It is now possible to login with SSH keys (not passwords) with the following additional users: oll-backup, core-services and root. If you don’t need to use this feature, you don’t need to do anything, all is still just as locked-down. This is just here for those who want it and for some upcoming features that will use it.
The keys for each user is in the ~/.ssh/authorized_keys (~=home folder path of the user) for each user and the file needs to be owned by the user (and the user’s group) in question and not writeable by others. This is the default for openssh, so nothing CORE-specific.
To see the SSH login log, you can use the following command:
journalctl _COMM=sshd -f -n 100