0ce90d58cc
Most importantly, this sets PrivateTmp, ProtectHome, and ProtectSystem so that Chrony flaws are mitigated, should they occur. Moving to ProtectSystem=full however, requires moving the chrony key files under /var/lib/chrony -- which should be fine, anyway. This also ensures ConditionCapability=CAP_SYS_TIME is set, ensuring that chronyd will only be launched in an environment where such a capability can be granted. Signed-off-by: Austin Seipp <aseipp@pobox.com>
127 lines
3.2 KiB
Nix
127 lines
3.2 KiB
Nix
{ config, lib, pkgs, ... }:
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with lib;
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let
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cfg = config.services.chrony;
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stateDir = "/var/lib/chrony";
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keyFile = "${stateDir}/chrony.keys";
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configFile = pkgs.writeText "chrony.conf" ''
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${concatMapStringsSep "\n" (server: "server " + server) cfg.servers}
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${optionalString
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cfg.initstepslew.enabled
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"initstepslew ${toString cfg.initstepslew.threshold} ${concatStringsSep " " cfg.initstepslew.servers}"
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}
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driftfile ${stateDir}/chrony.drift
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keyfile ${keyFile}
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${optionalString (!config.time.hardwareClockInLocalTime) "rtconutc"}
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${cfg.extraConfig}
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'';
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chronyFlags = "-m -u chrony -f ${configFile} ${toString cfg.extraFlags}";
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in
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{
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options = {
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services.chrony = {
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enable = mkOption {
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default = false;
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description = ''
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Whether to synchronise your machine's time using chrony.
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Make sure you disable NTP if you enable this service.
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'';
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};
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servers = mkOption {
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default = config.networking.timeServers;
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description = ''
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The set of NTP servers from which to synchronise.
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'';
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};
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initstepslew = mkOption {
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default = {
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enabled = true;
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threshold = 1000; # by default, same threshold as 'ntpd -g' (1000s)
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servers = cfg.servers;
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};
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description = ''
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Allow chronyd to make a rapid measurement of the system clock error at
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boot time, and to correct the system clock by stepping before normal
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operation begins.
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'';
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};
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extraConfig = mkOption {
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type = types.lines;
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default = "";
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description = ''
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Extra configuration directives that should be added to
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<literal>chrony.conf</literal>
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'';
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};
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extraFlags = mkOption {
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default = [];
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example = [ "-s" ];
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type = types.listOf types.str;
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description = "Extra flags passed to the chronyd command.";
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};
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};
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};
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config = mkIf cfg.enable {
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environment.systemPackages = [ pkgs.chrony ];
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users.groups = singleton
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{ name = "chrony";
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gid = config.ids.gids.chrony;
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};
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users.users = singleton
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{ name = "chrony";
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uid = config.ids.uids.chrony;
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group = "chrony";
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description = "chrony daemon user";
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home = stateDir;
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};
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services.timesyncd.enable = mkForce false;
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systemd.services.chronyd =
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{ description = "chrony NTP daemon";
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wantedBy = [ "multi-user.target" ];
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wants = [ "time-sync.target" ];
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before = [ "time-sync.target" ];
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after = [ "network.target" ];
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conflicts = [ "ntpd.service" "systemd-timesyncd.service" ];
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path = [ pkgs.chrony ];
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preStart = ''
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mkdir -m 0755 -p ${stateDir}
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touch ${keyFile}
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chmod 0640 ${keyFile}
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chown chrony:chrony ${stateDir} ${keyFile}
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'';
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serviceConfig =
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{ Type = "forking";
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ExecStart = "${pkgs.chrony}/bin/chronyd ${chronyFlags}";
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ProtectHome = "yes";
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ProtectSystem = "full";
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PrivateTmp = "yes";
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ConditionCapability = "CAP_SYS_TIME";
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};
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};
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};
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}
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