What's the best way to setup a firewall in Guix?

Guix
1

I’m interested in declaring a nftable in my config. I can see there is a default ruleset in the documentation %default-nftables-ruleset, however, it keeps the ssh port open which isn’t something I need on my desktop setup. What would be the best way to go about modifying this ruleset or declaring a custom one?

I’m relatively new to Guix and Scheme so any pointers would be much appreciated

2

This is what I’ve got.

            (service nftables-service-type
                     (nftables-configuration
                      (ruleset (plain-file "nftables.conf"
                                           "\
# A simple and safe firewall (based on %default-nftables-ruleset)
define pub_iface = \"enp11s0\"
define wg_iface = \"wg0\"
define wg_port = 51820
define ssh_port = 22
define guix_publish_port = 8080

table inet filter {
  chain input {
    type filter hook input priority 0; policy drop;

    # early drop of invalid connections
    ct state invalid drop

    # allow established/related connections
    ct state { established, related } accept

    # allow from loopback
    iif lo accept
    # drop connections to lo not coming from lo
    iif != lo ip daddr 127.0.0.1/8 drop
    iif != lo ip6 daddr ::1/128 drop

    # allow icmp
    ip protocol icmp accept
    ip6 nexthdr icmpv6 accept

    # allow ssh
    tcp dport $ssh_port accept

    # allow guix publish
    tcp dport $guix_publish_port accept

    # allow wireguard port
    udp dport $wg_port accept

    # reject everything else
    reject with icmpx type port-unreachable
  }
  chain output {
    type filter hook output priority 0; policy accept;
  }
}
"))))
3 Likes
3

Awesome, thanks a lot. I’ll use that for my config but with

tcp dport $ssh_port accept

commented out and a few tweaks :slight_smile:

4

Nice, thanks for the example!

What are people’s thoughts on nftables vs iptables? Looks like the syntax for nftables may be a little more expressive, are there other reasons why it’s a better choice?

5

By the way, welcome to the community @heq and @Themightyox!