{ config, lib, pkgs, ... }: with lib; let keysPath = "/var/lib/yggdrasil/keys.json"; cfg = config.services.yggdrasil; settingsProvided = cfg.settings != { }; configFileProvided = cfg.configFile != null; format = pkgs.formats.json { }; in { imports = [ (mkRenamedOptionModule [ "services" "yggdrasil" "config" ] [ "services" "yggdrasil" "settings" ]) ]; options = with types; { services.yggdrasil = { enable = mkEnableOption (lib.mdDoc "the yggdrasil system service"); settings = mkOption { type = format.type; default = { }; example = { Peers = [ "tcp://aa.bb.cc.dd:eeeee" "tcp://[aaaa:bbbb:cccc:dddd::eeee]:fffff" ]; Listen = [ "tcp://0.0.0.0:xxxxx" ]; }; description = lib.mdDoc '' Configuration for yggdrasil, as a Nix attribute set. Warning: this is stored in the WORLD-READABLE Nix store! Therefore, it is not appropriate for private keys. If you wish to specify the keys, use {option}`configFile`. If the {option}`persistentKeys` is enabled then the keys that are generated during activation will override those in {option}`settings` or {option}`configFile`. If no keys are specified then ephemeral keys are generated and the Yggdrasil interface will have a random IPv6 address each time the service is started. This is the default. If both {option}`configFile` and {option}`settings` are supplied, they will be combined, with values from {option}`configFile` taking precedence. You can use the command `nix-shell -p yggdrasil --run "yggdrasil -genconf"` to generate default configuration values with documentation. ''; }; configFile = mkOption { type = nullOr path; default = null; example = "/run/keys/yggdrasil.conf"; description = lib.mdDoc '' A file which contains JSON or HJSON configuration for yggdrasil. See the {option}`settings` option for more information. Note: This file must not be larger than 1 MB because it is passed to the yggdrasil process via systemd‘s LoadCredential mechanism. For details, see and `man 5 systemd.exec`. ''; }; group = mkOption { type = types.nullOr types.str; default = null; example = "wheel"; description = lib.mdDoc "Group to grant access to the Yggdrasil control socket. If `null`, only root can access the socket."; }; openMulticastPort = mkOption { type = bool; default = false; description = lib.mdDoc '' Whether to open the UDP port used for multicast peer discovery. The NixOS firewall blocks link-local communication, so in order to make incoming local peering work you will also need to configure `MulticastInterfaces` in your Yggdrasil configuration ({option}`settings` or {option}`configFile`). You will then have to add the ports that you configure there to your firewall configuration ({option}`networking.firewall.allowedTCPPorts` or {option}`networking.firewall.interfaces..allowedTCPPorts`). ''; }; denyDhcpcdInterfaces = mkOption { type = listOf str; default = [ ]; example = [ "tap*" ]; description = lib.mdDoc '' Disable the DHCP client for any interface whose name matches any of the shell glob patterns in this list. Use this option to prevent the DHCP client from broadcasting requests on the yggdrasil network. It is only necessary to do so when yggdrasil is running in TAP mode, because TUN interfaces do not support broadcasting. ''; }; package = mkPackageOption pkgs "yggdrasil" { }; persistentKeys = mkEnableOption (lib.mdDoc '' persistent keys. If enabled then keys will be generated once and Yggdrasil will retain the same IPv6 address when the service is restarted. Keys are stored at ${keysPath} ''); extraArgs = mkOption { type = listOf str; default = [ ]; example = [ "-loglevel" "info" ]; description = lib.mdDoc "Extra command line arguments."; }; }; }; config = mkIf cfg.enable ( let binYggdrasil = "${cfg.package}/bin/yggdrasil"; binHjson = "${pkgs.hjson-go}/bin/hjson-cli"; in { assertions = [{ assertion = config.networking.enableIPv6; message = "networking.enableIPv6 must be true for yggdrasil to work"; }]; # This needs to be a separate service. The yggdrasil service fails if # this is put into its preStart. systemd.services.yggdrasil-persistent-keys = lib.mkIf cfg.persistentKeys { wantedBy = [ "multi-user.target" ]; before = [ "yggdrasil.service" ]; serviceConfig.Type = "oneshot"; serviceConfig.RemainAfterExit = true; script = '' if [ ! -e ${keysPath} ] then mkdir --mode=700 -p ${builtins.dirOf keysPath} ${binYggdrasil} -genconf -json \ | ${pkgs.jq}/bin/jq \ 'to_entries|map(select(.key|endswith("Key")))|from_entries' \ > ${keysPath} fi ''; }; systemd.services.yggdrasil = { description = "Yggdrasil Network Service"; after = [ "network-pre.target" ]; wants = [ "network.target" ]; before = [ "network.target" ]; wantedBy = [ "multi-user.target" ]; # This script first prepares the config file, then it starts Yggdrasil. # The preparation could also be done in ExecStartPre/preStart but only # systemd versions >= v252 support reading credentials in ExecStartPre. As # of February 2023, systemd v252 is not yet in the stable branch of NixOS. # # This could be changed in the future once systemd version v252 has # reached NixOS but it does not have to be. Config file preparation is # fast enough, it does not need elevated privileges, and `set -euo # pipefail` should make sure that the service is not started if the # preparation fails. Therefore, it is not necessary to move the # preparation to ExecStartPre. script = '' set -euo pipefail # prepare config file ${(if settingsProvided || configFileProvided || cfg.persistentKeys then "echo " + (lib.optionalString settingsProvided "'${builtins.toJSON cfg.settings}'") + (lib.optionalString configFileProvided "$(${binHjson} -c \"$CREDENTIALS_DIRECTORY/yggdrasil.conf\")") + (lib.optionalString cfg.persistentKeys "$(cat ${keysPath})") + " | ${pkgs.jq}/bin/jq -s add | ${binYggdrasil} -normaliseconf -useconf" else "${binYggdrasil} -genconf") + " > /run/yggdrasil/yggdrasil.conf"} # start yggdrasil ${binYggdrasil} -useconffile /run/yggdrasil/yggdrasil.conf ${lib.strings.escapeShellArgs cfg.extraArgs} ''; serviceConfig = { ExecReload = "${pkgs.coreutils}/bin/kill -HUP $MAINPID"; Restart = "always"; DynamicUser = true; StateDirectory = "yggdrasil"; RuntimeDirectory = "yggdrasil"; RuntimeDirectoryMode = "0750"; BindReadOnlyPaths = lib.optional cfg.persistentKeys keysPath; LoadCredential = mkIf configFileProvided "yggdrasil.conf:${cfg.configFile}"; AmbientCapabilities = "CAP_NET_ADMIN CAP_NET_BIND_SERVICE"; CapabilityBoundingSet = "CAP_NET_ADMIN CAP_NET_BIND_SERVICE"; MemoryDenyWriteExecute = true; ProtectControlGroups = true; ProtectHome = "tmpfs"; ProtectKernelModules = true; ProtectKernelTunables = true; RestrictAddressFamilies = "AF_UNIX AF_INET AF_INET6 AF_NETLINK"; RestrictNamespaces = true; RestrictRealtime = true; SystemCallArchitectures = "native"; SystemCallFilter = [ "@system-service" "~@privileged @keyring" ]; } // (if (cfg.group != null) then { Group = cfg.group; } else { }); }; networking.dhcpcd.denyInterfaces = cfg.denyDhcpcdInterfaces; networking.firewall.allowedUDPPorts = mkIf cfg.openMulticastPort [ 9001 ]; # Make yggdrasilctl available on the command line. environment.systemPackages = [ cfg.package ]; } ); meta = { doc = ./yggdrasil.md; maintainers = with lib.maintainers; [ gazally ehmry ]; }; }