lib: pkgs: config:

with lib;

# See `man systemd.exec` and `man systemd.resource-control` for an explanation
# of the systemd-related options available through this file.
let self = {
  # These settings roughly follow systemd's "strict" security profile
  defaultHardening = {
      PrivateTmp = true;
      ProtectSystem = "strict";
      ProtectHome = true;
      NoNewPrivileges = true;
      PrivateDevices = true;
      MemoryDenyWriteExecute = true;
      ProtectKernelTunables = true;
      ProtectKernelModules = true;
      ProtectKernelLogs = true;
      ProtectClock = true;
      ProtectProc = "invisible";
      ProcSubset = "pid";
      ProtectControlGroups = true;
      RestrictAddressFamilies = "AF_UNIX AF_INET AF_INET6";
      RestrictNamespaces = true;
      LockPersonality = true;
      IPAddressDeny = "any";
      PrivateUsers = true;
      RestrictSUIDSGID = true;
      RemoveIPC = true;
      RestrictRealtime = true;
      ProtectHostname = true;
      CapabilityBoundingSet = "";
      # @system-service whitelist and docker seccomp blacklist (except for "clone"
      # which is a core requirement for systemd services)
      # @system-service is defined in src/shared/seccomp-util.c (systemd source)
      SystemCallFilter = [ "@system-service" "~add_key kcmp keyctl mbind move_pages name_to_handle_at personality process_vm_readv process_vm_writev request_key setns unshare userfaultfd" ];
      SystemCallArchitectures = "native";
  };

  allowNetlink = {
    RestrictAddressFamilies = self.defaultHardening.RestrictAddressFamilies + " AF_NETLINK";
  };

  # nodejs applications require memory write execute for JIT compilation
  nodejs = { MemoryDenyWriteExecute = false; };

  # Allow takes precedence over Deny.
  allowLocalIPAddresses = {
    IPAddressAllow = [
      "127.0.0.1/32"
      "::1/128"
      "169.254.0.0/16"
    ];
  };
  allowAllIPAddresses = { IPAddressAllow = "any"; };
  allowTor = self.allowLocalIPAddresses;
  allowedIPAddresses = onlyLocal:
    if onlyLocal
    then self.allowLocalIPAddresses
    else self.allowAllIPAddresses;

  tor = {
    proxy = mkOption {
      type = types.bool;
      default = false;
      description = "Whether to proxy outgoing connections with Tor.";
    };
    enforce = mkOption {
      type = types.bool;
      default = false;
      description = ''
        Whether to enforce Tor on this service by only allowing connections
        from and to localhost and link-local addresses.
      '';
    };
  };

  script = name: src: pkgs.writers.writeBash name ''
    set -eo pipefail
    ${src}
  '';

  # Used for ExecStart*
  rootScript = name: src: "+${self.script name src}";

  cliExec = mkOption {
    # Used by netns-isolation to execute the cli in the service's private netns
    internal = true;
    type = types.str;
    default = "exec";
  };

  mkOnionService = map: {
    map = [ map ];
    version = 3;
  };

  # Convert a bind address, which may be a special INADDR_ANY address,
  # to an actual IP address
  address = addr:
    if addr == "0.0.0.0" then
      "127.0.0.1"
    else if addr == "::" then
      "::1"
    else
      addr;

  addressWithPort = addr: port: "${self.address addr}:${toString port}";

  optionalAttr = cond: name: if cond then name else null;

  mkCertExtraAltNames = cert:
    builtins.concatStringsSep "," (
      (map (domain: "DNS:${domain}") cert.extraDomains) ++
      (map (ip: "IP:${ip}") cert.extraIPs)
    );

  test = {
    mkIfTest = test: mkIf (config.tests.${test} or false);
  };

}; in self