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