.\"	$NetBSD: kdc.8,v 1.5.22.1 2023/08/11 13:39:55 martin Exp $
.\"
.\" Copyright (c) 2003 - 2004 Kungliga Tekniska Högskolan
.\" (Royal Institute of Technology, Stockholm, Sweden).
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\"
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\"
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" 3. Neither the name of the Institute nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" Id
.\"
.Dd August 24, 2006
.Dt KDC 8
.Os
.Sh NAME
.Nm kdc
.Nd Kerberos 5 server
.Sh SYNOPSIS
.Nm
.Bk -words
.Oo Fl c Ar file \*(Ba Xo
.Fl Fl config-file= Ns Ar file
.Xc
.Oc
.Op Fl p | Fl Fl no-require-preauth
.Op Fl Fl max-request= Ns Ar size
.Op Fl H | Fl Fl enable-http
.Oo Fl r Ar string \*(Ba Xo
.Fl Fl v4-realm= Ns Ar string
.Xc
.Oc
.Oo Fl P Ar portspec \*(Ba Xo
.Fl Fl ports= Ns Ar portspec
.Xc
.Oc
.Op Fl Fl detach
.Op Fl Fl disable-des
.Op Fl Fl addresses= Ns Ar list of addresses
.Ek
.Sh DESCRIPTION
.Nm
serves requests for tickets.
When it starts, it first checks the flags passed, any options that are
not specified with a command line flag are taken from a config file,
or from a default compiled-in value.
.Pp
Options supported:
.Bl -tag -width Ds
.It Fl c Ar file , Fl Fl config-file= Ns Ar file
Specifies the location of the config file, the default is
.Pa /var/heimdal/kdc.conf .
This is the only value that can't be specified in the config file.
.It Fl p , Fl Fl no-require-preauth
Turn off the requirement for pre-autentication in the initial AS-REQ
for all principals.
The use of pre-authentication makes it more difficult to do offline
password attacks.
You might want to turn it off if you have clients
that don't support pre-authentication.
Since the version 4 protocol doesn't support any pre-authentication,
serving version 4 clients is just about the same as not requiring
pre-athentication.
The default is to require pre-authentication.
Adding the require-preauth per principal is a more flexible way of
handling this.
.It Fl Fl max-request= Ns Ar size
Gives an upper limit on the size of the requests that the kdc is
willing to handle.
.It Fl H , Fl Fl enable-http
Makes the kdc listen on port 80 and handle requests encapsulated in HTTP.
.It Fl r Ar string , Fl Fl v4-realm= Ns Ar string
What realm this server should act as when dealing with version 4
requests.
The database can contain any number of realms, but since the version 4
protocol doesn't contain a realm for the server, it must be explicitly
specified.
The default is whatever is returned by
.Fn krb_get_lrealm .
This option is only available if the KDC has been compiled with version
4 support.
.It Fl P Ar portspec , Fl Fl ports= Ns Ar portspec
Specifies the set of ports the KDC should listen on.
It is given as a
white-space separated list of services or port numbers.
.It Fl Fl addresses= Ns Ar list of addresses
The list of addresses to listen for requests on.
By default, the kdc will listen on all the locally configured
addresses.
If only a subset is desired, or the automatic detection fails, this
option might be used.
.It Fl Fl detach
detach from pty and run as a daemon.
.It Fl Fl disable-des
disable all des encryption types, makes the kdc not use them.
.El
.Pp
All activities are logged to one or more destinations, see
.Xr krb5.conf 5 ,
and
.Xr krb5_openlog 3 .
The entity used for logging is
.Nm kdc .
.Sh CONFIGURATION FILE
The configuration file has the same syntax as
.Xr krb5.conf 5 ,
but will be read before
.Pa /etc/krb5.conf ,
so it may override settings found there.
Options specific to the KDC only are found in the
.Dq [kdc]
section.
All the command-line options can preferably be added in the
configuration file.
The only difference is the pre-authentication flag, which has to be
specified as:
.Pp
.Dl require-preauth = no
.Pp
(in fact you can specify the option as
.Fl Fl require-preauth=no ) .
.Pp
And there are some configuration options which do not have
command-line equivalents:
.Bl -tag -width "xxx" -offset indent
.It Li enable-digest = Va boolean
turn on support for digest processing in the KDC.
The default is FALSE.
.It Li check-ticket-addresses = Va boolean
Check the addresses in the ticket when processing TGS requests.
The default is TRUE.
.It Li allow-null-ticket-addresses = Va boolean
Permit tickets with no addresses.
This option is only relevant when check-ticket-addresses is TRUE.
.It Li allow-anonymous = Va boolean
Permit anonymous tickets with no addresses.
.It Li historical_anon_realm = Va boolean
Enables pre-7.0 non-RFC-comformant KDC behavior.
With this option set to
.Li true
the client realm in anonymous pkinit AS replies will be the requested realm,
rather than the RFC-conformant
.Li WELLKNOWN:ANONYMOUS
realm.
This can have a security impact on servers that expect to grant access to
anonymous-but-authenticated to the KDC users of the realm in question:
they would also grant access to unauthenticated anonymous users.
As such, it is not recommend to set this option to
.Li true.
.It Li max-kdc-datagram-reply-length = Va number
Maximum packet size the UDP rely that the KDC will transmit, instead
the KDC sends back a reply telling the client to use TCP instead.
.It Li transited-policy = Li always-check \*(Ba \
Li allow-per-principal | Li always-honour-request
This controls how KDC requests with the
.Li disable-transited-check
flag are handled. It can be one of:
.Bl -tag -width "xxx" -offset indent
.It Li always-check
Always check transited encoding, this is the default.
.It Li allow-per-principal
Currently this is identical to
.Li always-check .
In a future release, it will be possible to mark a principal as able
to handle unchecked requests.
.It Li always-honour-request
Always do what the client asked.
In a future release, it will be possible to force a check per
principal.
.El
.It encode_as_rep_as_tgs_rep = Va boolean
Encode AS-Rep as TGS-Rep to be bug-compatible with old DCE code.
The Heimdal clients allow both.
.It kdc_warn_pwexpire = Va time
How long before password/principal expiration the KDC should start
sending out warning messages.
.El
.Pp
The configuration file is only read when the
.Nm
is started.
If changes made to the configuration file are to take effect, the
.Nm
needs to be restarted.
.Pp
An example of a config file:
.Bd -literal -offset indent
[kdc]
	require-preauth = no
	v4-realm = FOO.SE
.Ed
.Sh BUGS
If the machine running the KDC has new addresses added to it, the KDC
will have to be restarted to listen to them.
The reason it doesn't just listen to wildcarded (like INADDR_ANY)
addresses, is that the replies has to come from the same address they
were sent to, and most OS:es doesn't pass this information to the
application.
If your normal mode of operation require that you add and remove
addresses, the best option is probably to listen to a wildcarded TCP
socket, and make sure your clients use TCP to connect.
For instance, this will listen to IPv4 TCP port 88 only:
.Bd -literal -offset indent
kdc --addresses=0.0.0.0 --ports="88/tcp"
.Ed
.Pp
There should be a way to specify protocol, port, and address triplets,
not just addresses and protocol, port tuples.
.Sh SEE ALSO
.Xr kinit 1 ,
.Xr krb5.conf 5