1 /* $NetBSD: get_host_realm.c,v 1.1.1.2 2014/04/24 12:45:50 pettai Exp $ */
2
3 /*
4 * Copyright (c) 1997 - 2005 Kungliga Tekniska Högskolan
5 * (Royal Institute of Technology, Stockholm, Sweden).
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 *
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 *
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 *
19 * 3. Neither the name of the Institute nor the names of its contributors
20 * may be used to endorse or promote products derived from this software
21 * without specific prior written permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26 * ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * SUCH DAMAGE.
34 */
35
36 #include "krb5_locl.h"
37 #include <krb5/resolve.h>
38
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:
42 *
43 * _kerberos IN TXT "FOO.SE"
44 *
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.
48 *
49 * This method is described in draft-ietf-cat-krb-dns-locate-03.txt.
50 *
51 */
52
53 static int
copy_txt_to_realms(struct rk_resource_record * head,krb5_realm ** realms)54 copy_txt_to_realms (struct rk_resource_record *head,
55 krb5_realm **realms)
56 {
57 struct rk_resource_record *rr;
58 unsigned int n, i;
59
60 for(n = 0, rr = head; rr; rr = rr->next)
61 if (rr->type == rk_ns_t_txt)
62 ++n;
63
64 if (n == 0)
65 return -1;
66
67 *realms = malloc ((n + 1) * sizeof(krb5_realm));
68 if (*realms == NULL)
69 return -1;
70
71 for (i = 0; i < n + 1; ++i)
72 (*realms)[i] = NULL;
73
74 for (i = 0, rr = head; rr; rr = rr->next) {
75 if (rr->type == rk_ns_t_txt) {
76 char *tmp;
77
78 tmp = strdup(rr->u.txt);
79 if (tmp == NULL) {
80 for (i = 0; i < n; ++i)
81 free ((*realms)[i]);
82 free (*realms);
83 return -1;
84 }
85 (*realms)[i] = tmp;
86 ++i;
87 }
88 }
89 return 0;
90 }
91
92 static int
dns_find_realm(krb5_context context,const char * domain,krb5_realm ** realms)93 dns_find_realm(krb5_context context,
94 const char *domain,
95 krb5_realm **realms)
96 {
97 static const char *default_labels[] = { "_kerberos", NULL };
98 char dom[MAXHOSTNAMELEN];
99 struct rk_dns_reply *r;
100 const char **labels;
101 char **config_labels;
102 int i, ret;
103
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;
108 else
109 labels = default_labels;
110 if(*domain == '.')
111 domain++;
112 for (i = 0; labels[i] != NULL; i++) {
113 ret = snprintf(dom, sizeof(dom), "%s.%s.", labels[i], domain);
114 if(ret < 0 || (size_t)ret >= sizeof(dom)) {
115 if (config_labels)
116 krb5_config_free_strings(config_labels);
117 return -1;
118 }
119 r = rk_dns_lookup(dom, "TXT");
120 if(r != NULL) {
121 ret = copy_txt_to_realms (r->head, realms);
122 rk_dns_free_data(r);
123 if(ret == 0) {
124 if (config_labels)
125 krb5_config_free_strings(config_labels);
126 return 0;
127 }
128 }
129 }
130 if (config_labels)
131 krb5_config_free_strings(config_labels);
132 return -1;
133 }
134
135 /*
136 * Try to figure out what realms host in `domain' belong to from the
137 * configuration file.
138 */
139
140 static int
config_find_realm(krb5_context context,const char * domain,krb5_realm ** realms)141 config_find_realm(krb5_context context,
142 const char *domain,
143 krb5_realm **realms)
144 {
145 char **tmp = krb5_config_get_strings (context, NULL,
146 "domain_realm",
147 domain,
148 NULL);
149
150 if (tmp == NULL)
151 return -1;
152 *realms = tmp;
153 return 0;
154 }
155
156 /*
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
161 */
162
163 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)164 _krb5_get_host_realm_int (krb5_context context,
165 const char *host,
166 krb5_boolean use_dns,
167 krb5_realm **realms)
168 {
169 const char *p, *q;
170 krb5_boolean dns_locate_enable;
171
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) {
177 if(use_dns)
178 for (q = host; q != NULL; q = strchr(q + 1, '.'))
179 if(dns_find_realm(context, q, realms) == 0)
180 return 0;
181 continue;
182 } else
183 return 0;
184 }
185 else if(use_dns && dns_locate_enable) {
186 if(dns_find_realm(context, p, realms) == 0)
187 return 0;
188 }
189 }
190 p = strchr(host, '.');
191 if(p != NULL) {
192 p++;
193 *realms = malloc(2 * sizeof(krb5_realm));
194 if (*realms == NULL) {
195 krb5_set_error_message(context, ENOMEM, N_("malloc: out of memory", ""));
196 return ENOMEM;
197 }
198
199 (*realms)[0] = strdup(p);
200 if((*realms)[0] == NULL) {
201 free(*realms);
202 krb5_set_error_message(context, ENOMEM, N_("malloc: out of memory", ""));
203 return ENOMEM;
204 }
205 strupr((*realms)[0]);
206 (*realms)[1] = NULL;
207 return 0;
208 }
209 krb5_set_error_message(context, KRB5_ERR_HOST_REALM_UNKNOWN,
210 N_("unable to find realm of host %s", ""),
211 host);
212 return KRB5_ERR_HOST_REALM_UNKNOWN;
213 }
214
215 /*
216 * Return the realm(s) of `host' as a NULL-terminated list in
217 * `realms'. Free `realms' with krb5_free_host_realm().
218 */
219
220 KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
krb5_get_host_realm(krb5_context context,const char * targethost,krb5_realm ** realms)221 krb5_get_host_realm(krb5_context context,
222 const char *targethost,
223 krb5_realm **realms)
224 {
225 const char *host = targethost;
226 char hostname[MAXHOSTNAMELEN];
227 krb5_error_code ret;
228 int use_dns;
229
230 if (host == NULL) {
231 if (gethostname (hostname, sizeof(hostname))) {
232 *realms = NULL;
233 return errno;
234 }
235 host = hostname;
236 }
237
238 /*
239 * If our local hostname is without components, don't even try to dns.
240 */
241
242 use_dns = (strchr(host, '.') != NULL);
243
244 ret = _krb5_get_host_realm_int (context, host, use_dns, realms);
245 if (ret && targethost != NULL) {
246 /*
247 * If there was no realm mapping for the host (and we wasn't
248 * looking for ourself), guess at the local realm, maybe our
249 * KDC knows better then we do and we get a referral back.
250 */
251 ret = krb5_get_default_realms(context, realms);
252 if (ret) {
253 krb5_set_error_message(context, KRB5_ERR_HOST_REALM_UNKNOWN,
254 N_("Unable to find realm of host %s", ""),
255 host);
256 return KRB5_ERR_HOST_REALM_UNKNOWN;
257 }
258 }
259 return ret;
260 }
261