Hi,

I have sudo user prayag with following settings in visudo:

prayag ALL=(ALL) NOPASSWD: ALL


Now,prayag can enter the command

sudo su -
and login as root

i want to disable this feature(sudo su -)


how is it possible?

You should look into the commands you want to allow prayag to have and then limit them to that because their are several other methods that this user can use to get full root. But as it goes the difference between giving a user full sudo privilages is not far off from full root, they just need to mess about with their $PATHs and put sudo infront of everything...

Their is also "sudo /bin/sh" or "sudo /bin/bash" what would have similar effects to "sudo su -" or "sudo passwd root" to reset the root password. I would look more into actually setting proper sudo privilages and limiting what commands the user has access to.

Hi,

I have to allow
prayag ALL=(ALL) NOPASSWD: ALL

i.e sudo to all command except the ones which gives them root shell is it possible to achieve this...???

Only if you can list all the cmds you want to allow and you are certain none of them allows a shell escape. Harder than you think.
sudo enables specified cmds, there's no way to specify disallowing cmds. It just disallows any cmds not listed (ie that aren't specifically listed/enabled).

This isn't possible,

Even if you limited it down to all the basic methods, if your giving them sudo, you are still giving them the ability to install a shell and then run it as root... Also even if you remove all but root shells, giving them sudo to everything else means they can do anything root can do via the use as sudo and view everything root can see. It's pointless to give them EVERYTHING else but direct root logins since they can still do whatever it is you don't want them do via sudo. Review what commands they actually need and then limit the sudoers file to just those commands and only those commands.