A fresh Alma box has firewalld active, and the iptables-based harden-firewall.sh
refused to run there (caught by harden-ssh's '|| warn', so the host firewall was
silently skipped). Use firewalld natively on the rhel family instead of fighting it.
- harden-firewall.sh: family-aware backend. On rhel, apply/allow/deny/list/disable
drive firewall-cmd (deny-by-default zone, SSH + registered ports, ping policy,
source-restricted rich rules); Alpine/Debian keep the iptables engine unchanged.
FW_BACKEND=iptables|firewalld overrides.
- oslib: install_firewalld(); sshguard_backend() prefers sshg-fw-firewalld on rhel
so brute-force blocks land in firewalld (no INPUT->sshguard jump needed).
- Deployments already fall through to a firewall-cmd branch when the iptables
engine is absent, so they need no changes.
- README + script header document the per-family backend.
harden-ssh / harden-jumphost are unchanged -- they call harden-firewall.sh apply
and read sshguard_backend(), so the switch happens underneath them.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Add a reusable iptables baseline that hardens hosts with ICMP + SSH
defaults and lets deployments register the ports they need. INPUT is
deny-by-default (loopback, established, ICMP, SSH on the configured port,
plus registered ports); OUTPUT stays open and FORWARD is left untouched so
Docker container networking is unaffected.
Persistence is native -- no boot hook. Rules are saved and restored by the
distro's own package (iptables/ip6tables on Alpine, iptables-persistent on
Debian, iptables-services on Alma) via the new oslib helpers
install_iptables / fw_save_cmd / fw_enable_restore. The saved ruleset
carries the INPUT->sshguard jump, so brute-force protection survives reboot
without the old sshguard-iptables hook.
A self-contained /usr/local/sbin/firewall-apply rebuilds INPUT from
declarative drop-ins under /etc/firewall/ports.d and runs the native save,
so deployments add a port without needing the repo present:
printf '80/tcp\n443/tcp\n' > /etc/firewall/ports.d/mystack.rule
/usr/local/sbin/firewall-apply
- SSH port read live from sshd_config (custom bastion ports just work);
FW_SSH_SOURCE restricts the source CIDR; FW_ALLOW_PING gates echo
- harden-ssh.sh / harden-jumphost.sh install it when ENABLE_FIREWALL=1
(default) and skip the sshguard-only hook; ENABLE_FIREWALL=0 keeps it
- cloud-init base.yml / jumphost.yml forward the toggle
- the four stack deploy.sh open_web_ports() register 80/443 via the
firewall (ufw/firewalld kept as fallback); Docker-published ports bypass
INPUT, so this is belt-and-braces and self-documenting
- README + cloud-init/README document the mechanism, Docker caveat, and the
`disable` recovery path
57_WolveandClaude Opus 4.8