Re: Howto change login mechanism on OpenBSD

hello,

valdrin.muja@zoho.com (Valdrin MUJA), 2020.05.25 (Mon) 16:47 (CEST):
> Actually I updated the /etc/ttys file and add my program instead of
> getty. However, after boot, there was still OpenBSD login prompt
> before my program started. 

as already mentioned, init(8) respawns the program specified in ttys(5)
if the program stops. it also throttles respawning if it happens to
often. after changes to ttys(5), run "kill -s HUP 1".


> On the other hand, I tried chpass -s $myprogram $user, but still I'm

This only changes the login shell that is run after you have logged in
via login(1).

> In short,  I want to disable OpenBSD login prompt and execute my
> program. If user exits this external program, my program should run
> again etc.

use with care!

$ grep ttyC5 /etc/ttys
ttyC5 "/etc/ttymenu.getty" vt220 on secure

cat /etc/ttymenu.getty
#!/bin/sh -e
TERM=vt220 /etc/ttyprog < /dev/$1 > /dev/$1

/etc/ttyprog would be the program you want to run.
stdin and stdout are connected to the tty.

Marcus

> ---- On Thu, 21 May 2020 01:53:29 +0200 Jeff Joshua Rollin <jeff@jeffjoshua.club> wrote ----
>
>
> On Wed, 2020-05-20 at 17:00 -0500, Edgar Pettijohn wrote:
> > On Wed, May 20, 2020 at 09:50:17PM +
> > >
> > > I believe /etc/ttys controls getty, which may or not help. Getty is
> > > respawned too.
> > > https://man.openbsd.org/man5/ttys.5
> >
> > I think you're right. Might just need to change a line in /etc/ttys
> > to
> > execute /bin/{my_program}.
> >
> > Edgar
> >
>
> Perhaps a better way would be just to change the user's login shell to
> the name of your program: chpass -s $myprogram $user. That way you can
> use OpenBSD's login authentication, and login automatically runs the
> program when the user logs in; when the user quits the program they are
> automatically logged out. Provided there's no way to execute a shell
> from within the program, they therefore can't execute arbitrary code
> once logged in. It's easy to add a user for this single purpose: just
> add the user as normal, and specify $myprogram as the shell.
>
> Jeff.