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Setting Up Google Auth on SSH on CentOS-7

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ssh google-authentication 2fa security
Hugo
Author
Hugo
DevOps Engineer in London

Follow Digital Ocean tutorial for the setup: https://www.digitalocean.com/community/tutorials/how-to-set-up-multi-factor-authentication-for-ssh-on-centos-7

Notes on /etc/ssh/sshd_config:

  • With UsePAM yes, both password and keyboard-interactive follow /etc/pam.d/sshd
  • PasswordAuthentication yes is the same as AuthenticationMethods password

Differences between AuthenticationMethods password and keyboard-interactive:

  • password accepts only 1 response from the user
  • keyboard-interactive accepts multiple responses from user

Enforcing both password and Google Authenticator to login:

  • Use keyboard-interactive to ensure successful authentication with 2FA and password

Prompt differences:

  • password: (hugo@192.168.0.14) Password:
  • keyboard-interactive: Password:

Time synchronization:

  • Crucial for accurate authentication
  • For Docker, ensure the host’s clock is synchronized