89 lines
2.1 KiB
Nix
89 lines
2.1 KiB
Nix
{pkgs, config, ...}:
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let
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iptables = "${pkgs.iptables}/sbin/iptables";
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in
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{
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###### interface
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options = {
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networking.firewall.enable = pkgs.lib.mkOption {
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default = false;
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description =
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''
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Whether to enable the firewall.
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'';
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};
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networking.firewall.allowedTCPPorts = pkgs.lib.mkOption {
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default = [];
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example = [22 80];
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type = pkgs.lib.types.list pkgs.lib.types.int;
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description =
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''
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List of TCP ports on which incoming connections are
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accepted.
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'';
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};
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};
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###### implementation
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# !!! Maybe if `enable' is false, the firewall should still be built
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# but not started by default. However, currently nixos-rebuild
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# doesn't deal with such Upstart jobs properly (it starts them if
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# they are changed, regardless of whether the start condition
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# holds).
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config = pkgs.lib.mkIf config.networking.firewall.enable {
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environment.systemPackages = [pkgs.iptables];
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jobs = pkgs.lib.singleton
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{ name = "firewall";
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startOn = "network-interfaces/started";
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preStart =
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''
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${iptables} -F
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# Accept all traffic on the loopback interface.
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${iptables} -A INPUT -i lo -j ACCEPT
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# Accept packets from established or related connections.
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${iptables} -A INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
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# Accept connections to the allowed TCP ports.
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${pkgs.lib.concatMapStrings (port:
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''
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${iptables} -A INPUT -p tcp --dport ${toString port} -j ACCEPT
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''
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) config.networking.firewall.allowedTCPPorts
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}
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# Accept multicast. Not a big security risk since
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# probably nobody is listening anyway.
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${iptables} -A INPUT -d 224.0.0.0/4 -j ACCEPT
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# Drop everything else.
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${iptables} -A INPUT -j LOG --log-level info --log-prefix "firewall: "
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${iptables} -A INPUT -j DROP
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'';
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postStop =
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''
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${iptables} -F
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'';
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};
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};
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}
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