[tex-live] Status of restricted \write18 and epstopdf conversion

Alexander Cherepanov cherepan at mccme.ru
Sun Oct 18 22:39:43 CEST 2009

Hi Manuel!
On Sun, 18 Oct 2009 01:35:53 +0200, Manuel Pégourié-Gonnard <mpg at elzevir.fr> wrote:

>> And you can use backslash as a path separator on cygwin:
>>   ./repstopdf --outfile='dir\..\..\..\out.pdf' input.eps
>> (tested on cygwin1.5 only).

> Ok. Cygwin is quite complicated to get right, being sort of a mix of


> Unix and Windows. Thanks again for this information.

>> Approximate patch:

> It looks like a good start at first glance. I'll review it more
> thoroughly tomorrow (too tired now) and apply it.

>> +  # disallow quote
>> +  $ok = 0 if $OutputFilename =~ /"/;
>> +  # disallow newline (just to be on a safe side)
>> +  $ok = 0 if $OutputFilename =~ /\n/;

> This is not enough to prevent injection.
> repstopdf --debug --outfile="$(echo hi >~/pwned; echo foo.pdf)" foo.eps

(probably you mean single quotes here, so command substitution happens 
when calling gs, not when calling repstopdf)

> still gives arbitrary command execution. This one can be circumvented,
> at least on Unix, by quoting the outfile name with single quotes (and
> then disallow single quote in the value, or better escape them (since a
> legitimate user might want to use single quotes in his file names).

I've also thought about all this quoting but only after sending the 
email out:-( That requires some work...
Other issue here is environment variables like %TEMP% on Windows.

> But I'm thinking it would probably be better to use the list form of
> system() so that we avoid to call a shell at all, to really prevent
> injection.

This is also not that easy but you seem to manage it (just received 
your next mail), nice. Will look into the new version now.

Alexander Cherepanov

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