A.P. Lawrence

This article is from a FAQ concerning SCO operating systems. While some of the information may be applicable to any OS, or any Unix or Linux OS, it may be specific to SCO Xenix, Open Desktop or Openserver.

There is lots of Linux, Mac OS X and general Unix info elsewhere on this site: Search this site is the best way to find anything.

Unix, Xenix and ODT General FAQ

How can I prevent root logins over telnet?

First, you can limit root logins to a specific device by adding an entry to /etc/default/login:

 CONSOLE=/dev/tty01

 

restricts root to the ALT-F1 multiscreen only. Unfortunately, there doesn't seem to be any way to add more than one device with CONSOLE, so that locks root out of tty02 and all the rest.

Less secure, but still useful, is to test within /etc/profile to boot root out of any but the multiscreens. Code to do that might look like:

 IAM=`who am i | cut -d" " -f1`
 TTY=`tty`
 if [ $IAM = "root" ]
 then
  case $TTY in
   /dev/tty[0-1][0-9]) : ;;
   *) exit 0;;
   esac
 fi

 

But this simplistic approach can cause problems with single user mode login. To avoid that, you need something that uses "who -r" to test the run-level and avoid the other tests if it isn't multiuser.

The 5.0.6 release adds a REMOTE_ROOT_OK keyword that can be used in /etc/default/login that *will* allow network access while when CONSOLE is set! See "man login" (5.0.6).

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