stockholm/modules/tv/retiolum.nix

{ config, lib, pkgs, ... }:

with lib;

{

  ###### interface

  options = {
    services.retiolum = {

      enable = mkOption {
        type = types.bool;
        default = false;
        description = "Enable tinc daemon for Retiolum.";
      };

      name = mkOption {
        type = types.string;
        default = config.networking.hostName;
        # Description stolen from tinc.conf(5).
        description = ''
          This is the name which identifies this tinc daemon.  It must
          be unique for the virtual private network this daemon will
          connect to.  The Name may only consist of alphanumeric and
          underscore characters.  If Name starts with a $, then the
          contents of the environment variable that follows will be
          used.  In that case, invalid characters will be converted to
          underscores.  If Name is $HOST, but no such environment
          variable exist, the hostname will be read using the
          gethostnname() system call This is the name which identifies
          the this tinc daemon.
        '';
      };

      generateEtcHosts = mkOption {
        type = types.string;
        default = "both";
        description = ''
          If set to <literal>short</literal>, <literal>long</literal>, or <literal>both</literal>,
          then generate entries in <filename>/etc/hosts</filename> from subnets.
        '';
      };

      network = mkOption {
        type = types.string;
        default = "retiolum";
        description = ''
          The tinc network name.
          It is used to generate long host entries,
          derive the name of the user account under which tincd runs,
          and name the TUN device.
        '';
      };

      tincPackage = mkOption {
        type = types.package;
        default = pkgs.tinc;
        description = "Tincd package to use.";
      };

      hosts = mkOption {
        default = null;
        description = ''
          Hosts package or path to use.
          If a path is given, then it will be used to generate an ad-hoc package.
        '';
      };

      iproutePackage = mkOption {
        type = types.package;
        default = pkgs.iproute;
        description = "Iproute2 package to use.";
      };


      privateKeyFile = mkOption {
        # TODO if it's types.path then it gets copied to /nix/store with
        #      bad unsafe permissions...
        type = types.string;
        default = "/etc/tinc/retiolum/rsa_key.priv";
        description = "Generate file with <literal>tincd -K</literal>.";
      };

      connectTo = mkOption {
        type = types.listOf types.string;
        default = [ "fastpoke" "pigstarter" "kheurop" ];
        description = "TODO describe me";
      };

    };
  };


  ###### implementation

  config =
    let
      cfg = config.services.retiolum;
      tinc = cfg.tincPackage;
      hostsType = builtins.typeOf cfg.hosts;
      hosts =
        if hostsType == "package" then
          # use package as is
          cfg.hosts
        else if hostsType == "path" then
          # use path to generate a package
          pkgs.stdenv.mkDerivation {
            name = "custom-retiolum-hosts";
            src = cfg.hosts;
            installPhase = ''
              mkdir $out
              find . -name .git -prune -o -type f -print0 | xargs -0 cp --target-directory $out
            '';
          }
        else
          abort "The option `services.retiolum.hosts' must be set to a package or a path"
        ;
      iproute = cfg.iproutePackage;

      retiolumExtraHosts = import (pkgs.runCommand "retiolum-etc-hosts"
        { }
        ''
          generate() {
            (cd ${hosts}
              printf \'\'
              for i in `ls`; do
                names=$(hostnames $i)
                for j in `sed -En 's|^ *Aliases *= *(.+)|\1|p' $i`; do
                  names="$names $(hostnames $j)"
                done
                sed -En '
                  s|^ *Subnet *= *([^ /]*)(/[0-9]*)? *$|\1  '"$names"'|p
                ' $i
              done | sort
              printf \'\'
            )
          }

          case ${cfg.generateEtcHosts} in
            short)
              hostnames() { echo "$1"; }
              generate
              ;;
            long)
              hostnames() { echo "$1.${cfg.network}"; }
              generate
              ;;
            both)
              hostnames() { echo "$1.${cfg.network} $1"; }
              generate
              ;;
            *)
              echo '""'
              ;;
          esac > $out
        '');


      confDir = pkgs.runCommand "retiolum" {
        # TODO text
        executable = true;
        preferLocalBuild = true;
      } ''
        set -euf

        mkdir -p $out

        ln -s ${hosts} $out/hosts

        cat > $out/tinc.conf <<EOF
        Name = ${cfg.name}
        Device = /dev/net/tun
        Interface = ${cfg.network}
        ${concatStrings (map (c : "ConnectTo = " + c + "\n") cfg.connectTo)}
        PrivateKeyFile = ${cfg.privateKeyFile}
        EOF

        # source: krebscode/painload/retiolum/scripts/tinc_setup/tinc-up
        cat > $out/tinc-up <<EOF
        host=$out/hosts/${cfg.name}
        ${iproute}/sbin/ip link set \$INTERFACE up

        addr4=\$(sed -n 's|^ *Subnet *= *\(10[.][^ ]*\) *$|\1|p' \$host)
        if [ -n "\$addr4" ];then
            ${iproute}/sbin/ip -4 addr add \$addr4 dev \$INTERFACE
            ${iproute}/sbin/ip -4 route add 10.243.0.0/16 dev \$INTERFACE
        fi
        addr6=\$(sed -n 's|^ *Subnet *= *\(42[:][^ ]*\) *$|\1|p' \$host)
        ${iproute}/sbin/ip -6 addr add \$addr6 dev \$INTERFACE
        ${iproute}/sbin/ip -6 route add 42::/16 dev \$INTERFACE
        EOF

        chmod +x $out/tinc-up
      '';


      user = cfg.network + "-tinc";

    in

      mkIf cfg.enable {
        environment.systemPackages = [ tinc hosts iproute ];

        networking.extraHosts = retiolumExtraHosts;

        systemd.services.retiolum = {
          description = "Tinc daemon for Retiolum";
          after = [ "network.target" ];
          wantedBy = [ "multi-user.target" ];
          path = [ tinc iproute ];
          serviceConfig = {
            # TODO we cannot chroot (-R) b/c we use symlinks to hosts
            #      and the private key.
            ExecStart = "${tinc}/sbin/tincd -c ${confDir} -d 0 -U ${user} -D";
            SyslogIdentifier = "retiolum-tincd";
          };
          restartIfChanged = true;
        };

        users.extraUsers = singleton {
          name = user;
          uid = 42; # TODO config.ids.uids.retiolum
        };

      };

}