/*
* Copyright (c) 1997 - 2005 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.
*/
#include "krb5_locl.h"
#include <resolve.h>
/* To automagically find the correct realm of a host (without
* [domain_realm] in krb5.conf) add a text record for your domain with
* the name of your realm, like this:
*
* _kerberos IN TXT "FOO.SE"
*
* The search is recursive, so you can add entries for specific
* hosts. To find the realm of host a.b.c, it first tries
* _kerberos.a.b.c, then _kerberos.b.c and so on.
*
* This method is described in draft-ietf-cat-krb-dns-locate-03.txt.
*
*/
static int
copy_txt_to_realms(krb5_context context,
const char *domain,
struct rk_resource_record *head,
krb5_realm **realms)
{
struct rk_resource_record *rr;
unsigned int n, i;
for(n = 0, rr = head; rr; rr = rr->next)
if (rr->type == rk_ns_t_txt)
++n;
if (n == 0)
return -1;
*realms = malloc ((n + 1) * sizeof(krb5_realm));
if (*realms == NULL)
return krb5_enomem(context);;
for (i = 0; i < n + 1; ++i)
(*realms)[i] = NULL;
for (i = 0, rr = head; rr; rr = rr->next) {
if (rr->type == rk_ns_t_txt) {
char *tmp = NULL;
int invalid_tld = 1;
/* Check for a gTLD controlled interruption */
if (strcmp("Your DNS configuration needs immediate "
"attention see https://icann.org/namecollision",
rr->u.txt) != 0) {
invalid_tld = 0;
tmp = strdup(rr->u.txt);
}
if (tmp == NULL) {
for (i = 0; i < n; ++i)
free ((*realms)[i]);
free (*realms);
if (invalid_tld) {
krb5_warnx(context,
"Realm lookup failed: "
"Domain '%s' needs immediate attention "
"see https://icann.org/namecollision",
domain);
return KRB5_KDC_UNREACH;
}
return krb5_enomem(context);;
}
(*realms)[i] = tmp;
++i;
}
}
return 0;
}
static int
dns_find_realm(krb5_context context,
const char *domain,
krb5_realm **realms)
{
static const char *const default_labels[] = { "_kerberos", NULL };
char dom[MAXHOSTNAMELEN];
struct rk_dns_reply *r;
const char *const *labels;
char **config_labels;
int i, ret = 0;
if (krb5_config_get_bool(context, NULL, "libdefaults", "block_dns",
NULL)) {
ret = KRB5_KDC_UNREACH;
krb5_set_error_message(context, ret,
"Realm lookup failed: DNS blocked");
return ret;
}
config_labels = krb5_config_get_strings(context, NULL, "libdefaults",
"dns_lookup_realm_labels", NULL);
if(config_labels != NULL)
labels = (const char *const *)config_labels;
else
labels = default_labels;
if(*domain == '.')
domain++;
for (i = 0; labels[i] != NULL; i++) {
ret = snprintf(dom, sizeof(dom), "%s.%s.", labels[i], domain);
if(ret < 0 || (size_t)ret >= sizeof(dom)) {
ret = krb5_enomem(context);
goto out;
}
r = rk_dns_lookup(dom, "TXT");
if(r != NULL) {
ret = copy_txt_to_realms(context, domain, r->head, realms);
rk_dns_free_data(r);
if(ret == 0)
goto out;
}
}
krb5_set_error_message(context, KRB5_KDC_UNREACH,
"Realm lookup failed: "
"No DNS TXT record for %s",
domain);
ret = KRB5_KDC_UNREACH;
out:
if (config_labels)
krb5_config_free_strings(config_labels);
return ret;
}
/*
* Try to figure out what realms host in `domain' belong to from the
* configuration file.
*/
static int
config_find_realm(krb5_context context,
const char *domain,
krb5_realm **realms)
{
char **tmp = krb5_config_get_strings (context, NULL,
"domain_realm",
domain,
NULL);
if (tmp == NULL)
return -1;
*realms = tmp;
return 0;
}
/*
* This function assumes that `host' is a FQDN (and doesn't handle the
* special case of host == NULL either).
* Try to find mapping in the config file or DNS and it that fails,
* fall back to guessing
*/
KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
_krb5_get_host_realm_int(krb5_context context,
const char *host,
krb5_boolean use_dns,
krb5_realm **realms)
{
const char *p, *q;
const char *port;
char *freeme = NULL;
krb5_boolean dns_locate_enable;
krb5_error_code ret = 0;
/* Strip off any trailing ":port" suffix. */
port = strchr(host, ':');
if (port != NULL && port != host && port[1] != '\0') {
host = freeme = strndup(host, port - host);
if (host == NULL)
return krb5_enomem(context);
}
dns_locate_enable = krb5_config_get_bool_default(context, NULL, TRUE,
"libdefaults", "dns_lookup_realm", NULL);
for (p = host; p != NULL && p[0] != '\0'; p = strchr (p + 1, '.')) {
if (config_find_realm(context, p, realms) == 0) {
if (strcasecmp(*realms[0], "dns_locate") != 0)
break;
krb5_free_host_realm(context, *realms);
*realms = NULL;
if (!use_dns)
continue;
for (q = host; q != NULL; q = strchr(q + 1, '.'))
if (dns_find_realm(context, q, realms) == 0)
break;
if (q)
break;
} else if (use_dns && dns_locate_enable) {
if (dns_find_realm(context, p, realms) == 0)
break;
}
}
/*
* If 'p' is NULL, we did not find an explicit realm mapping in either the
* configuration file or DNS. Try the hostname suffix -upcased- as a realm
* as a last resort.
*
* NOTE: If we implement a KDC-specific variant of this function just for
* referrals, we could check whether we have a cross-realm TGT for the
* realm in question, and if not try the parent (loop again). Such a
* variant would have to have access to the HDB, naturally.
*
* We should start by adding an argument to this function that
* indicates whether this fallback here is desired (the KDC wouldn't
* desire it). Then when the KDC gets KRB5_ERR_HOST_REALM_UNKNOWN
* from this function, the KDC would search the HDB for cross-realm
* krbtgt principals that denote a hierarchical path to a realm that
* matches the host's domain suffix (or a suffix of it...).
*/
if (p == NULL) {
p = strchr(host, '.');
if (p != NULL) {
p++;
*realms = malloc(2 * sizeof(krb5_realm));
if (*realms != NULL &&
((*realms)[0] = strdup(p)) != NULL) {
strupr((*realms)[0]);
(*realms)[1] = NULL;
} else {
free(*realms);
ret = krb5_enomem(context);
}
} else {
krb5_set_error_message(context, KRB5_ERR_HOST_REALM_UNKNOWN,
N_("unable to find realm of host %s", ""),
host);
ret = KRB5_ERR_HOST_REALM_UNKNOWN;
}
}
free(freeme);
return ret;
}
/*
* Return the realm(s) of `host' as a NULL-terminated list in
* `realms'. Free `realms' with krb5_free_host_realm().
*/
KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
krb5_get_host_realm(krb5_context context,
const char *targethost,
krb5_realm **realms)
{
const char *host = targethost;
char hostname[MAXHOSTNAMELEN];
krb5_error_code ret;
int use_dns;
if (host == NULL) {
if (gethostname (hostname, sizeof(hostname))) {
*realms = NULL;
return errno;
}
host = hostname;
}
/*
* If our local hostname is without components, don't even try to dns.
*/
use_dns = (strchr(host, '.') != NULL);
ret = _krb5_get_host_realm_int (context, host, use_dns, realms);
if (ret && targethost != NULL) {
/*
* If there was no realm mapping for the host (and we wasn't
* looking for ourself), guess at the local realm, maybe our
* KDC knows better then we do and we get a referral back.
*/
ret = krb5_get_default_realms(context, realms);
if (ret) {
krb5_set_error_message(context, KRB5_ERR_HOST_REALM_UNKNOWN,
N_("Unable to find realm of host %s", ""),
host);
return KRB5_ERR_HOST_REALM_UNKNOWN;
}
}
return ret;
}