xref: /freebsd/crypto/heimdal/lib/krb5/get_host_realm.c (revision 1e413cf93298b5b97441a21d9a50fdcd0ee9945e)
1 /*
2  * Copyright (c) 1997 - 2001 Kungliga Tekniska H�gskolan
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 RCSID("$Id: get_host_realm.c,v 1.29 2002/08/28 13:36:57 nectar Exp $");
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
54 copy_txt_to_realms (struct resource_record *head,
55 		    krb5_realm **realms)
56 {
57     struct resource_record *rr;
58     int n, i;
59 
60     for(n = 0, rr = head; rr; rr = rr->next)
61 	if (rr->type == 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 == 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
93 dns_find_realm(krb5_context context,
94 	       const char *domain,
95 	       krb5_realm **realms)
96 {
97     static char *default_labels[] = { "_kerberos", NULL };
98     char dom[MAXHOSTNAMELEN];
99     struct dns_reply *r;
100     char **labels;
101     int i, ret;
102 
103     labels = krb5_config_get_strings(context, NULL, "libdefaults",
104 	"dns_lookup_realm_labels", NULL);
105     if(labels == NULL)
106 	labels = default_labels;
107     if(*domain == '.')
108 	domain++;
109     for (i = 0; labels[i] != NULL; i++) {
110 	if(snprintf(dom, sizeof(dom), "%s.%s.", labels[i], domain) >=
111 	    sizeof(dom))
112 	    return -1;
113     	r = dns_lookup(dom, "TXT");
114     	if(r != NULL) {
115 	    ret = copy_txt_to_realms (r->head, realms);
116 	    dns_free_data(r);
117 	    if(ret == 0)
118 		return 0;
119 	}
120     }
121     return -1;
122 }
123 
124 /*
125  * Try to figure out what realms host in `domain' belong to from the
126  * configuration file.
127  */
128 
129 static int
130 config_find_realm(krb5_context context,
131 		  const char *domain,
132 		  krb5_realm **realms)
133 {
134     char **tmp = krb5_config_get_strings (context, NULL,
135 					  "domain_realm",
136 					  domain,
137 					  NULL);
138 
139     if (tmp == NULL)
140 	return -1;
141     *realms = tmp;
142     return 0;
143 }
144 
145 /*
146  * This function assumes that `host' is a FQDN (and doesn't handle the
147  * special case of host == NULL either).
148  * Try to find mapping in the config file or DNS and it that fails,
149  * fall back to guessing
150  */
151 
152 krb5_error_code
153 krb5_get_host_realm_int (krb5_context context,
154 			 const char *host,
155 			 krb5_boolean use_dns,
156 			 krb5_realm **realms)
157 {
158     const char *p, *q;
159     krb5_boolean dns_locate_enable;
160 
161     dns_locate_enable = krb5_config_get_bool_default(context, NULL, TRUE,
162 	"libdefaults", "dns_lookup_realm", NULL);
163     for (p = host; p != NULL; p = strchr (p + 1, '.')) {
164 	if(config_find_realm(context, p, realms) == 0) {
165 	    if(strcasecmp(*realms[0], "dns_locate") == 0) {
166 		if(use_dns)
167 		    for (q = host; q != NULL; q = strchr(q + 1, '.'))
168 			if(dns_find_realm(context, q, realms) == 0)
169 			    return 0;
170 		continue;
171 	    } else
172 	    	return 0;
173 	}
174 	else if(use_dns && dns_locate_enable) {
175 	    if(dns_find_realm(context, p, realms) == 0)
176 		return 0;
177 	}
178     }
179     p = strchr(host, '.');
180     if(p != NULL) {
181 	p++;
182 	*realms = malloc(2 * sizeof(krb5_realm));
183 	if (*realms == NULL) {
184 	    krb5_set_error_string(context, "malloc: out of memory");
185 	    return ENOMEM;
186 	}
187 
188 	(*realms)[0] = strdup(p);
189 	if((*realms)[0] == NULL) {
190 	    free(*realms);
191 	    krb5_set_error_string(context, "malloc: out of memory");
192 	    return ENOMEM;
193 	}
194 	strupr((*realms)[0]);
195 	(*realms)[1] = NULL;
196 	return 0;
197     }
198     krb5_set_error_string(context, "unable to find realm of host %s", host);
199     return KRB5_ERR_HOST_REALM_UNKNOWN;
200 }
201 
202 /*
203  * Return the realm(s) of `host' as a NULL-terminated list in `realms'.
204  */
205 
206 krb5_error_code
207 krb5_get_host_realm(krb5_context context,
208 		    const char *host,
209 		    krb5_realm **realms)
210 {
211     char hostname[MAXHOSTNAMELEN];
212 
213     if (host == NULL) {
214 	if (gethostname (hostname, sizeof(hostname)))
215 	    return errno;
216 	host = hostname;
217     }
218 
219     return krb5_get_host_realm_int (context, host, 1, realms);
220 }
221