diff --git a/config/domains.nix b/config/domains.nix
index 3308d16..51a06c0 100644
--- a/config/domains.nix
+++ b/config/domains.nix
@@ -40,7 +40,7 @@
       local-groups = [ "fudo" "selby" "admin" ];
       local-admins = [ "niten" ];
       admin-email = "niten@fudo.org";
-      gssapi-realm = "FUDO.ORG";
+      gssapi-realm = "RUS.SELBY.CA";
     };
 
     "informis.land" = {
diff --git a/config/hosts/clunk.nix b/config/hosts/clunk.nix
index 1e1d12a..73d4f87 100644
--- a/config/hosts/clunk.nix
+++ b/config/hosts/clunk.nix
@@ -91,8 +91,8 @@ in {
       realm = "RUS.SELBY.CA";
       bind-addresses = [ "10.0.0.1" "127.0.0.1" "[::1]" ];
       acl = {
-        "niten" = { perms = [ "all" ]; };
-        "*/root" = { perms = [ "password" "list" ]; };
+        "niten" = { perms = [ "add" "change-password" "list" ]; };
+        "*/root" = { perms = [ "all" ]; };
       };
     };
 
diff --git a/config/networks/rus.selby.ca.nix b/config/networks/rus.selby.ca.nix
index 2cd6ba1..3b31147 100644
--- a/config/networks/rus.selby.ca.nix
+++ b/config/networks/rus.selby.ca.nix
@@ -1,13 +1,13 @@
 { config, lib, ... }:
 
+with lib;
 let local-domain = "rus.selby.ca";
-
 in {
   default-host = "10.0.0.1";
 
   mx = [ "mail.fudo.org" ];
 
-  gssapi-realm = "FUDO.ORG";
+  gssapi-realm = toUpper local-domain;
 
   hosts = {
     clunk = {
@@ -61,11 +61,11 @@ in {
       }];
       kerberos = [{
         port = 88;
-        host = "france.fudo.org";
+        host = "clunk.${local-domain}";
       }];
       kerberos-adm = [{
-        port = 88;
-        host = "france.fudo.org";
+        port = 749;
+        host = "clunk.${local-domain}";
       }];
       ssh = [{
         port = 22;
@@ -80,15 +80,15 @@ in {
       }];
       kerberos = [{
         port = 88;
-        host = "france.fudo.org";
+        host = "clunk.${local-domain}";
       }];
       kerboros-master = [{
         port = 88;
-        host = "france.fudo.org";
+        host = "clunk.${local-domain}";
       }];
       kpasswd = [{
         port = 464;
-        host = "france.fudo.org";
+        host = "clunk.${local-domain}";
       }];
     };
   };
diff --git a/config/profiles/common.nix b/config/profiles/common.nix
index 9c02ad6..9a3dc80 100644
--- a/config/profiles/common.nix
+++ b/config/profiles/common.nix
@@ -25,15 +25,22 @@ in {
   krb5 = {
     enable = true;
 
+    appdefaults = {
+      forwardable = true;
+      proxiable = true;
+      encrypt = true;
+      forward = true;
+    };
+
     libdefaults = {
       allow_weak_crypto = false;
       dns_lookup_kdc = true;
+      dns_lookup_realm = true;
       forwardable = true;
-      ignore_acceptor_hostname = true;
-      noaddresses = true;
-      rdns = false;
       proxiable = true;
     };
+
+    kerberos = pkgs.heimdalFull;
   };
 
   services = {
diff --git a/lib/fudo/hosts.nix b/lib/fudo/hosts.nix
index ef1f73d..3b6d544 100644
--- a/lib/fudo/hosts.nix
+++ b/lib/fudo/hosts.nix
@@ -85,6 +85,13 @@ let
       enable-gui = mkEnableOption "Install desktop GUI software.";
 
       docker-server = mkEnableOption "Enable Docker on the current host.";
+
+      kerberos-services = mkOption {
+        type = listOf str;
+        description =
+          "List of services which should exist for this host, if it belongs to a realm.";
+        default = [ "ssh" "host" ];
+      };
     };
   };
 
diff --git a/lib/fudo/kdc.nix b/lib/fudo/kdc.nix
index b27bf57..a4a4ef4 100644
--- a/lib/fudo/kdc.nix
+++ b/lib/fudo/kdc.nix
@@ -4,92 +4,82 @@ with lib;
 let
   cfg = config.fudo.auth.kdc;
 
-  kerberos-database = "${cfg.state-directory}/kerberos.db";
+  database-file = "${cfg.state-directory}/principals.db";
+  iprop-log = "${cfg.state-directory}/iprop.log";
+  acl-file = generate-acl-file cfg.acl;
+  kdc-conf =
+    generate-kdc-conf cfg.realm database-file cfg.master-key-file acl-file;
 
   get-domain-hosts = domain:
-    mapAttrsToList (host: hostOpts: "${host}.${domain}")
+    attrNames
     (filterAttrs (host: hostOpts: hostOpts.domain == domain) config.fudo.hosts);
 
-  add-host-principals = realm: db-name: host: ''
-    ${pkgs.krb5}/bin/kadmin.local -d ${db-name} addprinc -randkey host/${host} -r ${realm}
-    ${pkgs.krb5}/bin/kadmin.local -d ${db-name} addprinc -randkey ssh/${host} -r ${realm}
-  '';
+  get-host-principals = realm: hostname:
+    let host = config.fudo.hosts.${hostname};
+    in map (service: "${service}/${hostname}.${toLower realm}@${realm}")
+    host.kerberos-services;
 
-  initialize-db = realm: kdc-conf: user: group: key-file: db-name:
+  add-principal-str = kdc-conf: principal:
+    "${pkgs.heimdalFull}/bin/kadmin -l -c ${kdc-conf} -- add --random-key --use-defaults ${principal}";
+
+  add-hosts-principals = realm: kdc-conf:
+    concatStringsSep "\n" (map (add-principal-str kdc-conf)
+      (concatMap (get-host-principals realm)
+        (get-domain-hosts (toLower realm))));
+
+  initialize-db =
+    realm: user: group: kdc-conf: key-file: db-name: max-lifetime: max-renewal: primary-keytab: kadmin-keytab: local-hostname:
     pkgs.writeShellScript "initialize-kdc-db.sh" ''
-      if [ ! -e ${db-name} ]; then
-        KRB5_CONFIG=/etc/krb5.conf
-        KRB5_KDC_PROFILE=${kdc-conf}
-        PWD=$(${pkgs.pwgen}/bin/pwgen 40 1)
-        printf "$PWD\n$PWD\n$PWD\n" | ${pkgs.krb5}/bin/kdb5_util -r ${realm} -sf ${key-file} -d ${db-name} -m create -s
-        ${pkgs.coreutils}/bin/chown -R ${user}:${group} $(dirname ${db-name})
+      if [ ! -e ${key-file} ]; then
+        ${pkgs.heimdalFull}/bin/kstash --key-file=${key-file} --random-key
+        ${pkgs.heimdalFull}/bin/kadmin -l -c ${kdc-conf} -- init --realm-max-ticket-life="${max-lifetime}" --realm-max-renewable-life="${max-renewal}" RUS.SELBY.CA
+        ${add-hosts-principals realm kdc-conf}
+        ${pkgs.heimdalFull}/bin/kadmin -l -c ${kdc-conf} -- add --random-key --use-defaults kadmin/${local-hostname}@${realm}
+        ${pkgs.heimdalFull}/bin/kadmin -l -c ${kdc-conf} -- ext_keytab --keytab=${primary-keytab} */${local-hostname}@${realm}
+        ${pkgs.heimdalFull}/bin/kadmin -l -c ${kdc-conf} -- ext_keytab --keytab=${kadmin-keytab} kadmin/${local-hostname}@${realm}
+        ${pkgs.coreutils}/bin/chown ${user}:${group} ${key-file}
+        ${pkgs.coreutils}/bin/chown ${user}:${group} ${db-name}
+        ${pkgs.coreutils}/bin/chown ${user}:${group} ${iprop-log}
+        ${pkgs.coreutils}/bin/chown ${user}:${group} ${primary-keytab}
+        ${pkgs.coreutils}/bin/chown ${user}:${group} ${kadmin-keytab}
       fi
     '';
 
-  initialize-kadmin = realm: db-name: user: group: kadmin-keytab: host:
-    let
-      domain = toLower realm;
-      hosts = get-domain-hosts domain;
-    in pkgs.writeShellScript "initialize-kadmin.sh" ''
-      if [ ! -e ${kadmin-keytab} ]; then
-        # ${pkgs.krb5}/bin/kadmin.local -d ${db-name} addprinc -randkey kadmin/${host}.${domain}
-        # ${pkgs.krb5}/bin/kadmin.local -d ${db-name} ktadd -k ${kadmin-keytab} kadmin/${host}.${domain}
-        # TODO: extract kadmin keytab
-        # ${
-          concatStringsSep "\n" (map (add-host-principals realm db-name) hosts)
-        }
-      fi
-    '';
-
-  generate-kdc-conf =
-    realm: database: kdc-listen-addrs: kadmin-listen-addrs: kpasswd-listen-addrs: acl-file: kadmin-keytab: key-stash-file:
+  generate-kdc-conf = realm: db-file: key-file: acl-file:
     pkgs.writeText "kdc.conf" ''
-      [kdcdefaults]
-        kdc_listen = ${concatStringsSep "," kdc-listen-addrs}
-        kdc_tcp_listen = ${concatStringsSep "," kdc-listen-addrs}
-
-      [realm]
-        ${realm} = {
-          kadmind_listen = ${concatStringsSep "," kadmin-listen-addrs}
-          kpasswd_listen = ${concatStringsSep "," kpasswd-listen-addrs}
-          max_life = 24h 0m 0s
-          max_renewable_life = 14d 0h 0m 0s
+      [kdc]
+        database = {
+          dbname = sqlite:${db-file}
+          realm = ${realm}
+          mkey_file = ${key-file}
           acl_file = ${acl-file}
-          admin_keytab = ${kadmin-keytab}
-          key_stash_file = ${key-stash-file}
+          log_file = ${iprop-log}
         }
 
-      [dbmodules]
+      [realms]
         ${realm} = {
-          database_name = ${database}
-          db_library = db2
+          enable-http = false
         }
 
       [logging]
-        kdc = SYSLOG
-        admin_server = SYSLOG
         default = SYSLOG
     '';
 
-  perm-map = {
-    "add" = "a";
-    "all" = "x";
-    "password" = "c";
-    "delete" = "d";
-    "inquire" = "i";
-    "list" = "l";
-    "modify" = "m";
-    "propagate" = "p";
-    "set-key" = "s";
-  };
-
-  perms-to-permstring = perms:
-    concatStringsSep "" (map (perm: perm-map.${perm}) perms);
-
   aclEntry = { principal, ... }: {
     options = with types; {
-      perms = mkOption {
-        type = listOf (enum (attrNames perm-map));
+      perms = let
+        perms = [
+          "change-password"
+          "add"
+          "list"
+          "delete"
+          "modify"
+          "get"
+          "get-keys"
+          "all"
+        ];
+      in mkOption {
+        type = listOf (enum perms);
         description = "List of permissions.";
         default = [ ];
       };
@@ -103,6 +93,8 @@ let
     };
   };
 
+  perms-to-permstring = perms: concatStringsSep "," perms;
+
   generate-acl-file = acl-entries:
     pkgs.writeText "kdc.acl" (concatStringsSep "\n" (mapAttrsToList
       (principal: opts:
@@ -110,15 +102,10 @@ let
           optionalString (opts.target != null) " ${opts.target}"
         }") acl-entries));
 
-  acl-file = generate-acl-file cfg.acl;
-
-  kdc-listen-addrs = map (ip: "${ip}:88") cfg.bind-addresses;
-  kadmin-listen-addrs = map (ip: "${ip}:749") cfg.bind-addresses;
-  kpasswd-listen-addrs = map (ip: "${ip}:464") cfg.bind-addresses;
-
-  kdc-conf = generate-kdc-conf cfg.realm kerberos-database kdc-listen-addrs
-    kadmin-listen-addrs kpasswd-listen-addrs acl-file cfg.kadmin-keytab
-    cfg.master-key-file;
+  kadmin-local = kdc-conf: kadmin-keytab:
+    pkgs.writeShellScriptBin "kadmin.local" ''
+      ${pkgs.heimdalFull}/bin/kadmin -l -c ${kdc-conf} --keytab=${kadmin-keytab}
+    '';
 
 in {
 
@@ -170,18 +157,50 @@ in {
       default = "/var/kerberos/master.key";
     };
 
+    primary-keytab = mkOption {
+      type = str;
+      description = "Location of keytab for kadmind.";
+      default = "/var/kerberos/host.keytab";
+    };
+
     kadmin-keytab = mkOption {
       type = str;
       description = "Location of keytab for kadmind.";
       default = "/var/kerberos/kadmind.keytab";
     };
+
+    kdc-internal-port = mkOption {
+      type = port;
+      description =
+        "Localhost port on which to listen for KDC traffic. Port 88 will be forwarded";
+      default = 4088;
+    };
+
+    k5login-directory = mkOption {
+      type = str;
+      description =
+        "Directory in which k5login files are stored for local users (equivalent to ~/.k5login).";
+      default = "/var/kerberos/k5login";
+    };
+
+    max-ticket-lifetime = mkOption {
+      type = str;
+      description = "Maximum lifetime of a single ticket in this realm.";
+      default = "1d";
+    };
+
+    max-ticket-renewal = mkOption {
+      type = str;
+      description = "Maximum time a ticket may be renewed in this realm.";
+      default = "7d";
+    };
   };
 
   config = mkIf cfg.enable {
     users = {
       users.${cfg.user} = {
         isSystemUser = true;
-        home = "/var/heimdal";
+        home = "/var/kerberos";
         group = cfg.group;
       };
 
@@ -189,26 +208,21 @@ in {
     };
 
     krb5 = {
-      libdefaults = { default_realm = mkDefault cfg.realm; };
-      realms.${cfg.realm} = { key_stash_file = cfg.master-key-file; };
-      extraConfig = mkAfter ''
-        [dbmodules]
-          ${cfg.realm} = {
-            database_name = ${kerberos-database}
-          }
-
-        [realm]
-          ${cfg.realm} = {
-            kadmind_listen = ${concatStringsSep "," kadmin-listen-addrs}
-            kpasswd_listen = ${concatStringsSep "," kpasswd-listen-addrs}
-            acl_file = ${acl-file}
-            admin_keytab = ${cfg.kadmin-keytab}
-            key_stash_file = ${cfg.master-key-file}
-          }
+      libdefaults = {
+        k5login_directory = cfg.k5login-directory;
+        ticket_lifetime = cfg.max-ticket-lifetime;
+        renew_lifetime = cfg.max-ticket-renewal;
+      };
+      realms = { ${cfg.realm} = { enable-http = false; }; };
+      extraConfig = ''
+        default = SYSLOG
       '';
     };
 
-    environment = { systemPackages = [ pkgs.kerberos pkgs.krb5 ]; };
+    environment = {
+      systemPackages =
+        [ pkgs.heimdalFull (kadmin-local kdc-conf cfg.kadmin-keytab) ];
+    };
 
     fudo.system = {
       ensure-directories = {
@@ -217,64 +231,79 @@ in {
           group = cfg.group;
           perms = "0740";
         };
-        "/run/mit-kdc" = {
-          user = cfg.user;
-          group = cfg.group;
-          perms = "0744";
-        };
-        "/run/mit-kadmin" = {
-          user = cfg.user;
-          group = cfg.group;
-          perms = "0744";
+      };
+
+      internal-port-map = {
+        kdc = {
+          internal-port = cfg.kdc-internal-port;
+          external-port = 88;
+          protocols = [ "tcp" "udp" ];
         };
       };
 
       services = {
-        mit-kdc = {
+        heimdal-kdc = {
           wantedBy = [ "multi-user.target" ];
           after = [ "network.target" ];
-          type = "forking";
-          description = "MIT Kerberos Key Distribution Center (ticket server).";
+          description =
+            "Heimdal Kerberos Key Distribution Center (ticket server).";
           execStart =
-            "${pkgs.krb5}/bin/krb5kdc -r ${cfg.realm} -d ${kerberos-database} -P /run/mit-kdc/mit-kdc.pid";
-          readWritePaths = [ "/run/mit-kdc" ];
-          environment = {
-            KRB5_CONFIG = "/etc/krb5.conf";
-            KRB5_KDC_PROFILE = "${kdc-conf}";
-          };
+            "${pkgs.heimdalFull}/libexec/heimdal/kdc -c ${kdc-conf} --ports=${
+              toString cfg.kdc-internal-port
+            } --addresses=127.0.0.1";
+          environment = { KRB5_CONFIG = "/etc/krb5.conf"; };
           user = cfg.user;
           group = cfg.group;
           workingDirectory = cfg.state-directory;
-          preStart = "${initialize-db cfg.realm kdc-conf cfg.user cfg.group
-            cfg.master-key-file kerberos-database}";
           privateNetwork = false;
           addressFamilies = [ "AF_INET" "AF_INET6" ];
-          requiredCapabilities = [ "CAP_NET_BIND_SERVICE+ep" ];
         };
 
-        mit-kadmin = {
-          wantedBy = [ "multi-user.target" ];
-          after = [ "network.target" ];
-          requires = [ "mit-kdc.service" ];
-          description = "MIT Kerberos Remote Administration Server.";
-          execStart =
-            "${pkgs.krb5}/bin/kadmind -r ${cfg.realm} -P /run/mit-kadmin/mit-kadmin.pid";
-          readWritePaths = [ "/run/mit-kadmin" ];
-          environment = {
-            KRB5_CONFIG = "/etc/krb5.conf";
-            KRB5_KDC_PROFILE = "${kdc-conf}";
-          };
+        heimdal-kdc-init = {
+          requires = [ "heimdal-kdc.service" ];
+          description = "Initialization script for Heimdal KDC.";
+          type = "oneshot";
+          execStart = "${initialize-db cfg.realm cfg.user cfg.group kdc-conf
+            cfg.master-key-file database-file cfg.max-ticket-lifetime
+            cfg.max-ticket-renewal cfg.primary-keytab cfg.kadmin-keytab
+            "${config.networking.hostName}.${toLower cfg.realm}"}";
           user = cfg.user;
           group = cfg.group;
           workingDirectory = cfg.state-directory;
-          privateNetwork = false;
-          # postStart =
-          #   "${initialize-kadmin cfg.realm kerberos-database cfg.user cfg.group
-          #   cfg.kadmin-keytab config.networking.hostName}";
-          addressFamilies = [ "AF_INET" "AF_INET6" ];
-          requiredCapabilities = [ "CAP_NET_BIND_SERVICE" ];
+          environment = { KRB5_CONFIG = "/etc/krb5.conf"; };
         };
       };
     };
+
+    systemd.tmpfiles.rules = mkIf (cfg.primary-keytab != "/etc/krb5.keytab")
+      [ "L /etc/krb5.keytab - - - - ${cfg.primary-keytab}" ];
+
+    services.xinetd = {
+      enable = true;
+
+      services = [
+        {
+          name = "kerberos-adm";
+          user = cfg.user;
+          server = "${pkgs.heimdalFull}/libexec/heimdal/kadmind";
+          protocol = "tcp";
+          serverArgs =
+            "--config-file=${kdc-conf} --keytab=${cfg.kadmin-keytab}";
+        }
+        {
+          name = "kpasswd";
+          user = cfg.user;
+          server = "${pkgs.heimdalFull}/libexec/heimdal/kpasswdd";
+          protocol = "udp";
+          serverArgs =
+            "--config-file=${kdc-conf} --keytab=${cfg.kadmin-keytab}";
+        }
+      ];
+    };
+
+    networking.firewall = {
+      allowedTCPPorts = [ 88 749 ];
+      allowedUDPPorts = [ 88 464 ];
+    };
   };
 }
diff --git a/lib/fudo/system.nix b/lib/fudo/system.nix
index 025a515..3acf379 100644
--- a/lib/fudo/system.nix
+++ b/lib/fudo/system.nix
@@ -260,12 +260,12 @@ let
             "A list of paths which should be inaccessible to the service.";
           default = [ "/home" "/root" ];
         };
-        noExecPaths = mkOption {
-          type = listOf str;
-          description =
-            "A list of paths where the service will not be allowed to run executables.";
-          default = [ "/home" "/root" "/tmp" "/var" ];
-        };
+        # noExecPaths = mkOption {
+        #   type = listOf str;
+        #   description =
+        #     "A list of paths where the service will not be allowed to run executables.";
+        #   default = [ "/home" "/root" "/tmp" "/var" ];
+        # };
         readOnlyPaths = mkOption {
           type = listOf str;
           description =
@@ -390,11 +390,11 @@ let
         type = port;
         description = "External port on which to listen for traffic.";
       };
-      protocol = mkOption {
-        type = nullOr str;
+      protocols = mkOption {
+        type = listOf str;
         description =
-          "Protocol for which to forward ports. Default is tcp & udp.";
-        default = null;
+          "Protocols for which to forward ports. Default is tcp-only.";
+        default = [ "tcp" ];
       };
     };
   };
@@ -464,15 +464,22 @@ in {
     #     opts.external-port) cfg.internal-port-map);
     # };
 
-    services.xinetd = {
+    services.xinetd = mkIf ((length (attrNames cfg.internal-port-map)) > 0) {
       enable = true;
-      services = mapAttrsToList (name: opts: {
-        name = name;
+      services = let
+        svcs = mapAttrsToList (name: opts: opts // { name = name; })
+          cfg.internal-port-map;
+        svcs-protocols = concatMap
+          (svc: map (protocol: svc // { protocol = protocol; }) svc.protocols)
+          svcs;
+      in map (opts: {
+        name = opts.name;
         unlisted = true;
         port = opts.external-port;
         server = "${pkgs.coreutils}/bin/false";
         extraConfig = "redirect = localhost ${toString opts.internal-port}";
-      }) cfg.internal-port-map;
+        protocol = opts.protocol;
+      }) svcs-protocols;
     };
 
     systemd.timers = mapAttrs (name: opts: {
@@ -559,7 +566,8 @@ in {
         ReadWritePaths = opts.readWritePaths;
         ReadOnlyPaths = opts.readOnlyPaths;
         InaccessiblePaths = opts.inaccessiblePaths;
-        NoExecPaths = opts.noExecPaths;
+        # Apparently not supported yet?
+        # NoExecPaths = opts.noExecPaths;
         ExecPaths = opts.execPaths;
       };
     }) config.fudo.system.services;