{ config, lib, pkgs, ... }:

let
  inherit (builtins) attrNames head match readFile;
  inherit (lib) types;
  inherit (config.environment) etc;
  cfg = config.security.apparmor;
  aa-teardown = pkgs.writeShellScriptBin "aa-teardown" ''
    SECURITYFS=/sys/kernel/security
    SFS_MOUNTPOINT="$SECURITYFS/apparmor"
    ${pkgs.gnused}/bin/sed -e "s/ (\(enforce\|complain\))$//" "$SFS_MOUNTPOINT/profiles" | \
    LC_COLLATE=C ${pkgs.coreutils}/bin/sort | ${pkgs.gnugrep}/bin/grep -v // | {
      while read -r profile ; do
        printf "%s" "$profile" > "$SFS_MOUNTPOINT/.remove"
        rc=$?
        if [ "$rc" -ne 0 ] ; then
          retval=$rc
        fi
      done
      exit "''${retval:-0}"
    }
  '';
in

{
  options = {
    security.apparmor = {
      enable = lib.mkEnableOption "Whether to enable the AppArmor Mandatory Access Control system.";
      enableCache = lib.mkOption {
        type = types.bool;
        default = true;
        example = false;
        description = ''
          Whether to enable caching of AppArmor profiles
          in <literal>/var/cache/apparmor/</literal>.
        '';
      };
      profiles = lib.mkOption {
        type = types.attrsOf types.lines;
        default = {};
        description = ''
          Available AppArmor profiles.
        '';
        apply = lib.mapAttrs (name: text: pkgs.writeText "${name}" text);
      };
      enforceProfiles = lib.mkOption {
        type = (types.listOf (types.enum (attrNames cfg.profiles))) // {
          description = "list of profiles";
        };
        default = [];
        description = "List of AppArmor profiles to be enforced.";
      };
      complainProfiles = lib.mkOption {
        type = (types.listOf (types.enum (attrNames cfg.profiles))) // {
          description = "list of profiles";
        };
        default = [];
        description = "List of AppArmor profiles to be complained.";
      };
      includes = lib.mkOption {
        type = types.listOf types.path;
        default = [];
        description = ''
          List of paths to be added to AppArmor's searched paths
          when resolving absolute #include directives.
        '';
        # Prepends /etc/apparmor.d so that apparmor.profiles
        # are included in priority over apparmor.includes.
        apply = is: ["/etc/apparmor.d"] ++ is;
      };
    };
  };

  config = lib.mkIf cfg.enable {
    environment.systemPackages = [ pkgs.apparmor-utils aa-teardown ];
    environment.etc."apparmor.d".source = pkgs.linkFarm "apparmor.d" (
      lib.mapAttrsToList (name: path: {inherit name path;}) cfg.profiles
    );
    environment.etc."apparmor/parser.conf".text = ''
      ${if cfg.enableCache then "write-cache" else "skip-cache"}
      cache-loc /var/cache/apparmor
    '' + lib.concatMapStringsSep "\n" (p: "Include ${p}") cfg.includes;
    environment.etc."apparmor/logprof.conf".text = ''
      [settings]
        profiledir = /etc/apparmor.d
        inactive_profiledir = ${pkgs.apparmor-profiles}/share/apparmor/extra-profiles
        logfiles = /var/log/audit/audit.log /var/log/syslog /var/log/messages

        parser = ${pkgs.apparmor-parser}/bin/apparmor_parser
        ldd = ${pkgs.glibc.bin}/bin/ldd
        logger = ${pkgs.utillinux}/bin/logger

        # customize how file ownership permissions are presented
        # 0 - off
        # 1 - default of what ever mode the log reported
        # 2 - force the new permissions to be user
        # 3 - force all perms on the rule to be user
        default_owner_prompt = 1

        # custom directory locations to look for #includes
        #
        # each name should be a valid directory containing possible #include
        # candidate files under the profile dir which by default is /etc/apparmor.d.
        #
        # So an entry of my-includes will allow /etc/apparmor.d/my-includes to
        # be used by the yast UI and profiling tools as a source of #include
        # files.
        custom_includes =

      [qualifiers]
        ${pkgs.runtimeShell} = icnu
    '' + head (match "^.*\\[qualifiers](.*)" # Drop the original [settings] section.
                     (readFile "${pkgs.apparmor-utils}/etc/apparmor/logprof.conf"));
    security.apparmor.profiles = {
      "abstractions/tunables/alias" = ''
        alias /bin -> /run/current-system/sw/bin,
        #alias /etc -> /run/current-system/etc,
        alias /lib/modules -> /run/current-system/kernel/lib/modules,
        alias /sbin -> /run/current-system/sw/sbin,
        alias /usr -> /run/current-system/sw,
      '';
      "abstractions/base" = ''
         #include ${pkgs.apparmor-profiles}/etc/apparmor.d/abstractions/base
         ${etc."hosts".source} r,
         /etc/ld-nix.so.preload r,
         ${etc."ld-nix.so.preload".source} r,
         ${lib.concatMapStrings (p: lib.optionalString (p != "") (p+" mr,\n"))
                                (lib.splitString "\n" etc."ld-nix.so.preload".text)
           # TODO: export the content of ld-nix.so.preload as a list or attrset
           # and make services.config.malloc use it.
         }
         ${pkgs.tzdata}/share/zoneinfo/** r,
      '';
      "abstractions/consoles" = ''
         #include ${pkgs.apparmor-profiles}/etc/apparmor.d/abstractions/consoles
      '';
      "abstractions/ldapclient" = ''
         #include ${pkgs.apparmor-profiles}/etc/apparmor.d/abstractions/ldapclient
      '';
      "abstractions/kerberosclient" = ''
         #include ${pkgs.apparmor-profiles}/etc/apparmor.d/abstractions/kerberosclient
      '';
      "abstractions/likewise" = ''
         #include ${pkgs.apparmor-profiles}/etc/apparmor.d/abstractions/likewise
      '';
      "abstractions/mdns" = ''
         #include ${pkgs.apparmor-profiles}/etc/apparmor.d/abstractions/mdns
      '';
      "abstractions/nameservice" = ''
         #include ${pkgs.apparmor-profiles}/etc/apparmor.d/abstractions/nameservice
      '';
      "abstractions/nis" = ''
         #include ${pkgs.apparmor-profiles}/etc/apparmor.d/abstractions/nis
      '';
      "abstractions/ssl_certs" = ''
         #include ${pkgs.apparmor-profiles}/etc/apparmor.d/abstractions/ssl_certs
         ${etc."ssl/certs/ca-certificates.crt".source} r,
         ${etc."ssl/certs/ca-bundle.crt".source} r,
      '';
      "abstractions/winbind" = ''
         #include ${pkgs.apparmor-profiles}/etc/apparmor.d/abstractions/winbind
      '';
    };
    security.apparmor.includes = [ (pkgs.apparmor-profiles+"/etc/apparmor.d/") ];

    boot.kernelParams = [ "apparmor=1" "security=apparmor" ];

    systemd.services.apparmor = {
      after = [
        "local-fs.target"
        "systemd-journald-audit.socket"
      ];
      before = [ "sysinit.target" ];
      wantedBy = [ "multi-user.target" ];
      restartTriggers = [
        etc."apparmor/parser.conf".source
        etc."apparmor.d".source
      ] ++ cfg.includes;
      unitConfig = {
        Description="Load AppArmor profiles";
        DefaultDependencies = "no";
        ConditionSecurity = "apparmor";
      };
      environment.LANG="C"; # Avoid searchs in /usr/share/locale/
      # Restart because reloading would not remove confinement from removed profiles.
      # However, restarting apparmor.service will restart services
      # which Requires= apparmor.service.
      restartIfChanged = true;
      serviceConfig =
        let commonOpts = p: ''--verbose --show-cache ${cfg.profiles."${p}"}'';
        in {
        Type = "oneshot";
        RemainAfterExit = "yes";
        ExecStartPre = "${aa-teardown}/bin/aa-teardown";
        ExecStart =
          map (p: ''${pkgs.strace}/bin/strace -f -e file ${pkgs.apparmor-parser}/bin/apparmor_parser --add ${commonOpts p}'') cfg.enforceProfiles ++
          map (p: ''${pkgs.strace}/bin/strace -f -e file ${pkgs.apparmor-parser}/bin/apparmor_parser --add --complain ${commonOpts p}'') cfg.complainProfiles;
        ExecReload = # WARNING: reloading does NOT remove AppArmor confinement from running processes
                     # (as we would not be able to re-confine them without restarting them).
                     # However, processes confined with profiles just removed
                     # from cfg.enforceProfiles or cfg.complainProfiles,
                     # will stay confined with those removed profiles.
          map (p: ''${pkgs.apparmor-parser}/bin/apparmor_parser --replace ${commonOpts p}'') cfg.enforceProfiles ++
          map (p: ''${pkgs.apparmor-parser}/bin/apparmor_parser --replace --complain ${commonOpts p}'') cfg.complainProfiles;
        ExecStop = "${aa-teardown}/bin/aa-teardown";
      } // lib.optionalAttrs cfg.enableCache {
        #WorkingDirectory = "/var/cache/apparmor";
        CacheDirectory = [ "apparmor" ];
        CacheDirectoryMode = "0700";
      };
    };
  };

  meta.maintainers = with lib.maintainers; [ julm ];
}