get_host_realm.c revision 102644 
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
37RCSID("$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
53static int
54copy_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
92static int
93dns_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
129static int
130config_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
152krb5_error_code
153krb5_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
206krb5_error_code
207krb5_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