Created attachment 2621 [details]
bug fix to correctly handle pam_setcred and pam_open_session failure

Currently, when the system has a PAM module configured for the auth PAM stack that does not actually exist, OpenSSH still allows a user to log in, if user authentication method is not keyboard-interactive or password.

For example, in /etc/pam.d/other:

auth required           pam_dhkeys.so.1
auth required           pam_do_not_exist.so.1  <----------- bad
auth binding            pam_unix_auth.so.1 server_policy 


In the above situation, pam_setcred() does return an error, but
server only give a warning and still allow a user to log in if he/she doesn't use keyboard-interacitve user auth. 

This is not an expected behavior.  OpenSSH server should be changed to exit out when pam_setcred() or pam_open_session() fail.