.\" Copyright 1989 by the Massachusetts Institute of Technology.
.\"
.\" For copying and distribution information,
.\" please see the file <mit-copyright.h>.
.\"
.\"	$OpenBSD: krb_realmofhost.3,v 1.2 1997/05/30 03:11:28 gene Exp $
.TH KRB_REALMOFHOST 3 "Kerberos Version 4.0" "MIT Project Athena"
.SH NAME
krb_realmofhost, krb_get_phost, krb_get_krbhst, krb_get_admhst,
krb_get_lrealm \- additional Kerberos utility routines
.SH SYNOPSIS
.nf
.nj
.ft B
#include <kerberosIV/krb.h>
#include <kerberosIV/des.h>
#include <kerberosIV/netinet/in.h>
.PP
.ft B
char *krb_realmofhost(host)
char *host;
.PP
.ft B
char *krb_get_phost(alias)
char *alias;
.PP
.ft B
krb_get_krbhst(host,realm,n)
char *host;
char *realm;
int n;
.PP
.ft B
krb_get_admhst(host,realm,n)
char *host;
char *realm;
int n;
.PP
.ft B
krb_get_lrealm(realm,n)
char *realm;
int n;
.fi
.ft R
.SH DESCRIPTION
.I krb_realmofhost
returns the Kerberos realm of the host
.IR host ,
as determined by the translation table
.IR /etc/krb.realms .
.I host
should be the fully-qualified domain-style primary host name of the host
in question.  In order to prevent certain security attacks, this routine
must either have 
.I a priori
knowledge of a host's realm, or obtain such information securely.
.PP
The format of the translation file is described by 
.IR krb.realms (5).
If
.I host
exactly matches a host_name line, the corresponding realm
is returned.
Otherwise, if the domain portion of
.I host
matches a domain_name line, the corresponding realm
is returned.
If
.I host
contains a domain, but no translation is found,
.IR host 's
domain is converted to upper-case and returned.
If 
.I host
contains no discernable domain, or an error occurs,
the local realm name, as supplied by 
.IR krb_get_lrealm (3),
is returned.
.PP
.I krb_get_phost
converts the hostname
.I alias
(which can be either an official name or an alias) into the instance
name to be used in obtaining Kerberos tickets for most services,
including the Berkeley rcmd suite (rlogin, rcp, rsh).
.br
The current convention is to return the first segment of the official
domain-style name after conversion to lower case.
.PP
.I krb_get_krbhst
fills in
.I host
with the hostname of the
.IR n th
host running a Kerberos key distribution center (KDC)
for realm
.IR realm ,
as specified in the configuration file (\fI/etc/krb.conf\fR).
The configuration file is described by 
.IR krb.conf (5).
If the host is successfully filled in, the routine
returns KSUCCESS.
If the file cannot be opened, and
.I n
equals 1, then the value of KRB_HOST as defined in
.I <krb.h>
is filled in, and KSUCCESS is returned.  If there are fewer than
.I n
hosts running a Kerberos KDC for the requested realm, or the
configuration file is malformed, the routine
returns KFAILURE.
.PP
.I krb_get_admhst
fills in
.I host
with the hostname of the
.IR n th
host running a Kerberos KDC database administration server
for realm
.IR realm ,
as specified in the configuration file (\fI/etc/krb.conf\fR).
If the file cannot be opened or is malformed, or there are fewer than
.I n
hosts running a Kerberos KDC database administration server,
the routine returns KFAILURE.
.PP
The character arrays used as return values for
.IR krb_get_krbhst ,
.IR krb_get_admhst ,
should be large enough to
hold any hostname (MAXHOSTNAMELEN from <sys/param.h>).
.PP
.I krb_get_lrealm
fills in
.I realm
with the
.IR n th
realm of the local host, as specified in the configuration file.
.I realm
should be at least REALM_SZ (from
.IR <krb.h>) characters long.
.PP
.SH SEE ALSO
kerberos(3), krb.conf(5), krb.realms(5)
.SH FILES
.TP 20n
/etc/krb.realms
translation file for host-to-realm mapping.
.TP
/etc/krb.conf
local realm-name and realm/server configuration file.
.SH BUGS
The current convention for instance names is too limited; the full
domain name should be used.
.PP
.I krb_get_lrealm
currently only supports 
.I n
= 1.  It should really consult the user's ticket cache to determine the
user's current realm, rather than consulting a file on the host.