Proposal to add a DisableAuthentication option to sshd ServerOptions

[Henry Qin]

Thanks for the pointer!
I played around with PamServiceName set to 'sshd_disable_auth' and got it
working with the minimum contents below in the file
/etc/pam.d/sshd_disable_auth.

auth required pam_permit.so
account required pam_permit.so
session required pam_permit.so

Thus, this does indeed enable disabling authentication.

Unfortunately, as far as I can tell, only root can create files in
/etc/pam.d in most default system configurations.
Moreover, it is somewhat common to disallow root in an actual deployed
environment.

That means that this approach is infeasible when running sshd as an
ordinary user, both generally and in deployed environments, unless the
container or deployed VM already has a pam configuration file such as
/etc/pam.d/sshd_disable_auth deployed with it.

Thus, I'm still interested in your opinions on the proposed patch, which
would grant more flexibility to ordinary users, and allow ad hoc usage in
deployed scenarios without having to prepare a container with a bespoke pam
configuration file.

~Henry

On Thu, Jun 27, 2024 at 10:58 AM Peter Moody <mindrot at hda3.com> wrote:

> see pam_permit(8)
>
>
> On Thu, Jun 27, 2024 at 10:37 AM Henry Qin <hq6 at cs.stanford.edu> wrote:
> >
> > When I  looked at `man pam_unix`, I did not see any obvious options that
> > would
> > cause ssh to authenticate without prompting for a password at all, short
> of
> > setting an empty password which is similar to PermitEmptyPasswords
> option.
> >
> > However, I am not very familiar with the internals of PAM, so pointers to
> > documentation would be greatly appreciated.
> >
> > Also, I think adding a single line to sshd_config is simpler for most
> users
> > to
> > do correctly than configuring an alternate PAM stack without breaking
> their
> > primary sshd setup, which is why I think the patch may still be useful.
> >
> > On Thu, Jun 27, 2024 at 7:57 AM Carson Gaspar <carson at taltos.org> wrote:
> >
> > > On 6/26/2024 9:34 PM, Henry Qin wrote:
> > > > Hi folks,
> > > >
> > > > I've recently started to work on a patch for openssh that introduces
> a
> > > new
> > > > option to disable authentication.
> > > > I'd like to explain why I think this might be generally useful, and
> > > solicit
> > > > opinions on whether such a patch would be acceptable to the
> maintainers
> > > as
> > > > a pull request.
> > >
> > > Why not just use a different PAM stack? The new release allows
> > > specifying the stack name. This should do what you want with no code
> > > changes using Password / KbdInteractive AuthN.
> > >
> > > --
> > >
> > > Carson
> > >
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