QNetworkReply: update decompress error message and handling

The error message was quite vague since it would then not require
any additional translations. However, in hindsight this was a mistake
since now developers just thought their downloads were being corrupted.

Fixes: QTBUG-101942
Change-Id: Ie9af42510ca027d15248e5bcf21e836e709898d9
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>
(cherry picked from commit d642c16fe745e156a93129fbb3750784b361ee39)
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

src/network/access/qdecompresshelper.cpp

@@ -41,6 +41,7 @@
 
 #include <QtCore/private/qbytearray_p.h>
 #include <QtCore/qiodevice.h>
+#include <QtCore/qcoreapplication.h>
 
 #include <limits>
 #include <zlib.h>
@@ -131,13 +132,16 @@ bool QDecompressHelper::setEncoding(const QByteArray &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) {
-        qWarning("An unsupported content encoding was selected: %s", encoding.data());
+        errorStr = QCoreApplication::translate("QHttp", "Unsupported content encoding: %1")
+                           .arg(QLatin1String(encoding));
         return false;
     }
+    errorStr = QString(); // clear error
     return setEncoding(ce);
 }
 
@@ -179,7 +183,8 @@ bool QDecompressHelper::setEncoding(ContentEncoding ce)
         break;
     }
     if (!decoderPointer) {
-        qWarning("Failed to initialize the decoder.");
+        errorStr = QCoreApplication::translate("QHttp",
+                                               "Failed to initialize the compression decoder.");
         contentEncoding = QDecompressHelper::None;
         return false;
     }
@@ -386,8 +391,13 @@ qsizetype QDecompressHelper::read(char *data, qsizetype maxSize)
         uncompressedBytes -= bytesRead;
 
     totalUncompressedBytes += bytesRead;
-    if (isPotentialArchiveBomb())
+    if (isPotentialArchiveBomb()) {
+        errorStr = QCoreApplication::translate(
+                "QHttp",
+                "The decompressed output exceeds the limits specified by "
+                "QNetworkRequest::decompressedSafetyCheckThreshold()");
         return -1;
+    }
 
     return bytesRead;
 }
@@ -458,11 +468,29 @@ qint64 QDecompressHelper::encodedBytesAvailable() const
     return compressedDataBuffer.byteAmount();
 }
 
+/*!
+    \internal
+    Returns whether or not the object is valid.
+    If it becomes invalid after an operation has been performed
+    then an error has occurred.
+    \sa errorString()
+*/
 bool QDecompressHelper::isValid() const
 {
     return contentEncoding != None;
 }
 
+/*!
+    \internal
+    Returns a string describing the error that occurred or an empty
+    string if no error occurred.
+    \sa isValid()
+*/
+QString QDecompressHelper::errorString() const
+{
+    return errorStr;
+}
+
 void QDecompressHelper::clear()
 {
     switch (contentEncoding) {
@@ -504,6 +532,8 @@ void QDecompressHelper::clear()
     uncompressedBytes = 0;
     totalUncompressedBytes = 0;
     totalCompressedBytes = 0;
+
+    errorStr.clear();
 }
 
 qsizetype QDecompressHelper::readZLib(char *data, const qsizetype maxSize)
@@ -659,8 +689,9 @@ qsizetype QDecompressHelper::readBrotli(char *data, const qsizetype maxSize)
 
         switch (result) {
         case BROTLI_DECODER_RESULT_ERROR:
-            qWarning("Brotli error: %s",
+            errorStr = QLatin1String("Brotli error: %1")
-                     BrotliDecoderErrorString(BrotliDecoderGetErrorCode(brotliDecoderState)));
+                               .arg(QString::fromUtf8(BrotliDecoderErrorString(
+                                       BrotliDecoderGetErrorCode(brotliDecoderState))));
             return -1;
         case BROTLI_DECODER_RESULT_SUCCESS:
             BrotliDecoderDestroyInstance(brotliDecoderState);
@@ -706,7 +737,8 @@ qsizetype QDecompressHelper::readZstandard(char *data, const qsizetype maxSize)
     while (outBuf.pos < outBuf.size && (inBuf.pos < inBuf.size || decoderHasData)) {
         size_t retValue = ZSTD_decompressStream(zstdStream, &outBuf, &inBuf);
         if (ZSTD_isError(retValue)) {
-            qWarning("ZStandard error: %s", ZSTD_getErrorName(retValue));
+            errorStr = QLatin1String("ZStandard error: %1")
+                               .arg(QString::fromUtf8(ZSTD_getErrorName(retValue)));
             return -1;
         } else {
             decoderHasData = false;

src/network/access/qdecompresshelper_p.h

@@ -96,6 +96,8 @@ public:
     static bool isSupportedEncoding(const QByteArray &encoding);
     static QByteArrayList acceptedEncoding();
 
+    QString errorString() const;
+
 private:
     bool isPotentialArchiveBomb() const;
 
@@ -117,6 +119,8 @@ private:
     std::unique_ptr<QDecompressHelper> countHelper;
     qint64 uncompressedBytes = 0;
 
+    QString errorStr;
+
     // Used for calculating the ratio
     qint64 archiveBombCheckThreshold = 10 * 1024 * 1024;
     qint64 totalUncompressedBytes = 0;

src/network/access/qhttp2protocolhandler.cpp

@@ -1297,9 +1297,11 @@ void QHttp2ProtocolHandler::updateStream(Stream &stream, const Frame &frame,
                     output.resize(read);
                     replyPrivate->responseData.append(std::move(output));
                 } else if (read < 0) {
-                    finishStreamWithError(
+                    const QString decompressError =
-                            stream, QNetworkReply::ProtocolFailure,
+                            QCoreApplication::translate("QHttp", "Decompression failed: %1")
-                            QCoreApplication::translate("QHttp", "Data corrupted"));
+                                    .arg(replyPrivate->decompressHelper.errorString());
+                    finishStreamWithError(stream, QNetworkReply::UnknownContentError,
+                                          decompressError);
                     return;
                 }
             }

src/network/access/qhttpprotocolhandler.cpp

@@ -203,7 +203,13 @@ void QHttpProtocolHandler::_q_receiveReply()
                     }
                 } else if (haveRead == -1) {
                     // Some error occurred
-                    m_connection->d_func()->emitReplyError(m_socket, m_reply, QNetworkReply::ProtocolFailure);
+                    if (replyPrivate->autoDecompress && !replyPrivate->decompressHelper.isValid()) {
+                        m_connection->d_func()->emitReplyError(m_socket, m_reply,
+                                                               QNetworkReply::UnknownContentError);
+                    } else {
+                        m_connection->d_func()->emitReplyError(m_socket, m_reply,
+                                                               QNetworkReply::ProtocolFailure);
+                    }
                     break;
                 }
             }

src/network/doc/src/qt6-changes.qdoc

@@ -193,4 +193,14 @@
     \code
     request.setAttribute(QNetworkRequest::Http2AllowedAttribute, false);
     \endcode
+
+    \section2 QNetworkAccessManager now guards against archive bombs
+
+    Starting with Qt 6.2 QNetworkAccessManager will guard against compressed
+    files that decompress to files which are much larger than their compressed
+    form by erroring out the reply if the decompression ratio exceeds a certain
+    threshold.
+    This check is only applied to files larger than a certain size, which can be
+    customized (or disabled by passing -1) by calling
+    \l{QNetworkRequest::setDecompressedSafetyCheckThreshold()}.
 */

tests/auto/network/access/qdecompresshelper/tst_qdecompresshelper.cpp

@@ -424,10 +424,13 @@ void tst_QDecompressHelper::archiveBomb()
     QVERIFY(bytesRead <= output.size());
     QVERIFY(helper.isValid());
 
-    if (shouldFail)
+    if (shouldFail) {
         QCOMPARE(bytesRead, -1);
-    else
+        QVERIFY(!helper.errorString().isEmpty());
+    } else {
         QVERIFY(bytesRead > 0);
+        QVERIFY(helper.errorString().isEmpty());
+    }
 }
 
 void tst_QDecompressHelper::bigZlib()

tests/auto/network/access/qnetworkreply/tst_qnetworkreply.cpp

@@ -7077,7 +7077,7 @@ void tst_QNetworkReply::compressedHttpReplyBrokenGzip()
 
     QCOMPARE(waitForFinish(reply), int(Failure));
 
-    QCOMPARE(reply->error(), QNetworkReply::ProtocolFailure);
+    QCOMPARE(reply->error(), QNetworkReply::UnknownContentError);
 }
 
 // TODO add similar test for FTP