[avahi] chroot & symlink

Lennart Poettering lennart at poettering.net
Sat Jan 12 07:31:32 PST 2008

On Fri, 11.01.08 23:43, Philipp Kempgen (philipp.kempgen at amooma.de) wrote:

> Philipp Kempgen wrote:
> > Avahi seems to chroot before reading /etc/avahi/services/*.service .
> > So if one of those is a symlink to some file outside of the chroot
> > environment Avahi can't read it.
> > Works fine with --no-chroot or --no-drop-root .
> OK, as I have not received any reply:
> - Didn't I make it clear enough that the described behavior
>   causes problems?
> - Do you think it's not a bug? (although such a setup is
>   possible with other daemons)
> - As I'm using Avahi on Debian, should I have contacted the
>   package maintainer first although I don't think the problem
>   is specific to Debian?
> - Is it that nobody has the time to look into it and/or
>   fix it anyway? (which would be perfectly understandable -
>   just tell me)
> Just to make it clear: A "patches are welcome" type of reply
> would be fine with me.

Oh. I didn't get that this was intended to be a real problem report,

Yes, I wouldn't consider this a real bug. Just something people should
be aware of. Fixing this is far from trivial and might introduce
possible security holes (since we'd need to punch additional holes
into the chrooting for accessing more files outside of it), and I am
quite sure that the benefit of fixing this would not be worth it.

I would happily merge a patch though, that would document this
behaviour in the man pages, and possibly some additional code that
warns the user via syslog if an absolute symlink or one that points
outside of the chroot is found in the services dir. So: Patches are



Lennart Poettering                        Red Hat, Inc.
lennart [at] poettering [dot] net         ICQ# 11060553
http://0pointer.net/lennart/           GnuPG 0x1A015CC4

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