Re: Two problems with current ruby scripts

[Hans Hagen <pragma@wxs.nl>]

Norbert Preining wrote:
> Dear all!
>
> THe packages of ConTeXt I am currently preparing are tested by a user
> and he send back the following questions/comments. Could you please
> comment on this.
>
> For the background: I install all the stubs from 
> 	scripts/context/stubs/unix
> into /usr/bin, add a texmfstart stub that calls ruby with the right path
> to texmfstart.rb.
>
> ----- Forwarded message from Mike Bird <mgb@yosemite.net> -----
>   
>> From: Mike Bird <mgb@yosemite.net>
>> Subject: New texexec very confused
>> To: debian-tex-maint@lists.debian.org
>> Date: Tue, 24 Oct 2006 20:52:30 -0700
>>
>> The new ruby texexec is very confused.  The problem of output
>> defaulting to pdf instead of dvi has already been noted.  Here
>> are some additional problems:
>>
>> Command:            texexec --output=dvips foo
>> Should produce:     foo.dvi
>> Actually produces:  foo.pdf
>>     
hm, i need to check that, maybe there is no dvips option
>> Command:            texexec --dvi foo
>> Should produce:     foo.dvi
>> Actually produces:  foo.dvi AND OVERWRITES foo.ps
>>
>> --Mike Bird
>>     
that's because the backend is called as well (dvips) ; the latest 
version has a --nobackend option

> ----- End forwarded message -----
>
>
> ----- Forwarded message from Mike Bird <mgb@yosemite.net> -----
>   
>> From: Mike Bird <mgb@yosemite.net>
>> Subject: Is texmfstart secure?
>> To: debian-tex-maint@lists.debian.org
>> Date: Tue, 24 Oct 2006 21:08:53 -0700
>>
>> Package: context 2006.08.08-0.4
>>
>> If anyone who knows Ruby has time, can you tell if texmfstart is
>> secure?  I was really surprised to see client-server code.  Even
>> localhost services can lead to privilege escalation if not careful.
>>     
hm, if you don't invoke that code it's not used so there can hardly be a 
leak then;

the server/client code is a bit experimental and is related to 
distributed ruby code; imagine a situation where one has many (frozen) 
tex trees on a server that is used for automated tex processing; in that 
case, instead of calling kpsewhich each time, a service will keep the 
file databases (for multiple trees) in memory etc etc ; as said, the 
average user never enters this code, and it's not even loaded when your 
system is not explicitly configured to do so

>> For example, /usr/share/texmf/scripts/context/ruby/texmfstart.rb
>> contains the following.  I'm not a Ruby programmer but the comment
>> leads me to think there is a potential problem here:
>>
>>                 # danger lurking
>>                 buffer = ' ' * 260
>>                 length = filemethod.call(filename,buffer,buffer.size)
>>                 if length>0 then
>>                     return buffer.slice(0..length-1)
>>     
this has to do with windows long/short names and this branch is never 
entered under unix ; also, buffer is just a string and has nothing to do 
with "buffers that produce those buffer overflows"
>> It looks like PRAGMA is trying to reinvent kpsewhich, integrate internet
>>     
well, it's mostly a wrapper around kpsewhich; it would be natural to 
have kpse as a library but (1) it's not stable [api cq. names changes] 
and i don't see a stable kpse lib usable in script languages show up; 
(and yes: i rewrote kpse in ruby, and surprise, in some case it even 
runs faster than the c version); consider that in context there can be  
runs with (say) 400 calls to metapost and then it really pays off to 
bypass this ls-r loading
>> explorer, launch editors, and do a whole bunch of other stuff I haven't
>>     
this launching is only used when one starts documentation -- we use this 
in editors: context sensitive help started by a few keystrokes

another option is to use file associations but that has some disadvantaged

anyhow, i see no security risks here since all happens inside the tex 
domain; i don't need tex to crash an internet browser (on any system) -)
>> figured out.  texexec should be a simple wrapper around tex or pdftex
>> but it works via texmfstart.rb which is 2541 lines of Ruby - and that's
>> a lot of Ruby.  It may all be wonderful (I am not a Ruby programmer) but
>>     
well, if kpse* would have evolved ... sure, but it didn't; also, since i 
run tex on windows, linux and macosx, i want one launcher for all of 
them, not all kind of os dependent scripts
>> it makes me nervous.
>>     
well, i would be more worried about tons of cryptic perl code, even if 
i've written it myself, after a few years i can no longer figure out 
what it does;
>> Is an older/simpler texexec still available?
>>     
there is still texexec.pl (will always be around) but i will no longer 
develop the perl scripts

Hans

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