicallyRandomNumber.h>
#include <wtf/MathExtras.h>
#include <wtf/text/MakeString.h>
#include <wtf/text/ParsingUtilities.h>
namespace WebCore {
// Constants for hybi-10 frame format.
constexpr uint8_t finalBit = 0x80;
constexpr uint8_t compressBit = 0x40;
constexpr uint8_t reserved2Bit = 0x20;
constexpr uint8_t reserved3Bit = 0x10;
constexpr uint8_t opCodeMask = 0xF;
constexpr uint8_t maskBit = 0x80;
constexpr uint8_t payloadLengthMask = 0x7F;
constexpr size_t maxPayloadLengthWithoutExtendedLengthField = 125;
constexpr size_t payloadLengthWithTwoByteExtendedLengthField = 126;
constexpr size_t payloadLengthWithEightByteExtendedLengthField = 127;
constexpr size_t maskingKeyWidthInBytes = 4;
bool WebSocketFrame::needsExtendedLengthField(size_t payloadLength)
{
return payloadLength > maxPayloadLengthWithoutExtendedLengthField;
}
WebSocketFrame::ParseFrameResult WebSocketFrame::parseFrame(std::span<uint8_t> data, WebSocketFrame& frame, const uint8_t*& frameEnd, String& errorString)
{
if (data.size() < 2)
return FrameIncomplete;
auto firstByte = data[0];
auto secondByte = data[1];
skip(data, 2);
bool final = firstByte & finalBit;
bool compress = firstByte & compressBit;
bool reserved2 = firstByte & reserved2Bit;
bool reserved3 = firstByte & reserved3Bit;
auto opCode = firstByte & opCodeMask;
bool masked = secondByte & maskBit;
uint64_t payloadLength64 = secondByte & payloadLengthMask;
if (payloadLength64 > maxPayloadLengthWithoutExtendedLengthField) {
size_t extendedPayloadLengthSize;
if (payloadLength64 == payloadLengthWithTwoByteExtendedLengthField)
extendedPayloadLengthSize = 2;
else {
ASSERT(payloadLength64 == payloadLengthWithEightByteExtendedLengthField);
extendedPayloadLengthSize = 8;
}
if (data.size() < extendedPayloadLengthSize)
return FrameIncomplete;
payloadLength64 = 0;
for (size_t i = 0; i < extendedPayloadLengthSize; ++i) {
payloadLength64 <<= 8;
payloadLength64 |= data[i];
}
skip(data, extendedPayloadLengthSize);
if (extendedPayloadLengthSize == 2 && payloadLength64 <= maxPayloadLengthWithoutExtendedLengthField) {
errorString = "The minimal number of bytes MUST be used to encode the length"_s;
return FrameError;
}
if (extendedPayloadLengthSize == 8 && payloadLength64 <= 0xFFFF) {
errorString = "The minimal number of bytes MUST be used to encode the length"_s;
return FrameError;
}
}
constexpr uint64_t maxPayloadLength = UINT64_C(0x7FFFFFFFFFFFFFFF);
size_t maskingKeyLength = masked ? maskingKeyWidthInBytes : 0;
if (payloadLength64 > maxPayloadLength || payloadLength64 + maskingKeyLength > std::numeric_limits<size_t>::max()) {
errorString = makeString("WebSocket frame length too large: "_s, payloadLength64, " bytes"_s);
return FrameError;
}
size_t payloadLength = static_cast<size_t>(payloadLength64);
if (data.size() < maskingKeyLength + payloadLength)
return FrameIncomplete;
if (masked) {
auto maskingKey = data;
auto payload = data.subspan(maskingKeyWidthInBytes);
for (size_t i = 0; i < payloadLength; ++i)
payload[i] ^= maskingKey[i % maskingKeyWidthInBytes]; // Unmask the payload.
}
frame.opCode = static_cast<WebSocketFrame::OpCode>(opCode);
frame.final = final;
frame.compress = compress;
frame.reserved2 = reserved2;
frame.reserved3 = reserved3;
frame.masked = masked;
frame.payload = data.subspan(maskingKeyLength, payloadLength);
frameEnd = data.subspan(maskingKeyLength + payloadLength).data();
return FrameOK;
}
static void appendFramePayload(const WebSocketFrame& frame, Vector<uint8_t>& frameData)
{
size_t maskingKeyStart = 0;
if (frame.masked) {
maskingKeyStart = frameData.size();
frameData.grow(frameData.size() + maskingKeyWidthInBytes); // Add placeholder for masking key. Will be overwritten.
}
size_t payloadStart = frameData.size();
frameData.append(frame.payload);
if (frame.masked) {
cryptographicallyRandomValues(frameData.mutableSpan().subspan(maskingKeyStart, maskingKeyWidthInBytes));
for (size_t i = 0; i < frame.payload.size(); ++i)
frameData[payloadStart + i] ^= frameData[maskingKeyStart + i % maskingKeyWidthInBytes];
}
}
void WebSocketFrame::makeFrameData(Vector<uint8_t>& frameData)
{
ASSERT(!(opCode & ~opCodeMask)); // Checks whether "opCode" fits in the range of opCodes.
frameData.resize(2);
frameData.at(0) = (final ? finalBit : 0) | (compress ? compressBit : 0) | opCode;
frameData.at(1) = masked ? maskBit : 0;
if (payload.size() <= maxPayloadLengthWithoutExtendedLengthField)
frameData.at(1) |= payload.size();
else if (payload.size() <= 0xFFFF) {
frameData.at(1) |= payloadLengthWithTwoByteExtendedLengthField;
frameData.append((payload.size() & 0xFF00) >> 8);
frameData.append(payload.size() & 0xFF);
} else {
frameData.at(1) |= payloadLengthWithEightByteExtendedLengthField;
std::array<uint8_t, 8> extendedPayloadLength;
size_t remaining = payload.size();
// Fill the length into extendedPayloadLength in the network byte order.
for (int i = 0; i < 8; ++i) {
extendedPayloadLength[7 - i] = remaining & 0xFF;
remaining >>= 8;
}
ASSERT(!remaining);
frameData.append(std::span { extendedPayloadLength });
}
appendFramePayload(*this, frameData);
}
WebSocketFrame::WebSocketFrame(OpCode opCode, bool final, bool compress, bool masked, std::span<const uint8_t> payload)
: opCode(opCode)
, final(final)
, compress(compress)
, reserved2(false)
, reserved3(false)
, masked(masked)
, payload(payload)
{
}
} // namespace WebCore
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