two factor authentification under ssh with google authenticator
apt-get install libpam-google-authenticator
root@mattionline:~# google-authenticator
Do you want authentication tokens to be time-based (y/n) y Do you want me to update your "/root/.google_authenticator" file (y/n) y Do you want to disallow multiple uses of the same authentication token? This restricts you to one login about every 30s, but it increases your chances to notice or even prevent man-in-the-middle attacks (y/n) y By default, tokens are good for 30 seconds and in order to compensate for possible time-skew between the client and the server, we allow an extra token before and after the current time. If you experience problems with poor time synchronization, you can increase the window from its default size of 1:30min to about 4min. Do you want to do so (y/n) n If the computer that you are logging into isn't hardened against brute-force login attempts, you can enable rate-limiting for the authentication module. By default, this limits attackers to no more than 3 login attempts every 30s. Do you want to enable rate-limiting (y/n) y
Then you scan the qr code with the google authenticator app on your smartphone.
nano /etc/pam.d/sshd #@include common-auth #add this to the end of the file auth required pam_google_authenticator.so
#authenticate via the ssh key file. not with a password!
nano /etc/ssh/sshd_config PasswordAuthentication no ChallengeResponseAuthentication yes PermitRootLogin yes #to the end of the file AuthenticationMethods publickey,keyboard-interactive
/etc/init.d/ssh restart
Troubleshooting
Password is wrong -> PermitRootLogin yes (i’ve learned it after two hours and 5-6 reboots into the rescue system…)
It was configured this way „PermitRootLogin without-password“ and this doesn’t work with google authenticator 😉
