Make qdecompresshelper archive bomb check only trigger for large files

This is to avoid false positives.
By default files are large if uncompressed size > 10 MB. Only configurable internally.
Also add auto tests.

Task-number: QTBUG-91392
Change-Id: I32258cb7c957f2a23a05157ba4ed5c0af2ba585e
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
(cherry picked from commit be73ca7eb1cebcc15064666e647bc337b5c2baa2)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

4 files changed, 50 insertions, 0 deletions

diff --git a/src/network/access/qdecompresshelper.cpp b/src/network/access/qdecompresshelper.cpp
index 2e44a58cf4..d0e75ef0dc 100644
--- a/src/network/access/qdecompresshelper.cpp
+++ b/src/network/access/qdecompresshelper.cpp
@@ -405,6 +405,11 @@ void QDecompressHelper::setArchiveBombDetectionEnabled(bool enable)
         countHelper->setArchiveBombDetectionEnabled(enable);
 }
 
+void QDecompressHelper::setMinimumArchiveBombSize(qint64 threshold)
+{
+    minimumArchiveBombSize = threshold;
+}
+
 bool QDecompressHelper::isPotentialArchiveBomb() const
 {
     if (!archiveBombDetectionEnabled)
@@ -413,6 +418,9 @@ bool QDecompressHelper::isPotentialArchiveBomb() const
     if (totalCompressedBytes == 0)
         return false;
 
+    if (totalUncompressedBytes <= minimumArchiveBombSize)
+        return false;
+
     // Some protection against malicious or corrupted compressed files that expand far more than
     // is reasonable.
     double ratio = double(totalUncompressedBytes) / double(totalCompressedBytes);
diff --git a/src/network/access/qdecompresshelper_p.h b/src/network/access/qdecompresshelper_p.h
index 4e66581022..6a77775790 100644
--- a/src/network/access/qdecompresshelper_p.h
+++ b/src/network/access/qdecompresshelper_p.h
@@ -92,6 +92,7 @@ public:
     void clear();
 
     void setArchiveBombDetectionEnabled(bool enable);
+    void setMinimumArchiveBombSize(qint64 threshold);
 
     static bool isSupportedEncoding(const QByteArray &encoding);
     static QByteArrayList acceptedEncoding();
@@ -119,6 +120,7 @@ private:
 
     // Used for calculating the ratio
     bool archiveBombDetectionEnabled = true;
+    qint64 minimumArchiveBombSize = 10 * 1024 * 1024;
     qint64 totalUncompressedBytes = 0;
     qint64 totalCompressedBytes = 0;
 
diff --git a/tests/auto/network/access/qdecompresshelper/10K.gz b/tests/auto/network/access/qdecompresshelper/10K.gz
new file mode 100644
index 0000000000..c5c4959763
--- /dev/null
+++ b/tests/auto/network/access/qdecompresshelper/10K.gz
diff --git a/tests/auto/network/access/qdecompresshelper/tst_qdecompresshelper.cpp b/tests/auto/network/access/qdecompresshelper/tst_qdecompresshelper.cpp
index c31ab294cc..cfeff188f4 100644
--- a/tests/auto/network/access/qdecompresshelper/tst_qdecompresshelper.cpp
+++ b/tests/auto/network/access/qdecompresshelper/tst_qdecompresshelper.cpp
@@ -64,6 +64,9 @@ private Q_SLOTS:
     void decompressBigData_data();
     void decompressBigData();
 
+    void archiveBomb_data();
+    void archiveBomb();
+
 #if QT_POINTER_SIZE >= 8
     void bigZlib();
 #endif
@@ -392,6 +395,43 @@ void tst_QDecompressHelper::decompressBigData()
     QTEST(totalSize, "size");
 }
 
+void tst_QDecompressHelper::archiveBomb_data()
+{
+    QTest::addColumn<QByteArray>("encoding");
+    QTest::addColumn<QString>("path");
+    QTest::addColumn<bool>("shouldFail");
+
+    QTest::newRow("gzip-10K") << QByteArray("gzip") << (srcDir + "/10K.gz") << false;
+    QTest::newRow("gzip-4G") << QByteArray("gzip") << QString(":/4G.gz") << true;
+}
+
+void tst_QDecompressHelper::archiveBomb()
+{
+    QFETCH(bool, shouldFail);
+    QFETCH(QString, path);
+    QFile file(path);
+    QVERIFY(file.open(QIODevice::ReadOnly));
+
+    QDecompressHelper helper;
+    QFETCH(QByteArray, encoding);
+    helper.setEncoding(encoding);
+    QVERIFY(helper.isValid());
+
+    constexpr qint64 SafeSizeLimit = 10 * 1024 * 1024;
+    constexpr qint64 RatioLimit = 40;
+    qint64 bytesToRead = std::min(SafeSizeLimit / RatioLimit, file.bytesAvailable());
+    QByteArray output(1 + bytesToRead * RatioLimit, Qt::Uninitialized);
+    helper.feed(file.read(bytesToRead));
+    qsizetype bytesRead = helper.read(output.data(), output.size());
+    QVERIFY(bytesRead <= output.size());
+    QVERIFY(helper.isValid());
+
+    if (shouldFail)
+        QCOMPARE(bytesRead, -1);
+    else
+        QVERIFY(bytesRead > 0);
+}
+
 #if QT_POINTER_SIZE >= 8
 void tst_QDecompressHelper::bigZlib()
 {