In order to enable SSH agent authentication in a PAM module, you need to enter
them in the module's configuratio in /etc/pam.d/. For details, see the
pam_ssh_agent_auth(8) man page; the common use cases are outlined here.

sudo
====

For use with sudo, a common configuration is entering the line

auth     sufficient    pam_ssh_agent_auth.so file=/etc/security/authorized_keys

into /etc/pam.d/sudo before the common-auth line.

Then, concatenate the relevant SSH public key lines into
/etc/security/authorized_keys.


chsh
====

In order to make chsh available on machines without configured user passwords,
add the following line in /etc/pam.d/chsh before the common-auth line:

auth    sufficient    pam_ssh_agent_auth.so file=~/.ssh/authorized_keys
