google-authenticator-libpam

Dependencies

Build Dependencies

Add 2-factor authentication for ssh:
  echo "auth required $HOMEBREW_PREFIX/opt/google-authenticator-libpam/lib/security/pam_google_authenticator.so" \
  | sudo tee -a /etc/pam.d/sshd

Add 2-factor authentication for ssh allowing users to log in without OTP:
  echo "auth required $HOMEBREW_PREFIX/opt/google-authenticator-libpam/lib/security/pam_google_authenticator.so" \
  "nullok" | sudo tee -a /etc/pam.d/sshd

(Or just manually edit /etc/pam.d/sshd)