Query regarding trap and preventing user breakout

[Adam Noble]

I would be grateful if somebody could assist me with the following:-

We are providing users with the facility to add userid's for a specific application by using a menu. I am using sudo and a menu script to enable them to do this but need to prevent them from being able to break out of the script. I have set the following at the start of the script trap " " 01 02 03 15 and this appears to prevent all forms of user breakout apart from ctrl D. I can through the initial case statement ensure that if ctrl D is entered it simply starts again, but as the script goes on this becomes more difficult can ctrl D be trapped in the same way as say ctrl-C. Any ideas would be appreciated.

[David_246]

Hi Adam,

What I did to prevent this is the following.

/home/user/.profile :

exec /program/to/run
exit

So, whenever a user logs in, the specific program you mention is being exec(uted) from within the .profile. If they get a chance to breakout of that program they very easily continue in the .profile. And that says an exit.
Easy isn't it ?

Regs David

[Stefan Farrelly]

Using a script, even with trap, is never guaranteed to stop someone breaking out. They could simply keep hitting Ctrl-C and eventually would get lucky and break out of it before the trap command was executed.

Only way to ensure this is write it in a C program - then modify their login shell in /etc/passwd to be the C program.