Recently, I tried to setup passwordless SSH access between two hosts but I was still being prompted for a password.
I used ssh -vv in order to try to debug was going wrong.
One thing that it was different this time, it was the absence of authorized_keys file in the remote host, so I tried to created it without taking care the file permissions.
The simple creation of the authorized_keys file caused this file being more permissive than sshd allows by default.
Thefore, by executing the following command, the passwordless SSH communication worked:
chmod 600 $HOME/.ssh/authorized_keys