Re: Root shell vixie cron exploit

[jk () CSUCHICO EDU (John Kennedy)]

On Wed, Sep 01, 1999 at 09:08:55PM +0400, Seva Gluschenko wrote:
> man sendmail:
> /-C
> ...skipping...
>       -Cfile  Use alternate configuration file.  Sendmail refuses to run
>               as root if an alternate configuration file is specified.
>
> and it does, for sure %-).
>
> Just tested this on different versions of FreeBSD and had no effects
> except Mail Delivery message:
>
> The following address has permanent fatal errors:
> -C/tmp/vixie-cf gvs
>
> So, sendmail _really_ refuses to accept -C key when run as root

  ???  I haven't looked hard at that exploit, but I know sendmail and that
is untrue.

  When an average (non-root) user tries to use a -C in sendmail, sendmail
will drop all its suid privs.  You can (mis-)configure sendmail to do
stupid things like run an arbitrary program is root -- your average user
just can't do that themselves.

  I had assumed that the whole problem with the vixie-cron exploit was
that cron allowed users to invoke sendmail with arbitrary command-line
options *as root*, so dropping SUID status doesn't do any good.
Sendmail doesn't try to protect the root user from themselves.