136 lines
4.5 KiB
Nix
136 lines
4.5 KiB
Nix
{ config, pkgs, lib, ... }:
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with lib;
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let
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cfg = config.networking.nftables;
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in
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{
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###### interface
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options = {
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networking.nftables.enable = mkOption {
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type = types.bool;
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default = false;
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description =
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''
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Whether to enable nftables. nftables is a Linux-based packet
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filtering framework intended to replace frameworks like iptables.
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This conflicts with the standard networking firewall, so make sure to
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disable it before using nftables.
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Note that if you have Docker enabled you will not be able to use
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nftables without intervention. Docker uses iptables internally to
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setup NAT for containers. This module disables the ip_tables kernel
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module, however Docker automatically loads the module. Please see [1]
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for more information.
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There are other programs that use iptables internally too, such as
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libvirt.
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[1]: https://github.com/NixOS/nixpkgs/issues/24318#issuecomment-289216273
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'';
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};
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networking.nftables.ruleset = mkOption {
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type = types.lines;
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example = ''
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# Check out https://wiki.nftables.org/ for better documentation.
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# Table for both IPv4 and IPv6.
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table inet filter {
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# Block all incomming connections traffic except SSH and "ping".
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chain input {
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type filter hook input priority 0;
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# accept any localhost traffic
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iifname lo accept
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# accept traffic originated from us
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ct state {established, related} accept
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# ICMP
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# routers may also want: mld-listener-query, nd-router-solicit
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ip6 nexthdr icmpv6 icmpv6 type { destination-unreachable, packet-too-big, time-exceeded, parameter-problem, nd-router-advert, nd-neighbor-solicit, nd-neighbor-advert } accept
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ip protocol icmp icmp type { destination-unreachable, router-advertisement, time-exceeded, parameter-problem } accept
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# allow "ping"
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ip6 nexthdr icmpv6 icmpv6 type echo-request accept
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ip protocol icmp icmp type echo-request accept
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# accept SSH connections (required for a server)
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tcp dport 22 accept
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# count and drop any other traffic
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counter drop
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}
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# Allow all outgoing connections.
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chain output {
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type filter hook output priority 0;
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accept
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}
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chain forward {
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type filter hook forward priority 0;
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accept
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}
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}
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'';
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description =
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''
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The ruleset to be used with nftables. Should be in a format that
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can be loaded using "/bin/nft -f". The ruleset is updated atomically.
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'';
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};
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networking.nftables.rulesetFile = mkOption {
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type = types.path;
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default = pkgs.writeTextFile {
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name = "nftables-rules";
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text = cfg.ruleset;
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};
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description =
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''
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The ruleset file to be used with nftables. Should be in a format that
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can be loaded using "nft -f". The ruleset is updated atomically.
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'';
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};
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};
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###### implementation
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config = mkIf cfg.enable {
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assertions = [{
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assertion = config.networking.firewall.enable == false;
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message = "You can not use nftables and iptables at the same time. networking.firewall.enable must be set to false.";
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}];
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boot.blacklistedKernelModules = [ "ip_tables" ];
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environment.systemPackages = [ pkgs.nftables ];
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systemd.services.nftables = {
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description = "nftables firewall";
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before = [ "network-pre.target" ];
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wants = [ "network-pre.target" ];
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wantedBy = [ "multi-user.target" ];
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reloadIfChanged = true;
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serviceConfig = let
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rulesScript = pkgs.writeScript "nftables-rules" ''
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#! ${pkgs.nftables}/bin/nft -f
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flush ruleset
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include "${cfg.rulesetFile}"
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'';
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checkScript = pkgs.writeScript "nftables-check" ''
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#! ${pkgs.runtimeShell} -e
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if $(${pkgs.kmod}/bin/lsmod | grep -q ip_tables); then
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echo "Unload ip_tables before using nftables!" 1>&2
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exit 1
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else
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${rulesScript}
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fi
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'';
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in {
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Type = "oneshot";
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RemainAfterExit = true;
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ExecStart = checkScript;
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ExecReload = checkScript;
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ExecStop = "${pkgs.nftables}/bin/nft flush ruleset";
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};
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};
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};
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}
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