/*
* Copyright (c) 2015, Peter Thorson. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of the WebSocket++ Project nor the
* names of its contributors may be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL PETER THORSON BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/*
* Author: Benjamin Sergeant
* Copyright (c) 2018 Machine Zone, Inc. All rights reserved.
*
* Adapted from websocketpp/extensions/permessage_deflate/enabled.hpp
* (same license as MZ: https://opensource.org/licenses/BSD-3-Clause)
*
* - Reused zlib compression + decompression bits.
* - Refactored to have 2 class for compression and decompression, to allow multi-threading
* and make sure that _compressBuffer is not shared between threads.
* - Original code wasn't working for some reason, I had to add checks
* for the presence of the kEmptyUncompressedBlock at the end of buffer so that servers
* would start accepting receiving/decoding compressed messages. Original code was probably
* modifying the passed in buffers before processing in enabled.hpp ?
* - Added more documentation.
*
* Per message Deflate RFC: https://tools.ietf.org/html/rfc7692
* Chrome websocket -> https://github.com/chromium/chromium/tree/2ca8c5037021c9d2ecc00b787d58a31ed8fc8bcb/net/websockets
*
*/
#include "IXWebSocketPerMessageDeflate.h"
#include "IXWebSocketPerMessageDeflateOptions.h"
#include <iostream>
#include <cassert>
#include <string.h>
namespace
{
// The passed in size (4) is important, without it the string litteral
// is treated as a char* and the null termination (\x00) makes it
// look like an empty string.
const std::string kEmptyUncompressedBlock = std::string("\x00\x00\xff\xff", 4);
const int kBufferSize = 1 << 14;
}
namespace ix
{
//
// Compressor
//
WebSocketPerMessageDeflateCompressor::WebSocketPerMessageDeflateCompressor()
: _compressBufferSize(kBufferSize)
{
memset(&_deflateState, 0, sizeof(_deflateState));
_deflateState.zalloc = Z_NULL;
_deflateState.zfree = Z_NULL;
_deflateState.opaque = Z_NULL;
}
WebSocketPerMessageDeflateCompressor::~WebSocketPerMessageDeflateCompressor()
{
deflateEnd(&_deflateState);
}
bool WebSocketPerMessageDeflateCompressor::init(uint8_t deflateBits,
bool clientNoContextTakeOver)
{
int ret = deflateInit2(
&_deflateState,
Z_DEFAULT_COMPRESSION,
Z_DEFLATED,
-1*deflateBits,
4, // memory level 1-9
Z_DEFAULT_STRATEGY
);
if (ret != Z_OK) return false;
_compressBuffer.reset(new unsigned char[_compressBufferSize]);
_flush = (clientNoContextTakeOver)
? Z_FULL_FLUSH
: Z_SYNC_FLUSH;
return true;
}
bool WebSocketPerMessageDeflateCompressor::endsWith(const std::string& value,
const std::string& ending)
{
if (ending.size() > value.size()) return false;
return std::equal(ending.rbegin(), ending.rend(), value.rbegin());
}
bool WebSocketPerMessageDeflateCompressor::compress(const std::string& in,
std::string& out)
{
//
// 7.2.1. Compression
//
// An endpoint uses the following algorithm to compress a message.
//
// 1. Compress all the octets of the payload of the message using
// DEFLATE.
//
// 2. If the resulting data does not end with an empty DEFLATE block
// with no compression (the "BTYPE" bits are set to 00), append an
// empty DEFLATE block with no compression to the tail end.
//
// 3. Remove 4 octets (that are 0x00 0x00 0xff 0xff) from the tail end.
// After this step, the last octet of the compressed data contains
// (possibly part of) the DEFLATE header bits with the "BTYPE" bits
// set to 00.
//
size_t output;
if (in.empty())
{
uint8_t buf[6] = {0x02, 0x00, 0x00, 0x00, 0xff, 0xff};
out.append((char *)(buf), 6);
return true;
}
_deflateState.avail_in = (uInt) in.size();
_deflateState.next_in = (Bytef*) in.data();
do
{
// Output to local buffer
_deflateState.avail_out = (uInt) _compressBufferSize;
_deflateState.next_out = _compressBuffer.get();
deflate(&_deflateState, _flush);
output = _compressBufferSize - _deflateState.avail_out;
out.append((char *)(_compressBuffer.get()),output);
} while (_deflateState.avail_out == 0);
if (endsWith(out, kEmptyUncompressedBlock))
{
out.resize(out.size() - 4);
}
return true;
}
//
// Decompressor
//
WebSocketPerMessageDeflateDecompressor::WebSocketPerMessageDeflateDecompressor()
: _compressBufferSize(kBufferSize)
{
memset(&_inflateState, 0, sizeof(_inflateState));
_inflateState.zalloc = Z_NULL;
_inflateState.zfree = Z_NULL;
_inflateState.opaque = Z_NULL;
_inflateState.avail_in = 0;
_inflateState.next_in = Z_NULL;
}
WebSocketPerMessageDeflateDecompressor::~WebSocketPerMessageDeflateDecompressor()
{
inflateEnd(&_inflateState);
}
bool WebSocketPerMessageDeflateDecompressor::init(uint8_t inflateBits,
bool clientNoContextTakeOver)
{
int ret = inflateInit2(
&_inflateState,
-1*inflateBits
);
if (ret != Z_OK) return false;
_compressBuffer.reset(new unsigned char[_compressBufferSize]);
_flush = (clientNoContextTakeOver)
? Z_FULL_FLUSH
: Z_SYNC_FLUSH;
return true;
}
bool WebSocketPerMessageDeflateDecompressor::decompress(const std::string& in,
std::string& out)
{
//
// 7.2.2. Decompression
//
// An endpoint uses the following algorithm to decompress a message.
//
// 1. Append 4 octets of 0x00 0x00 0xff 0xff to the tail end of the
// payload of the message.
//
// 2. Decompress the resulting data using DEFLATE.
//
std::string inFixed(in);
inFixed += kEmptyUncompressedBlock;
_inflateState.avail_in = (uInt) inFixed.size();
_inflateState.next_in = (unsigned char *)(const_cast<char *>(inFixed.data()));
do
{
_inflateState.avail_out = (uInt) _compressBufferSize;
_inflateState.next_out = _compressBuffer.get();
int ret = inflate(&_inflateState, Z_SYNC_FLUSH);
if (ret == Z_NEED_DICT || ret == Z_DATA_ERROR || ret == Z_MEM_ERROR)
{
return false; // zlib error
}
out.append(
reinterpret_cast<char *>(_compressBuffer.get()),
_compressBufferSize - _inflateState.avail_out
);
} while (_inflateState.avail_out == 0);
return true;
}
WebSocketPerMessageDeflate::WebSocketPerMessageDeflate()
{
_compressor.reset(new WebSocketPerMessageDeflateCompressor());
_decompressor.reset(new WebSocketPerMessageDeflateDecompressor());
}
WebSocketPerMessageDeflate::~WebSocketPerMessageDeflate()
{
_compressor.reset();
_decompressor.reset();
}
bool WebSocketPerMessageDeflate::init(const WebSocketPerMessageDeflateOptions& perMessageDeflateOptions)
{
bool clientNoContextTakeover =
perMessageDeflateOptions.getClientNoContextTakeover();
uint8_t deflateBits = perMessageDeflateOptions.getClientMaxWindowBits();
uint8_t inflateBits = perMessageDeflateOptions.getServerMaxWindowBits();
return _compressor->init(deflateBits, clientNoContextTakeover) &&
_decompressor->init(inflateBits, clientNoContextTakeover);
}
bool WebSocketPerMessageDeflate::compress(const std::string& in,
std::string& out)
{
return _compressor->compress(in, out);
}
bool WebSocketPerMessageDeflate::decompress(const std::string& in,
std::string &out)
{
return _decompressor->decompress(in, out);
}
}