oss-security - Re: CVE request -- coreutils -- tty hijacking possible in "su" via TIOCSTI ioctl

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Date: Tue, 21 Jun 2011 10:59:15 -0400 (EDT)
From: Josh Bressers <bressers@...hat.com>
To: oss-security@...ts.openwall.com
Cc: "Steven M. Christey" <coley@...us.mitre.org>
Subject: Re: CVE request -- coreutils -- tty hijacking
 possible in "su" via TIOCSTI ioctl

----- Original Message -----
> Jan Lieskovsky wrote:
> > Hello Josh, Steve, vendors,
> >
> >    based on Debian BTS report:
> >    [1] http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=628843
> >        (first CVE-2011-XXYY required for Debian case)
> >
> > looked more into original report:
> > [2] https://bugzilla.redhat.com/show_bug.cgi?id=173008
> >
> > and the first paragraph of [2] suggests:
> > "When starting a program via "su - user -c program" the user session
> > can escape to the parent session by using the TIOCSTI ioctl to push
> > characters into the input buffer. This allows for example a non-root
> > session to push "chmod 666 /etc/shadow" or similarly bad commands
> > into
> > the input buffer such that after the end of the session they are
> > executed."
> >
> > this should get a CVE-2005-YYZZ CVE id.
> >
> > Could you allocate these?
> 
> ping! :-)
> 

I'm not sure if this should get two IDs. It's really one issue, which isn't
actually fixed in su.

The fundamental issue is that tools like su and sudo keep the tty open.
The patch in question closes the tty for the case of su -c, but not for
just running su by itself. It is incomplete.

It should get a 2005 ID at the very least, MITRE will have to do that.
Perhaps two 2005 IDs? One for the issue, the second for the incomplete fix
(which is still not fixed)?

I think the bigger issue is it needs to be decided what is proper behavior
and document that. I'm not smart enough to know if this can be fixed
properly without crippling these tools.

Thanks.

-- 
    JB

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