Plugins: fix crash if the binary JSON data contains invalid size

Eight bytes into the Binary JSON header there's a 32-bit little-endian
size, which qJsonFromRawLibraryMetaData uses to determine the size of
the stored metadata. That value is passed as a size to QByteArray, which
means certain values could cause crashes due to being too big or via
sign-extension in 64-bit.

[ChangeLog][QtCore][QPluginLoader] Fixed an issue that could cause a
crash when certain damaged or corrupt plugin files were scanned.

Change-Id: I117816bf0f5e469b8d34fffd153dc5425cec39a7
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

src/corelib/plugin/qfactoryloader.cpp

@@ -1,6 +1,7 @@
 /****************************************************************************
 **
 ** Copyright (C) 2016 The Qt Company Ltd.
+** Copyright (C) 2018 Intel Corporation.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the QtCore module of the Qt Toolkit.
@@ -58,6 +59,29 @@
 
 QT_BEGIN_NAMESPACE
 
+static inline int metaDataSignatureLength()
+{
+    return sizeof("QTMETADATA  ") - 1;
+}
+
+QJsonDocument qJsonFromRawLibraryMetaData(const char *raw, qsizetype sectionSize)
+{
+    raw += metaDataSignatureLength();
+    sectionSize -= metaDataSignatureLength();
+
+    // the size of the embedded JSON object can be found 8 bytes into the data (see qjson_p.h)
+    uint size = qFromLittleEndian<uint>(raw + 8);
+    // but the maximum size of binary JSON is 128 MB
+    size = qMin(size, 128U * 1024 * 1024);
+    // and it doesn't include the size of the header (8 bytes)
+    size += 8;
+    // finally, it can't be bigger than the file or section size
+    size = qMin(sectionSize, qsizetype(size));
+
+    QByteArray json(raw, size);
+    return QJsonDocument::fromBinaryData(json);
+}
+
 class QFactoryLoaderPrivate : public QObjectPrivate
 {
     Q_DECLARE_PUBLIC(QFactoryLoader)

src/corelib/plugin/qfactoryloader_p.h

@@ -66,14 +66,7 @@
 
 QT_BEGIN_NAMESPACE
 
-inline QJsonDocument qJsonFromRawLibraryMetaData(const char *raw)
-{
-    raw += strlen("QTMETADATA  ");
-    // the size of the embedded JSON object can be found 8 bytes into the data (see qjson_p.h),
-    // but doesn't include the size of the header (8 bytes)
-    QByteArray json(raw, qFromLittleEndian<uint>(*(const uint *)(raw + 8)) + 8);
-    return QJsonDocument::fromBinaryData(json);
-}
+QJsonDocument qJsonFromRawLibraryMetaData(const char *raw, qsizetype size);
 
 class QFactoryLoaderPrivate;
 class Q_CORE_EXPORT QFactoryLoader : public QObject

src/corelib/plugin/qlibrary.cpp

@@ -317,7 +317,7 @@ static bool findPatternUnloaded(const QString &library, QLibraryPrivate *lib)
     if (pos >= 0) {
         if (hasMetaData) {
             const char *data = filedata + pos;
-            QJsonDocument doc = qJsonFromRawLibraryMetaData(data);
+            QJsonDocument doc = qJsonFromRawLibraryMetaData(data, qsizetype(fdlen));
             lib->metaData = doc.object();
             if (qt_debug_component())
                 qWarning("Found metadata in lib %s, metadata=\n%s\n",
@@ -691,7 +691,8 @@ static bool qt_get_metadata(QtPluginQueryVerificationDataFunction pfn, QLibraryP
     if (!szData)
         return false;
 
-    QJsonDocument doc = qJsonFromRawLibraryMetaData(szData);
+    // the data is already loaded, so the size doesn't matter
+    QJsonDocument doc = qJsonFromRawLibraryMetaData(szData, INT_MAX);
     if (doc.isNull())
         return false;
     priv->metaData = doc.object();

src/corelib/plugin/qpluginloader.cpp

@@ -1,6 +1,7 @@
 /****************************************************************************
 **
 ** Copyright (C) 2016 The Qt Company Ltd.
+** Copyright (C) 2018 Intel Corporation.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the QtCore module of the Qt Toolkit.
@@ -474,7 +475,10 @@ QVector<QStaticPlugin> QPluginLoader::staticPlugins()
 */
 QJsonObject QStaticPlugin::metaData() const
 {
-    return qJsonFromRawLibraryMetaData(rawMetaData()).object();
+    // the data is already loaded, so this doesn't matter
+    qsizetype rawMetaDataSize = INT_MAX;
+
+    return qJsonFromRawLibraryMetaData(rawMetaData(), rawMetaDataSize).object();
 }
 
 QT_END_NAMESPACE

tests/auto/corelib/plugin/qplugin/invalidplugin/invalidplugin.pro

@@ -0,0 +1,5 @@
+QT = core
+TEMPLATE = lib
+CONFIG += plugin
+SOURCES = main.cpp
+DESTDIR = ../plugins

tests/auto/corelib/plugin/qplugin/invalidplugin/main.cpp

@@ -0,0 +1,49 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 Intel Corporation.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:GPL-EXCEPT$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <qplugin.h>
+
+QT_PLUGIN_METADATA_SECTION
+static const char pluginMetaData[512] = {
+    'q', 'p', 'l', 'u', 'g', 'i', 'n', ' ',
+    't', 'e', 's', 't', 'f', 'i', 'l', 'e'
+};
+
+extern "C" {
+
+const void *qt_plugin_query_metadata()
+{
+    return pluginMetaData;
+}
+
+Q_DECL_EXPORT void *qt_plugin_instance()
+{
+    return nullptr;
+}
+
+}

tests/auto/corelib/plugin/qplugin/qplugin.pro

@@ -1,5 +1,5 @@
 TEMPLATE = subdirs
-TESTPLUGINS =
+TESTPLUGINS = invalidplugin
 
 win32 {
     contains(QT_CONFIG, debug): TESTPLUGINS += debugplugin
@@ -8,7 +8,7 @@ win32 {
     CONFIG(debug, debug|release): TESTPLUGINS += debugplugin
     CONFIG(release, debug|release): TESTPLUGINS += releaseplugin
 } else {
-    TESTPLUGINS = debugplugin releaseplugin
+    TESTPLUGINS += debugplugin releaseplugin
 }
 
 SUBDIRS += main $$TESTPLUGINS

tests/auto/corelib/plugin/qplugin/tst_qplugin.cpp

@@ -37,6 +37,7 @@ class tst_QPlugin : public QObject
     Q_OBJECT
 
     QDir dir;
+    QString invalidPluginName;
 
 public:
     tst_QPlugin();
@@ -45,6 +46,8 @@ private slots:
     void initTestCase();
     void loadDebugPlugin();
     void loadReleasePlugin();
+    void scanInvalidPlugin_data();
+    void scanInvalidPlugin();
 };
 
 tst_QPlugin::tst_QPlugin()
@@ -57,6 +60,10 @@ void tst_QPlugin::initTestCase()
     QVERIFY2(dir.exists(),
              qPrintable(QString::fromLatin1("Cannot find the 'plugins' directory starting from '%1'").
                         arg(QDir::toNativeSeparators(QDir::currentPath()))));
+
+    const auto fileNames = dir.entryList({"*invalid*"}, QDir::Files);
+    if (!fileNames.isEmpty())
+        invalidPluginName = dir.absoluteFilePath(fileNames.first());
 }
 
 void tst_QPlugin::loadDebugPlugin()
@@ -112,5 +119,105 @@ void tst_QPlugin::loadReleasePlugin()
     }
 }
 
+void tst_QPlugin::scanInvalidPlugin_data()
+{
+    QTest::addColumn<QByteArray>("metadata");
+    QTest::addColumn<bool>("loads");
+
+    QByteArray prefix = "QTMETADATA  ";
+
+    {
+        QJsonObject obj;
+        obj.insert("IID", "org.qt-project.tst_qplugin");
+        obj.insert("className", "tst");
+        obj.insert("version", int(QT_VERSION));
+#ifdef QT_NO_DEBUG
+        obj.insert("debug", false);
+#else
+        obj.insert("debug", true);
+#endif
+        obj.insert("MetaData", QJsonObject());
+        QTest::newRow("control") << (prefix + QJsonDocument(obj).toBinaryData()) << true;
+    }
+
+    QTest::newRow("zeroes") << prefix << false;
+
+    prefix += "qbjs";
+    QTest::newRow("bad-json-version0") << prefix << false;
+    QTest::newRow("bad-json-version2") << (prefix + QByteArray("\2\0\0\0", 4)) << false;
+
+    // valid qbjs version 1
+    prefix += QByteArray("\1\0\0\0");
+
+    // too large for the file (100 MB)
+    QTest::newRow("bad-json-size-large1") << (prefix + QByteArray("\0\0\x40\x06")) << false;
+
+    // too large for binary JSON (512 MB)
+    QTest::newRow("bad-json-size-large2") << (prefix + QByteArray("\0\0\0\x20")) << false;
+
+    // could overflow
+    QTest::newRow("bad-json-size-large3") << (prefix + "\xff\xff\xff\x7f") << false;
+
+}
+
+static const char invalidPluginSignature[] = "qplugin testfile";
+static qsizetype locateMetadata(const uchar *data, qsizetype len)
+{
+    const uchar *dataend = data + len - strlen(invalidPluginSignature);
+
+    for (const uchar *ptr = data; ptr < dataend; ++ptr) {
+        if (*ptr != invalidPluginSignature[0])
+            continue;
+
+        int r = memcmp(ptr, invalidPluginSignature, strlen(invalidPluginSignature));
+        if (r)
+            continue;
+
+        return ptr - data;
+    }
+
+    return -1;
+}
+
+void tst_QPlugin::scanInvalidPlugin()
+{
+    QVERIFY(!invalidPluginName.isEmpty());
+
+    // copy the file
+    QFileInfo fn(invalidPluginName);
+    QTemporaryDir tmpdir;
+    QVERIFY(tmpdir.isValid());
+
+    QString newName = tmpdir.path() + '/' + fn.fileName();
+    QVERIFY(QFile::copy(invalidPluginName, newName));
+
+    {
+        QFile f(newName);
+        QVERIFY(f.open(QIODevice::ReadWrite | QIODevice::Unbuffered));
+        QVERIFY(f.size() > qint64(strlen(invalidPluginSignature)));
+        uchar *data = f.map(0, f.size());
+        QVERIFY(data);
+
+        static const qsizetype offset = locateMetadata(data, f.size());
+        QVERIFY(offset > 0);
+
+        QFETCH(QByteArray, metadata);
+
+        // sanity check
+        QVERIFY(metadata.size() < 512);
+
+        // replace the data
+        memcpy(data + offset, metadata.constData(), metadata.size());
+        memset(data + offset + metadata.size(), 0, 512 - metadata.size());
+    }
+
+    // now try to load this
+    QFETCH(bool, loads);
+    QPluginLoader loader(newName);
+    QCOMPARE(loader.load(), loads);
+    if (loads)
+        loader.unload();
+}
+
 QTEST_MAIN(tst_QPlugin)
 #include "tst_qplugin.moc"