From ce17e968e4cf900d28ca5b46f6e095febc42b4f0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sebastian=20Dr=C3=B6ge?= <sebastian@centricular.com>
Date: Thu, 10 Aug 2023 15:45:01 +0300
Subject: [PATCH] mxfdemux: Fix integer overflow causing out of bounds writes
 when handling invalid uncompressed video

Check ahead of time when parsing the track information whether
width, height and bpp are valid and usable without overflows.

Fixes ZDI-CAN-21660, CVE-2023-40474

Fixes https://gitlab.freedesktop.org/gstreamer/gstreamer/-/issues/2896

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5362>
---
 gst/mxf/mxfup.c | 51 +++++++++++++++++----
 1 file changed, 43 insertions(+), 8 deletions(-)

diff --git a/gst/mxf/mxfup.c b/gst/mxf/mxfup.c
index d72ed22cb7a..0c0178c1c9e 100644
--- a/gst/mxf/mxfup.c
+++ b/gst/mxf/mxfup.c
@@ -118,6 +118,8 @@ mxf_up_handle_essence_element (const MXFUL * key, GstBuffer * buffer,
     gpointer mapping_data, GstBuffer ** outbuf)
 {
   MXFUPMappingData *data = mapping_data;
+  gsize expected_in_stride = 0, out_stride = 0;
+  gsize expected_in_size = 0, out_size = 0;
 
   /* SMPTE 384M 7.1 */
   if (key->u[12] != 0x15 || (key->u[14] != 0x01 && key->u[14] != 0x02
@@ -146,22 +148,25 @@ mxf_up_handle_essence_element (const MXFUL * key, GstBuffer * buffer,
     }
   }
 
-  if (gst_buffer_get_size (buffer) != data->bpp * data->width * data->height) {
+  // Checked for overflows when parsing the descriptor
+  expected_in_stride = data->bpp * data->width;
+  out_stride = GST_ROUND_UP_4 (expected_in_stride);
+  expected_in_size = expected_in_stride * data->height;
+  out_size = out_stride * data->height;
+
+  if (gst_buffer_get_size (buffer) != expected_in_size) {
     GST_ERROR ("Invalid buffer size");
     gst_buffer_unref (buffer);
     return GST_FLOW_ERROR;
   }
 
-  if (data->bpp != 4
-      || GST_ROUND_UP_4 (data->width * data->bpp) != data->width * data->bpp) {
+  if (data->bpp != 4 || out_stride != expected_in_stride) {
     guint y;
     GstBuffer *ret;
     GstMapInfo inmap, outmap;
     guint8 *indata, *outdata;
 
-    ret =
-        gst_buffer_new_and_alloc (GST_ROUND_UP_4 (data->width * data->bpp) *
-        data->height);
+    ret = gst_buffer_new_and_alloc (out_size);
     gst_buffer_map (buffer, &inmap, GST_MAP_READ);
     gst_buffer_map (ret, &outmap, GST_MAP_WRITE);
     indata = inmap.data;
@@ -169,8 +174,8 @@ mxf_up_handle_essence_element (const MXFUL * key, GstBuffer * buffer,
 
     for (y = 0; y < data->height; y++) {
       memcpy (outdata, indata, data->width * data->bpp);
-      outdata += GST_ROUND_UP_4 (data->width * data->bpp);
-      indata += data->width * data->bpp;
+      outdata += out_stride;
+      indata += expected_in_stride;
     }
 
     gst_buffer_unmap (buffer, &inmap);
@@ -378,6 +383,36 @@ mxf_up_create_caps (MXFMetadataTimelineTrack * track, GstTagList ** tags,
     return NULL;
   }
 
+  if (caps) {
+    MXFUPMappingData *data = *mapping_data;
+    gsize expected_in_stride = 0, out_stride = 0;
+    gsize expected_in_size = 0, out_size = 0;
+
+    // Do some checking of the parameters to see if they're valid and
+    // we can actually work with them.
+    if (data->image_start_offset > data->image_end_offset) {
+      GST_WARNING ("Invalid image start/end offset");
+      g_free (data);
+      *mapping_data = NULL;
+      gst_clear_caps (&caps);
+
+      return NULL;
+    }
+
+    if (!g_size_checked_mul (&expected_in_stride, data->bpp, data->width) ||
+        (out_stride = GST_ROUND_UP_4 (expected_in_stride)) < expected_in_stride
+        || !g_size_checked_mul (&expected_in_size, expected_in_stride,
+            data->height)
+        || !g_size_checked_mul (&out_size, out_stride, data->height)) {
+      GST_ERROR ("Invalid resolution or bit depth");
+      g_free (data);
+      *mapping_data = NULL;
+      gst_clear_caps (&caps);
+
+      return NULL;
+    }
+  }
+
   return caps;
 }
 
-- 
GitLab

