nixos/hosts/delta/knot-resolver.nix

81 lines
3.1 KiB
Nix

{
config,
pkgs,
...
}: {
# Knot Resolver is a minimalistic implementation of a caching validating DNS
# resolver. Modular architecture keeps the core tiny and efficient, and it
# provides a state-machine like API for extensions.
# https://knot-resolver.readthedocs.io/en/stable/index.html
#
# Test resolver:
# > nix shell nixpkgs#knot-dns
# > kdig -d @dns.caspervk.net example.com
# > kdig -d +https @dns.caspervk.net example.com
# > kdig -d +tls @dns.caspervk.net example.com
#
# Connect to control socket:
# > nix shell nixpkgs#socat -c sudo socat readline UNIX-CONNECT:/run/knot-resolver/control/1
# >> help()
# >> cache.clear("example.com")
# https://knot-resolver.readthedocs.io/en/stable/daemon-scripting.html
services.kresd = {
enable = true;
# For maximum performance, there should be as many kresd processes as there
# are available CPU threads.
# https://knot-resolver.readthedocs.io/en/stable/systemd-multiinst.html
instances = 2;
# Explicitly listen to DNS/DoH/DoT on the external interface(s). This
# allows systemd-resolved to listen on localhost as on every other system.
listenPlain = [
"159.69.4.2:53"
"[2a01:4f8:1c0c:70d1::1]:53"
];
listenTLS = [
"159.69.4.2:853"
"[2a01:4f8:1c0c:70d1::1]:853"
];
listenDoH = [
"159.69.4.2:443"
"[2a01:4f8:1c0c:70d1::1]:443"
];
extraConfig = ''
-- TLS certificate for DoT and DoH
-- https://knot-resolver.readthedocs.io/en/stable/daemon-bindings-net_tlssrv.html
net.tls(
"${config.security.acme.certs."caspervk.net".directory}/fullchain.pem",
"${config.security.acme.certs."caspervk.net".directory}/key.pem"
)
-- Cache is stored in /var/cache/knot-resolver, which is mounted as
-- tmpfs. Allow using 75% of the partition for caching.
-- https://knot-resolver.readthedocs.io/en/stable/daemon-bindings-cache.html
cache.size = math.floor(cache.fssize() * 0.75)
-- The predict module helps to keep the cache hot by prefetching
-- records. Any time the resolver answers with records that are about to
-- expire, they get refreshed.
-- https://knot-resolver.readthedocs.io/en/stable/modules-predict.html
modules.load("predict")
-- Block spam and advertising domains
-- https://knot-resolver.readthedocs.io/en/stable/modules-policy.html#response-policy-zones
policy.add(
policy.rpz(
policy.ANSWER({ [kres.type.A] = {rdata=kres.str2ip("0.0.0.0"), ttl = 600} }),
"${pkgs.runCommand "stevenblack-blocklist-rpz" {} ''grep '^0\.0\.0\.0' ${pkgs.stevenblack-blocklist}/hosts | awk '{print $2 " 600 IN CNAME .\n*." $2 " 600 IN CNAME ."}' > $out''}"
)
)
-- Test domain to verify DNS server is being used
policy.add(
policy.domains(
policy.ANSWER({ [kres.type.A] = {rdata = kres.str2ip("192.0.2.0"), ttl = 5} }),
policy.todnames({"test.dns.caspervk.net"})
)
)
'';
};
networking.firewall = {
allowedTCPPorts = [443 853];
allowedUDPPorts = [53];
};
}