Re: Prog/script to securely reject a login? (summary)

From: Stephen Page (
Date: Wed Jul 01 1992 - 03:47:26 CDT

I asked for advice on how to block out "expired" users, writing a message and
sleeping. I was looking for a secure way to get a prog executed instead of
the user's default shell.

Thanks to those who responded. I was pleased to see there wasn't any nasty
loophole I was opening. There were broadly two categories of solution:

1. Use a shell script, which just does echo "message".

2. Use a C program.

Both of these seem to defeat FTP, rsh and logins. Breaking out of either
causes immediate logout. FTP fails because the script or prog is not in

One person included disabling of SIGHUP, SIGINT, SIGQUIT, and SIGTSTP in
the code. This doesn't seem to be necessary, though.

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