Linux

In our servers we don't have proper groups and No active Directory.
We are adding Users locally and providing users a public key, that's the way they can connect to the servers using .ppk file.

My manager ask me to prompt for a password based login when they try for Sudo. (Currently it was set up for no password in sudoers file)

Since we don't have a Password set up on these boxes is there any way we can achieve this task.

I am thinking as below:
Please let me know is there any other way we can address this thank you for your valuable suggestions

Thanks

AFAIK:
If you want the users to type a password for sudo, then they must have a password for their own account.
Where there is no password for one owns account, it cannot be entered upon sudo, however, one can have an account with password with a passwordless sudo.

Another idea, but i dont know how to implement, would be ssh-key files.
See: ssh-keygen and probably ssh-copy-id of openssh package for more details.

Hope this helps to get you started.