File: get_host_realm.c

package info (click to toggle)
heimdal 7.1.0+dfsg-13+deb9u3
  • links: PTS, VCS
  • area: main
  • in suites: stretch
  • size: 41,436 kB
  • sloc: ansic: 354,938; sh: 12,104; makefile: 4,353; yacc: 1,774; perl: 1,572; python: 748; lex: 732; java: 119; awk: 41
file content (300 lines) | stat: -rw-r--r-- 9,001 bytes parent folder | download | duplicates (2)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
/*
 * Copyright (c) 1997 - 2005 Kungliga Tekniska Högskolan
 * (Royal Institute of Technology, Stockholm, Sweden).
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * 3. Neither the name of the Institute nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include "krb5_locl.h"
#include <resolve.h>

/* To automagically find the correct realm of a host (without
 * [domain_realm] in krb5.conf) add a text record for your domain with
 * the name of your realm, like this:
 *
 * _kerberos	IN	TXT	"FOO.SE"
 *
 * The search is recursive, so you can add entries for specific
 * hosts. To find the realm of host a.b.c, it first tries
 * _kerberos.a.b.c, then _kerberos.b.c and so on.
 *
 * This method is described in draft-ietf-cat-krb-dns-locate-03.txt.
 *
 */

static int
copy_txt_to_realms(krb5_context context,
		   const char *domain,
		   struct rk_resource_record *head,
		   krb5_realm **realms)
{
    struct rk_resource_record *rr;
    unsigned int n, i;

    for(n = 0, rr = head; rr; rr = rr->next)
	if (rr->type == rk_ns_t_txt)
	    ++n;

    if (n == 0)
	return -1;

    *realms = malloc ((n + 1) * sizeof(krb5_realm));
    if (*realms == NULL)
	return krb5_enomem(context);;

    for (i = 0; i < n + 1; ++i)
	(*realms)[i] = NULL;

    for (i = 0, rr = head; rr; rr = rr->next) {
	if (rr->type == rk_ns_t_txt) {
	    char *tmp = NULL;
	    int invalid_tld = 1;

	    /* Check for a gTLD controlled interruption */
	    if (strcmp("Your DNS configuration needs immediate "
			"attention see https://icann.org/namecollision",
			rr->u.txt) != 0) {
		invalid_tld = 0;
		tmp = strdup(rr->u.txt);
	    }
	    if (tmp == NULL) {
		for (i = 0; i < n; ++i)
		    free ((*realms)[i]);
		free (*realms);
		if (invalid_tld) {
		    krb5_warnx(context,
			       "Realm lookup failed: "
			       "Domain '%s' needs immediate attention "
			       "see https://icann.org/namecollision",
				domain);
		    return KRB5_KDC_UNREACH;
		}
		return krb5_enomem(context);;
	    }
	    (*realms)[i] = tmp;
	    ++i;
	}
    }
    return 0;
}

static int
dns_find_realm(krb5_context context,
	       const char *domain,
	       krb5_realm **realms)
{
    static const char *default_labels[] = { "_kerberos", NULL };
    char dom[MaxHostNameLen];
    struct rk_dns_reply *r;
    const char **labels;
    char **config_labels;
    int i, ret = 0;

    config_labels = krb5_config_get_strings(context, NULL, "libdefaults",
					    "dns_lookup_realm_labels", NULL);
    if(config_labels != NULL)
	labels = (const char **)config_labels;
    else
	labels = default_labels;
    if(*domain == '.')
	domain++;
    for (i = 0; labels[i] != NULL; i++) {
	ret = snprintf(dom, sizeof(dom), "%s.%s.", labels[i], domain);
	if(ret < 0 || (size_t)ret >= sizeof(dom)) {
	    ret = krb5_enomem(context);
	    goto out;
	}
    	r = rk_dns_lookup(dom, "TXT");
    	if(r != NULL) {
	    ret = copy_txt_to_realms(context, domain, r->head, realms);
	    rk_dns_free_data(r);
	    if(ret == 0)
		goto out;
	}
    }
    krb5_set_error_message(context, KRB5_KDC_UNREACH,
			    "Realm lookup failed: "
			    "No DNS TXT record for %s",
			    domain);
    ret = KRB5_KDC_UNREACH;
out:
    if (config_labels)
	krb5_config_free_strings(config_labels);
    return ret;
}

/*
 * Try to figure out what realms host in `domain' belong to from the
 * configuration file.
 */

static int
config_find_realm(krb5_context context,
		  const char *domain,
		  krb5_realm **realms)
{
    char **tmp = krb5_config_get_strings (context, NULL,
					  "domain_realm",
					  domain,
					  NULL);

    if (tmp == NULL)
	return -1;
    *realms = tmp;
    return 0;
}

/*
 * This function assumes that `host' is a FQDN (and doesn't handle the
 * special case of host == NULL either).
 * Try to find mapping in the config file or DNS and it that fails,
 * fall back to guessing
 */

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)
{
    const char *p, *q;
    const char *port;
    krb5_boolean dns_locate_enable;
    krb5_error_code ret = 0;

    /* Strip off any trailing ":port" suffix. */
    port = strchr(host, ':');
    if (port != NULL) {
        host = strndup(host, port - host);
        if (host == NULL)
            return krb5_enomem(context);
    }

    dns_locate_enable = krb5_config_get_bool_default(context, NULL, TRUE,
        "libdefaults", "dns_lookup_realm", NULL);
    for (p = host; p != NULL; p = strchr (p + 1, '.')) {
        if (config_find_realm(context, p, realms) == 0) {
            if (strcasecmp(*realms[0], "dns_locate") != 0)
                break;
	    krb5_free_host_realm(context, *realms);
	    *realms = NULL;
            if (!use_dns)
                continue;
            for (q = host; q != NULL; q = strchr(q + 1, '.'))
                if (dns_find_realm(context, q, realms) == 0)
                    break;
            if (q)
                break;
        } else if (use_dns && dns_locate_enable) {
            if (dns_find_realm(context, p, realms) == 0)
                break;
        }
    }

    /*
     * If 'p' is NULL, we did not find an explicit realm mapping in either the
     * configuration file or DNS.  Try the hostname suffix as a last resort.
     *
     * XXX: If we implement a KDC-specific variant of this function just for
     * referrals, we could check whether we have a cross-realm TGT for the
     * realm in question, and if not try the parent (loop again).
     */
    if (p == NULL) {
        p = strchr(host, '.');
        if (p != NULL) {
            p++;
            *realms = malloc(2 * sizeof(krb5_realm));
            if (*realms != NULL &&
                ((*realms)[0] = strdup(p)) != NULL) {
                strupr((*realms)[0]);
                (*realms)[1] = NULL;
            } else {
                free(*realms);
                ret = krb5_enomem(context);
            }
        } else {
            krb5_set_error_message(context, KRB5_ERR_HOST_REALM_UNKNOWN,
                                   N_("unable to find realm of host %s", ""),
                                   host);
            ret = KRB5_ERR_HOST_REALM_UNKNOWN;
        }
    }

    /* If 'port' is not NULL, we have a copy of 'host' to free. */
    if (port)
        free((void *)host);
    return ret;
}

/*
 * Return the realm(s) of `host' as a NULL-terminated list in
 * `realms'. Free `realms' with krb5_free_host_realm().
 */

KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
krb5_get_host_realm(krb5_context context,
		    const char *targethost,
		    krb5_realm **realms)
{
    const char *host = targethost;
    char hostname[MaxHostNameLen];
    krb5_error_code ret;
    int use_dns;

    if (host == NULL) {
	if (gethostname (hostname, sizeof(hostname))) {
	    *realms = NULL;
	    return errno;
	}
	host = hostname;
    }

    /*
     * If our local hostname is without components, don't even try to dns.
     */

    use_dns = (strchr(host, '.') != NULL);

    ret = _krb5_get_host_realm_int (context, host, use_dns, realms);
    if (ret && targethost != NULL) {
	/*
	 * If there was no realm mapping for the host (and we wasn't
	 * looking for ourself), guess at the local realm, maybe our
	 * KDC knows better then we do and we get a referral back.
	 */
	ret = krb5_get_default_realms(context, realms);
	if (ret) {
	    krb5_set_error_message(context, KRB5_ERR_HOST_REALM_UNKNOWN,
				   N_("Unable to find realm of host %s", ""),
				   host);
	    return KRB5_ERR_HOST_REALM_UNKNOWN;
	}
    }
    return ret;
}