Based on Linux PAM module, we can easily configure the related pam file and use the functionality that it provides. I just examine login authentication mechanism from PAM a little bit. The scenario is like this:
I change the login authentication mechanism from key pair to password and to see what happens in /var/log/auth.log if I give the wrong password.
The value to change:
PubkeyAuthentication yes ==> no
PasswordAuthentication no ==> yes
$> service ssh restart
After restarting ssh daemon, I give the wrong password and then I can see the error message in the log file:
The following image is for reference if everything is correct.