Line data Source code
1 : /*
2 : * Copyright (c) 1997 - 2005 Kungliga Tekniska Högskolan
3 : * (Royal Institute of Technology, Stockholm, Sweden).
4 : * All rights reserved.
5 : *
6 : * Redistribution and use in source and binary forms, with or without
7 : * modification, are permitted provided that the following conditions
8 : * are met:
9 : *
10 : * 1. Redistributions of source code must retain the above copyright
11 : * notice, this list of conditions and the following disclaimer.
12 : *
13 : * 2. Redistributions in binary form must reproduce the above copyright
14 : * notice, this list of conditions and the following disclaimer in the
15 : * documentation and/or other materials provided with the distribution.
16 : *
17 : * 3. Neither the name of the Institute nor the names of its contributors
18 : * may be used to endorse or promote products derived from this software
19 : * without specific prior written permission.
20 : *
21 : * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
22 : * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 : * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 : * ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
25 : * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 : * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 : * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 : * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 : * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 : * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 : * SUCH DAMAGE.
32 : */
33 :
34 : #include "krb5_locl.h"
35 : #include <resolve.h>
36 :
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:
40 : *
41 : * _kerberos IN TXT "FOO.SE"
42 : *
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.
46 : *
47 : * This method is described in draft-ietf-cat-krb-dns-locate-03.txt.
48 : *
49 : */
50 :
51 : static int
52 0 : copy_txt_to_realms(krb5_context context,
53 : const char *domain,
54 : struct rk_resource_record *head,
55 : krb5_realm **realms)
56 : {
57 : struct rk_resource_record *rr;
58 : unsigned int n, i;
59 :
60 0 : for(n = 0, rr = head; rr; rr = rr->next)
61 0 : if (rr->type == rk_ns_t_txt)
62 0 : ++n;
63 :
64 0 : if (n == 0)
65 0 : return -1;
66 :
67 0 : *realms = malloc ((n + 1) * sizeof(krb5_realm));
68 0 : if (*realms == NULL)
69 0 : return krb5_enomem(context);;
70 :
71 0 : for (i = 0; i < n + 1; ++i)
72 0 : (*realms)[i] = NULL;
73 :
74 0 : for (i = 0, rr = head; rr; rr = rr->next) {
75 0 : if (rr->type == rk_ns_t_txt) {
76 0 : char *tmp = NULL;
77 0 : int invalid_tld = 1;
78 :
79 : /* Check for a gTLD controlled interruption */
80 0 : if (strcmp("Your DNS configuration needs immediate "
81 : "attention see https://icann.org/namecollision",
82 0 : rr->u.txt) != 0) {
83 0 : invalid_tld = 0;
84 0 : tmp = strdup(rr->u.txt);
85 : }
86 0 : if (tmp == NULL) {
87 0 : for (i = 0; i < n; ++i)
88 0 : free ((*realms)[i]);
89 0 : free (*realms);
90 0 : if (invalid_tld) {
91 0 : krb5_warnx(context,
92 : "Realm lookup failed: "
93 : "Domain '%s' needs immediate attention "
94 : "see https://icann.org/namecollision",
95 : domain);
96 0 : return KRB5_KDC_UNREACH;
97 : }
98 0 : return krb5_enomem(context);;
99 : }
100 0 : (*realms)[i] = tmp;
101 0 : ++i;
102 : }
103 : }
104 0 : return 0;
105 : }
106 :
107 : static int
108 0 : dns_find_realm(krb5_context context,
109 : const char *domain,
110 : krb5_realm **realms)
111 : {
112 : static const char *default_labels[] = { "_kerberos", NULL };
113 : char dom[MAXHOSTNAMELEN];
114 : struct rk_dns_reply *r;
115 : const char **labels;
116 : char **config_labels;
117 0 : int i, ret = 0;
118 :
119 0 : config_labels = krb5_config_get_strings(context, NULL, "libdefaults",
120 : "dns_lookup_realm_labels", NULL);
121 0 : if(config_labels != NULL)
122 0 : labels = (const char **)config_labels;
123 : else
124 0 : labels = default_labels;
125 0 : if(*domain == '.')
126 0 : domain++;
127 0 : for (i = 0; labels[i] != NULL; i++) {
128 0 : ret = snprintf(dom, sizeof(dom), "%s.%s.", labels[i], domain);
129 0 : if(ret < 0 || (size_t)ret >= sizeof(dom)) {
130 0 : ret = krb5_enomem(context);
131 0 : goto out;
132 : }
133 0 : r = rk_dns_lookup(dom, "TXT");
134 0 : if(r != NULL) {
135 0 : ret = copy_txt_to_realms(context, domain, r->head, realms);
136 0 : rk_dns_free_data(r);
137 0 : if(ret == 0)
138 0 : goto out;
139 : }
140 : }
141 0 : krb5_set_error_message(context, KRB5_KDC_UNREACH,
142 : "Realm lookup failed: "
143 : "No DNS TXT record for %s",
144 : domain);
145 0 : ret = KRB5_KDC_UNREACH;
146 0 : out:
147 0 : if (config_labels)
148 0 : krb5_config_free_strings(config_labels);
149 0 : return ret;
150 : }
151 :
152 : /*
153 : * Try to figure out what realms host in `domain' belong to from the
154 : * configuration file.
155 : */
156 :
157 : static int
158 33011 : config_find_realm(krb5_context context,
159 : const char *domain,
160 : krb5_realm **realms)
161 : {
162 33011 : char **tmp = krb5_config_get_strings (context, NULL,
163 : "domain_realm",
164 : domain,
165 : NULL);
166 :
167 33011 : if (tmp == NULL)
168 33011 : return -1;
169 0 : *realms = tmp;
170 0 : return 0;
171 : }
172 :
173 : /*
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
178 : */
179 :
180 : KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
181 19603 : _krb5_get_host_realm_int(krb5_context context,
182 : const char *host,
183 : krb5_boolean use_dns,
184 : krb5_realm **realms)
185 : {
186 : const char *p, *q;
187 : const char *port;
188 : krb5_boolean dns_locate_enable;
189 19603 : krb5_error_code ret = 0;
190 :
191 : /* Strip off any trailing ":port" suffix. */
192 19603 : port = strchr(host, ':');
193 19603 : if (port != NULL) {
194 0 : host = strndup(host, port - host);
195 0 : if (host == NULL)
196 0 : return krb5_enomem(context);
197 : }
198 :
199 19603 : dns_locate_enable = krb5_config_get_bool_default(context, NULL, TRUE,
200 : "libdefaults", "dns_lookup_realm", NULL);
201 52614 : for (p = host; p != NULL; p = strchr (p + 1, '.')) {
202 33011 : if (config_find_realm(context, p, realms) == 0) {
203 0 : if (strcasecmp(*realms[0], "dns_locate") != 0)
204 0 : break;
205 0 : krb5_free_host_realm(context, *realms);
206 0 : *realms = NULL;
207 0 : if (!use_dns)
208 0 : continue;
209 0 : for (q = host; q != NULL; q = strchr(q + 1, '.'))
210 0 : if (dns_find_realm(context, q, realms) == 0)
211 0 : break;
212 0 : if (q)
213 0 : break;
214 33011 : } else if (use_dns && dns_locate_enable) {
215 0 : if (dns_find_realm(context, p, realms) == 0)
216 0 : break;
217 : }
218 : }
219 :
220 : /*
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.
223 : *
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).
227 : */
228 19603 : if (p == NULL) {
229 19603 : p = strchr(host, '.');
230 19603 : if (p != NULL) {
231 4348 : p++;
232 4348 : *realms = malloc(2 * sizeof(krb5_realm));
233 8696 : if (*realms != NULL &&
234 4348 : ((*realms)[0] = strdup(p)) != NULL) {
235 4348 : strupr((*realms)[0]);
236 4348 : (*realms)[1] = NULL;
237 : } else {
238 0 : free(*realms);
239 0 : ret = krb5_enomem(context);
240 : }
241 : } else {
242 15255 : krb5_set_error_message(context, KRB5_ERR_HOST_REALM_UNKNOWN,
243 15255 : N_("unable to find realm of host %s", ""),
244 : host);
245 15255 : ret = KRB5_ERR_HOST_REALM_UNKNOWN;
246 : }
247 : }
248 :
249 : /* If 'port' is not NULL, we have a copy of 'host' to free. */
250 19603 : if (port)
251 0 : free((void *)host);
252 19603 : return ret;
253 : }
254 :
255 : /*
256 : * Return the realm(s) of `host' as a NULL-terminated list in
257 : * `realms'. Free `realms' with krb5_free_host_realm().
258 : */
259 :
260 : KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
261 19603 : krb5_get_host_realm(krb5_context context,
262 : const char *targethost,
263 : krb5_realm **realms)
264 : {
265 19603 : const char *host = targethost;
266 : char hostname[MAXHOSTNAMELEN];
267 : krb5_error_code ret;
268 : int use_dns;
269 :
270 19603 : if (host == NULL) {
271 8 : if (gethostname (hostname, sizeof(hostname))) {
272 0 : *realms = NULL;
273 0 : return errno;
274 : }
275 8 : host = hostname;
276 : }
277 :
278 : /*
279 : * If our local hostname is without components, don't even try to dns.
280 : */
281 :
282 19603 : use_dns = (strchr(host, '.') != NULL);
283 :
284 19603 : ret = _krb5_get_host_realm_int (context, host, use_dns, realms);
285 19603 : if (ret && targethost != NULL) {
286 : /*
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.
290 : */
291 15255 : ret = krb5_get_default_realms(context, realms);
292 15255 : if (ret) {
293 0 : krb5_set_error_message(context, KRB5_ERR_HOST_REALM_UNKNOWN,
294 0 : N_("Unable to find realm of host %s", ""),
295 : host);
296 0 : return KRB5_ERR_HOST_REALM_UNKNOWN;
297 : }
298 : }
299 19603 : return ret;
300 : }
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