Date: Tue, 10 Feb 2015 11:01:51 +0100 From: Mateusz Guzik <mjguzik@gmail.com> To: Rui Paulo <rpaulo@me.com> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org, Rui Paulo <rpaulo@FreeBSD.org> Subject: Re: svn commit: r278479 - in head: etc sys/kern Message-ID: <20150210100151.GA5994@dft-labs.eu> In-Reply-To: <EE5E14DC-D44C-495B-BB2B-ADFCC6B07B59@me.com> References: <201502092313.t19NDpoS083043@svn.freebsd.org> <20150210024317.GA21779@dft-labs.eu> <EE5E14DC-D44C-495B-BB2B-ADFCC6B07B59@me.com>
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On Mon, Feb 09, 2015 at 06:57:36PM -0800, Rui Paulo wrote:
> On Feb 9, 2015, at 18:43, Mateusz Guzik <mjguzik@gmail.com> wrote:
> >
> > On Mon, Feb 09, 2015 at 11:13:51PM +0000, Rui Paulo wrote:
> >> +notify 10 {
> >> + match "system" "kernel";
> >> + match "subsystem" "signal";
> >> + match "type" "coredump";
> >> + action "logger $comm $core";
> >> +};
> >> +
> >> */
> >>
> > [..]
> >> + if (vn_fullpath_global(td, p->p_textvp, &fullpath, &freepath) != 0)
> >> + goto out;
> >> + snprintf(data, len, "comm=%s", fullpath);
> >
> > I cannot test it right now, but it looks like immediate privilege
> > escalation.
> >
> > Path is not sanitized in any way and devd passes it to 'sh -c'.
> >
> > So a file named "a.out; /bin/id; meh" or so should result in execution
> > of aforementioned /bin/id.
>
> Well, you can't have a file name with "/" but you're right.
>
I mean the whole path. You are resolving the name along with all dirs,
so it's just a matter of some mkdirs.
> > Another note is that currently devctl is record oriented, but this may
> > change at some point and free form userspace text could be used to forge
> > new events.
> >
> > As such is trongly suggest we sanitize this somehow. Maybe a base64 or
> > something.
>
> I was trying hard to avoid this issue in unpublished my crash helper, but I forgot that devd runs execl("sh -c", ....); :-(
>
> It might just be easier to inspect the path names and allow only [a-z][A-Z][0-9] and '/' before sending the devctl message.
>
I'm pretty sure sooner or later people will want something with a space,
so I would prefer a reasonably complete solution.
A hack like the one yu mention should suffice fr now though (with the
addition of a dot).
--
Mateusz Guzik <mjguzik gmail.com>
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