qfilesystemengine.cpp

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// 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
 
#include "qfilesystemengine_p.h"
#include <QtCore/qdir.h>
#include <QtCore/qset.h>
#include <QtCore/qstringbuilder.h>
#include <QtCore/private/qabstractfileengine_p.h>
#ifdef QT_BUILD_CORE_LIB
#include <QtCore/private/qresource_p.h>
#endif
#include <QtCore/private/qduplicatetracker_p.h>
 
QT_BEGIN_NAMESPACE
 
/*! \class QFileSystemEngine
    \internal
 
    QFileSystemEngine offers OS-independent API for native system library
    methods, which work with files on physical disk drives; using such methods
    directly is faster than using a custom file engine (see QAbstractFileEngine
    and its sub-classes). Typically, you need a custom file engine when working
    with virtual file systems (for example QResource). Various Qt classes,
    for example QDir, QFile, and QFileInfo, can handle both types of files by
    detecting the file path scheme, for example, \c file:///, \c :/someresource
    (QResource).
 
    \sa QAbstractFileEngine, QAbstractFileEngineHandler, QFSFileEngine, QResourceFileEngine
*/
 
/*!
    \internal
 
    Returns the canonicalized form of \a path (i.e., with all symlinks
    resolved, and all redundant path elements removed.
*/
QString QFileSystemEngine::slowCanonicalized(const QString &path)
{
    if (path.isEmpty())
        return path;
 
    QFileInfo fi;
    const QChar slash(u'/');
    QString tmpPath = path;
    qsizetype separatorPos = 0;
    QSet<QString> nonSymlinks;
    QDuplicateTracker<QString> known;
 
    (void)known.hasSeen(path);
    do {
#ifdef Q_OS_WIN
        if (separatorPos == 0) {
            if (tmpPath.size() >= 2 && tmpPath.at(0) == slash && tmpPath.at(1) == slash) {
                // UNC, skip past the first two elements
                separatorPos = tmpPath.indexOf(slash, 2);
            } else if (tmpPath.size() >= 3 && tmpPath.at(1) == u':' && tmpPath.at(2) == slash) {
                // volume root, skip since it can not be a symlink
                separatorPos = 2;
            }
        }
        if (separatorPos != -1)
#endif
        separatorPos = tmpPath.indexOf(slash, separatorPos + 1);
        QString prefix = separatorPos == -1 ? tmpPath : tmpPath.left(separatorPos);
        if (!nonSymlinks.contains(prefix)) {
            fi.setFile(prefix);
            if (fi.isSymLink()) {
                QString target = fi.symLinkTarget();
                if (separatorPos != -1) {
                    if (fi.isDir() && !target.endsWith(slash))
                        target.append(slash);
                    target.append(QStringView{tmpPath}.mid(separatorPos));
                }
                tmpPath = QDir::cleanPath(target);
                separatorPos = 0;
 
                if (known.hasSeen(tmpPath))
                    return QString();
            } else {
                nonSymlinks.insert(prefix);
            }
        }
    } while (separatorPos != -1);
 
    return QDir::cleanPath(tmpPath);
}
 
static inline bool _q_checkEntry(QFileSystemEntry &entry, QFileSystemMetaData &data, bool resolvingEntry)
{
    if (resolvingEntry) {
        if (!QFileSystemEngine::fillMetaData(entry, data, QFileSystemMetaData::ExistsAttribute)
                || !data.exists()) {
            data.clear();
            return false;
        }
    }
 
    return true;
}
 
static inline bool _q_checkEntry(std::unique_ptr<QAbstractFileEngine> &engine, bool resolvingEntry)
{
    if (resolvingEntry) {
        if (!(engine->fileFlags(QAbstractFileEngine::FlagsMask) & QAbstractFileEngine::ExistsFlag)) {
            engine.reset();
            return false;
        }
    }
 
    return true;
}
 
static bool _q_createLegacyEngine_recursive(QFileSystemEntry &entry, QFileSystemMetaData &data,
                                            std::unique_ptr<QAbstractFileEngine> &engine,
                                            bool resolvingEntry = false)
{
    QString const &filePath = entry.filePath();
    if ((engine = qt_custom_file_engine_handler_create(filePath)))
        return _q_checkEntry(engine, resolvingEntry);
 
#if defined(QT_BUILD_CORE_LIB)
    for (qsizetype prefixSeparator = 0; prefixSeparator < filePath.size(); ++prefixSeparator) {
        QChar const ch = filePath[prefixSeparator];
        if (ch == u'/')
            break;
 
        if (ch == u':') {
            if (prefixSeparator == 0) {
                engine = std::make_unique<QResourceFileEngine>(filePath);
                return _q_checkEntry(engine, resolvingEntry);
            }
 
            if (prefixSeparator == 1)
                break;
 
            const QStringList &paths = QDir::searchPaths(filePath.left(prefixSeparator));
            for (int i = 0; i < paths.size(); i++) {
                entry = QFileSystemEntry(QDir::cleanPath(
                        paths.at(i) % u'/' % QStringView{filePath}.mid(prefixSeparator + 1)));
                // Recurse!
                if (_q_createLegacyEngine_recursive(entry, data, engine, true))
                    return true;
            }
 
            // entry may have been clobbered at this point.
            return false;
        }
 
        //  There's no need to fully validate the prefix here. Consulting the
        //  unicode tables could be expensive and validation is already
        //  performed in QDir::setSearchPaths.
        //
        //  if (!ch.isLetterOrNumber())
        //      break;
    }
#endif // defined(QT_BUILD_CORE_LIB)
 
    return _q_checkEntry(entry, data, resolvingEntry);
}
 
Q_CORE_EXPORT bool qt_isCaseSensitive(const QFileSystemEntry &entry, QFileSystemMetaData &data)
{
    // called from QtGui (QFileSystemModel, QFileInfoGatherer)
    return QFileSystemEngine::isCaseSensitive(entry, data);
}
 
/*!
    \internal
 
    Resolves the \a entry (see QDir::searchPaths) and returns an engine for
    it, but never a QFSFileEngine.
 
    Returns a file engine that can be used to access the entry. Returns 0 if
    QFileSystemEngine API should be used to query and interact with the file
    system object.
*/
std::unique_ptr<QAbstractFileEngine>
QFileSystemEngine::createLegacyEngine(QFileSystemEntry &entry, QFileSystemMetaData &data)
{
    QFileSystemEntry copy = entry;
    std::unique_ptr<QAbstractFileEngine> engine;
 
    if (_q_createLegacyEngine_recursive(copy, data, engine))
        // Reset entry to resolved copy.
        entry = copy;
    else
        data.clear();
 
    return engine;
}
 
std::unique_ptr<QAbstractFileEngine>
QFileSystemEngine::createLegacyEngine(const QString &fileName)
{
    QFileSystemEntry entry(fileName);
    QFileSystemMetaData metaData;
    return createLegacyEngine(entry, metaData);
}
 
//static
QString QFileSystemEngine::resolveUserName(const QFileSystemEntry &entry, QFileSystemMetaData &metaData)
{
#if defined(Q_OS_WIN)
    Q_UNUSED(metaData);
    return QFileSystemEngine::owner(entry, QAbstractFileEngine::OwnerUser);
#else //(Q_OS_UNIX)
    if (!metaData.hasFlags(QFileSystemMetaData::UserId))
        QFileSystemEngine::fillMetaData(entry, metaData, QFileSystemMetaData::UserId);
    if (!metaData.exists())
        return QString();
    return resolveUserName(metaData.userId());
#endif
}
 
//static
QString QFileSystemEngine::resolveGroupName(const QFileSystemEntry &entry, QFileSystemMetaData &metaData)
{
#if defined(Q_OS_WIN)
    Q_UNUSED(metaData);
    return QFileSystemEngine::owner(entry, QAbstractFileEngine::OwnerGroup);
#else //(Q_OS_UNIX)
    if (!metaData.hasFlags(QFileSystemMetaData::GroupId))
        QFileSystemEngine::fillMetaData(entry, metaData, QFileSystemMetaData::GroupId);
    if (!metaData.exists())
        return QString();
    return resolveGroupName(metaData.groupId());
#endif
}
 
//static
QFileSystemEntry QFileSystemEngine::getJunctionTarget(const QFileSystemEntry &link,
                                                      QFileSystemMetaData &data)
{
#if defined(Q_OS_WIN)
    return junctionTarget(link, data);
#else
    Q_UNUSED(link);
    Q_UNUSED(data);
    return {};
#endif
}
 
QT_END_NAMESPACE