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ImageMagick ReadSGIImage() Heap Overflow
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SUMMARY
<http://www.imagemagick.org> ImageMagick is "a free software suite to
create, edit, and compose bitmap images. It can read, convert and write
images in a large variety of formats". Remote exploitation of a heap
overflow vulnerability in ImageMagick could allow execution of arbitrary
code or cause denial of service.
DETAILS
A heap overflow exists in ReadSGIImage() function, that is used to decode
a SGI image files. The vulnerable code is:
coders/sgi.c:
static Image *ReadSGIImage(const ImageInfo *image_info,ExceptionInfo
*exception)
{
..
iris_info.bytes_per_pixel=(unsigned char) ReadBlobByte(image);
..
image->columns=iris_info.columns;
image->rows=iris_info.rows;
..
bytes_per_pixel=(size_t) iris_info.bytes_per_pixel;
number_pixels=(MagickSizeType) iris_info.columns*iris_info.rows;
..
iris_pixels=(unsigned char
*)AcquireMagickMemory(4*bytes_per_pixel*iris_info.columns*iris_info.rows);
We can manipulate with iris_info.rows, iris_info.columns and
bytes_per_pixel value. Allocation of memory to "iris_pixels" is based on
this values. When rows*cols*bytes_per_pixe*4 overflow integer variable, we
can alloc not enough memory for next operations, and cause heap overflow.
Proof of Concept:
Example crafted SGI file: <http://overflow.pl/poc/imheap.sgi>
http://overflow.pl/poc/imheap.sgi
[pucik@overflow ImageMagick-6.2.8]$ display imheap.sgi
*** glibc detected *** free(): invalid next size (fast): 0x08055dd0 ***
Abort (core dumped)
[pucik@overflow ImageMagick-6.2.8]$
ADDITIONAL INFORMATION
The information has been provided by <mailto:pucik@overflow.pl> Damian
Put.
The original article can be found at:
<http://www.overflow.pl/adv/imsgiheap.txt>
http://www.overflow.pl/adv/imsgiheap.txt
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