## security

I'm curious what the security implications of having this plugin on a
publically writable wiki are.

First, it looks like the way it looks up the stylesheet file will happily
use a regular .mdwn wiki page as the stylsheet. Which means any user can
create a stylesheet and have it be used, without needing permission to
upload arbitrary files. That probably needs to be fixed; one way would be
to mandate that the `srcfile` has a `.xsl` extension.

Secondly, if an attacker is able to upload a stylesheet file somehow, could
this be used to attack the server where it is built? I know that xslt is
really a full programming language, so I assume at least DOS attacks are
possible. Can it also read other arbitrary files, run other programs, etc?
--[[Joey]] 

> For the first point, agreed.  It should probably check that the data file has a `.xml` extension also.  Have now fixed.

> For the second point, I think the main concern would be resource usage.  XSLT is a pretty limited language; it can read other XML files, but it can't run other programs so far as I know.

> -- [[KathrynAndersen]]

>> XSLT is, indeed, a Turing-complete programming language.
   However, [XML::LibXSLT][] provides a set of functions to help
   to minimize the damage that may be caused by running a random
   program.

>> In particular, `max_depth ()` allows for the maximum
   recursion depth to be set, while
   `read_file ()`, `write_file ()`, `create_dir ()`,
   `read_net ()` and `write_net ()`
   are the callbacks that allow any of the possible file
   operations to be denied.

>> To be honest, I'd prefer for the `read_file ()` callback to
   only grant access to the files below the Ikiwiki source
   directory, and for all the `write_`… and
   …`_net` callbacks to deny the access unconditionally.

>> One more wishlist item: allow the set of locations to take
   `.xsl` files from to be preconfigured, so that, e. g.,
   one could allow (preasumably trusted) system stylesheets,
   while disallowing any stylesheets that are placed on the Wiki
   itself.

>> — Ivan Shmakov, 2010-03-28Z.

[XML::LibXSLT]: http://search.cpan.org/~PAJAS/XML-LibXSLT/LibXSLT.pm