pyrox.dev
1{
2 config,
3 lib,
4 pkgs,
5 ...
6}:
7
8let
9 inherit (lib) mkIf mkOption;
10 inherit (lib.types)
11 nullOr
12 path
13 bool
14 listOf
15 str
16 ;
17 keysPath = "/var/lib/yggdrasil/keys.json";
18
19 cfg = config.services.yggdrasil;
20 settingsProvided = cfg.settings != { };
21 configFileProvided = cfg.configFile != null;
22
23 format = pkgs.formats.json { };
24in
25{
26 imports = [
27 (lib.mkRenamedOptionModule
28 [ "services" "yggdrasil" "config" ]
29 [ "services" "yggdrasil" "settings" ]
30 )
31 ];
32
33 options = {
34 services.yggdrasil = {
35 enable = lib.mkEnableOption "the yggdrasil system service";
36
37 settings = mkOption {
38 type = format.type;
39 default = { };
40 example = {
41 Peers = [
42 "tcp://aa.bb.cc.dd:eeeee"
43 "tcp://[aaaa:bbbb:cccc:dddd::eeee]:fffff"
44 ];
45 Listen = [
46 "tcp://0.0.0.0:xxxxx"
47 ];
48 };
49 description = ''
50 Configuration for yggdrasil, as a Nix attribute set.
51
52 Warning: this is stored in the WORLD-READABLE Nix store!
53 Therefore, it is not appropriate for private keys. If you
54 wish to specify the keys, use {option}`configFile`.
55
56 If the {option}`persistentKeys` is enabled then the
57 keys that are generated during activation will override
58 those in {option}`settings` or
59 {option}`configFile`.
60
61 If no keys are specified then ephemeral keys are generated
62 and the Yggdrasil interface will have a random IPv6 address
63 each time the service is started. This is the default.
64
65 If both {option}`configFile` and {option}`settings`
66 are supplied, they will be combined, with values from
67 {option}`configFile` taking precedence.
68
69 You can use the command `nix-shell -p yggdrasil --run "yggdrasil -genconf"`
70 to generate default configuration values with documentation.
71 '';
72 };
73
74 configFile = mkOption {
75 type = nullOr path;
76 default = null;
77 example = "/run/keys/yggdrasil.conf";
78 description = ''
79 A file which contains JSON or HJSON configuration for yggdrasil. See
80 the {option}`settings` option for more information.
81
82 Note: This file must not be larger than 1 MB because it is passed to
83 the yggdrasil process via systemd‘s LoadCredential mechanism. For
84 details, see <https://systemd.io/CREDENTIALS/> and `man 5
85 systemd.exec`.
86 '';
87 };
88
89 group = mkOption {
90 type = nullOr str;
91 default = null;
92 example = "wheel";
93 description = "Group to grant access to the Yggdrasil control socket. If `null`, only root can access the socket.";
94 };
95
96 openMulticastPort = mkOption {
97 type = bool;
98 default = false;
99 description = ''
100 Whether to open the UDP port used for multicast peer discovery. The
101 NixOS firewall blocks link-local communication, so in order to make
102 incoming local peering work you will also need to configure
103 `MulticastInterfaces` in your Yggdrasil configuration
104 ({option}`settings` or {option}`configFile`). You will then have to
105 add the ports that you configure there to your firewall configuration
106 ({option}`networking.firewall.allowedTCPPorts` or
107 {option}`networking.firewall.interfaces.<name>.allowedTCPPorts`).
108 '';
109 };
110
111 denyDhcpcdInterfaces = mkOption {
112 type = listOf str;
113 default = [ ];
114 example = [ "tap*" ];
115 description = ''
116 Disable the DHCP client for any interface whose name matches
117 any of the shell glob patterns in this list. Use this
118 option to prevent the DHCP client from broadcasting requests
119 on the yggdrasil network. It is only necessary to do so
120 when yggdrasil is running in TAP mode, because TUN
121 interfaces do not support broadcasting.
122 '';
123 };
124
125 package = lib.mkPackageOption pkgs "yggdrasil" { };
126
127 persistentKeys = lib.mkEnableOption ''
128 persistent keys. If enabled then keys will be generated once and Yggdrasil
129 will retain the same IPv6 address when the service is
130 restarted. Keys are stored at ${keysPath}
131 '';
132
133 extraArgs = mkOption {
134 type = listOf str;
135 default = [ ];
136 example = [
137 "-loglevel"
138 "info"
139 ];
140 description = "Extra command line arguments.";
141 };
142
143 };
144 };
145
146 config = mkIf cfg.enable (
147 let
148 binYggdrasil = "${cfg.package}/bin/yggdrasil";
149 binHjson = "${pkgs.hjson-go}/bin/hjson-cli";
150 in
151 {
152 assertions = [
153 {
154 assertion = config.networking.enableIPv6;
155 message = "networking.enableIPv6 must be true for yggdrasil to work";
156 }
157 ];
158
159 # This needs to be a separate service. The yggdrasil service fails if
160 # this is put into its preStart.
161 systemd.services.yggdrasil-persistent-keys = lib.mkIf cfg.persistentKeys {
162 wantedBy = [ "multi-user.target" ];
163 before = [ "yggdrasil.service" ];
164 serviceConfig.Type = "oneshot";
165 serviceConfig.RemainAfterExit = true;
166 script = ''
167 if [ ! -e ${keysPath} ]
168 then
169 mkdir --mode=700 -p ${builtins.dirOf keysPath}
170 ${binYggdrasil} -genconf -json \
171 | ${pkgs.jq}/bin/jq \
172 'to_entries|map(select(.key|endswith("Key")))|from_entries' \
173 > ${keysPath}
174 fi
175 '';
176 };
177
178 systemd.services.yggdrasil = {
179 description = "Yggdrasil Network Service";
180 after = [ "network-pre.target" ];
181 wants = [ "network.target" ];
182 before = [ "network.target" ];
183 wantedBy = [ "multi-user.target" ];
184
185 # This script first prepares the config file, then it starts Yggdrasil.
186 # The preparation could also be done in ExecStartPre/preStart but only
187 # systemd versions >= v252 support reading credentials in ExecStartPre. As
188 # of February 2023, systemd v252 is not yet in the stable branch of NixOS.
189 #
190 # This could be changed in the future once systemd version v252 has
191 # reached NixOS but it does not have to be. Config file preparation is
192 # fast enough, it does not need elevated privileges, and `set -euo
193 # pipefail` should make sure that the service is not started if the
194 # preparation fails. Therefore, it is not necessary to move the
195 # preparation to ExecStartPre.
196 script = ''
197 set -euo pipefail
198
199 # prepare config file
200 ${
201 (
202 if settingsProvided || configFileProvided || cfg.persistentKeys then
203 "echo "
204
205 + (lib.optionalString settingsProvided "'${builtins.toJSON cfg.settings}'")
206 + (lib.optionalString configFileProvided "$(${binHjson} -c \"$CREDENTIALS_DIRECTORY/yggdrasil.conf\")")
207 + (lib.optionalString cfg.persistentKeys "$(cat ${keysPath})")
208 + " | ${pkgs.jq}/bin/jq -s add | ${binYggdrasil} -normaliseconf -useconf"
209 else
210 "${binYggdrasil} -genconf"
211 )
212 + " > /run/yggdrasil/yggdrasil.conf"
213 }
214
215 # start yggdrasil
216 exec ${binYggdrasil} -useconffile /run/yggdrasil/yggdrasil.conf ${lib.strings.escapeShellArgs cfg.extraArgs}
217 '';
218
219 serviceConfig =
220 {
221 ExecReload = "${pkgs.coreutils}/bin/kill -HUP $MAINPID";
222 Restart = "always";
223
224 DynamicUser = true;
225 StateDirectory = "yggdrasil";
226 RuntimeDirectory = "yggdrasil";
227 RuntimeDirectoryMode = "0750";
228 BindReadOnlyPaths = lib.optional cfg.persistentKeys keysPath;
229 LoadCredential = mkIf configFileProvided "yggdrasil.conf:${cfg.configFile}";
230
231 AmbientCapabilities = "CAP_NET_ADMIN CAP_NET_BIND_SERVICE";
232 CapabilityBoundingSet = "CAP_NET_ADMIN CAP_NET_BIND_SERVICE";
233 MemoryDenyWriteExecute = true;
234 ProtectControlGroups = true;
235 ProtectHome = "tmpfs";
236 ProtectKernelModules = true;
237 ProtectKernelTunables = true;
238 RestrictAddressFamilies = "AF_UNIX AF_INET AF_INET6 AF_NETLINK";
239 RestrictNamespaces = true;
240 RestrictRealtime = true;
241 SystemCallArchitectures = "native";
242 SystemCallFilter = [
243 "@system-service"
244 "~@privileged @keyring"
245 ];
246 }
247 // (
248 if (cfg.group != null) then
249 {
250 Group = cfg.group;
251 }
252 else
253 { }
254 );
255 };
256
257 networking.dhcpcd.denyInterfaces = cfg.denyDhcpcdInterfaces;
258 networking.firewall.allowedUDPPorts = mkIf cfg.openMulticastPort [ 9001 ];
259
260 # Make yggdrasilctl available on the command line.
261 environment.systemPackages = [ cfg.package ];
262 }
263 );
264 meta = {
265 doc = ./yggdrasil.md;
266 maintainers = with lib.maintainers; [
267 gazally
268 ehmry
269 nagy
270 ];
271 };
272}