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vmncdec: Sanity-check width/height before using it

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We will allocate a screen area of width*height*bpp bytes, however this
calculation can easily overflow if too high width or height are given
inside the stream. Nonetheless we would just assume that enough memory
was allocated, try to fill it and overwrite as much memory as wanted.

Also allocate the screen area filled with zeroes to ensure that we start
with full-black and not any random (or not so random) data.

https://scarybeastsecurity.blogspot.gr/2016/11/0day-poc-risky-design-decisions-in.html

Ideally we should just remove this plugin in favour of the one in
gst-libav, which generally seems to be of better code quality.

https://bugzilla.gnome.org/show_bug.cgi?id=774533
This commit is contained in:
Sebastian Dröge 2016-11-16 20:41:39 +02:00
parent c7192f0450
commit 4cb1bcf142
1 changed files with 5 additions and 1 deletions
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6
gst/vmnc/vmncdec.c
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@ -260,7 +260,7 @@ vmnc_handle_wmvi_rectangle (GstVMncDec * dec, struct RfbRectangle *rect,
gst_video_codec_state_unref (state); gst_video_codec_state_unref (state);
g_free (dec->imagedata); g_free (dec->imagedata);
dec->imagedata = g_malloc (dec->format.width * dec->format.height * dec->imagedata = g_malloc0 (dec->format.width * dec->format.height *
dec->format.bytes_per_pixel); dec->format.bytes_per_pixel);
GST_DEBUG_OBJECT (dec, "Allocated image data at %p", dec->imagedata); GST_DEBUG_OBJECT (dec, "Allocated image data at %p", dec->imagedata);
@ -790,6 +790,10 @@ vmnc_handle_packet (GstVMncDec * dec, const guint8 * data, int len,
GST_WARNING_OBJECT (dec, "Rectangle out of range, type %d", r.type); GST_WARNING_OBJECT (dec, "Rectangle out of range, type %d", r.type);
return ERROR_INVALID; return ERROR_INVALID;
} }
} else if (r.width > 16384 || r.height > 16384) {
GST_WARNING_OBJECT (dec, "Width or height too high: %ux%u", r.width,
r.height);
return ERROR_INVALID;
} }
switch (r.type) { switch (r.type) {