Catch FLI buffer overrun

python-pillow · Jan 2, 2020 · c40bc25 · c40bc25
1 parent 138bd71
commit c40bc25
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Showing 3 changed files with 12 additions and 2 deletions.
diff --git a/Tests/images/fli_overrun2.bin b/Tests/images/fli_overrun2.bin
diff --git a/Tests/test_image.py b/Tests/test_image.py
@@ -598,6 +598,13 @@ def test_overrun(self):
                 except OSError as e:
                     self.assertEqual(str(e), "buffer overrun when reading image file")
 
+        with Image.open("Tests/images/fli_overrun2.bin") as im:
+            try:
+                im.seek(1)
+                self.assertFail()
+            except OSError as e:
+                self.assertEqual(str(e), "buffer overrun when reading image file")
+
 
 class MockEncoder:
     pass

diff --git a/src/libImaging/FliDecode.c b/src/libImaging/FliDecode.c
@@ -40,8 +40,7 @@ ImagingFliDecode(Imaging im, ImagingCodecState state, UINT8* buf, Py_ssize_t byt
 	return 0;
 
     /* We don't decode anything unless we have a full chunk in the
-       input buffer (on the other hand, the Python part of the driver
-       makes sure this is always the case) */
+       input buffer */
 
     ptr = buf;
 
@@ -52,6 +51,10 @@ ImagingFliDecode(Imaging im, ImagingCodecState state, UINT8* buf, Py_ssize_t byt
     /* Make sure this is a frame chunk.  The Python driver takes
        case of other chunk types. */
 
+    if (bytes < 8) {
+        state->errcode = IMAGING_CODEC_OVERRUN;
+        return -1;
+    }
     if (I16(ptr+4) != 0xF1FA) {
 	state->errcode = IMAGING_CODEC_UNKNOWN;
 	return -1;