diff options
Diffstat (limited to 'nixos/modules/services/continuous-integration/github-runner/service.nix')
| -rw-r--r-- | nixos/modules/services/continuous-integration/github-runner/service.nix | 254 |
1 files changed, 254 insertions, 0 deletions
diff --git a/nixos/modules/services/continuous-integration/github-runner/service.nix b/nixos/modules/services/continuous-integration/github-runner/service.nix new file mode 100644 index 0000000000000..4dc8445495a60 --- /dev/null +++ b/nixos/modules/services/continuous-integration/github-runner/service.nix @@ -0,0 +1,254 @@ +{ config +, lib +, pkgs + +, cfg ? config.services.github-runner +, svcName + +, systemdDir ? "${svcName}/${cfg.name}" + # %t: Runtime directory root (usually /run); see systemd.unit(5) +, runtimeDir ? "%t/${systemdDir}" + # %S: State directory root (usually /var/lib); see systemd.unit(5) +, stateDir ? "%S/${systemdDir}" + # %L: Log directory root (usually /var/log); see systemd.unit(5) +, logsDir ? "%L/${systemdDir}" + # Name of file stored in service state directory +, currentConfigTokenFilename ? ".current-token" + +, ... +}: + +with lib; + +{ + description = "GitHub Actions runner"; + + wantedBy = [ "multi-user.target" ]; + wants = [ "network-online.target" ]; + after = [ "network.target" "network-online.target" ]; + + environment = { + HOME = runtimeDir; + RUNNER_ROOT = stateDir; + } // cfg.extraEnvironment; + + path = (with pkgs; [ + bash + coreutils + git + gnutar + gzip + ]) ++ [ + config.nix.package + ] ++ cfg.extraPackages; + + serviceConfig = rec { + ExecStart = "${cfg.package}/bin/Runner.Listener run --startuptype service"; + + # Does the following, sequentially: + # - If the module configuration or the token has changed, purge the state directory, + # and create the current and the new token file with the contents of the configured + # token. While both files have the same content, only the later is accessible by + # the service user. + # - Configure the runner using the new token file. When finished, delete it. + # - Set up the directory structure by creating the necessary symlinks. + ExecStartPre = + let + # Wrapper script which expects the full path of the state, runtime and logs + # directory as arguments. Overrides the respective systemd variables to provide + # unambiguous directory names. This becomes relevant, for example, if the + # caller overrides any of the StateDirectory=, RuntimeDirectory= or LogDirectory= + # to contain more than one directory. This causes systemd to set the respective + # environment variables with the path of all of the given directories, separated + # by a colon. + writeScript = name: lines: pkgs.writeShellScript "${svcName}-${name}.sh" '' + set -euo pipefail + + STATE_DIRECTORY="$1" + RUNTIME_DIRECTORY="$2" + LOGS_DIRECTORY="$3" + + ${lines} + ''; + runnerRegistrationConfig = getAttrs [ "name" "tokenFile" "url" "runnerGroup" "extraLabels" "ephemeral" ] cfg; + newConfigPath = builtins.toFile "${svcName}-config.json" (builtins.toJSON runnerRegistrationConfig); + currentConfigPath = "$STATE_DIRECTORY/.nixos-current-config.json"; + newConfigTokenPath= "$STATE_DIRECTORY/.new-token"; + currentConfigTokenPath = "$STATE_DIRECTORY/${currentConfigTokenFilename}"; + + runnerCredFiles = [ + ".credentials" + ".credentials_rsaparams" + ".runner" + ]; + unconfigureRunner = writeScript "unconfigure" '' + copy_tokens() { + # Copy the configured token file to the state dir and allow the service user to read the file + install --mode=666 ${escapeShellArg cfg.tokenFile} "${newConfigTokenPath}" + # Also copy current file to allow for a diff on the next start + install --mode=600 ${escapeShellArg cfg.tokenFile} "${currentConfigTokenPath}" + } + clean_state() { + find "$STATE_DIRECTORY/" -mindepth 1 -delete + copy_tokens + } + diff_config() { + changed=0 + # Check for module config changes + [[ -f "${currentConfigPath}" ]] \ + && ${pkgs.diffutils}/bin/diff -q '${newConfigPath}' "${currentConfigPath}" >/dev/null 2>&1 \ + || changed=1 + # Also check the content of the token file + [[ -f "${currentConfigTokenPath}" ]] \ + && ${pkgs.diffutils}/bin/diff -q "${currentConfigTokenPath}" ${escapeShellArg cfg.tokenFile} >/dev/null 2>&1 \ + || changed=1 + # If the config has changed, remove old state and copy tokens + if [[ "$changed" -eq 1 ]]; then + echo "Config has changed, removing old runner state." + echo "The old runner will still appear in the GitHub Actions UI." \ + "You have to remove it manually." + clean_state + fi + } + if [[ "${optionalString cfg.ephemeral "1"}" ]]; then + # In ephemeral mode, we always want to start with a clean state + clean_state + elif [[ "$(ls -A "$STATE_DIRECTORY")" ]]; then + # There are state files from a previous run; diff them to decide if we need a new registration + diff_config + else + # The state directory is entirely empty which indicates a first start + copy_tokens + fi ''; + configureRunner = writeScript "configure" '' + if [[ -e "${newConfigTokenPath}" ]]; then + echo "Configuring GitHub Actions Runner" + args=( + --unattended + --disableupdate + --work "$RUNTIME_DIRECTORY" + --url ${escapeShellArg cfg.url} + --labels ${escapeShellArg (concatStringsSep "," cfg.extraLabels)} + --name ${escapeShellArg cfg.name} + ${optionalString cfg.replace "--replace"} + ${optionalString (cfg.runnerGroup != null) "--runnergroup ${escapeShellArg cfg.runnerGroup}"} + ${optionalString cfg.ephemeral "--ephemeral"} + ) + # If the token file contains a PAT (i.e., it starts with "ghp_"), we have to use the --pat option, + # if it is not a PAT, we assume it contains a registration token and use the --token option + token=$(<"${newConfigTokenPath}") + if [[ "$token" =~ ^ghp_* ]]; then + args+=(--pat "$token") + else + args+=(--token "$token") + fi + ${cfg.package}/bin/config.sh "''${args[@]}" + # Move the automatically created _diag dir to the logs dir + mkdir -p "$STATE_DIRECTORY/_diag" + cp -r "$STATE_DIRECTORY/_diag/." "$LOGS_DIRECTORY/" + rm -rf "$STATE_DIRECTORY/_diag/" + # Cleanup token from config + rm "${newConfigTokenPath}" + # Symlink to new config + ln -s '${newConfigPath}' "${currentConfigPath}" + fi + ''; + setupRuntimeDir = writeScript "setup-runtime-dirs" '' + # Link _diag dir + ln -s "$LOGS_DIRECTORY" "$RUNTIME_DIRECTORY/_diag" + + # Link the runner credentials to the runtime dir + ln -s "$STATE_DIRECTORY"/{${lib.concatStringsSep "," runnerCredFiles}} "$RUNTIME_DIRECTORY/" + ''; + in + map (x: "${x} ${escapeShellArgs [ stateDir runtimeDir logsDir ]}") [ + "+${unconfigureRunner}" # runs as root + configureRunner + setupRuntimeDir + ]; + + # If running in ephemeral mode, restart the service on-exit (i.e., successful de-registration of the runner) + # to trigger a fresh registration. + Restart = if cfg.ephemeral then "on-success" else "no"; + + # Contains _diag + LogsDirectory = [ systemdDir ]; + # Default RUNNER_ROOT which contains ephemeral Runner data + RuntimeDirectory = [ systemdDir ]; + # Home of persistent runner data, e.g., credentials + StateDirectory = [ systemdDir ]; + StateDirectoryMode = "0700"; + WorkingDirectory = runtimeDir; + + InaccessiblePaths = [ + # Token file path given in the configuration, if visible to the service + "-${cfg.tokenFile}" + # Token file in the state directory + "${stateDir}/${currentConfigTokenFilename}" + ]; + + KillSignal = "SIGINT"; + + # Hardening (may overlap with DynamicUser=) + # The following options are only for optimizing: + # systemd-analyze security github-runner + AmbientCapabilities = ""; + CapabilityBoundingSet = ""; + # ProtectClock= adds DeviceAllow=char-rtc r + DeviceAllow = ""; + NoNewPrivileges = true; + PrivateDevices = true; + PrivateMounts = true; + PrivateTmp = true; + PrivateUsers = true; + ProtectClock = true; + ProtectControlGroups = true; + ProtectHome = true; + ProtectHostname = true; + ProtectKernelLogs = true; + ProtectKernelModules = true; + ProtectKernelTunables = true; + ProtectSystem = "strict"; + RemoveIPC = true; + RestrictNamespaces = true; + RestrictRealtime = true; + RestrictSUIDSGID = true; + UMask = "0066"; + ProtectProc = "invisible"; + SystemCallFilter = [ + "~@clock" + "~@cpu-emulation" + "~@module" + "~@mount" + "~@obsolete" + "~@raw-io" + "~@reboot" + "~capset" + "~setdomainname" + "~sethostname" + ]; + RestrictAddressFamilies = [ "AF_INET" "AF_INET6" "AF_UNIX" "AF_NETLINK" ]; + + # Needs network access + PrivateNetwork = false; + # Cannot be true due to Node + MemoryDenyWriteExecute = false; + + # The more restrictive "pid" option makes `nix` commands in CI emit + # "GC Warning: Couldn't read /proc/stat" + # You may want to set this to "pid" if not using `nix` commands + ProcSubset = "all"; + # Coverage programs for compiled code such as `cargo-tarpaulin` disable + # ASLR (address space layout randomization) which requires the + # `personality` syscall + # You may want to set this to `true` if not using coverage tooling on + # compiled code + LockPersonality = false; + + # Note that this has some interactions with the User setting; so you may + # want to consult the systemd docs if using both. + DynamicUser = true; + } // ( + lib.optionalAttrs (cfg.user != null) { User = cfg.user; } + ) // cfg.serviceOverrides; +} |