qmimemagicrule.cpp

Go to the documentation of this file.

// Copyright (C) 2016 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
// Qt-Security score:critical reason:data-parser
 
#define QT_NO_CAST_FROM_ASCII
 
#include "qmimemagicrule_p.h"
 
#include "qmimetypeparser_p.h"
#include <QtCore/QList>
#include <QtCore/QDebug>
#include <qendian.h>
 
#include <private/qoffsetstringarray_p.h>
#include <private/qtools_p.h>
 
QT_BEGIN_NAMESPACE
 
using namespace Qt::StringLiterals;
using namespace QtMiscUtils;
 
// in the same order as Type!
static constexpr auto magicRuleTypes = qOffsetStringArray(
    "invalid",
    "string",
    "host16",
    "host32",
    "big16",
    "big32",
    "little16",
    "little32",
    "byte"
);
 
QMimeMagicRule::Type QMimeMagicRule::type(const QByteArray &theTypeName)
{
    for (int i = String; i <= Byte; ++i) {
        if (theTypeName == magicRuleTypes.viewAt(i))
            return Type(i);
    }
    return Invalid;
}
 
QByteArray QMimeMagicRule::typeName(QMimeMagicRule::Type theType)
{
    return magicRuleTypes.at(theType);
}
 
bool QMimeMagicRule::operator==(const QMimeMagicRule &other) const
{
    return m_type == other.m_type &&
           m_value == other.m_value &&
           m_startPos == other.m_startPos &&
           m_endPos == other.m_endPos &&
           m_mask == other.m_mask &&
           m_pattern == other.m_pattern &&
           m_number == other.m_number &&
           m_numberMask == other.m_numberMask &&
           m_matchFunction == other.m_matchFunction;
}
 
// Used by both providers
bool QMimeMagicRule::matchSubstring(const char *dataPtr, qsizetype dataSize, quint64 rangeStart,
                                    quint64 rangeLength, quint64 valueLength, const char *valueData,
                                    const char *mask)
{
    // The range and the value length can come straight out of the binary mime.cache, so
    // nothing can be assumed about them: rangeStart can point past the data, and the value
    // read at the last position of the range has to stay inside it, too.
    const quint64 size = quint64(dataSize);
    if (rangeStart >= size || valueLength == 0 || rangeLength == 0
        || valueLength > size - rangeStart)
        return false;
    // Clamp the range to the data that is actually there, so that rangeStart + rangeLength
    // neither overflows nor points past the end.
    rangeLength = qMin(rangeLength, size - rangeStart);
 
    // Size of searched data.
    // Example: value="ABC", rangeLength=3 -> we need 3+3-1=5 bytes (ABCxx,xABCx,xxABC would match)
    const quint64 dataNeeded = qMin(rangeLength + valueLength - 1, size - rangeStart);
 
    if (!mask) {
        // callgrind says QByteArray::indexOf is much slower, since our strings are typically too
        // short for be worth Boyer-Moore matching (1 to 71 bytes, 11 bytes on average).
        bool found = false;
        for (quint64 i = rangeStart; i < rangeStart + rangeLength; ++i) {
            if (i + valueLength > size)
                break;
 
            if (memcmp(valueData, dataPtr + i, size_t(valueLength)) == 0) {
                found = true;
                break;
            }
        }
        if (!found)
            return false;
    } else {
        bool found = false;
        const char *readDataBase = dataPtr + rangeStart;
        // Example (continued from above):
        // deviceSize is 4, so dataNeeded was max'ed to 4.
        // maxStartPos = 4 - 3 + 1 = 2, and indeed
        // we need to check for a match a positions 0 and 1 (ABCx and xABC).
        const quint64 maxStartPos = dataNeeded - valueLength + 1;
        for (quint64 i = 0; i < maxStartPos; ++i) {
            const char *d = readDataBase + i;
            bool valid = true;
            for (quint64 idx = 0; idx < valueLength; ++idx) {
                if (((*d++) & mask[idx]) != (valueData[idx] & mask[idx])) {
                    valid = false;
                    break;
                }
            }
            if (valid) {
                found = true;
                break;
            }
        }
        if (!found)
            return false;
    }
    //qDebug() << "Found" << value << "in" << searchedData;
    return true;
}
 
bool QMimeMagicRule::matchString(const QByteArray &data) const
{
    const int rangeLength = m_endPos - m_startPos + 1;
    return QMimeMagicRule::matchSubstring(data.constData(), data.size(), m_startPos, rangeLength, m_pattern.size(), m_pattern.constData(), m_mask.constData());
}
 
template <typename T>
bool QMimeMagicRule::matchNumber(const QByteArray &data) const
{
    const T value(m_number);
    const T mask(m_numberMask);
 
    //qDebug() << "matchNumber" << "0x" << QString::number(m_number, 16) << "size" << sizeof(T);
    //qDebug() << "mask" << QString::number(m_numberMask, 16);
 
    const char *p = data.constData() + m_startPos;
    const char *e = data.constData() + qMin(data.size() - int(sizeof(T)), m_endPos);
    for ( ; p <= e; ++p) {
        if ((qFromUnaligned<T>(p) & mask) == (value & mask))
            return true;
    }
 
    return false;
}
 
static inline QByteArray makePattern(const QByteArray &value)
{
    QByteArray pattern(value.size(), Qt::Uninitialized);
    char *data = pattern.data();
 
    const char *p = value.constData();
    const char *e = p + value.size();
    for ( ; p < e; ++p) {
        if (*p == '\\' && ++p < e) {
            if (*p == 'x') { // hex (\\xff)
                char c = 0;
                for (int i = 0; i < 2 && p + 1 < e; ++i) {
                    ++p;
                    if (const int h = fromHex(*p); h != -1)
                        c = (c << 4) + h;
                    else
                        continue;
                }
                *data++ = c;
            } else if (isOctalDigit(*p)) { // oct (\\7, or \\77, or \\377)
                char c = *p - '0';
                if (p + 1 < e && isOctalDigit(p[1])) {
                    c = (c << 3) + *(++p) - '0';
                    if (p + 1 < e && isOctalDigit(p[1]) && p[-1] <= '3')
                        c = (c << 3) + *(++p) - '0';
                }
                *data++ = c;
            } else if (*p == 'n') {
                *data++ = '\n';
            } else if (*p == 'r') {
                *data++ = '\r';
            } else if (*p == 't') {
                *data++ = '\t';
            } else { // escaped
                *data++ = *p;
            }
        } else {
            *data++ = *p;
        }
    }
    pattern.truncate(data - pattern.data());
 
    return pattern;
}
 
// Evaluate a magic match rule like
//  <match value="must be converted with BinHex" type="string" offset="11"/>
//  <match value="0x9501" type="big16" offset="0:64"/>
 
QMimeMagicRule::QMimeMagicRule(const QString &type,
                               const QByteArray &value,
                               const QString &offsets,
                               const QByteArray &mask,
                               QString *errorString)
    : m_type(QMimeMagicRule::type(type.toLatin1())),
      m_value(value),
      m_mask(mask),
      m_matchFunction(nullptr)
{
    if (Q_UNLIKELY(m_type == Invalid)) {
        if (errorString)
            *errorString = "Type "_L1 + type + " is not supported"_L1;
        return;
    }
 
    // Parse for offset as "1" or "1:10"
    const qsizetype colonIndex = offsets.indexOf(u':');
    const QStringView startPosStr = QStringView{offsets}.mid(0, colonIndex); // \ These decay to returning 'offsets'
    const QStringView endPosStr   = QStringView{offsets}.mid(colonIndex + 1);// / unchanged when colonIndex == -1
    if (Q_UNLIKELY(!QMimeTypeParserBase::parseNumber(startPosStr, &m_startPos, errorString)) ||
        Q_UNLIKELY(!QMimeTypeParserBase::parseNumber(endPosStr, &m_endPos, errorString))) {
        m_type = Invalid;
        return;
    }
    if (m_startPos < 0 || m_endPos < 0 || m_endPos < m_startPos) {
        if (errorString)
            *errorString = "Invalid offset range \""_L1 + offsets + u'"';
        m_type = Invalid;
        return;
    }
 
    if (Q_UNLIKELY(m_value.isEmpty())) {
        m_type = Invalid;
        if (errorString)
            *errorString = QStringLiteral("Invalid empty magic rule value");
        return;
    }
 
    if (m_type >= Host16 && m_type <= Byte) {
        bool ok;
        m_number = m_value.toUInt(&ok, 0); // autodetect base
        if (Q_UNLIKELY(!ok)) {
            m_type = Invalid;
            if (errorString)
                *errorString = "Invalid magic rule value \""_L1 + QLatin1StringView(m_value) + u'"';
            return;
        }
        m_numberMask = !m_mask.isEmpty() ? m_mask.toUInt(&ok, 0) : 0; // autodetect base
    }
 
    switch (m_type) {
    case String:
        m_pattern = makePattern(m_value);
        m_pattern.squeeze();
        if (!m_mask.isEmpty()) {
            if (Q_UNLIKELY(m_mask.size() < 4 || !m_mask.startsWith("0x"))) {
                m_type = Invalid;
                if (errorString)
                    *errorString = "Invalid magic rule mask \""_L1 + QLatin1StringView(m_mask) + u'"';
                return;
            }
            const QByteArray &tempMask = QByteArray::fromHex(QByteArray::fromRawData(
                                                     m_mask.constData() + 2, m_mask.size() - 2));
            if (Q_UNLIKELY(tempMask.size() != m_pattern.size())) {
                m_type = Invalid;
                if (errorString)
                    *errorString = "Invalid magic rule mask size \""_L1 + QLatin1StringView(m_mask) + u'"';
                return;
            }
            m_mask = tempMask;
        } else {
            m_mask.fill(char(-1), m_pattern.size());
        }
        m_mask.squeeze();
        m_matchFunction = &QMimeMagicRule::matchString;
        break;
    case Byte:
        if (m_number <= quint8(-1)) {
            if (m_numberMask == 0)
                m_numberMask = quint8(-1);
            m_matchFunction = &QMimeMagicRule::matchNumber<quint8>;
        }
        break;
    case Big16:
    case Little16:
        if (m_number <= quint16(-1)) {
            m_number = m_type == Little16 ? qFromLittleEndian<quint16>(m_number) : qFromBigEndian<quint16>(m_number);
            if (m_numberMask != 0)
                m_numberMask = m_type == Little16 ? qFromLittleEndian<quint16>(m_numberMask) : qFromBigEndian<quint16>(m_numberMask);
        }
        Q_FALLTHROUGH();
    case Host16:
        if (m_number <= quint16(-1)) {
            if (m_numberMask == 0)
                m_numberMask = quint16(-1);
            m_matchFunction = &QMimeMagicRule::matchNumber<quint16>;
        }
        break;
    case Big32:
    case Little32:
        m_number = m_type == Little32 ? qFromLittleEndian<quint32>(m_number) : qFromBigEndian<quint32>(m_number);
        if (m_numberMask != 0)
            m_numberMask = m_type == Little32 ? qFromLittleEndian<quint32>(m_numberMask) : qFromBigEndian<quint32>(m_numberMask);
        Q_FALLTHROUGH();
    case Host32:
        if (m_numberMask == 0)
            m_numberMask = quint32(-1);
        m_matchFunction = &QMimeMagicRule::matchNumber<quint32>;
        break;
    default:
        break;
    }
}
 
QByteArray QMimeMagicRule::mask() const
{
    QByteArray result = m_mask;
    if (m_type == String) {
        // restore '0x'
        result = "0x" + result.toHex();
    }
    return result;
}
 
bool QMimeMagicRule::matches(const QByteArray &data) const
{
    const bool ok = m_matchFunction && (this->*m_matchFunction)(data);
    if (!ok)
        return false;
 
    // No submatch? Then we are done.
    if (m_subMatches.isEmpty())
        return true;
 
    //qDebug() << "Checking" << m_subMatches.count() << "sub-rules";
    // Check that one of the submatches matches too
    for ( QList<QMimeMagicRule>::const_iterator it = m_subMatches.begin(), end = m_subMatches.end() ;
          it != end ; ++it ) {
        if ((*it).matches(data)) {
            // One of the hierarchies matched -> mimetype recognized.
            return true;
        }
    }
    return false;
 
 
}
 
QT_END_NAMESPACE