[Poppler-bugs] [Bug 101504] New: NULL dereference in GfxState.cc:6127
bugzilla-daemon at freedesktop.org
bugzilla-daemon at freedesktop.org
Mon Jun 19 17:57:34 UTC 2017
https://bugs.freedesktop.org/show_bug.cgi?id=101504
Bug ID: 101504
Summary: NULL dereference in GfxState.cc:6127
Product: poppler
Version: unspecified
Hardware: Other
OS: All
Status: NEW
Severity: normal
Priority: medium
Component: general
Assignee: poppler-bugs at lists.freedesktop.org
Reporter: foca at salesforce.com
Created attachment 132068
--> https://bugs.freedesktop.org/attachment.cgi?id=132068&action=edit
Proof of concept
There is a NULL dereference in GfxState.cc:6127.
The function drawSoftMaskedImage calls getLine() at CairoOutputDev.cc:2710
which returns NULL, and stores that in pix. The value is than passed on to the
getGrayLine function which tries to dereference it, resulting in a null
dereference.
2708 for (y = 0; y < maskHeight; y++) {
2709 maskDest = (unsigned char *) (maskBuffer + y * row_stride);
2710 pix = maskImgStr->getLine();
2711 maskColorMap->getGrayLine (pix, maskDest, maskWidth);
2712 }
The reason NULL is returned by getLine due to the following
`ImageStream::getLine`
529 if (unlikely(inputLine == NULL)) {
530 return NULL;
531 }
At the point inp is set to whatever pix was( pix=in), in our case pix was NULL.
On line 6127 the dereference takes place and poppler crashes trying to
dereference a NULL pointer.
6123 default:
6124 inp = in;
6125 for (j = 0; j < length; j++)
6126 for (i = 0; i < nComps; i++) {
6127 *inp = byte_lookup[*inp * nComps + i];
6128 inp++;
6129 }
A solution could be an additional check at CairoOutputDev.cc:2710 to check the
line isn't NULL:
2710 pix = maskImgStr->getLine();
2711 if (pix == NULL) continue;
2712 maskColorMap->getGrayLine (pix, maskDest, maskWidth);
PoC is attached.
This vulnerability has been found by Offensive Research at Salesforce.com:
Alberto Garcia (@algillera), Francisco Oca (@francisco_oca) & Suleman Ali
(@Salbei_)
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