source: heimdal/trunk/lib/krb5/get_host_realm.c

Last change on this file was 1, checked in by Paul Smedley, 10 years ago

Initial commit of Heimdal 1.5.3
File size: 7.1 KB
Line 
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
51static int
52copy_txt_to_realms (struct rk_resource_record *head,
53 krb5_realm **realms)
54{
55 struct rk_resource_record *rr;
56 unsigned int n, i;
57
58 for(n = 0, rr = head; rr; rr = rr->next)
59 if (rr->type == rk_ns_t_txt)
60 ++n;
61
62 if (n == 0)
63 return -1;
64
65 *realms = malloc ((n + 1) * sizeof(krb5_realm));
66 if (*realms == NULL)
67 return -1;
68
69 for (i = 0; i < n + 1; ++i)
70 (*realms)[i] = NULL;
71
72 for (i = 0, rr = head; rr; rr = rr->next) {
73 if (rr->type == rk_ns_t_txt) {
74 char *tmp;
75
76 tmp = strdup(rr->u.txt);
77 if (tmp == NULL) {
78 for (i = 0; i < n; ++i)
79 free ((*realms)[i]);
80 free (*realms);
81 return -1;
82 }
83 (*realms)[i] = tmp;
84 ++i;
85 }
86 }
87 return 0;
88}
89
90static int
91dns_find_realm(krb5_context context,
92 const char *domain,
93 krb5_realm **realms)
94{
95 static const char *default_labels[] = { "_kerberos", NULL };
96 char dom[MAXHOSTNAMELEN];
97 struct rk_dns_reply *r;
98 const char **labels;
99 char **config_labels;
100 int i, ret;
101
102 config_labels = krb5_config_get_strings(context, NULL, "libdefaults",
103 "dns_lookup_realm_labels", NULL);
104 if(config_labels != NULL)
105 labels = (const char **)config_labels;
106 else
107 labels = default_labels;
108 if(*domain == '.')
109 domain++;
110 for (i = 0; labels[i] != NULL; i++) {
111 ret = snprintf(dom, sizeof(dom), "%s.%s.", labels[i], domain);
112 if(ret < 0 || (size_t)ret >= sizeof(dom)) {
113 if (config_labels)
114 krb5_config_free_strings(config_labels);
115 return -1;
116 }
117 r = rk_dns_lookup(dom, "TXT");
118 if(r != NULL) {
119 ret = copy_txt_to_realms (r->head, realms);
120 rk_dns_free_data(r);
121 if(ret == 0) {
122 if (config_labels)
123 krb5_config_free_strings(config_labels);
124 return 0;
125 }
126 }
127 }
128 if (config_labels)
129 krb5_config_free_strings(config_labels);
130 return -1;
131}
132
133/*
134 * Try to figure out what realms host in `domain' belong to from the
135 * configuration file.
136 */
137
138static int
139config_find_realm(krb5_context context,
140 const char *domain,
141 krb5_realm **realms)
142{
143 char **tmp = krb5_config_get_strings (context, NULL,
144 "domain_realm",
145 domain,
146 NULL);
147
148 if (tmp == NULL)
149 return -1;
150 *realms = tmp;
151 return 0;
152}
153
154/*
155 * This function assumes that `host' is a FQDN (and doesn't handle the
156 * special case of host == NULL either).
157 * Try to find mapping in the config file or DNS and it that fails,
158 * fall back to guessing
159 */
160
161KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
162_krb5_get_host_realm_int (krb5_context context,
163 const char *host,
164 krb5_boolean use_dns,
165 krb5_realm **realms)
166{
167 const char *p, *q;
168 krb5_boolean dns_locate_enable;
169
170 dns_locate_enable = krb5_config_get_bool_default(context, NULL, TRUE,
171 "libdefaults", "dns_lookup_realm", NULL);
172 for (p = host; p != NULL; p = strchr (p + 1, '.')) {
173 if(config_find_realm(context, p, realms) == 0) {
174 if(strcasecmp(*realms[0], "dns_locate") == 0) {
175 if(use_dns)
176 for (q = host; q != NULL; q = strchr(q + 1, '.'))
177 if(dns_find_realm(context, q, realms) == 0)
178 return 0;
179 continue;
180 } else
181 return 0;
182 }
183 else if(use_dns && dns_locate_enable) {
184 if(dns_find_realm(context, p, realms) == 0)
185 return 0;
186 }
187 }
188 p = strchr(host, '.');
189 if(p != NULL) {
190 p++;
191 *realms = malloc(2 * sizeof(krb5_realm));
192 if (*realms == NULL) {
193 krb5_set_error_message(context, ENOMEM, N_("malloc: out of memory", ""));
194 return ENOMEM;
195 }
196
197 (*realms)[0] = strdup(p);
198 if((*realms)[0] == NULL) {
199 free(*realms);
200 krb5_set_error_message(context, ENOMEM, N_("malloc: out of memory", ""));
201 return ENOMEM;
202 }
203 strupr((*realms)[0]);
204 (*realms)[1] = NULL;
205 return 0;
206 }
207 krb5_set_error_message(context, KRB5_ERR_HOST_REALM_UNKNOWN,
208 N_("unable to find realm of host %s", ""),
209 host);
210 return KRB5_ERR_HOST_REALM_UNKNOWN;
211}
212
213/*
214 * Return the realm(s) of `host' as a NULL-terminated list in
215 * `realms'. Free `realms' with krb5_free_host_realm().
216 */
217
218KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
219krb5_get_host_realm(krb5_context context,
220 const char *targethost,
221 krb5_realm **realms)
222{
223 const char *host = targethost;
224 char hostname[MAXHOSTNAMELEN];
225 krb5_error_code ret;
226 int use_dns;
227
228 if (host == NULL) {
229 if (gethostname (hostname, sizeof(hostname))) {
230 *realms = NULL;
231 return errno;
232 }
233 host = hostname;
234 }
235
236 /*
237 * If our local hostname is without components, don't even try to dns.
238 */
239
240 use_dns = (strchr(host, '.') != NULL);
241
242 ret = _krb5_get_host_realm_int (context, host, use_dns, realms);
243 if (ret && targethost != NULL) {
244 /*
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.
248 */
249 ret = krb5_get_default_realms(context, realms);
250 if (ret) {
251 krb5_set_error_message(context, KRB5_ERR_HOST_REALM_UNKNOWN,
252 N_("Unable to find realm of host %s", ""),
253 host);
254 return KRB5_ERR_HOST_REALM_UNKNOWN;
255 }
256 }
257 return ret;
258}
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