apparmor: fix and improve the service
This commit is contained in:
Julien Moutinho
@@ -1,59 +1,198 @@
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{ config, lib, pkgs, ... }:
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let
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inherit (lib) mkIf mkOption types concatMapStrings;
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inherit (builtins) attrNames head map match readFile;
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inherit (lib) types;
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inherit (config.environment) etc;
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cfg = config.security.apparmor;
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mkDisableOption = name: lib.mkEnableOption name // {
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default = true;
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example = false;
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};
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enabledPolicies = lib.filterAttrs (n: p: p.enable) cfg.policies;
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in
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{
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options = {
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security.apparmor = {
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enable = mkOption {
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type = types.bool;
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default = false;
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description = "Enable the AppArmor Mandatory Access Control system.";
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};
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profiles = mkOption {
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type = types.listOf types.path;
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default = [];
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description = "List of files containing AppArmor profiles.";
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};
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packages = mkOption {
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type = types.listOf types.package;
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default = [];
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description = "List of packages to be added to apparmor's include path";
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};
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};
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};
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imports = [
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(lib.mkRenamedOptionModule [ "security" "virtualization" "flushL1DataCache" ] [ "security" "virtualisation" "flushL1DataCache" ])
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(lib.mkRemovedOptionModule [ "security" "apparmor" "confineSUIDApplications" ] "Please use the new options: `security.apparmor.policies.<policy>.enable'.")
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(lib.mkRemovedOptionModule [ "security" "apparmor" "profiles" ] "Please use the new option: `security.apparmor.policies'.")
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apparmor/includes.nix
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apparmor/profiles.nix
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];
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config = mkIf cfg.enable {
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environment.systemPackages = [ pkgs.apparmor-utils ];
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options = {
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security.apparmor = {
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enable = lib.mkEnableOption ''the AppArmor Mandatory Access Control system.
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boot.kernelParams = [ "apparmor=1" "security=apparmor" ];
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If you're enabling this module on a running system,
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note that a reboot will be required to activate AppArmor in the kernel.
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systemd.services.apparmor = let
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paths = concatMapStrings (s: " -I ${s}/etc/apparmor.d")
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([ pkgs.apparmor-profiles ] ++ cfg.packages);
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in {
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after = [ "local-fs.target" ];
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before = [ "sysinit.target" ];
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wantedBy = [ "multi-user.target" ];
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unitConfig = {
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DefaultDependencies = "no";
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};
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serviceConfig = {
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Type = "oneshot";
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RemainAfterExit = "yes";
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ExecStart = map (p:
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''${pkgs.apparmor-parser}/bin/apparmor_parser -rKv ${paths} "${p}"''
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) cfg.profiles;
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ExecStop = map (p:
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''${pkgs.apparmor-parser}/bin/apparmor_parser -Rv "${p}"''
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) cfg.profiles;
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ExecReload = map (p:
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''${pkgs.apparmor-parser}/bin/apparmor_parser --reload ${paths} "${p}"''
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) cfg.profiles;
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};
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};
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};
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Also, beware that enabling this module will by default
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try to kill unconfined but confinable running processes,
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in order to obtain a confinement matching what is declared in the NixOS configuration.
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This will happen when upgrading to a NixOS revision
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introducing an AppArmor profile for the executable of a running process.
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This is because enabling an AppArmor profile for an executable
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can only confine new or already confined processes of that executable,
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but leaves already running processes unconfined.
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Set <link linkend="opt-security.apparmor.killUnconfinedConfinables">killUnconfinedConfinables</link>
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to <literal>false</literal> if you prefer to leave those processes running'';
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policies = lib.mkOption {
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description = ''
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AppArmor policies.
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'';
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type = types.attrsOf (types.submodule ({ name, config, ... }: {
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options = {
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enable = mkDisableOption "loading of the profile into the kernel";
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enforce = mkDisableOption "enforcing of the policy or only complain in the logs";
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profile = lib.mkOption {
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description = "The policy of the profile.";
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type = types.lines;
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apply = pkgs.writeText name;
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};
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};
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}));
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default = {};
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};
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includes = lib.mkOption {
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type = types.attrsOf types.lines;
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default = {};
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description = ''
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List of paths to be added to AppArmor's searched paths
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when resolving <literal>include</literal> directives.
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'';
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apply = lib.mapAttrs pkgs.writeText;
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};
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packages = lib.mkOption {
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type = types.listOf types.package;
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default = [];
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description = "List of packages to be added to AppArmor's include path";
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};
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enableCache = lib.mkEnableOption ''caching of AppArmor policies
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in <literal>/var/cache/apparmor/</literal>.
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Beware that AppArmor policies almost always contain Nix store paths,
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and thus produce at each change of these paths
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a new cached version accumulating in the cache'';
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killUnconfinedConfinables = mkDisableOption ''killing of processes
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which have an AppArmor profile enabled
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(in <link linkend="opt-security.apparmor.policies">policies</link>)
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but are not confined (because AppArmor can only confine new processes).
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Beware that due to a current limitation of AppArmor,
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only profiles with exact paths (and no name) can enable such kills'';
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};
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};
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config = lib.mkIf cfg.enable {
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assertions = map (policy:
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{ assertion = match ".*/.*" policy == null;
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message = "`security.apparmor.policies.\"${policy}\"' must not contain a slash.";
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# Because, for instance, aa-remove-unknown uses profiles_names_list() in rc.apparmor.functions
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# which does not recurse into sub-directories.
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}
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) (attrNames cfg.policies);
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environment.systemPackages = [ pkgs.apparmor-utils ];
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environment.etc."apparmor.d".source = pkgs.linkFarm "apparmor.d" (
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# It's important to put only enabledPolicies here and not all cfg.policies
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# because aa-remove-unknown reads profiles from all /etc/apparmor.d/*
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lib.mapAttrsToList (name: p: {inherit name; path=p.profile;}) enabledPolicies ++
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lib.mapAttrsToList (name: path: {inherit name path;}) cfg.includes
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);
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environment.etc."apparmor/parser.conf".text = ''
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${if cfg.enableCache then "write-cache" else "skip-cache"}
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cache-loc /var/cache/apparmor
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Include /etc/apparmor.d
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'' +
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lib.concatMapStrings (p: "Include ${p}/etc/apparmor.d\n") cfg.packages;
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# For aa-logprof
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environment.etc."apparmor/apparmor.conf".text = ''
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'';
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# For aa-logprof
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environment.etc."apparmor/severity.db".source = pkgs.apparmor-utils + "/etc/apparmor/severity.db";
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environment.etc."apparmor/logprof.conf".text = ''
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[settings]
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# /etc/apparmor.d/ is read-only on NixOS
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profiledir = /var/cache/apparmor/logprof
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inactive_profiledir = /etc/apparmor.d/disable
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# Use: journalctl -b --since today --grep audit: | aa-logprof
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logfiles = /dev/stdin
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parser = ${pkgs.apparmor-parser}/bin/apparmor_parser
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ldd = ${pkgs.glibc.bin}/bin/ldd
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logger = ${pkgs.utillinux}/bin/logger
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# customize how file ownership permissions are presented
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# 0 - off
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# 1 - default of what ever mode the log reported
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# 2 - force the new permissions to be user
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# 3 - force all perms on the rule to be user
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default_owner_prompt = 1
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custom_includes = /etc/apparmor.d ${lib.concatMapStringsSep " " (p: "${p}/etc/apparmor.d") cfg.packages}
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[qualifiers]
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${pkgs.runtimeShell} = icnu
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${pkgs.bashInteractive}/bin/sh = icnu
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${pkgs.bashInteractive}/bin/bash = icnu
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'' + head (match "^.*\\[qualifiers](.*)" # Drop the original [settings] section.
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(readFile "${pkgs.apparmor-utils}/etc/apparmor/logprof.conf"));
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boot.kernelParams = [ "apparmor=1" "security=apparmor" ];
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systemd.services.apparmor = {
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after = [
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"local-fs.target"
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"systemd-journald-audit.socket"
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];
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before = [ "sysinit.target" ];
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wantedBy = [ "multi-user.target" ];
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unitConfig = {
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Description="Load AppArmor policies";
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DefaultDependencies = "no";
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ConditionSecurity = "apparmor";
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};
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# Reloading instead of restarting enables to load new AppArmor profiles
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# without necessarily restarting all services which have Requires=apparmor.service
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reloadIfChanged = true;
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restartTriggers = [
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etc."apparmor/parser.conf".source
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etc."apparmor.d".source
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];
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serviceConfig = let
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killUnconfinedConfinables = pkgs.writeShellScript "apparmor-kill" ''
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set -eu
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${pkgs.apparmor-utils}/bin/aa-status --json |
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${pkgs.jq}/bin/jq --raw-output '.processes | .[] | .[] | select (.status == "unconfined") | .pid' |
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xargs --verbose --no-run-if-empty --delimiter='\n' \
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kill
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'';
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commonOpts = p: "--verbose --show-cache ${lib.optionalString (!p.enforce) "--complain "}${p.profile}";
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in {
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Type = "oneshot";
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RemainAfterExit = "yes";
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ExecStartPre = "${pkgs.apparmor-utils}/bin/aa-teardown";
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ExecStart = lib.mapAttrsToList (n: p: "${pkgs.apparmor-parser}/bin/apparmor_parser --add ${commonOpts p}") enabledPolicies;
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ExecStartPost = lib.optional cfg.killUnconfinedConfinables killUnconfinedConfinables;
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ExecReload =
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# Add or replace into the kernel profiles in enabledPolicies
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# (because AppArmor can do that without stopping the processes already confined).
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lib.mapAttrsToList (n: p: "${pkgs.apparmor-parser}/bin/apparmor_parser --replace ${commonOpts p}") enabledPolicies ++
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# Remove from the kernel any profile whose name is not
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# one of the names within the content of the profiles in enabledPolicies
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# (indirectly read from /etc/apparmor.d/*, without recursing into sub-directory).
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# Note that this does not remove profiles dynamically generated by libvirt.
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[ "${pkgs.apparmor-utils}/bin/aa-remove-unknown" ] ++
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# Optionaly kill the processes which are unconfined but now have a profile loaded
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# (because AppArmor can only start to confine new processes).
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lib.optional cfg.killUnconfinedConfinables killUnconfinedConfinables;
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ExecStop = "${pkgs.apparmor-utils}/bin/aa-teardown";
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CacheDirectory = [ "apparmor" "apparmor/logprof" ];
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CacheDirectoryMode = "0700";
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};
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};
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};
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meta.maintainers = with lib.maintainers; [ julm ];
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}
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