Restrict telnet from telnet

[Ahmed_58]

Hi,
How can I restrict user to telnet fron his telnet session.
In another word, he login to HP-UX using VPN then telnet and then restrict him to telnet from his session.

Rrg, Ahmed

[Matti_Kurkela · Accepted solution]

Do you mean "allow the use of the telnet command only" or "stop the user from telnetting any further"?

If you mean "telnet only", change the user's shell to /usr/bin/telnet, or write a script that allows the user to choose a destination and then use that as the user's shell.

If you mean "stop this particular user telnetting any further", that's what passwords and security patches are for. The user can try, but unless he has a valid password for his destination, he will fail.

You could change the permissions of the telnet command so that the user could no longer run it. If the user is knowledgeable enough he can bring his own telnet binary to the system and use it, so this way is not very secure.

If it's acceptable that *nobody* can telnet out of a particular server, you could install the ipfilter package and then use it to block all outgoing connections to TCP port 23 (the telnet port). Learn how ipfilter works before you try this, so you won't accidentally disable all network connections.

[Ahmed_58]

Thanks Matti,

Yes "stop this particular user telnetting any further".
I know password is what used for. but thinking of a more scure way.

Ahmed