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feat: I think this is a better firewall setup, still need to properly test it

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silver 2023-01-28 15:31:46 +00:00
parent 1668db7390
commit b29daa0ea1
1 changed files with 66 additions and 28 deletions
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94
applications/firewall.nix
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@ -58,8 +58,23 @@
# beware of EOL conversion.
networking.nftables.ruleset =
''
# Check out https://wiki.nftables.org/ for better documentation.
# Table for both IPv4 and IPv6.
# using https://oxcrag.net/2021/12/25/build-your-own-router-with-nftables-part-1/ as a guide
# Clear out any existing rules
flush ruleset
# Our future selves will thank us for noting what cable goes where and labeling the relevant network interfaces if it isn't already done out-of-the-box.
# red cabled
define WANLINK = eno1
# yellow cable
define LANLINK = eno2
# We never expect to see the following address ranges on the Internet
define BOGONS4 = { 0.0.0.0/8, 10.0.0.0/8, 10.64.0.0/10, 127.0.0.0/8, 127.0.53.53, 169.254.0.0/16, 172.16.0.0/12, 192.0.0.0/24, 192.0.2.0/24, 192.168.0.0/16, 198.18.0.0/15, 198.51.100.0/24, 203.0.113.0/24, 224.0.0.0/4, 240.0.0.0/4, 255.255.255.255/32 }
# Network address translation: What allows us to glue together a private network with the Internet even though we only have one routable address, as per IPv4 limitations
table ip nat {
chain prerouting {
type nat hook prerouting priority dstnat; policy accept;
@ -84,46 +99,69 @@
}
}
table ip filter {
chain input {
type filter hook input priority filter; policy accept;
# The actual firewall starts here
table inet filter {
# Additional rules for traffic from the Internet
chain inbound_world {
# this is actually a good idea
# Drop obviously spoofed inbound traffic
ip saddr { $BOGONS4 } drop
}
# Additional rules for traffic from our private network
chain inbound_private {
# We want to allow remote access over ssh, incoming DNS traffic, and incoming DHCP traffic
# for the host machiene
# hardcoded in so that we can always have access
tcp dport 22 counter packets 0 bytes 0 accept
# TCP
${lib.strings.concatMapStrings (x: x + "\n") (map (port: "tcp dport ${toString port} counter packets 0 bytes 0 accept") config.skynet_firewall.own.ports.tcp)}
# UDP
${lib.strings.concatMapStrings (x: x + "\n") (map (port: "udp dport ${toString port} counter packets 0 bytes 0 accept") config.skynet_firewall.own.ports.udp)}
}
chain forward {
type filter hook forward priority filter; policy drop;
counter packets 0 bytes 0 jump rejects
# Our funnel for inbound traffic from any network
chain inbound {
# Default Deny
type filter hook input priority 0; policy drop;
# accept these ip/ports
# ip saddr 193.1.99.123 tcp dport 443 counter packets 0 bytes 0 accept
# Allow established and related connections: Allows Internet servers to respond to requests from our Internal network
ct state vmap { established : accept, related : accept, invalid : drop} counter
# ICMP is - mostly - our friend. Limit incoming pings somewhat but allow necessary information.
ip protocol icmp icmp type {
destination-unreachable, echo-reply, echo-request, source-quench, time-exceeded
} limit rate 5/second accept
# guy must have had a lot of trouble with spoofed ips
# Drop obviously spoofed loopback traffic
iifname "lo" ip daddr != 127.0.0.0/8 drop
# Separate rules for traffic from Internet and from the internal network
iifname vmap { lo: accept, $WANLINK : jump inbound_world, $LANLINK : jump inbound_private }
}
# Rules for sending traffic from one network interface to another
chain forward {
# Default deny, again
type filter hook forward priority 0; policy drop;
# Accept established and related traffic
ct state vmap { established : accept, related : accept, invalid : drop }
# Let traffic from this router and from the Internal network get out onto the Internet
iifname { lo, $LANLINK } accept
# Only allow specific inbound traffic from the Internet (only relevant if we present services to the Internet).
# tcp dport { $PORTFORWARDS } counter
# can basically make each machiene responsibile for their own forwarding (in config at least)
${lib.strings.concatMapStrings (x: x + "\n") config.skynet_firewall.forward}
counter packets 0 bytes 0 reject with icmp type admin-prohibited
}
chain output {
type filter hook output priority filter; policy accept;
# no outgoing limits (for now)
}
chain fail2ban-ssh {
# ban these
# ip saddr 104.236.151.120 counter packets 0 bytes 0 drop
counter packets 0 bytes 0 return
}
chain rejects {
# Reject all these
# ip saddr 220.119.33.251 counter packets 0 bytes 0 reject with icmp type admin-prohibited
}
}
'';