Re: Call for review: restricted hardlinks.

From: Cédric Devillers (cedric.devillers_at_script.jussieu.fr)
Date: 03/09/04

  • Next message: Pawel Jakub Dawidek: "Re: Call for review: restricted hardlinks." 
    Date: Tue, 9 Mar 2004 09:16:39 +0100
To: freebsd-security@freebsd.org

    If you create several partition ( /var /usr /home ), this problem is
    resolved. Generally, in /usr, there are no directory write-able for all.
    If you have a partition for /usr, no hard link to a set-uid binary ( in
    the /usr tree ) is possible.

    On Mon, 8 Mar 2004 23:08:28 +0100
    Pawel Jakub Dawidek <pjd@freebsd.org> wrote:

    > On Mon, Mar 08, 2004 at 10:10:38PM +0100, Georg-W. Koltermann wrote:
    > +> When you restrict links, do you want to restrict copying as well?
    > +>
    > +> Seems somewhat paranoid to me. You already need write permission
    > on the+> directory where you create the link, and permissions are
    > checked against+> the inode on open(2) anyway.
    >
    > This is because this gives an attacker some possibilities.
    > For example he is able to create hard link to some set-uid binary.
    > After some time, a security-related bug will be found in this
    > application, administrator will change it with good version, but old,
    > vulnerable version will be still in system.
    > Administrator have to be really careful when fixing such problems
    > and check number of hard links or just remove such program using 'rm
    > -P'.
    >
    > --
    > Pawel Jakub Dawidek http://www.FreeBSD.org
    > pjd@FreeBSD.org http://garage.freebsd.pl
    > FreeBSD committer Am I Evil? Yes, I Am!
    >
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