kerberos-server: add kerberos option

Allow switching out kerberos server implementation.

Sharing config is probably sensible, but implementation is different enough to
be worth splitting into two files. Not sure this is the correct way to split an
implementation, but it works for now.

Uses the switch from config.krb5 to select implementation.

nixos/modules/module-list.nix

@@ -690,7 +690,7 @@
   ./services/system/dbus.nix
   ./services/system/earlyoom.nix
   ./services/system/localtime.nix
-  ./services/system/kerberos.nix
+  ./services/system/kerberos/default.nix
   ./services/system/nscd.nix
   ./services/system/saslauthd.nix
   ./services/system/uptimed.nix

nixos/modules/services/system/kerberos.nix

@@ -1,48 +0,0 @@
-{pkgs, config, lib, ...}:
-
-let
-  inherit (lib) mkOption mkIf;
-  cfg = config.services.kerberos_server;
-  stateDir = "/var/heimdal";
-in
-
-{
-  ###### interface
-  options = {
-    services.kerberos_server = {
-      enable = mkOption {
-        default = false;
-        description = ''
-          Enable the kerberos authentification server.
-        '';
-      };
-
-    };
-  };
-
-
-  ###### implementation
-
-  config = mkIf cfg.enable {
-    environment.systemPackages = [ pkgs.heimdalFull ];
-    systemd.services.kadmind = {
-      description = "Kerberos Administration Daemon";
-      serviceConfig.ExecStart = "${pkgs.heimdalFull}/libexec/heimdal/kadmind";
-    };
-
-    systemd.services.kdc = {
-      description = "Key Distribution Center daemon";
-      wantedBy = [ "multi-user.target" ];
-      preStart = ''
-        mkdir -m 0755 -p ${stateDir}
-      '';
-      serviceConfig.ExecStart = "${pkgs.heimdalFull}/libexec/heimdal/kdc";
-    };
-
-    systemd.services.kpasswdd = {
-      description = "Kerberos Password Changing daemon";
-      wantedBy = [ "multi-user.target" ];
-      serviceConfig.ExecStart = "${pkgs.heimdalFull}/libexec/heimdal/kpasswdd";
-    };
-  };
-}

nixos/modules/services/system/kerberos/default.nix

@@ -0,0 +1,76 @@
+{pkgs, config, lib, ...}:
+
+let
+  inherit (lib) mkOption mkIf types;
+  cfg = config.services.kerberos_server;
+  kerberos = config.krb5.kerberos;
+
+  aclEntry = {
+    options = {
+      principal = mkOption {
+        type = types.str;
+        description = "Which principal the rule applies to";
+      };
+      access = mkOption {
+        type = types.either
+          (types.listOf (types.enum ["add" "cpw" "delete" "get" "list" "modify"]))
+          (types.enum ["all"]);
+        default = "all";
+        description = "The changes the principal is allowed to make.";
+      };
+      target = mkOption {
+        type = types.str;
+        default = "*";
+        description = "The principals that 'access' applies to.";
+      };
+    };
+  };
+
+  realm = {
+    options = {
+      acl = mkOption {
+        type = types.listOf (types.submodule aclEntry);
+        default = [
+          { principal = "*/admin"; access = "all"; }
+          { principal = "admin"; access = "all"; }
+        ];
+        description = ''
+          The privileges granted to a user.
+        '';
+      };
+    };
+  };
+in
+
+{
+  imports = [
+    ./mit.nix
+    ./heimdal.nix
+  ];
+
+  ###### interface
+  options = {
+    services.kerberos_server = {
+      enable = mkOption {
+        default = false;
+        description = ''
+          Enable the kerberos authentification server.
+        '';
+      };
+
+      realms = mkOption {
+        type = types.attrsOf (types.submodule realm);
+        description = ''
+          The realm(s) to serve keys for.
+        '';
+      };
+    };
+  };
+
+
+  ###### implementation
+
+  config = mkIf cfg.enable {
+    environment.systemPackages = [ kerberos ];
+  };
+}

nixos/modules/services/system/kerberos/heimdal.nix

@@ -0,0 +1,74 @@
+{ pkgs, config, lib, ... } :
+
+let
+  inherit (lib) mkIf concatStringsSep concatMapStrings toList mapAttrs'
+    nameValuePair attrNames attrValues;
+  cfg = config.services.kerberos_server;
+  kerberos = config.krb5.kerberos;
+  stateDir = "/var/heimdal";
+  aclFiles = mapAttrs'
+    (name: {acl, ...}: nameValuePair "${name}.acl" (
+      pkgs.writeText "${name}.acl" (concatMapStrings ((
+        {principal, access, target, ...} :
+        "${principal}\t${concatStringsSep "," (toList access)}\t${target}\n"
+      )) acl)
+    )) cfg.realms;
+
+  kdcConfigs = map (name: ''
+    database = {
+      dbname = ${stateDir}/heimdal
+      acl_file = /etc/heimdal-kdc/${name}.acl
+    }
+  '') (attrNames cfg.realms);
+  kdcConfFile = pkgs.writeText "kdc.conf" ''
+    [kdc]
+    ${concatStringsSep "\n" kdcConfigs}
+  '';
+in
+
+{
+  # No documentation about correct triggers, so guessing at them.
+
+  config = mkIf (cfg.enable && kerberos == pkgs.heimdalFull) {
+    systemd.services.kadmind = {
+      description = "Kerberos Administration Daemon";
+      wantedBy = [ "multi-user.target" ];
+      preStart = ''
+        mkdir -m 0755 -p ${stateDir}
+      '';
+      serviceConfig.ExecStart =
+        "${kerberos}/libexec/heimdal/kadmind --config-file=/etc/heimdal-kdc/kdc.conf";
+      restartTriggers = [ kdcConfFile ] ++ (attrValues aclFiles);
+    };
+
+    systemd.services.kdc = {
+      description = "Key Distribution Center daemon";
+      wantedBy = [ "multi-user.target" ];
+      preStart = ''
+        mkdir -m 0755 -p ${stateDir}
+      '';
+      serviceConfig.ExecStart =
+        "${kerberos}/libexec/heimdal/kdc --config-file=/etc/heimdal-kdc/kdc.conf";
+      restartTriggers = [ kdcConfFile ];
+    };
+
+    systemd.services.kpasswdd = {
+      description = "Kerberos Password Changing daemon";
+      wantedBy = [ "multi-user.target" ];
+      preStart = ''
+        mkdir -m 0755 -p ${stateDir}
+      '';
+      serviceConfig.ExecStart = "${kerberos}/libexec/heimdal/kpasswdd";
+      restartTriggers = [ kdcConfFile ] ++ (attrValues aclFiles);
+    };
+
+    environment.etc = {
+      # Can be set via the --config-file option to KDC
+      "heimdal-kdc/kdc.conf".source = kdcConfFile;
+    } // (
+      mapAttrs'
+      (name: value: nameValuePair "heimdal-kdc/${name}" {source = value;})
+      aclFiles
+    );
+  };
+}

nixos/modules/services/system/kerberos/mit.nix

@@ -0,0 +1,74 @@
+{ pkgs, config, lib, ... } :
+
+let
+  inherit (lib) mkIf concatStrings concatStringsSep concatMapStrings toList
+    mapAttrs' nameValuePair attrNames attrValues;
+  cfg = config.services.kerberos_server;
+  kerberos = config.krb5.kerberos;
+  stateDir = "/var/lib/krb5kdc";
+  PIDFile = "/run/kdc.pid";
+  aclMap = {
+    add = "a"; cpw = "c"; delete = "d"; get = "i"; list = "l"; modify = "m";
+    all = "*";
+  };
+  aclFiles = mapAttrs'
+    (name: {acl, ...}: nameValuePair "${name}.acl" (
+      pkgs.writeText "${name}.acl" (concatMapStrings (
+        {principal, access, target, ...} :
+        let access_code = map (a: aclMap.${a}) (toList access); in
+        "${principal} ${concatStrings access_code} ${target}\n"
+      ) acl)
+    )) cfg.realms;
+  kdcConfigs = map (name: ''
+    ${name} = {
+      acl_file = /etc/krb5kdc/${name}.acl
+    }
+  '') (attrNames cfg.realms);
+  kdcConfFile = pkgs.writeText "kdc.conf" ''
+    [realms]
+    ${concatStringsSep "\n" kdcConfigs}
+  '';
+  env = {
+    # What Debian uses, could possibly link directly to Nix store?
+    KRB5_KDC_PROFILE = "/etc/krb5kdc/kdc.conf";
+  };
+in
+
+{
+  config = mkIf (cfg.enable && kerberos == pkgs.krb5Full) {
+    systemd.services.kadmind = {
+      description = "Kerberos Administration Daemon";
+      wantedBy = [ "multi-user.target" ];
+      preStart = ''
+        mkdir -m 0755 -p ${stateDir}
+      '';
+      serviceConfig.ExecStart = "${kerberos}/bin/kadmind -nofork";
+      restartTriggers = [ kdcConfFile ] ++ (attrValues aclFiles);
+      environment = env;
+    };
+
+    systemd.services.kdc = {
+      description = "Key Distribution Center daemon";
+      wantedBy = [ "multi-user.target" ];
+      preStart = ''
+        mkdir -m 0755 -p ${stateDir}
+      '';
+      serviceConfig = {
+        Type = "forking";
+        PIDFile = PIDFile;
+        ExecStart = "${kerberos}/bin/krb5kdc -P ${PIDFile}";
+      };
+      restartTriggers = [ kdcConfFile ];
+      environment = env;
+    };
+
+    environment.etc = {
+      "krb5kdc/kdc.conf".source = kdcConfFile;
+    } // (
+      mapAttrs'
+      (name: value: nameValuePair "krb5kdc/${name}" {source = value;})
+      aclFiles
+    );
+    environment.variables = env;
+  };
+}

nixos/tests/kerberos/default.nix

@@ -0,0 +1,5 @@
+{ system ? builtins.currentSystem }:
+{
+  mit = import ./mit.nix { inherit system; };
+  heimdal = import ./heimdal.nix { inherit system; };
+}

nixos/tests/kerberos/heimdal.nix

@@ -0,0 +1,53 @@
+import ../make-test.nix ({pkgs, ...}: {
+  name = "kerberos_server-heimdal";
+  machine = { config, libs, pkgs, ...}:
+  { services.kerberos_server =
+    { enable = true;
+      realms = {
+        "FOO.BAR".acl = [{principal = "admin"; access = ["add" "cpw"];}];
+      };
+    };
+    krb5 = {
+      enable = true;
+      kerberos = pkgs.heimdalFull;
+      libdefaults = {
+        default_realm = "FOO.BAR";
+      };
+      realms = {
+        "FOO.BAR" = {
+          admin_server = "machine";
+          kdc = "machine";
+        };
+      };
+    };
+  };
+
+  testScript = ''
+    $machine->start;
+
+    $machine->succeed(
+      "kadmin -l init --realm-max-ticket-life='8 day' \\
+       --realm-max-renewable-life='10 day' FOO.BAR"
+    );
+
+    $machine->succeed("systemctl restart kadmind.service kdc.service");
+    $machine->waitForUnit("kadmind.service");
+    $machine->waitForUnit("kdc.service");
+    $machine->waitForUnit("kpasswdd.service");
+
+    $machine->succeed(
+      "kadmin -l add --password=admin_pw --use-defaults admin"
+    );
+    $machine->succeed(
+      "kadmin -l ext_keytab --keytab=admin.keytab admin"
+    );
+    $machine->succeed(
+      "kadmin -p admin -K admin.keytab add --password=alice_pw --use-defaults \\
+       alice"
+    );
+    $machine->succeed(
+      "kadmin -l ext_keytab --keytab=alice.keytab alice"
+    );
+    $machine->succeed("kinit -kt alice.keytab alice");
+  '';
+})

nixos/tests/kerberos/mit.nix

@@ -0,0 +1,45 @@
+import ../make-test.nix ({pkgs, ...}: {
+  name = "kerberos_server-mit";
+  machine = { config, libs, pkgs, ...}:
+  { services.kerberos_server =
+    { enable = true;
+      realms = {
+        "FOO.BAR".acl = [{principal = "admin"; access = ["add" "cpw"];}];
+      };
+    };
+    krb5 = {
+      enable = true;
+      kerberos = pkgs.krb5Full;
+      libdefaults = {
+        default_realm = "FOO.BAR";
+      };
+      realms = {
+        "FOO.BAR" = {
+          admin_server = "machine";
+          kdc = "machine";
+        };
+      };
+    };
+    users.extraUsers.alice = { isNormalUser = true; };
+  };
+
+  testScript = ''
+    $machine->start;
+
+    $machine->succeed(
+      "kdb5_util create -s -r FOO.BAR -P master_key"
+    );
+
+    $machine->succeed("systemctl restart kadmind.service kdc.service");
+    $machine->waitForUnit("kadmind.service");
+    $machine->waitForUnit("kdc.service");
+
+    $machine->succeed(
+      "kadmin.local add_principal -pw admin_pw admin"
+    );
+    $machine->succeed(
+      "kadmin -p admin -w admin_pw addprinc -pw alice_pw alice"
+    );
+    $machine->succeed("echo alice_pw | sudo -u alice kinit");
+  '';
+})