Fix the JPEG EXIF reader to deal with some broken/corrupt filesv5.7.1

We parse the EXIF header in order to get the proper orientation, so
let's be a bit more careful in what we accept. This patch adds better
handling for reading past the end of the stream, plus it limits the
number of IFDs read (to avoid processing too much data) and deals with a
pathological case of the EXIF file format: EXIF (due to its TIFF
origins) permits the offset to the next IFD to be backwards in the file,
which means it could result in a loop or pointing to plain corrupt data.
We disallow any backwards pointers, since it seems that's what other
decoders do (libexif, for example).

Change-Id: Iaeecaffe26af4535b416fffd1489332db92e3888
(cherry picked from 5.6 commit 02150649f95b8f46f826e6e002be3fa0b6d009bc)
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>

1 files changed, 14 insertions, 3 deletions

diff --git a/tests/auto/gui/image/qimage/tst_qimage.cpp b/tests/auto/gui/image/qimage/tst_qimage.cpp
index 85d258de5b..26772d5655 100644
--- a/tests/auto/gui/image/qimage/tst_qimage.cpp
+++ b/tests/auto/gui/image/qimage/tst_qimage.cpp
@@ -183,7 +183,8 @@ private slots:
     void exifOrientation();
 
     void exif_QTBUG45865();
-    void exif_invalid_data_QTBUG46870();
+    void exifInvalidData_data();
+    void exifInvalidData();
 
     void cleanupFunctions();
 
@@ -3028,10 +3029,20 @@ void tst_QImage::exif_QTBUG45865()
     QCOMPARE(image.size(), QSize(5, 8));
 }
 
-void tst_QImage::exif_invalid_data_QTBUG46870()
+void tst_QImage::exifInvalidData_data()
+{
+    QTest::addColumn<bool>("$never used");
+    QTest::newRow("QTBUG-46870");
+    QTest::newRow("back_pointers");
+    QTest::newRow("past_end");
+    QTest::newRow("too_many_ifds");
+    QTest::newRow("too_many_tags");
+}
+
+void tst_QImage::exifInvalidData()
 {
     QImage image;
-    QVERIFY(image.load(m_prefix + "jpeg_exif_invalid_data_QTBUG-46870.jpg"));
+    QVERIFY(image.load(m_prefix + "jpeg_exif_invalid_data_" + QTest::currentDataTag() + ".jpg"));
     QVERIFY(!image.isNull());
 }