From bc2d42aab02b5ef9e27ee59a03543b41d99adf04 Mon Sep 17 00:00:00 2001
From: Egor Tensin <Egor.Tensin@gmail.com>
Date: Tue, 8 Aug 2023 20:14:32 +0200
Subject: add firewall role

---
 roles/firewall/templates/rules.v4 | 48 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)
 create mode 100644 roles/firewall/templates/rules.v4

(limited to 'roles/firewall/templates/rules.v4')

diff --git a/roles/firewall/templates/rules.v4 b/roles/firewall/templates/rules.v4
new file mode 100644
index 0000000..7ea1162
--- /dev/null
+++ b/roles/firewall/templates/rules.v4
@@ -0,0 +1,48 @@
+*filter
+
+# By default, drop incoming packets:
+:INPUT DROP [0:0]
+:FORWARD DROP [0:0]
+# By default, accept outgoing packets:
+:OUTPUT ACCEPT [0:0]
+
+# Accept packets for localhost:
+-A INPUT -i lo -j ACCEPT
+
+# Accept any packet for an open connection:
+-A INPUT -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
+-A FORWARD -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
+
+# The SSH port is always open:
+{% set ssh_port = hostvars[inventory_hostname].ansible_port %}
+
+# Open TCP ports:
+{% set tcp_ports = firewall_ports_tcp + firewall_ports4_tcp + [ssh_port] %}
+{% set tcp_ports = tcp_ports | unique %}
+
+{% for port in tcp_ports %}
+{% set num = port.port if port.port is defined else port %}
+{% set src = '-s ' + port.source if port.source is defined else '' %}
+-A INPUT -p tcp {{ src }} --dport {{ num }} -m conntrack --ctstate NEW -j ACCEPT
+{% endfor %}
+
+# Open UDP ports:
+{% set udp_ports = firewall_ports_udp + firewall_ports4_udp %}
+{% set udp_ports = udp_ports | unique %}
+
+{% for port in udp_ports %}
+{% set num = port.port if port.port is defined else port %}
+{% set src = '-s ' + port.source if port.source is defined else '' %}
+-A INPUT -p udp {{ src }} --dport {{ num }} -j ACCEPT
+{% endfor %}
+
+# Any additional IPv4 rules:
+{{ firewall_rules4 | join('\n') }}
+
+# ICMP; allow only pings and rate-limit them:
+-A INPUT -p icmp --icmp-type echo-request -m hashlimit --hashlimit-upto 5/s --hashlimit-mode srcip --hashlimit-srcmask 32 --hashlimit-name icmp-echo-drop -j ACCEPT
+
+# Log denies (this must be at the bottom of the file):
+-A INPUT -m limit --limit 3/min -j LOG --log-prefix "iptables denied: " --log-level 4
+
+COMMIT
-- 
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