nixpkgs/nixos/modules/services/continuous-integration/github-runner.nix
Vincent Haupert 3f075e5bb1 nixos/github-runner: add PAT support
This commit introduces support for runner registrations through a
personal access token (PAT). To use a PAT instead of a registration
token, place an appropriately scoped PAT in `tokenFile`. If the file
contains a PAT, the configuration script queries a new runner
registration token. Using a runner registration token directly continues
to work as before.
2022-08-15 13:13:58 -04:00

349 lines
13 KiB
Nix

{ config, pkgs, lib, ... }:
with lib;
let
cfg = config.services.github-runner;
svcName = "github-runner";
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/${systemdDir}";
# Name of file stored in service state directory
currentConfigTokenFilename = ".current-token";
in
{
options.services.github-runner = {
enable = mkOption {
default = false;
example = true;
description = lib.mdDoc ''
Whether to enable GitHub Actions runner.
Note: GitHub recommends using self-hosted runners with private repositories only. Learn more here:
[About self-hosted runners](https://docs.github.com/en/actions/hosting-your-own-runners/about-self-hosted-runners).
'';
type = lib.types.bool;
};
url = mkOption {
type = types.str;
description = lib.mdDoc ''
Repository to add the runner to.
Changing this option triggers a new runner registration.
IMPORTANT: If your token is org-wide (not per repository), you need to
provide a github org link, not a single repository, so do it like this
`https://github.com/nixos`, not like this
`https://github.com/nixos/nixpkgs`.
Otherwise, you are going to get a `404 NotFound`
from `POST https://api.github.com/actions/runner-registration`
in the configure script.
'';
example = "https://github.com/nixos/nixpkgs";
};
tokenFile = mkOption {
type = types.path;
description = lib.mdDoc ''
The full path to a file which contains either a runner registration token or a
personal access token (PAT).
The file should contain exactly one line with the token without any newline.
If a registration token is given, it can be used to re-register a runner of the same
name but is time-limited. If the file contains a PAT, the service creates a new
registration token on startup as needed. Make sure the PAT has a scope of
`admin:org` for organization-wide registrations or a scope of
`repo` for a single repository.
Changing this option or the file's content triggers a new runner registration.
'';
example = "/run/secrets/github-runner/nixos.token";
};
name = mkOption {
# Same pattern as for `networking.hostName`
type = types.strMatching "^$|^[[:alnum:]]([[:alnum:]_-]{0,61}[[:alnum:]])?$";
description = lib.mdDoc ''
Name of the runner to configure. Defaults to the hostname.
Changing this option triggers a new runner registration.
'';
example = "nixos";
default = config.networking.hostName;
defaultText = literalExpression "config.networking.hostName";
};
runnerGroup = mkOption {
type = types.nullOr types.str;
description = lib.mdDoc ''
Name of the runner group to add this runner to (defaults to the default runner group).
Changing this option triggers a new runner registration.
'';
default = null;
};
extraLabels = mkOption {
type = types.listOf types.str;
description = lib.mdDoc ''
Extra labels in addition to the default (`["self-hosted", "Linux", "X64"]`).
Changing this option triggers a new runner registration.
'';
example = literalExpression ''[ "nixos" ]'';
default = [ ];
};
replace = mkOption {
type = types.bool;
description = lib.mdDoc ''
Replace any existing runner with the same name.
Without this flag, registering a new runner with the same name fails.
'';
default = false;
};
extraPackages = mkOption {
type = types.listOf types.package;
description = lib.mdDoc ''
Extra packages to add to `PATH` of the service to make them available to workflows.
'';
default = [ ];
};
package = mkOption {
type = types.package;
description = lib.mdDoc ''
Which github-runner derivation to use.
'';
default = pkgs.github-runner;
defaultText = literalExpression "pkgs.github-runner";
};
};
config = mkIf cfg.enable {
warnings = optionals (isStorePath cfg.tokenFile) [
''
`services.github-runner.tokenFile` points to the Nix store and, therefore, is world-readable.
Consider using a path outside of the Nix store to keep the token private.
''
];
systemd.services.${svcName} = {
description = "GitHub Actions runner";
wantedBy = [ "multi-user.target" ];
wants = [ "network-online.target" ];
after = [ "network.target" "network-online.target" ];
environment = {
HOME = runtimeDir;
RUNNER_ROOT = stateDir;
};
path = (with pkgs; [
bash
coreutils
git
gnutar
gzip
]) ++ [
config.nix.package
] ++ cfg.extraPackages;
serviceConfig = rec {
ExecStart = "${cfg.package}/bin/runsvc.sh";
# Does the following, sequentially:
# - If the module configuration or the token has changed, purge the state directory,
# and create the current and the new token file with the contents of the configured
# token. While both files have the same content, only the later is accessible by
# the service user.
# - Configure the runner using the new token file. When finished, delete it.
# - Set up the directory structure by creating the necessary symlinks.
ExecStartPre =
let
# Wrapper script which expects the full path of the state, runtime and logs
# directory as arguments. Overrides the respective systemd variables to provide
# unambiguous directory names. This becomes relevant, for example, if the
# caller overrides any of the StateDirectory=, RuntimeDirectory= or LogDirectory=
# to contain more than one directory. This causes systemd to set the respective
# environment variables with the path of all of the given directories, separated
# by a colon.
writeScript = name: lines: pkgs.writeShellScript "${svcName}-${name}.sh" ''
set -euo pipefail
STATE_DIRECTORY="$1"
RUNTIME_DIRECTORY="$2"
LOGS_DIRECTORY="$3"
${lines}
'';
currentConfigPath = "$STATE_DIRECTORY/.nixos-current-config.json";
runnerRegistrationConfig = getAttrs [ "name" "tokenFile" "url" "runnerGroup" "extraLabels" ] cfg;
newConfigPath = builtins.toFile "${svcName}-config.json" (builtins.toJSON runnerRegistrationConfig);
newConfigTokenFilename = ".new-token";
runnerCredFiles = [
".credentials"
".credentials_rsaparams"
".runner"
];
unconfigureRunner = writeScript "unconfigure" ''
differs=
# Set `differs = 1` if current and new runner config differ or if `currentConfigPath` does not exist
${pkgs.diffutils}/bin/diff -q '${newConfigPath}' "${currentConfigPath}" >/dev/null 2>&1 || differs=1
# Also trigger a registration if the token content changed
${pkgs.diffutils}/bin/diff -q \
"$STATE_DIRECTORY"/${currentConfigTokenFilename} \
${escapeShellArg cfg.tokenFile} \
>/dev/null 2>&1 || differs=1
if [[ -n "$differs" ]]; 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."
find "$STATE_DIRECTORY/" -mindepth 1 -delete
# Copy the configured token file to the state dir and allow the service user to read the file
install --mode=666 ${escapeShellArg cfg.tokenFile} "$STATE_DIRECTORY/${newConfigTokenFilename}"
# Also copy current file to allow for a diff on the next start
install --mode=600 ${escapeShellArg cfg.tokenFile} "$STATE_DIRECTORY/${currentConfigTokenFilename}"
fi
'';
configureRunner = writeScript "configure" ''
if [[ -e "$STATE_DIRECTORY/${newConfigTokenFilename}" ]]; then
echo "Configuring GitHub Actions Runner"
args=(
--unattended
--disableupdate
--work "$RUNTIME_DIRECTORY"
--url ${escapeShellArg cfg.url}
--labels ${escapeShellArg (concatStringsSep "," cfg.extraLabels)}
--name ${escapeShellArg cfg.name}
${optionalString cfg.replace "--replace"}
${optionalString (cfg.runnerGroup != null) "--runnergroup ${escapeShellArg cfg.runnerGroup}"}
)
# If the token file contains a PAT (i.e., it starts with "ghp_"), we have to use the --pat option,
# if it is not a PAT, we assume it contains a registration token and use the --token option
token=$(<"$STATE_DIRECTORY/${newConfigTokenFilename}")
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 "$STATE_DIRECTORY/${newConfigTokenFilename}"
# 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
];
# 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
cfg.tokenFile
# Token file in the state directory
"${stateDir}/${currentConfigTokenFilename}"
];
# By default, use a dynamically allocated user
DynamicUser = true;
KillMode = "process";
KillSignal = "SIGTERM";
# 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;
};
};
};
}