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

with lib;

let

  cfg = config.krb5;

in

{
  ###### interface

  options = {

    krb5 = {

      enable = mkOption {
        default = false;
        description = "Whether to enable Kerberos V.";
      };

      defaultRealm = mkOption {
        default = "ATENA.MIT.EDU";
        description = "Default realm.";
      };

      domainRealm = mkOption {
        default = "atena.mit.edu";
        description = "Default domain realm.";
      };

      kdc = mkOption {
        default = "kerberos.mit.edu";
        description = "Key Distribution Center";
      };

      kerberosAdminServer = mkOption {
        default = "kerberos.mit.edu";
        description = "Kerberos Admin Server.";
      };

    };

  };

  ###### implementation

  config = mkIf config.krb5.enable {

    environment.systemPackages = [ pkgs.krb5Full ];

    environment.etc."krb5.conf".text =
      ''
        [libdefaults]
            default_realm = ${cfg.defaultRealm}
            encrypt = true

        # The following krb5.conf variables are only for MIT Kerberos.
            krb4_config = /etc/krb.conf
            krb4_realms = /etc/krb.realms
            kdc_timesync = 1
            ccache_type = 4
            forwardable = true
            proxiable = true

        # The following encryption type specification will be used by MIT Kerberos
        # if uncommented.  In general, the defaults in the MIT Kerberos code are
        # correct and overriding these specifications only serves to disable new
        # encryption types as they are added, creating interoperability problems.

        #   default_tgs_enctypes = aes256-cts arcfour-hmac-md5 des3-hmac-sha1 des-cbc-crc des-cbc-md5
        #   default_tkt_enctypes = aes256-cts arcfour-hmac-md5 des3-hmac-sha1 des-cbc-crc des-cbc-md5
        #   permitted_enctypes = aes256-cts arcfour-hmac-md5 des3-hmac-sha1 des-cbc-crc des-cbc-md5

        # The following libdefaults parameters are only for Heimdal Kerberos.
            v4_instance_resolve = false
            v4_name_convert = {
                host = {
                    rcmd = host
                    ftp = ftp
                }
                plain = {
                    something = something-else
                }
            }
            fcc-mit-ticketflags = true

        [realms]
            ${cfg.defaultRealm} = {
                kdc = ${cfg.kdc}
                admin_server = ${cfg.kerberosAdminServer}
                #kpasswd_server = ${cfg.kerberosAdminServer}
            }
            ATHENA.MIT.EDU = {
                kdc = kerberos.mit.edu:88
                kdc = kerberos-1.mit.edu:88
                kdc = kerberos-2.mit.edu:88
                admin_server = kerberos.mit.edu
                default_domain = mit.edu
            }
            MEDIA-LAB.MIT.EDU = {
                kdc = kerberos.media.mit.edu
                admin_server = kerberos.media.mit.edu
            }
            ZONE.MIT.EDU = {
                kdc = casio.mit.edu
                kdc = seiko.mit.edu
                admin_server = casio.mit.edu
            }
            MOOF.MIT.EDU = {
                kdc = three-headed-dogcow.mit.edu:88
                kdc = three-headed-dogcow-1.mit.edu:88
                admin_server = three-headed-dogcow.mit.edu
            }
            CSAIL.MIT.EDU = {
                kdc = kerberos-1.csail.mit.edu
                kdc = kerberos-2.csail.mit.edu
                admin_server = kerberos.csail.mit.edu
                default_domain = csail.mit.edu
                krb524_server = krb524.csail.mit.edu
            }
            IHTFP.ORG = {
                kdc = kerberos.ihtfp.org
                admin_server = kerberos.ihtfp.org
            }
            GNU.ORG = {
                kdc = kerberos.gnu.org
                kdc = kerberos-2.gnu.org
                kdc = kerberos-3.gnu.org
                admin_server = kerberos.gnu.org
            }
            1TS.ORG = {
                kdc = kerberos.1ts.org
                admin_server = kerberos.1ts.org
            }
            GRATUITOUS.ORG = {
                kdc = kerberos.gratuitous.org
                admin_server = kerberos.gratuitous.org
            }
            DOOMCOM.ORG = {
                kdc = kerberos.doomcom.org
                admin_server = kerberos.doomcom.org
            }
            ANDREW.CMU.EDU = {
                kdc = vice28.fs.andrew.cmu.edu
                kdc = vice2.fs.andrew.cmu.edu
                kdc = vice11.fs.andrew.cmu.edu
                kdc = vice12.fs.andrew.cmu.edu
                admin_server = vice28.fs.andrew.cmu.edu
                default_domain = andrew.cmu.edu
            }
            CS.CMU.EDU = {
                kdc = kerberos.cs.cmu.edu
                kdc = kerberos-2.srv.cs.cmu.edu
                admin_server = kerberos.cs.cmu.edu
            }
            DEMENTIA.ORG = {
                kdc = kerberos.dementia.org
                kdc = kerberos2.dementia.org
                admin_server = kerberos.dementia.org
            }
            stanford.edu = {
                kdc = krb5auth1.stanford.edu
                kdc = krb5auth2.stanford.edu
                kdc = krb5auth3.stanford.edu
                admin_server = krb5-admin.stanford.edu
                default_domain = stanford.edu
            }

        [domain_realm]
            .${cfg.domainRealm} = ${cfg.defaultRealm}
            ${cfg.domainRealm} = ${cfg.defaultRealm}
            .mit.edu = ATHENA.MIT.EDU
            mit.edu = ATHENA.MIT.EDU
            .media.mit.edu = MEDIA-LAB.MIT.EDU
            media.mit.edu = MEDIA-LAB.MIT.EDU
            .csail.mit.edu = CSAIL.MIT.EDU
            csail.mit.edu = CSAIL.MIT.EDU
            .whoi.edu = ATHENA.MIT.EDU
            whoi.edu = ATHENA.MIT.EDU
            .stanford.edu = stanford.edu

        [logging]
            kdc = SYSLOG:INFO:DAEMON
            admin_server = SYSLOG:INFO:DAEMON
            default = SYSLOG:INFO:DAEMON
            krb4_convert = true
            krb4_get_tickets = false

        [appdefaults]
            pam = {
                debug = false
                ticket_lifetime = 36000
                renew_lifetime = 36000
                max_timeout = 30
                timeout_shift = 2
                initial_timeout = 1
            }
      '';

  };

}