I am working with a CentOS7 minimal install. I configured pam_radius with pam_script and was always able to ssh to the server using pubkey auth: that was on purpose. But after hardening the server according to STIG guide (a comprehensive walkthrough can be found here) I was no longer able to SSH into the system; or more acculturately I would login then get kicked out immediately. The error in the /var/log/secure file said:
sshd: error: PAM: pam_open_session(): Cannot make/remove an entry for the specified session
Disabling selinux, as is par for the course, resolved the issue. But obviously that is not an acceptable resolution.