krb5: Adds kerberos service

Ports the NixOS module for building krb5.conf

modules/module-list.nix

@@ -58,6 +58,7 @@
   ./services/hercules-ci-agent
   ./services/ipfs.nix
   ./services/karabiner-elements
+  ./services/krb5
   ./services/khd
   ./services/kwm
   ./services/lorri.nix

modules/services/krb5/default.nix

@@ -0,0 +1,274 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+
+  cfg = config.krb5;
+
+  filterEmbeddedMetadata = value:
+    if isAttrs value then
+      (filterAttrs
+        (attrName: attrValue: attrName != "_module" && attrValue != null) value)
+    else
+      value;
+
+  indent = "  ";
+
+  mkRelation = name: value:
+    if (isList value) then
+      concatMapStringsSep "\n" (mkRelation name) value
+    else
+      "${name} = ${mkVal value}";
+
+  mkVal = value:
+    if (value == true) then
+      "true"
+    else if (value == false) then
+      "false"
+    else if (isInt value) then
+      (toString value)
+    else if (isAttrs value) then
+      let
+        configLines = concatLists
+          (map (splitString "\n") (mapAttrsToList mkRelation value));
+      in (concatStringsSep ''
+
+        ${indent}'' ([ "{" ] ++ configLines)) + ''
+
+          }''
+    else
+      value;
+
+  mkMappedAttrsOrString = value:
+    concatMapStringsSep "\n"
+    (line: if builtins.stringLength line > 0 then "${indent}${line}" else line)
+    (splitString "\n" (if isAttrs value then
+      concatStringsSep "\n" (mapAttrsToList mkRelation value)
+    else
+      value));
+
+in {
+
+  ###### interface
+
+  options = {
+    krb5 = {
+      enable = mkEnableOption
+        (lib.mdDoc "building krb5.conf, configuration file for Kerberos V");
+
+      kerberos = mkOption {
+        type = types.package;
+        default = pkgs.krb5;
+        defaultText = literalExpression "pkgs.krb5";
+        example = literalExpression "pkgs.heimdal";
+        description = lib.mdDoc ''
+          The Kerberos implementation that will be present in
+          `environment.systemPackages` after enabling this
+          service.
+        '';
+      };
+
+      libdefaults = mkOption {
+        type = with types; either attrs lines;
+        default = { };
+        apply = attrs: filterEmbeddedMetadata attrs;
+        example = literalExpression ''
+          {
+            default_realm = "ATHENA.MIT.EDU";
+          };
+        '';
+        description = lib.mdDoc ''
+          Settings used by the Kerberos V5 library.
+        '';
+      };
+
+      realms = mkOption {
+        type = with types; either attrs lines;
+        default = { };
+        example = literalExpression ''
+          {
+            "ATHENA.MIT.EDU" = {
+              admin_server = "athena.mit.edu";
+              kdc = [
+                "athena01.mit.edu"
+                "athena02.mit.edu"
+              ];
+            };
+          };
+        '';
+        apply = attrs: filterEmbeddedMetadata attrs;
+        description =
+          lib.mdDoc "Realm-specific contact information and settings.";
+      };
+
+      domain_realm = mkOption {
+        type = with types; either attrs lines;
+        default = { };
+        example = literalExpression ''
+          {
+            "example.com" = "EXAMPLE.COM";
+            ".example.com" = "EXAMPLE.COM";
+          };
+        '';
+        apply = attrs: filterEmbeddedMetadata attrs;
+        description = lib.mdDoc ''
+          Map of server hostnames to Kerberos realms.
+        '';
+      };
+
+      capaths = mkOption {
+        type = with types; either attrs lines;
+        default = { };
+        example = literalExpression ''
+          {
+            "ATHENA.MIT.EDU" = {
+              "EXAMPLE.COM" = ".";
+            };
+            "EXAMPLE.COM" = {
+              "ATHENA.MIT.EDU" = ".";
+            };
+          };
+        '';
+        apply = attrs: filterEmbeddedMetadata attrs;
+        description = lib.mdDoc ''
+          Authentication paths for non-hierarchical cross-realm authentication.
+        '';
+      };
+
+      appdefaults = mkOption {
+        type = with types; either attrs lines;
+        default = { };
+        example = literalExpression ''
+          {
+            pam = {
+              debug = false;
+              ticket_lifetime = 36000;
+              renew_lifetime = 36000;
+              max_timeout = 30;
+              timeout_shift = 2;
+              initial_timeout = 1;
+            };
+          };
+        '';
+        apply = attrs: filterEmbeddedMetadata attrs;
+        description = lib.mdDoc ''
+          Settings used by some Kerberos V5 applications.
+        '';
+      };
+
+      plugins = mkOption {
+        type = with types; either attrs lines;
+        default = { };
+        example = literalExpression ''
+          {
+            ccselect = {
+              disable = "k5identity";
+            };
+          };
+        '';
+        apply = attrs: filterEmbeddedMetadata attrs;
+        description = lib.mdDoc ''
+          Controls plugin module registration.
+        '';
+      };
+
+      extraConfig = mkOption {
+        type = with types; nullOr lines;
+        default = null;
+        example = ''
+          [logging]
+            kdc          = SYSLOG:NOTICE
+            admin_server = SYSLOG:NOTICE
+            default      = SYSLOG:NOTICE
+        '';
+        description = lib.mdDoc ''
+          These lines go to the end of `krb5.conf` verbatim.
+          `krb5.conf` may include any of the relations that are
+          valid for `kdc.conf` (see `man kdc.conf`),
+          but it is not a recommended practice.
+        '';
+      };
+
+      config = mkOption {
+        type = with types; nullOr lines;
+        default = null;
+        example = ''
+          [libdefaults]
+            default_realm = EXAMPLE.COM
+
+          [realms]
+            EXAMPLE.COM = {
+              admin_server = kerberos.example.com
+              kdc = kerberos.example.com
+              default_principal_flags = +preauth
+            }
+
+          [domain_realm]
+            example.com  = EXAMPLE.COM
+            .example.com = EXAMPLE.COM
+
+          [logging]
+            kdc          = SYSLOG:NOTICE
+            admin_server = SYSLOG:NOTICE
+            default      = SYSLOG:NOTICE
+        '';
+        description = lib.mdDoc ''
+          Verbatim `krb5.conf` configuration.  Note that this
+          is mutually exclusive with configuration via
+          `libdefaults`, `realms`,
+          `domain_realm`, `capaths`,
+          `appdefaults`, `plugins` and
+          `extraConfig` configuration options.  Consult
+          `man krb5.conf` for documentation.
+        '';
+      };
+    };
+  };
+
+  ###### implementation
+
+  config = mkIf cfg.enable {
+
+    environment.systemPackages = [ cfg.kerberos ];
+
+    environment.etc."krb5.conf".text = if isString cfg.config then
+      cfg.config
+    else
+      (''
+        [libdefaults]
+        ${mkMappedAttrsOrString cfg.libdefaults}
+
+        [realms]
+        ${mkMappedAttrsOrString cfg.realms}
+
+        [domain_realm]
+        ${mkMappedAttrsOrString cfg.domain_realm}
+
+        [capaths]
+        ${mkMappedAttrsOrString cfg.capaths}
+
+        [appdefaults]
+        ${mkMappedAttrsOrString cfg.appdefaults}
+
+        [plugins]
+        ${mkMappedAttrsOrString cfg.plugins}
+      '' + optionalString (cfg.extraConfig != null) ("\n" + cfg.extraConfig));
+
+    assertions = [{
+      assertion = !(cfg.config != null && ((builtins.any (value: value != { }) [
+        cfg.libdefaults
+        cfg.realms
+        cfg.domain_realm
+        cfg.capaths
+        cfg.appdefaults
+        cfg.plugins
+      ]) || cfg.extraConfig != null));
+      message = ''
+        Configuration of krb5.conf using krb.config is mutually exclusive with
+        configuration by section.  If you want to mix the two, you can pass
+        lines to any configuration section or lines to krb5.extraConfig.
+      '';
+    }];
+  };
+}

tests/krb5.nix

@@ -0,0 +1,86 @@
+{ config, pkgs, ... }: {
+  krb5 = {
+    enable = true;
+    kerberos = pkgs.krb5;
+    libdefaults = { default_realm = "ATHENA.MIT.EDU"; };
+    realms = {
+      "ATHENA.MIT.EDU" = {
+        admin_server = "athena.mit.edu";
+        kdc = [ "athena01.mit.edu" "athena02.mit.edu" ];
+      };
+    };
+    domain_realm = {
+      "example.com" = "EXAMPLE.COM";
+      ".example.com" = "EXAMPLE.COM";
+    };
+    capaths = {
+      "ATHENA.MIT.EDU" = { "EXAMPLE.COM" = "."; };
+      "EXAMPLE.COM" = { "ATHENA.MIT.EDU" = "."; };
+    };
+    appdefaults = {
+      pam = {
+        debug = false;
+        ticket_lifetime = 36000;
+        renew_lifetime = 36000;
+        max_timeout = 30;
+        timeout_shift = 2;
+        initial_timeout = 1;
+      };
+    };
+    plugins = { ccselect = { disable = "k5identity"; }; };
+    extraConfig = ''
+      [logging]
+        kdc          = SYSLOG:NOTICE
+        admin_server = SYSLOG:NOTICE
+        default      = SYSLOG:NOTICE
+    '';
+  };
+  test = let
+    snapshot = pkgs.writeText "krb5-with-example-config.conf" ''
+      [libdefaults]
+        default_realm = ATHENA.MIT.EDU
+
+      [realms]
+        ATHENA.MIT.EDU = {
+          admin_server = athena.mit.edu
+          kdc = athena01.mit.edu
+          kdc = athena02.mit.edu
+        }
+
+      [domain_realm]
+        .example.com = EXAMPLE.COM
+        example.com = EXAMPLE.COM
+
+      [capaths]
+        ATHENA.MIT.EDU = {
+          EXAMPLE.COM = .
+        }
+        EXAMPLE.COM = {
+          ATHENA.MIT.EDU = .
+        }
+
+      [appdefaults]
+        pam = {
+          debug = false
+          initial_timeout = 1
+          max_timeout = 30
+          renew_lifetime = 36000
+          ticket_lifetime = 36000
+          timeout_shift = 2
+        }
+
+      [plugins]
+        ccselect = {
+          disable = k5identity
+        }
+
+      [logging]
+        kdc          = SYSLOG:NOTICE
+        admin_server = SYSLOG:NOTICE
+        default      = SYSLOG:NOTICE
+    '';
+  in ''
+    echo "checking correctness of krb5.conf" >&2
+    diff /etc/krb5.conf ${snapshot}
+  '';
+}