crypto/heimdal-0.6.3/lib/krb5/get_host_realm.c

   1 /*
   2  * Copyright (c) 1997 - 2001 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 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 }