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Let's do an ikiwiki security analysis..
If you are using ikiwiki to render pages that only you can edit, do not
generate any wrappers, and do not use the cgi, then there are no more
security issues with this program than with cat(1). If, however, you let
others edit pages in your wiki, then some possible security issues do need
to be kept in mind.
# Probable holes
## html attacks
ikiwiki does not attempt to do any santization of the html on the wiki.
[[MarkDown]] allows embedding of arbitrary html into a markdown document. If
you let anyone else edit files on the wiki, then anyone can have fun exploiting
the web browser bug of the day. This type of attack is typically referred
to as an XSS attack ([google](http://www.google.com/search?q=xss+attack)).
## image files etc attacks
If it enounters a file type it does not understand, ikiwiki just copies it
into place. So if you let users add any kind of file they like, they can
upload images, movies, windows executables, css files, etc. If these files exploit security holes in the browser of someone who's viewing the wiki, that can be a security problem.
Of course nobody else seems to worry about this in other wikis, so should we?
## web server attacks
If your web server does any parsing of special sorts of files (for example,
server parsed html files), then if you let anyone else add files to the wiki,
they can try to use this to exploit your web server.
## symlink attacks
Could a committer trick ikiwiki into following a symlink and operating on
some other tree that it shouldn't? svn supports symlinks, so one can get
into the repo. ikiwiki uses File::Find to traverse the repo, and does not
tell it to follow symlinks, but it might be possible to race replacing a
directory with a symlink and trick it into following.
It would certianly be possible to start out with a directory, let ikiwiki
run and find a file in there, then replace it with a symlink, and ikiwiki
would then go ahead and follow the symlink when it went to open that file
to read it. If it was some private file and was running suid, that could be
bad.
TODO: seems that locking to prevent more than one ikiwiki run at a time
would both fix this and is a good idea in general. With locking, an
attacker couldn't get ikiwiki to svn up while another instance was running.
Even with locking, if an attacker has local write access to the checkout,
they could still fool ikiwiki using similar races. So it's best if only one
person can ever write to the checkout that ikiwiki compiles the moo from.
## webserver symlink attacks
If someone checks in a symlink to /etc/passwd, ikiwiki would publish that.
To aoid this, ikiwiki will need to avoid reading files that are symlinks.
TODO and note discussion of races above.
## cgi security
When ikiwiki runs as a cgi to edit a page, it is passed the name of the
page to edit. It has to make sure to sanitise this page, to prevent eg,
editing of ../../../foo, or editing of files that are not part of the wiki,
such as subversion dotfiles. This is done by sanitising the filename
removing unallowed characters, then making sure it doesn't start with "/"
or contain ".." or "/.svn/". Annoyingly ad-hoc, this kind of code is where
security holes breed. It needs a test suite at the very least.
----
# Probable non-holes
## exploting ikiwiki with bad content
Someone could add bad content to the wiki and hope to exploit ikiwiki.
Note that ikiwiki runs with perl taint checks on, so this is unlikely.
## publishing cgi scripts
ikiwiki does not allow cgi scripts to be published as part of the wiki. Or
rather, the script is published, but it's not marked executable, so
hopefully your web server will not run it.
## suid wrappers
ikiwiki --wrapper is intended to generate a wrapper program that
runs ikiwiki to update a given wiki. The wrapper can in turn be made suid,
for example to be used in a [[post-commit]] hook by people who cannot write
to the html pages, etc.
If the wrapper script is made suid, then any bugs in this wrapper would be
security holes. The wrapper is written as securely as I know how, is based on code that has a history of security use long before ikiwiki, and there's been no problem yet.
## shell exploits
ikiwiki does not expose untrusted data to the shell. In fact it doesn't use system() at all, and the only use of backticks is on data supplied by the wiki admin. And it runs with taint checks on of course..
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