Decrypt "/etc/shadow" file for user

Question

Hi All
I want to write a script that give's a user access to kill his own processes. But to authenticate him I want him to log into this program with his unix user and password. How do I decrypt his password from the /etc/shadow file, or it there is a better way to do this I'm open for suggestions.
Many thanks in advance.
Kind Regards
Johnny

Answer 1

This sounds like a good excuse for you to look into RBAC and setup a role specifically for this purpose. This role would be given permission to run the pkill command using the -U switch to specify the UID to kill. But the more I think about this approach, the more problems I see with creating a role for this e.g. how do you prevent a user from killing someone else using this role cuz the role will have no way to truely know a specific user is supposed to be killing anything. But you may be able to think long and hard about this and figure something out.
A better approach might be for you to update the login logic you are already using. If the login logic sees that a user is already logged in twice, it puts up a screen showing the PPIDs of the process trees that the user is already logged into - obviously NOT showing the PPID of the current login session e.g. the one currently being used to kill the other login sessions.
The user can then selects which session to terminate. The login logic runs pkill to kill the selected PPID for that user. This "kill" login session is immedately exited and the user can login again with a clean session.
In this case, the user would have no reason to log into a second login which would then have to "login" again to kill a user's own processes.