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34 #include "krb5_locl.h"
37 RCSID("$Id: get_host_realm.c 18541 2006-10-17 19:28:36Z lha $");
39 /* To automagically find the correct realm of a host (without
40 * [domain_realm] in krb5.conf) add a text record for your domain with
41 * the name of your realm, like this:
43 * _kerberos IN TXT "FOO.SE"
45 * The search is recursive, so you can add entries for specific
46 * hosts. To find the realm of host a.b.c, it first tries
47 * _kerberos.a.b.c, then _kerberos.b.c and so on.
49 * This method is described in draft-ietf-cat-krb-dns-locate-03.txt.
54 copy_txt_to_realms (struct resource_record *head,
57 struct resource_record *rr;
60 for(n = 0, rr = head; rr; rr = rr->next)
61 if (rr->type == T_TXT)
67 *realms = malloc ((n + 1) * sizeof(krb5_realm));
71 for (i = 0; i < n + 1; ++i)
74 for (i = 0, rr = head; rr; rr = rr->next) {
75 if (rr->type == T_TXT) {
78 tmp = strdup(rr->u.txt);
80 for (i = 0; i < n; ++i)
93 dns_find_realm(krb5_context context,
97 static const char *default_labels[] = { "_kerberos", NULL };
98 char dom[MAXHOSTNAMELEN];
101 char **config_labels;
104 config_labels = krb5_config_get_strings(context, NULL, "libdefaults",
105 "dns_lookup_realm_labels", NULL);
106 if(config_labels != NULL)
107 labels = (const char **)config_labels;
109 labels = default_labels;
112 for (i = 0; labels[i] != NULL; i++) {
113 ret = snprintf(dom, sizeof(dom), "%s.%s.", labels[i], domain);
114 if(ret < 0 || ret >= sizeof(dom)) {
116 krb5_config_free_strings(config_labels);
119 r = dns_lookup(dom, "TXT");
121 ret = copy_txt_to_realms (r->head, realms);
125 krb5_config_free_strings(config_labels);
131 krb5_config_free_strings(config_labels);
136 * Try to figure out what realms host in `domain' belong to from the
137 * configuration file.
141 config_find_realm(krb5_context context,
145 char **tmp = krb5_config_get_strings (context, NULL,
157 * This function assumes that `host' is a FQDN (and doesn't handle the
158 * special case of host == NULL either).
159 * Try to find mapping in the config file or DNS and it that fails,
160 * fall back to guessing
163 krb5_error_code KRB5_LIB_FUNCTION
164 _krb5_get_host_realm_int (krb5_context context,
166 krb5_boolean use_dns,
170 krb5_boolean dns_locate_enable;
172 dns_locate_enable = krb5_config_get_bool_default(context, NULL, TRUE,
173 "libdefaults", "dns_lookup_realm", NULL);
174 for (p = host; p != NULL; p = strchr (p + 1, '.')) {
175 if(config_find_realm(context, p, realms) == 0) {
176 if(strcasecmp(*realms[0], "dns_locate") == 0) {
178 for (q = host; q != NULL; q = strchr(q + 1, '.'))
179 if(dns_find_realm(context, q, realms) == 0)
185 else if(use_dns && dns_locate_enable) {
186 if(dns_find_realm(context, p, realms) == 0)
190 p = strchr(host, '.');
193 *realms = malloc(2 * sizeof(krb5_realm));
194 if (*realms == NULL) {
195 krb5_set_error_string(context, "malloc: out of memory");
199 (*realms)[0] = strdup(p);
200 if((*realms)[0] == NULL) {
202 krb5_set_error_string(context, "malloc: out of memory");
205 strupr((*realms)[0]);
209 krb5_set_error_string(context, "unable to find realm of host %s", host);
210 return KRB5_ERR_HOST_REALM_UNKNOWN;
214 * Return the realm(s) of `host' as a NULL-terminated list in
215 * `realms'. Free `realms' with krb5_free_host_realm().
218 krb5_error_code KRB5_LIB_FUNCTION
219 krb5_get_host_realm(krb5_context context,
220 const char *targethost,
223 const char *host = targethost;
224 char hostname[MAXHOSTNAMELEN];
229 if (gethostname (hostname, sizeof(hostname))) {
237 * If our local hostname is without components, don't even try to dns.
240 use_dns = (strchr(host, '.') != NULL);
242 ret = _krb5_get_host_realm_int (context, host, use_dns, realms);
243 if (ret && targethost != NULL) {
245 * If there was no realm mapping for the host (and we wasn't
246 * looking for ourself), guess at the local realm, maybe our
247 * KDC knows better then we do and we get a referral back.
249 ret = krb5_get_default_realms(context, realms);
251 krb5_set_error_string(context, "Unable to find realm of host %s",
253 return KRB5_ERR_HOST_REALM_UNKNOWN;