Files
2026-03-16 12:39:51 -05:00

306 lines
9.3 KiB
Nix

{ inputs, lib, ... }:
let
# Options that will be in common between
opts = {
enable = lib.mkEnableOption "Enable mTLS";
caURL = lib.mkOption {
description = "URL to the certificate authority";
type = lib.types.str;
};
subject = lib.mkOption {
description = "The Common Name, DNS Name, or IP address that will be set as the Subject Common Name for the certificate. If no Subject Alternative Names (SANs) are configured (via the --san flag) then the subject will be set as the only SAN.";
type = lib.types.str;
};
keyFilename = lib.mkOption {
description = "String filename for the private key";
type = lib.types.str;
default = "key.pem";
};
certFilename = lib.mkOption {
description = "String filename for the public certificate";
type = lib.types.str;
default = "cert.pem";
};
bundleFilename = lib.mkOption {
description = "String filename for the mTLS key bundle";
type = lib.types.str;
default = "mtls.pem";
};
san = lib.mkOption {
description = "List of SAN to give the mTLS cert";
type = lib.types.listOf lib.types.str;
default = [ ];
};
provisioner = lib.mkOption {
type = lib.types.str;
default = "admin";
};
lifetime = lib.mkOption {
type = lib.types.str;
default = "6h";
};
renew = {
enable = lib.mkOption {
description = "Enable automatic mTLS certificate renewal using a systemd timer.";
type = lib.types.bool;
default = true;
};
onCalendar = lib.mkOption {
description = "systemd OnCalendar schedule for mTLS certificate renewal checks.";
type = lib.types.str;
default = "*:1/15";
};
randomizedDelaySec = lib.mkOption {
description = "Randomized delay added to renewal timer runs to avoid synchronized renewals.";
type = lib.types.str;
default = "5m";
};
user = lib.mkOption {
description = "User account to run the mTLS renewal service as.";
type = lib.types.str;
default = "root";
};
group = lib.mkOption {
description = "Group to run the mTLS renewal service as. Defaults to the configured renewal user when null.";
type = lib.types.nullOr lib.types.str;
default = null;
};
reloadUnits = lib.mkOption {
description = "systemd units to try-reload-or-restart after a successful certificate renewal.";
type = lib.types.listOf lib.types.str;
default = [ ];
};
postCommands = lib.mkOption {
description = "Shell commands to run after a successful certificate renewal.";
type = lib.types.listOf lib.types.lines;
default = [ ];
};
};
};
mkMtlsRenewScript = {
pkgs,
tlsCert,
tlsKey,
mtlsBundle,
reloadUnits ? [ ],
postCommands ? [ ],
systemctlArgs ? [ ],
}:
let
renewReloadScript = lib.concatMapStringsSep "\n" (unit: ''
if ${lib.getExe' pkgs.systemd "systemctl"} ${lib.escapeShellArgs systemctlArgs} --quiet is-active "${unit}"; then
${lib.getExe' pkgs.systemd "systemctl"} ${lib.escapeShellArgs systemctlArgs} try-reload-or-restart "${unit}"
fi
'') reloadUnits;
renewPostCommands = lib.concatStringsSep "\n" postCommands;
in
pkgs.writeShellScriptBin "mtls-renew" ''
set -euo pipefail
if ${lib.getExe pkgs.step-cli} certificate needs-renewal "${tlsCert}"; then
echo "Renewing mTLS certificate"
else
echo "Skipping renew"
exit "$?"
fi
${lib.getExe pkgs.step-cli} ca renew --force "${tlsCert}" "${tlsKey}"
umask 077
${lib.getExe' pkgs.coreutils "cat"} "${tlsCert}" "${tlsKey}" > "${mtlsBundle}"
${renewReloadScript}
${renewPostCommands}
'';
mkNixosMtlsRenewService = {
pkgs,
tlsCert,
tlsKey,
mtlsBundle,
reloadUnits ? [ ],
postCommands ? [ ],
user ? "root",
group ? null,
}:
let
serviceGroup = if group == null then user else group;
renewScript = mkMtlsRenewScript {
inherit pkgs tlsCert tlsKey mtlsBundle reloadUnits postCommands;
};
in
{
description = "Renew the mTLS certificate when Smallstep marks it ready";
wantedBy = [ ];
after = [ "network-online.target" ];
wants = [ "network-online.target" ];
serviceConfig = {
Type = "oneshot";
User = user;
Group = serviceGroup;
ExecStart = lib.getExe renewScript;
};
};
mkNixosMtlsRenewTimer = {
onCalendar,
randomizedDelaySec,
unit ? "mtls-renew.service",
}: {
description = "Periodic Smallstep renewal for the mTLS certificate";
wantedBy = [ "timers.target" ];
timerConfig = {
Persistent = true;
OnCalendar = onCalendar;
AccuracySec = "1us";
RandomizedDelaySec = randomizedDelaySec;
Unit = unit;
};
};
mkHomeManagerMtlsRenewService = {
pkgs,
tlsCert,
tlsKey,
mtlsBundle,
reloadUnits ? [ ],
postCommands ? [ ],
}:
let
renewScript = mkMtlsRenewScript {
inherit pkgs tlsCert tlsKey mtlsBundle reloadUnits postCommands;
systemctlArgs = [ "--user" ];
};
in
{
Unit = {
Description = "Renew the mTLS certificate when Smallstep marks it ready";
After = [ "network-online.target" ];
Wants = [ "network-online.target" ];
};
Service = {
Type = "oneshot";
ExecStart = lib.getExe renewScript;
};
};
mkHomeManagerMtlsRenewTimer = {
onCalendar,
randomizedDelaySec,
unit ? "mtls-renew.service",
}: {
Unit = {
Description = "Periodic Smallstep renewal for the mTLS certificate";
};
Timer = {
Persistent = true;
OnCalendar = onCalendar;
AccuracySec = "1us";
RandomizedDelaySec = randomizedDelaySec;
Unit = unit;
};
Install = {
WantedBy = [ "timers.target" ];
};
};
in
{
flake.modules.nixos.mtls = { config, lib, pkgs, ... }:
let
cfg = config.mtls;
certDir = "/etc/step/certs";
tlsKey = "${certDir}/${cfg.keyFilename}";
tlsCert = "${certDir}/${cfg.certFilename}";
mtlsBundle = "${certDir}/${cfg.bundleFilename}";
rootCA = "${certDir}/root_ca.crt";
sanArgs = lib.concatMapStringsSep " " (san: "--san \"${san}\"") cfg.san;
in
{
options.mtls = opts;
config = lib.mkIf cfg.enable {
environment.systemPackages = with pkgs; lib.optionals cfg.enable [
(writeShellScriptBin "mtls-generate" ''
set -euo pipefail
${lib.getExe pkgs.step-cli} ca certificate \
${cfg.subject} ${tlsCert} ${tlsKey} \
--ca-url ${cfg.caURL} \
--root ${rootCA} \
--provisioner ${cfg.provisioner} \
--not-before=-5m --not-after=${cfg.lifetime} \
${sanArgs} \
"$@"
cat ${tlsCert} ${tlsKey} > ${mtlsBundle}
'')
(writeShellScriptBin "mtls-check" ''
${lib.getExe pkgs.openssl} x509 \
-noout -subject -issuer \
-ext subjectAltName,extendedKeyUsage \
-enddate -in ${mtlsBundle}
'')
];
systemd.services.mtls-renew = lib.mkIf cfg.renew.enable (mkNixosMtlsRenewService {
inherit pkgs tlsCert tlsKey mtlsBundle;
inherit (cfg.renew) reloadUnits postCommands user group;
});
systemd.timers.mtls-renew = lib.mkIf cfg.renew.enable (mkNixosMtlsRenewTimer {
inherit (cfg.renew) onCalendar randomizedDelaySec;
});
};
};
flake.modules.homeManager.mtls = { config, lib, pkgs, ... }:
let
cfg = config.mtls;
certDir = cfg.certDir;
tlsKey = "${certDir}/${cfg.keyFilename}";
tlsCert = "${certDir}/${cfg.certFilename}";
mtlsBundle = "${certDir}/${cfg.bundleFilename}";
rootCA = "${certDir}/root_ca.crt";
sanArgs = lib.concatMapStringsSep " " (san: "--san \"${san}\"") cfg.san;
in
{
options.mtls = opts // {
certDir = lib.mkOption {
description = "String path to where the mtls certs will be stored.";
type = lib.types.str;
default ="${config.home.homeDirectory}/.step/certs";
};
};
config = {
home.packages = with pkgs; lib.optionals cfg.enable [
step-cli
(writeShellScriptBin "mtls-generate" ''
set -euo pipefail
${lib.getExe pkgs.step-cli} ca certificate \
${cfg.subject} ${tlsCert} ${tlsKey} \
--not-before=-5m --not-after=${cfg.lifetime} \
--provisioner ${cfg.provisioner} \
${sanArgs} \
"$@"
cat ${tlsCert} ${tlsKey} > ${mtlsBundle}
'')
(writeShellScriptBin "mtls-check" ''
${lib.getExe pkgs.openssl} x509 \
-noout -subject -issuer \
-ext subjectAltName,extendedKeyUsage \
-enddate -in ${mtlsBundle}
'')
(mkMtlsRenewScript { inherit pkgs tlsCert tlsKey mtlsBundle; })
];
systemd.user.services.mtls-renew = lib.mkIf cfg.renew.enable (mkHomeManagerMtlsRenewService {
inherit pkgs tlsCert tlsKey mtlsBundle;
inherit (cfg.renew) reloadUnits postCommands;
});
systemd.user.timers.mtls-renew = lib.mkIf cfg.renew.enable (mkHomeManagerMtlsRenewTimer {
inherit (cfg.renew) onCalendar randomizedDelaySec;
});
};
};
}