qdecompresshelper.cpp

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// Copyright (C) 2020 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
#include "qdecompresshelper_p.h"
 
#include <QtCore/qiodevice.h>
#include <QtCore/qcoreapplication.h>
 
#include <limits>
#include <zlib.h>
 
#if QT_CONFIG(brotli)
#    include <brotli/decode.h>
#endif
 
#if QT_CONFIG(zstd)
#    include <zstd.h>
#endif
 
#include <array>
 
QT_BEGIN_NAMESPACE
namespace {
struct ContentEncodingMapping
{
    QByteArrayView name;
    QDecompressHelper::ContentEncoding encoding;
};
 
constexpr ContentEncodingMapping contentEncodingMapping[] {
#if QT_CONFIG(zstd)
    { "zstd", QDecompressHelper::Zstandard },
#endif
#if QT_CONFIG(brotli)
    { "br", QDecompressHelper::Brotli },
#endif
    { "gzip", QDecompressHelper::GZip },
    { "deflate", QDecompressHelper::Deflate },
};
 
QDecompressHelper::ContentEncoding encodingFromByteArray(QByteArrayView ce) noexcept
{
    for (const auto &mapping : contentEncodingMapping) {
        if (ce.compare(mapping.name, Qt::CaseInsensitive) == 0)
            return mapping.encoding;
    }
    return QDecompressHelper::None;
}
 
z_stream *toZlibPointer(void *ptr)
{
    return static_cast<z_stream_s *>(ptr);
}
 
#if QT_CONFIG(brotli)
BrotliDecoderState *toBrotliPointer(void *ptr)
{
    return static_cast<BrotliDecoderState *>(ptr);
}
#endif
 
#if QT_CONFIG(zstd)
ZSTD_DStream *toZstandardPointer(void *ptr)
{
    return static_cast<ZSTD_DStream *>(ptr);
}
#endif
}
 
bool QDecompressHelper::isSupportedEncoding(QByteArrayView encoding)
{
    return encodingFromByteArray(encoding) != QDecompressHelper::None;
}
 
QByteArrayList QDecompressHelper::acceptedEncoding()
{
    QByteArrayList list;
    list.reserve(std::size(contentEncodingMapping));
    for (const auto &mapping : contentEncodingMapping) {
        list << mapping.name.toByteArray();
    }
    return list;
}
 
QDecompressHelper::~QDecompressHelper()
{
    clear();
}
 
bool QDecompressHelper::setEncoding(QByteArrayView encoding)
{
    Q_ASSERT(contentEncoding == QDecompressHelper::None);
    if (contentEncoding != QDecompressHelper::None) {
        qWarning("Encoding is already set.");
        // This isn't an error, so it doesn't set errorStr, it's just wrong usage.
        return false;
    }
    ContentEncoding ce = encodingFromByteArray(encoding);
    if (ce == None) {
        errorStr = QCoreApplication::translate("QHttp", "Unsupported content encoding: %1")
                           .arg(QLatin1String(encoding));
        return false;
    }
    errorStr = QString(); // clear error
    return setEncoding(ce);
}
 
bool QDecompressHelper::setEncoding(ContentEncoding ce)
{
    Q_ASSERT(contentEncoding == None);
    contentEncoding = ce;
    switch (contentEncoding) {
    case None:
        Q_UNREACHABLE();
        break;
    case Deflate:
    case GZip: {
        z_stream *inflateStream = new z_stream;
        memset(inflateStream, 0, sizeof(z_stream));
        // "windowBits can also be greater than 15 for optional gzip decoding.
        // Add 32 to windowBits to enable zlib and gzip decoding with automatic header detection"
        // http://www.zlib.net/manual.html
        if (inflateInit2(inflateStream, MAX_WBITS + 32) != Z_OK) {
            delete inflateStream;
            inflateStream = nullptr;
        }
        decoderPointer = inflateStream;
        break;
    }
    case Brotli:
#if QT_CONFIG(brotli)
        decoderPointer = BrotliDecoderCreateInstance(nullptr, nullptr, nullptr);
#else
        Q_UNREACHABLE();
#endif
        break;
    case Zstandard:
#if QT_CONFIG(zstd)
        decoderPointer = ZSTD_createDStream();
#else
        Q_UNREACHABLE();
#endif
        break;
    }
    if (!decoderPointer) {
        errorStr = QCoreApplication::translate("QHttp",
                                               "Failed to initialize the compression decoder.");
        contentEncoding = QDecompressHelper::None;
        return false;
    }
    return true;
}
 
bool QDecompressHelper::isCountingBytes() const
{
    return countDecompressed;
}
 
void QDecompressHelper::setCountingBytesEnabled(bool shouldCount)
{
    // These are a best-effort check to ensure that no data has already been processed before this
    // gets enabled
    Q_ASSERT(compressedDataBuffer.byteAmount() == 0);
    Q_ASSERT(contentEncoding == None);
    countDecompressed = shouldCount;
}
 
qint64 QDecompressHelper::uncompressedSize() const
{
    Q_ASSERT(countDecompressed);
    // Use the 'totalUncompressedBytes' from the countHelper if it exceeds the amount of bytes
    // that we know about.
    auto totalUncompressed =
            countHelper && countHelper->totalUncompressedBytes > totalUncompressedBytes
            ? countHelper->totalUncompressedBytes
            : totalUncompressedBytes;
    return totalUncompressed - totalBytesRead;
}
 
void QDecompressHelper::feed(const QByteArray &data)
{
    return feed(QByteArray(data));
}
 
void QDecompressHelper::feed(QByteArray &&data)
{
    Q_ASSERT(contentEncoding != None);
    totalCompressedBytes += data.size();
    compressedDataBuffer.append(std::move(data));
    if (!countInternal(compressedDataBuffer[compressedDataBuffer.bufferCount() - 1]))
        clear(); // If our counting brother failed then so will we :|
}
 
void QDecompressHelper::feed(const QByteDataBuffer &buffer)
{
    Q_ASSERT(contentEncoding != None);
    totalCompressedBytes += buffer.byteAmount();
    compressedDataBuffer.append(buffer);
    if (!countInternal(buffer))
        clear(); // If our counting brother failed then so will we :|
}
 
void QDecompressHelper::feed(QByteDataBuffer &&buffer)
{
    Q_ASSERT(contentEncoding != None);
    totalCompressedBytes += buffer.byteAmount();
    const QByteDataBuffer copy(buffer);
    compressedDataBuffer.append(std::move(buffer));
    if (!countInternal(copy))
        clear(); // If our counting brother failed then so will we :|
}
 
bool QDecompressHelper::countInternal()
{
    Q_ASSERT(countDecompressed);
    while (hasDataInternal()
           && decompressedDataBuffer.byteAmount() < MaxDecompressedDataBufferSize) {
        const qsizetype toRead = 256 * 1024;
        QByteArray buffer(toRead, Qt::Uninitialized);
        qsizetype bytesRead = readInternal(buffer.data(), buffer.size());
        if (bytesRead == -1)
            return false;
        buffer.truncate(bytesRead);
        decompressedDataBuffer.append(std::move(buffer));
    }
    if (!hasDataInternal())
        return true; // handled all the data so far, just return
 
    while (countHelper->hasData()) {
        std::array<char, 1024> temp;
        qsizetype bytesRead = countHelper->read(temp.data(), temp.size());
        if (bytesRead == -1)
            return false;
    }
    return true;
}
 
bool QDecompressHelper::countInternal(const QByteArray &data)
{
    if (countDecompressed) {
        if (!countHelper) {
            countHelper = std::make_unique<QDecompressHelper>();
            countHelper->setDecompressedSafetyCheckThreshold(archiveBombCheckThreshold);
            countHelper->setEncoding(contentEncoding);
        }
        countHelper->feed(data);
        return countInternal();
    }
    return true;
}
 
bool QDecompressHelper::countInternal(const QByteDataBuffer &buffer)
{
    if (countDecompressed) {
        if (!countHelper) {
            countHelper = std::make_unique<QDecompressHelper>();
            countHelper->setDecompressedSafetyCheckThreshold(archiveBombCheckThreshold);
            countHelper->setEncoding(contentEncoding);
        }
        countHelper->feed(buffer);
        return countInternal();
    }
    return true;
}
 
qsizetype QDecompressHelper::read(char *data, qsizetype maxSize)
{
    if (maxSize <= 0)
        return 0;
 
    if (!isValid())
        return -1;
 
    if (!hasData())
        return 0;
 
    qsizetype cachedRead = 0;
    if (!decompressedDataBuffer.isEmpty()) {
        cachedRead = decompressedDataBuffer.read(data, maxSize);
        data += cachedRead;
        maxSize -= cachedRead;
    }
 
    qsizetype bytesRead = readInternal(data, maxSize);
    if (bytesRead == -1)
        return -1;
    totalBytesRead += bytesRead + cachedRead;
    return bytesRead + cachedRead;
}
 
qsizetype QDecompressHelper::readInternal(char *data, qsizetype maxSize)
{
    Q_ASSERT(isValid());
 
    if (maxSize <= 0)
        return 0;
 
    if (!hasDataInternal())
        return 0;
 
    qsizetype bytesRead = -1;
    switch (contentEncoding) {
    case None:
        Q_UNREACHABLE();
        break;
    case Deflate:
    case GZip:
        bytesRead = readZLib(data, maxSize);
        break;
    case Brotli:
        bytesRead = readBrotli(data, maxSize);
        break;
    case Zstandard:
        bytesRead = readZstandard(data, maxSize);
        break;
    }
    if (bytesRead == -1)
        clear();
 
    totalUncompressedBytes += bytesRead;
    if (isPotentialArchiveBomb()) {
        errorStr = QCoreApplication::translate(
                "QHttp",
                "The decompressed output exceeds the limits specified by "
                "QNetworkRequest::decompressedSafetyCheckThreshold()");
        return -1;
    }
 
    return bytesRead;
}
 
void QDecompressHelper::setDecompressedSafetyCheckThreshold(qint64 threshold)
{
    if (threshold == -1)
        threshold = std::numeric_limits<qint64>::max();
    archiveBombCheckThreshold = threshold;
}
 
bool QDecompressHelper::isPotentialArchiveBomb() const
{
    if (totalCompressedBytes == 0)
        return false;
 
    if (totalUncompressedBytes <= archiveBombCheckThreshold)
        return false;
 
    // Some protection against malicious or corrupted compressed files that expand far more than
    // is reasonable.
    double ratio = double(totalUncompressedBytes) / double(totalCompressedBytes);
    switch (contentEncoding) {
    case None:
        Q_UNREACHABLE();
        break;
    case Deflate:
    case GZip:
        // This value is mentioned in docs for
        // QNetworkRequest::setMinimumArchiveBombSize, keep synchronized
        if (ratio > 40) {
            return true;
        }
        break;
    case Brotli:
    case Zstandard:
        // This value is mentioned in docs for
        // QNetworkRequest::setMinimumArchiveBombSize, keep synchronized
        if (ratio > 100) {
            return true;
        }
        break;
    }
    return false;
}
 
bool QDecompressHelper::hasData() const
{
    return hasDataInternal() || !decompressedDataBuffer.isEmpty();
}
 
bool QDecompressHelper::hasDataInternal() const
{
    return encodedBytesAvailable() || decoderHasData;
}
 
qint64 QDecompressHelper::encodedBytesAvailable() const
{
    return compressedDataBuffer.byteAmount();
}
 
bool QDecompressHelper::isValid() const
{
    return contentEncoding != None;
}
 
QString QDecompressHelper::errorString() const
{
    return errorStr;
}
 
void QDecompressHelper::clear()
{
    switch (contentEncoding) {
    case None:
        break;
    case Deflate:
    case GZip: {
        z_stream *inflateStream = toZlibPointer(decoderPointer);
        if (inflateStream)
            inflateEnd(inflateStream);
        delete inflateStream;
        break;
    }
    case Brotli: {
#if QT_CONFIG(brotli)
        BrotliDecoderState *brotliDecoderState = toBrotliPointer(decoderPointer);
        if (brotliDecoderState)
            BrotliDecoderDestroyInstance(brotliDecoderState);
#endif
        break;
    }
    case Zstandard: {
#if QT_CONFIG(zstd)
        ZSTD_DStream *zstdStream = toZstandardPointer(decoderPointer);
        if (zstdStream)
            ZSTD_freeDStream(zstdStream);
#endif
        break;
    }
    }
    decoderPointer = nullptr;
    contentEncoding = None;
 
    compressedDataBuffer.clear();
    decompressedDataBuffer.clear();
    decoderHasData = false;
 
    countDecompressed = false;
    countHelper.reset();
    totalBytesRead = 0;
    totalUncompressedBytes = 0;
    totalCompressedBytes = 0;
 
    errorStr.clear();
}
 
qsizetype QDecompressHelper::readZLib(char *data, const qsizetype maxSize)
{
    bool triedRawDeflate = false;
 
    z_stream *inflateStream = toZlibPointer(decoderPointer);
    static const size_t zlibMaxSize =
            size_t(std::numeric_limits<decltype(inflateStream->avail_in)>::max());
 
    QByteArrayView input = compressedDataBuffer.readPointer();
    if (size_t(input.size()) > zlibMaxSize)
        input = input.sliced(zlibMaxSize);
 
    inflateStream->avail_in = input.size();
    inflateStream->next_in = reinterpret_cast<Bytef *>(const_cast<char *>(input.data()));
 
    bool bigMaxSize = (zlibMaxSize < size_t(maxSize));
    qsizetype adjustedAvailableOut = bigMaxSize ? qsizetype(zlibMaxSize) : maxSize;
    inflateStream->avail_out = adjustedAvailableOut;
    inflateStream->next_out = reinterpret_cast<Bytef *>(data);
 
    qsizetype bytesDecoded = 0;
    do {
        auto previous_avail_out = inflateStream->avail_out;
        int ret = inflate(inflateStream, Z_NO_FLUSH);
        // All negative return codes are errors, in the context of HTTP compression, Z_NEED_DICT is
        // also an error.
        // in the case where we get Z_DATA_ERROR this could be because we received raw deflate
        // compressed data.
        if (ret == Z_DATA_ERROR && !triedRawDeflate) {
            inflateEnd(inflateStream);
            triedRawDeflate = true;
            inflateStream->zalloc = Z_NULL;
            inflateStream->zfree = Z_NULL;
            inflateStream->opaque = Z_NULL;
            inflateStream->avail_in = 0;
            inflateStream->next_in = Z_NULL;
            int ret = inflateInit2(inflateStream, -MAX_WBITS);
            if (ret != Z_OK) {
                return -1;
            } else {
                inflateStream->avail_in = input.size();
                inflateStream->next_in =
                        reinterpret_cast<Bytef *>(const_cast<char *>(input.data()));
                continue;
            }
        } else if (ret < 0 || ret == Z_NEED_DICT) {
            return -1;
        }
        bytesDecoded += qsizetype(previous_avail_out - inflateStream->avail_out);
        if (ret == Z_STREAM_END) {
 
            // If there's more data after the stream then this is probably composed of multiple
            // streams.
            if (inflateStream->avail_in != 0) {
                inflateEnd(inflateStream);
                Bytef *next_in = inflateStream->next_in;
                uInt avail_in = inflateStream->avail_in;
                inflateStream->zalloc = Z_NULL;
                inflateStream->zfree = Z_NULL;
                inflateStream->opaque = Z_NULL;
                if (inflateInit2(inflateStream, MAX_WBITS + 32) != Z_OK) {
                    delete inflateStream;
                    decoderPointer = nullptr;
                    // Failed to reinitialize, so we'll just return what we have
                    compressedDataBuffer.advanceReadPointer(input.size() - avail_in);
                    return bytesDecoded;
                } else {
                    inflateStream->next_in = next_in;
                    inflateStream->avail_in = avail_in;
                    // Keep going to handle the other cases below
                }
            } else {
                // No extra data, stream is at the end. We're done.
                compressedDataBuffer.advanceReadPointer(input.size());
                return bytesDecoded;
            }
        }
 
        if (bigMaxSize && inflateStream->avail_out == 0) {
            // Need to adjust the next_out and avail_out parameters since we reached the end
            // of the current range
            bigMaxSize = (zlibMaxSize < size_t(maxSize - bytesDecoded));
            inflateStream->avail_out = bigMaxSize ? qsizetype(zlibMaxSize) : maxSize - bytesDecoded;
            inflateStream->next_out = reinterpret_cast<Bytef *>(data + bytesDecoded);
        }
 
        if (inflateStream->avail_in == 0 && inflateStream->avail_out > 0) {
            // Grab the next input!
            compressedDataBuffer.advanceReadPointer(input.size());
            input = compressedDataBuffer.readPointer();
            if (size_t(input.size()) > zlibMaxSize)
                input = input.sliced(zlibMaxSize);
            inflateStream->avail_in = input.size();
            inflateStream->next_in =
                    reinterpret_cast<Bytef *>(const_cast<char *>(input.data()));
        }
    } while (inflateStream->avail_out > 0 && inflateStream->avail_in > 0);
 
    compressedDataBuffer.advanceReadPointer(input.size() - inflateStream->avail_in);
 
    return bytesDecoded;
}
 
qsizetype QDecompressHelper::readBrotli(char *data, const qsizetype maxSize)
{
#if !QT_CONFIG(brotli)
    Q_UNUSED(data);
    Q_UNUSED(maxSize);
    Q_UNREACHABLE();
#else
    qint64 bytesDecoded = 0;
 
    BrotliDecoderState *brotliDecoderState = toBrotliPointer(decoderPointer);
 
    while (decoderHasData && bytesDecoded < maxSize) {
        Q_ASSERT(brotliUnconsumedDataPtr || BrotliDecoderHasMoreOutput(brotliDecoderState));
        if (brotliUnconsumedDataPtr) {
            Q_ASSERT(brotliUnconsumedAmount);
            size_t toRead = std::min(size_t(maxSize - bytesDecoded), brotliUnconsumedAmount);
            memcpy(data + bytesDecoded, brotliUnconsumedDataPtr, toRead);
            bytesDecoded += toRead;
            brotliUnconsumedAmount -= toRead;
            brotliUnconsumedDataPtr += toRead;
            if (brotliUnconsumedAmount == 0) {
                brotliUnconsumedDataPtr = nullptr;
                decoderHasData = false;
            }
        }
        if (BrotliDecoderHasMoreOutput(brotliDecoderState) == BROTLI_TRUE) {
            brotliUnconsumedDataPtr =
                    BrotliDecoderTakeOutput(brotliDecoderState, &brotliUnconsumedAmount);
            decoderHasData = true;
        }
    }
    if (bytesDecoded == maxSize)
        return bytesDecoded;
    Q_ASSERT(bytesDecoded < maxSize);
 
    QByteArrayView input = compressedDataBuffer.readPointer();
    const uint8_t *encodedPtr = reinterpret_cast<const uint8_t *>(input.data());
    size_t encodedBytesRemaining = input.size();
 
    uint8_t *decodedPtr = reinterpret_cast<uint8_t *>(data + bytesDecoded);
    size_t unusedDecodedSize = size_t(maxSize - bytesDecoded);
    while (unusedDecodedSize > 0) {
        auto previousUnusedDecodedSize = unusedDecodedSize;
        BrotliDecoderResult result = BrotliDecoderDecompressStream(
                brotliDecoderState, &encodedBytesRemaining, &encodedPtr, &unusedDecodedSize,
                &decodedPtr, nullptr);
        bytesDecoded += previousUnusedDecodedSize - unusedDecodedSize;
 
        switch (result) {
        case BROTLI_DECODER_RESULT_ERROR:
            errorStr = QLatin1String("Brotli error: %1")
                               .arg(QString::fromUtf8(BrotliDecoderErrorString(
                                       BrotliDecoderGetErrorCode(brotliDecoderState))));
            return -1;
        case BROTLI_DECODER_RESULT_SUCCESS:
            BrotliDecoderDestroyInstance(brotliDecoderState);
            decoderPointer = nullptr;
            compressedDataBuffer.clear();
            return bytesDecoded;
        case BROTLI_DECODER_RESULT_NEEDS_MORE_INPUT:
            compressedDataBuffer.advanceReadPointer(input.size());
            input = compressedDataBuffer.readPointer();
            if (!input.isEmpty()) {
                encodedPtr = reinterpret_cast<const uint8_t *>(input.constData());
                encodedBytesRemaining = input.size();
                break;
            }
            return bytesDecoded;
        case BROTLI_DECODER_RESULT_NEEDS_MORE_OUTPUT:
            // Some data is leftover inside the brotli decoder, remember for next time
            decoderHasData = BrotliDecoderHasMoreOutput(brotliDecoderState);
            Q_ASSERT(unusedDecodedSize == 0);
            break;
        }
    }
    compressedDataBuffer.advanceReadPointer(input.size() - encodedBytesRemaining);
    return bytesDecoded;
#endif
}
 
qsizetype QDecompressHelper::readZstandard(char *data, const qsizetype maxSize)
{
#if !QT_CONFIG(zstd)
    Q_UNUSED(data);
    Q_UNUSED(maxSize);
    Q_UNREACHABLE();
#else
    ZSTD_DStream *zstdStream = toZstandardPointer(decoderPointer);
 
    QByteArrayView input = compressedDataBuffer.readPointer();
    ZSTD_inBuffer inBuf { input.data(), size_t(input.size()), 0 };
 
    ZSTD_outBuffer outBuf { data, size_t(maxSize), 0 };
 
    qsizetype bytesDecoded = 0;
    while (outBuf.pos < outBuf.size && (inBuf.pos < inBuf.size || decoderHasData)) {
        size_t retValue = ZSTD_decompressStream(zstdStream, &outBuf, &inBuf);
        if (ZSTD_isError(retValue)) {
            errorStr = QLatin1String("ZStandard error: %1")
                               .arg(QString::fromUtf8(ZSTD_getErrorName(retValue)));
            return -1;
        } else {
            decoderHasData = false;
            bytesDecoded = outBuf.pos;
            // if pos == size then there may be data left over in internal buffers
            if (outBuf.pos == outBuf.size) {
                decoderHasData = true;
            } else if (inBuf.pos == inBuf.size) {
                compressedDataBuffer.advanceReadPointer(input.size());
                input = compressedDataBuffer.readPointer();
                inBuf = { input.constData(), size_t(input.size()), 0 };
            }
        }
    }
    compressedDataBuffer.advanceReadPointer(inBuf.pos);
    return bytesDecoded;
#endif
}
 
QT_END_NAMESPACE