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/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/* lib/krb5/os/hostream_dns.c - dns hostrealm module */
/*
* Copyright (C) 1990,1991,2002,2008,2009,2013 by the Massachusetts Institute
* of Technology. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* * 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.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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
* COPYRIGHT HOLDER 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.
*/
/*
* This file implements the built-in dns module for the hostrealm interface,
* which uses TXT records in the DNS to determine the default realm or the
* fallback realm of a host.
*/
#include "k5-int.h"
#include "os-proto.h"
#include <krb5/hostrealm_plugin.h>
#ifdef KRB5_DNS_LOOKUP
#include "dnsglue.h"
/* Try a _kerberos TXT lookup for fqdn and each parent domain; return the
* resulting realm (caller must free) or NULL. */
static char *
txt_lookup(krb5_context context, const char *fqdn)
{
char *realm;
while (fqdn != NULL && *fqdn != '\0') {
if (k5_try_realm_txt_rr(context, "_kerberos", fqdn, &realm) == 0)
return realm;
fqdn = strchr(fqdn, '.');
if (fqdn != NULL)
fqdn++;
}
return NULL;
}
static krb5_error_code
dns_fallback_realm(krb5_context context, krb5_hostrealm_moddata data,
const char *host, char ***realms_out)
{
krb5_error_code ret;
char *realm;
*realms_out = NULL;
if (!_krb5_use_dns_realm(context) || k5_is_numeric_address(host))
return KRB5_PLUGIN_NO_HANDLE;
/* Try a TXT record lookup for each component of host. */
realm = txt_lookup(context, host);
if (realm == NULL)
return KRB5_PLUGIN_NO_HANDLE;
ret = k5_make_realmlist(realm, realms_out);
free(realm);
return ret;
}
static krb5_error_code
dns_default_realm(krb5_context context, krb5_hostrealm_moddata data,
char ***realms_out)
{
krb5_error_code ret;
char localhost[MAXDNAME + 1], *realm;
*realms_out = NULL;
if (!_krb5_use_dns_realm(context))
return KRB5_PLUGIN_NO_HANDLE;
ret = krb5int_get_fq_local_hostname(localhost, sizeof(localhost));
if (ret)
return ret;
/* If we don't find a TXT record for localhost or any parent, look for a
* global record. */
realm = txt_lookup(context, localhost);
if (realm == NULL)
(void)k5_try_realm_txt_rr(context, "_kerberos", NULL, &realm);
if (realm == NULL)
return KRB5_PLUGIN_NO_HANDLE;
ret = k5_make_realmlist(realm, realms_out);
free(realm);
return ret;
}
static void
dns_free_realmlist(krb5_context context, krb5_hostrealm_moddata data,
char **list)
{
krb5_free_host_realm(context, list);
}
krb5_error_code
hostrealm_dns_initvt(krb5_context context, int maj_ver, int min_ver,
krb5_plugin_vtable vtable)
{
krb5_hostrealm_vtable vt = (krb5_hostrealm_vtable)vtable;
vt->name = "dns";
vt->fallback_realm = dns_fallback_realm;
vt->default_realm = dns_default_realm;
vt->free_list = dns_free_realmlist;
return 0;
}
#else /* KRB5_DNS_LOOKUP */
krb5_error_code
hostrealm_dns_initvt(krb5_context context, int maj_ver, int min_ver,
krb5_plugin_vtable vtable)
{
krb5_hostrealm_vtable vt = (krb5_hostrealm_vtable)vtable;
vt->name = "dns";
return 0;
}
#endif /* KRB5_DNS_LOOKUP */
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