317 lines
9.6 KiB
C
317 lines
9.6 KiB
C
/*
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* Copyright (c) 1997 - 2005 Kungliga Tekniska Högskolan
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* (Royal Institute of Technology, Stockholm, Sweden).
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* 3. Neither the name of the Institute nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include "krb5_locl.h"
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#include <resolve.h>
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/* To automagically find the correct realm of a host (without
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* [domain_realm] in krb5.conf) add a text record for your domain with
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* the name of your realm, like this:
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*
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* _kerberos IN TXT "FOO.SE"
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*
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* The search is recursive, so you can add entries for specific
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* hosts. To find the realm of host a.b.c, it first tries
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* _kerberos.a.b.c, then _kerberos.b.c and so on.
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*
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* This method is described in draft-ietf-cat-krb-dns-locate-03.txt.
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*
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*/
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static int
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copy_txt_to_realms(krb5_context context,
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const char *domain,
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struct rk_resource_record *head,
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krb5_realm **realms)
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{
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struct rk_resource_record *rr;
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unsigned int n, i;
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for(n = 0, rr = head; rr; rr = rr->next)
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if (rr->type == rk_ns_t_txt)
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++n;
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if (n == 0)
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return -1;
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*realms = malloc ((n + 1) * sizeof(krb5_realm));
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if (*realms == NULL)
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return krb5_enomem(context);;
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for (i = 0; i < n + 1; ++i)
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(*realms)[i] = NULL;
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for (i = 0, rr = head; rr; rr = rr->next) {
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if (rr->type == rk_ns_t_txt) {
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char *tmp = NULL;
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int invalid_tld = 1;
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/* Check for a gTLD controlled interruption */
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if (strcmp("Your DNS configuration needs immediate "
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"attention see https://icann.org/namecollision",
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rr->u.txt) != 0) {
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invalid_tld = 0;
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tmp = strdup(rr->u.txt);
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}
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if (tmp == NULL) {
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for (i = 0; i < n; ++i)
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free ((*realms)[i]);
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free (*realms);
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if (invalid_tld) {
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krb5_warnx(context,
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"Realm lookup failed: "
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"Domain '%s' needs immediate attention "
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"see https://icann.org/namecollision",
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domain);
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return KRB5_KDC_UNREACH;
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}
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return krb5_enomem(context);;
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}
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(*realms)[i] = tmp;
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++i;
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}
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}
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return 0;
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}
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static int
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dns_find_realm(krb5_context context,
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const char *domain,
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krb5_realm **realms)
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{
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static const char *const default_labels[] = { "_kerberos", NULL };
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char dom[MAXHOSTNAMELEN];
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struct rk_dns_reply *r;
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const char *const *labels;
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char **config_labels;
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int i, ret = 0;
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if (krb5_config_get_bool(context, NULL, "libdefaults", "block_dns",
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NULL)) {
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ret = KRB5_KDC_UNREACH;
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krb5_set_error_message(context, ret,
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"Realm lookup failed: DNS blocked");
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return ret;
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}
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config_labels = krb5_config_get_strings(context, NULL, "libdefaults",
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"dns_lookup_realm_labels", NULL);
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if(config_labels != NULL)
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labels = (const char *const *)config_labels;
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else
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labels = default_labels;
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if(*domain == '.')
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domain++;
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for (i = 0; labels[i] != NULL; i++) {
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ret = snprintf(dom, sizeof(dom), "%s.%s.", labels[i], domain);
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if(ret < 0 || (size_t)ret >= sizeof(dom)) {
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ret = krb5_enomem(context);
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goto out;
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}
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r = rk_dns_lookup(dom, "TXT");
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if(r != NULL) {
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ret = copy_txt_to_realms(context, domain, r->head, realms);
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rk_dns_free_data(r);
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if(ret == 0)
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goto out;
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}
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}
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krb5_set_error_message(context, KRB5_KDC_UNREACH,
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"Realm lookup failed: "
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"No DNS TXT record for %s",
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domain);
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ret = KRB5_KDC_UNREACH;
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out:
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if (config_labels)
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krb5_config_free_strings(config_labels);
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return ret;
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}
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/*
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* Try to figure out what realms host in `domain' belong to from the
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* configuration file.
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*/
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static int
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config_find_realm(krb5_context context,
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const char *domain,
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krb5_realm **realms)
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{
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char **tmp = krb5_config_get_strings (context, NULL,
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"domain_realm",
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domain,
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NULL);
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if (tmp == NULL)
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return -1;
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*realms = tmp;
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return 0;
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}
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/*
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* This function assumes that `host' is a FQDN (and doesn't handle the
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* special case of host == NULL either).
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* Try to find mapping in the config file or DNS and it that fails,
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* fall back to guessing
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*/
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KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
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_krb5_get_host_realm_int(krb5_context context,
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const char *host,
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krb5_boolean use_dns,
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krb5_realm **realms)
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{
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const char *p, *q;
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const char *port;
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char *freeme = NULL;
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krb5_boolean dns_locate_enable;
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krb5_error_code ret = 0;
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/* Strip off any trailing ":port" suffix. */
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port = strchr(host, ':');
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if (port != NULL && port != host && port[1] != '\0') {
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host = freeme = strndup(host, port - host);
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if (host == NULL)
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return krb5_enomem(context);
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}
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dns_locate_enable = krb5_config_get_bool_default(context, NULL, TRUE,
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"libdefaults", "dns_lookup_realm", NULL);
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for (p = host; p != NULL && p[0] != '\0'; p = strchr (p + 1, '.')) {
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if (config_find_realm(context, p, realms) == 0) {
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if (strcasecmp(*realms[0], "dns_locate") != 0)
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break;
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krb5_free_host_realm(context, *realms);
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*realms = NULL;
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if (!use_dns)
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continue;
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for (q = host; q != NULL; q = strchr(q + 1, '.'))
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if (dns_find_realm(context, q, realms) == 0)
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break;
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if (q)
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break;
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} else if (use_dns && dns_locate_enable) {
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if (dns_find_realm(context, p, realms) == 0)
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break;
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}
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}
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/*
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* If 'p' is NULL, we did not find an explicit realm mapping in either the
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* configuration file or DNS. Try the hostname suffix -upcased- as a realm
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* as a last resort.
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*
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* NOTE: If we implement a KDC-specific variant of this function just for
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* referrals, we could check whether we have a cross-realm TGT for the
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* realm in question, and if not try the parent (loop again). Such a
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* variant would have to have access to the HDB, naturally.
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*
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* We should start by adding an argument to this function that
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* indicates whether this fallback here is desired (the KDC wouldn't
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* desire it). Then when the KDC gets KRB5_ERR_HOST_REALM_UNKNOWN
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* from this function, the KDC would search the HDB for cross-realm
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* krbtgt principals that denote a hierarchical path to a realm that
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* matches the host's domain suffix (or a suffix of it...).
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*/
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if (p == NULL) {
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p = strchr(host, '.');
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if (p != NULL) {
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p++;
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*realms = malloc(2 * sizeof(krb5_realm));
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if (*realms != NULL &&
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((*realms)[0] = strdup(p)) != NULL) {
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strupr((*realms)[0]);
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(*realms)[1] = NULL;
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} else {
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free(*realms);
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ret = krb5_enomem(context);
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}
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} else {
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krb5_set_error_message(context, KRB5_ERR_HOST_REALM_UNKNOWN,
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N_("unable to find realm of host %s", ""),
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host);
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ret = KRB5_ERR_HOST_REALM_UNKNOWN;
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}
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}
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free(freeme);
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return ret;
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}
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/*
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* Return the realm(s) of `host' as a NULL-terminated list in
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* `realms'. Free `realms' with krb5_free_host_realm().
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*/
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KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
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krb5_get_host_realm(krb5_context context,
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const char *targethost,
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krb5_realm **realms)
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{
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const char *host = targethost;
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char hostname[MAXHOSTNAMELEN];
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krb5_error_code ret;
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int use_dns;
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if (host == NULL) {
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if (gethostname (hostname, sizeof(hostname))) {
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*realms = NULL;
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return errno;
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}
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host = hostname;
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}
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/*
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* If our local hostname is without components, don't even try to dns.
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*/
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use_dns = (strchr(host, '.') != NULL);
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ret = _krb5_get_host_realm_int (context, host, use_dns, realms);
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if (ret && targethost != NULL) {
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/*
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* If there was no realm mapping for the host (and we wasn't
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* looking for ourself), guess at the local realm, maybe our
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* KDC knows better then we do and we get a referral back.
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*/
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ret = krb5_get_default_realms(context, realms);
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if (ret) {
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krb5_set_error_message(context, KRB5_ERR_HOST_REALM_UNKNOWN,
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N_("Unable to find realm of host %s", ""),
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host);
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return KRB5_ERR_HOST_REALM_UNKNOWN;
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}
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}
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return ret;
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}
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