Add configuration files required for two-factor authentication
via Google Authenticator:
- sshd-pam: PAM configuration integrating Google Authenticator
with standard Unix authentication, using nullok for gradual
rollout allowing users without 2FA to still authenticate
- sshd-2fa-config: SSH daemon configuration additions enabling
ChallengeResponseAuthentication and KeyboardInteractive
authentication methods required for 2FA flow
These configs support the KNEL security baseline requiring 2FA
for SSH access while maintaining backward compatibility during
user onboarding.
Related: KNELServerBuild/ProjectCode/Modules/Security/secharden-2fa.sh
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