Re: hardlinks to setuid binaries

[Michael Richardson <mcr%sandelman.ca@localhost>]

Jan Schaumann <jschauma%netmeister.org@localhost> wrote:
    > Suppose you have a setuid /usr/pkg/bin/sudo from sudo version 1.8.11,
    > which is vulnerable to CVE-2014-9680.  You create a hardlink in your
    > home directory, so you get setuid, owned by root, mode 511 '~/sudo'.

So, that would require that all pieces be on the same partition.

I would claim that /home should be mounted nosuid, and that it wasn't is
really the bug.

    > On Linux, there appears to be a proc(5) restriction via
    > /proc/sys/fs/protected_hardlinks making this impossible, but on NetBSD
    > at least up to 9.2 this is possible.

    > Any thoughts on this?  Should there be a sysctl to disable this?  This
    > is not a new discovery; has this been discussed before?