2 * Copyright (c) 1997 - 2005 Kungliga Tekniska Högskolan
3 * (Royal Institute of Technology, Stockholm, Sweden).
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34 #include "krb5_locl.h"
37 /* To automagically find the correct realm of a host (without
38 * [domain_realm] in krb5.conf) add a text record for your domain with
39 * the name of your realm, like this:
41 * _kerberos IN TXT "FOO.SE"
43 * The search is recursive, so you can add entries for specific
44 * hosts. To find the realm of host a.b.c, it first tries
45 * _kerberos.a.b.c, then _kerberos.b.c and so on.
47 * This method is described in draft-ietf-cat-krb-dns-locate-03.txt.
52 copy_txt_to_realms(krb5_context context,
54 struct rk_resource_record *head,
57 struct rk_resource_record *rr;
60 for(n = 0, rr = head; rr; rr = rr->next)
61 if (rr->type == rk_ns_t_txt)
67 *realms = malloc ((n + 1) * sizeof(krb5_realm));
69 return krb5_enomem(context);;
71 for (i = 0; i < n + 1; ++i)
74 for (i = 0, rr = head; rr; rr = rr->next) {
75 if (rr->type == rk_ns_t_txt) {
79 /* Check for a gTLD controlled interruption */
80 if (strcmp("Your DNS configuration needs immediate "
81 "attention see https://icann.org/namecollision",
84 tmp = strdup(rr->u.txt);
87 for (i = 0; i < n; ++i)
92 "Realm lookup failed: "
93 "Domain '%s' needs immediate attention "
94 "see https://icann.org/namecollision",
96 return KRB5_KDC_UNREACH;
98 return krb5_enomem(context);;
108 dns_find_realm(krb5_context context,
112 static const char *default_labels[] = { "_kerberos", NULL };
113 char dom[MAXHOSTNAMELEN];
114 struct rk_dns_reply *r;
116 char **config_labels;
119 config_labels = krb5_config_get_strings(context, NULL, "libdefaults",
120 "dns_lookup_realm_labels", NULL);
121 if(config_labels != NULL)
122 labels = (const char **)config_labels;
124 labels = default_labels;
127 for (i = 0; labels[i] != NULL; i++) {
128 ret = snprintf(dom, sizeof(dom), "%s.%s.", labels[i], domain);
129 if(ret < 0 || (size_t)ret >= sizeof(dom)) {
130 ret = krb5_enomem(context);
133 r = rk_dns_lookup(dom, "TXT");
135 ret = copy_txt_to_realms(context, domain, r->head, realms);
141 krb5_set_error_message(context, KRB5_KDC_UNREACH,
142 "Realm lookup failed: "
143 "No DNS TXT record for %s",
145 ret = KRB5_KDC_UNREACH;
148 krb5_config_free_strings(config_labels);
153 * Try to figure out what realms host in `domain' belong to from the
154 * configuration file.
158 config_find_realm(krb5_context context,
162 char **tmp = krb5_config_get_strings (context, NULL,
174 * This function assumes that `host' is a FQDN (and doesn't handle the
175 * special case of host == NULL either).
176 * Try to find mapping in the config file or DNS and it that fails,
177 * fall back to guessing
180 KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
181 _krb5_get_host_realm_int(krb5_context context,
183 krb5_boolean use_dns,
188 krb5_boolean dns_locate_enable;
189 krb5_error_code ret = 0;
191 /* Strip off any trailing ":port" suffix. */
192 port = strchr(host, ':');
194 host = strndup(host, port - host);
196 return krb5_enomem(context);
199 dns_locate_enable = krb5_config_get_bool_default(context, NULL, TRUE,
200 "libdefaults", "dns_lookup_realm", NULL);
201 for (p = host; p != NULL; p = strchr (p + 1, '.')) {
202 if (config_find_realm(context, p, realms) == 0) {
203 if (strcasecmp(*realms[0], "dns_locate") != 0)
205 krb5_free_host_realm(context, *realms);
209 for (q = host; q != NULL; q = strchr(q + 1, '.'))
210 if (dns_find_realm(context, q, realms) == 0)
214 } else if (use_dns && dns_locate_enable) {
215 if (dns_find_realm(context, p, realms) == 0)
221 * If 'p' is NULL, we did not find an explicit realm mapping in either the
222 * configuration file or DNS. Try the hostname suffix as a last resort.
224 * XXX: If we implement a KDC-specific variant of this function just for
225 * referrals, we could check whether we have a cross-realm TGT for the
226 * realm in question, and if not try the parent (loop again).
229 p = strchr(host, '.');
232 *realms = malloc(2 * sizeof(krb5_realm));
233 if (*realms != NULL &&
234 ((*realms)[0] = strdup(p)) != NULL) {
235 strupr((*realms)[0]);
239 ret = krb5_enomem(context);
242 krb5_set_error_message(context, KRB5_ERR_HOST_REALM_UNKNOWN,
243 N_("unable to find realm of host %s", ""),
245 ret = KRB5_ERR_HOST_REALM_UNKNOWN;
249 /* If 'port' is not NULL, we have a copy of 'host' to free. */
256 * Return the realm(s) of `host' as a NULL-terminated list in
257 * `realms'. Free `realms' with krb5_free_host_realm().
260 KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
261 krb5_get_host_realm(krb5_context context,
262 const char *targethost,
265 const char *host = targethost;
266 char hostname[MAXHOSTNAMELEN];
271 if (gethostname (hostname, sizeof(hostname))) {
279 * If our local hostname is without components, don't even try to dns.
282 use_dns = (strchr(host, '.') != NULL);
284 ret = _krb5_get_host_realm_int (context, host, use_dns, realms);
285 if (ret && targethost != NULL) {
287 * If there was no realm mapping for the host (and we wasn't
288 * looking for ourself), guess at the local realm, maybe our
289 * KDC knows better then we do and we get a referral back.
291 ret = krb5_get_default_realms(context, realms);
293 krb5_set_error_message(context, KRB5_ERR_HOST_REALM_UNKNOWN,
294 N_("Unable to find realm of host %s", ""),
296 return KRB5_ERR_HOST_REALM_UNKNOWN;