Sophos oder Google Authenticator für SSH nutzen
Um eine Zwei-Wege-Authentifizierung für SSH hinzubekommen braucht es unter Debian (& Co.) nur ein paar Schritte :
# apt install libpam-google-authenticator
in der /etc/pam.d/sshd ankleben:
auth required pam_google_authenticator.so
in der /etc/ssh/sshd_config ändern:
ChallengeResponseAuthentication yes
dann für die ssh Nutzer jeweils einmal:
# google-authenticator
Do you want authentication tokens to be time-based (y/n) y
Do you want me to update your "^/.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. 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 +-1min (window size of 3) to about +-4min (window size of
17 acceptable tokens).
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
Das ganze aktivieren:
# service sshd restart