j-hpn-ssh/HOWTO.ssh-keycat

The ssh-keycat retrieves the content of the ~/.ssh/authorized_keys
of an user in any environment. This includes environments with
polyinstantiation of home directories and SELinux MLS policy enabled.

To use ssh-keycat, set these options in /etc/ssh/sshd_config file:
        AuthorizedKeysCommand /usr/libexec/openssh/ssh-keycat
        AuthorizedKeysCommandUser root

Do not forget to enable public key authentication:
        PubkeyAuthentication yes