crypto/dist/heimdal/lib/krb5/get_host_realm.c

   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 __RCSID("$Heimdal: get_host_realm.c 18541 2006-10-17 19:28:36Z lha $"
  38         "$NetBSD$");
  39
  40 /* To automagically find the correct realm of a host (without
  41  * [domain_realm] in krb5.conf) add a text record for your domain with
  42  * the name of your realm, like this:
  43  *
  44  * _kerberos    IN      TXT     "FOO.SE"
  45  *
  46  * The search is recursive, so you can add entries for specific
  47  * hosts. To find the realm of host a.b.c, it first tries
  48  * _kerberos.a.b.c, then _kerberos.b.c and so on.
  49  *
  50  * This method is described in draft-ietf-cat-krb-dns-locate-03.txt.
  51  *
  52  */
  53
  54 static int
  55 copy_txt_to_realms (struct resource_record *head,
  56                     krb5_realm **realms)
  57 {
  58     struct resource_record *rr;
  59     int n, i;
  60
  61     for(n = 0, rr = head; rr; rr = rr->next)
  62         if (rr->type == T_TXT)
  63             ++n;
  64
  65     if (n == 0)
  66         return -1;
  67
  68     *realms = malloc ((n + 1) * sizeof(krb5_realm));
  69     if (*realms == NULL)
  70         return -1;
  71
  72     for (i = 0; i < n + 1; ++i)
  73         (*realms)[i] = NULL;
  74
  75     for (i = 0, rr = head; rr; rr = rr->next) {
  76         if (rr->type == T_TXT) {
  77             char *tmp;
  78
  79             tmp = strdup(rr->u.txt);
  80             if (tmp == NULL) {
  81                 for (i = 0; i < n; ++i)
  82                     free ((*realms)[i]);
  83                 free (*realms);
  84                 return -1;
  85             }
  86             (*realms)[i] = tmp;
  87             ++i;
  88         }
  89     }
  90     return 0;
  91 }
  92
  93 static int
  94 dns_find_realm(krb5_context context,
  95                const char *domain,
  96                krb5_realm **realms)
  97 {
  98     static const char *default_labels[] = { "_kerberos", NULL };
  99     char dom[MAXHOSTNAMELEN];
 100     struct dns_reply *r;
 101     const char **labels;
 102     char **config_labels;
 103     int i, ret;
 104
 105     config_labels = krb5_config_get_strings(context, NULL, "libdefaults",
 106                                             "dns_lookup_realm_labels", NULL);
 107     if(config_labels != NULL)
 108         labels = (const char **)config_labels;
 109     else
 110         labels = default_labels;
 111     if(*domain == '.')
 112         domain++;
 113     for (i = 0; labels[i] != NULL; i++) {
 114         ret = snprintf(dom, sizeof(dom), "%s.%s.", labels[i], domain);
 115         if(ret < 0 || ret >= sizeof(dom)) {
 116             if (config_labels)
 117                 krb5_config_free_strings(config_labels);
 118             return -1;
 119         }
 120         r = dns_lookup(dom, "TXT");
 121         if(r != NULL) {
 122             ret = copy_txt_to_realms (r->head, realms);
 123             dns_free_data(r);
 124             if(ret == 0) {
 125                 if (config_labels)
 126                     krb5_config_free_strings(config_labels);
 127                 return 0;
 128             }
 129         }
 130     }
 131     if (config_labels)
 132         krb5_config_free_strings(config_labels);
 133     return -1;
 134 }
 135
 136 /*
 137  * Try to figure out what realms host in `domain' belong to from the
 138  * configuration file.
 139  */
 140
 141 static int
 142 config_find_realm(krb5_context context,
 143                   const char *domain,
 144                   krb5_realm **realms)
 145 {
 146     char **tmp = krb5_config_get_strings (context, NULL,
 147                                           "domain_realm",
 148                                           domain,
 149                                           NULL);
 150
 151     if (tmp == NULL)
 152         return -1;
 153     *realms = tmp;
 154     return 0;
 155 }
 156
 157 /*
 158  * This function assumes that `host' is a FQDN (and doesn't handle the
 159  * special case of host == NULL either).
 160  * Try to find mapping in the config file or DNS and it that fails,
 161  * fall back to guessing
 162  */
 163
 164 krb5_error_code KRB5_LIB_FUNCTION
 165 _krb5_get_host_realm_int (krb5_context context,
 166                           const char *host,
 167                           krb5_boolean use_dns,
 168                           krb5_realm **realms)
 169 {
 170     const char *p, *q;
 171     krb5_boolean dns_locate_enable;
 172
 173     dns_locate_enable = krb5_config_get_bool_default(context, NULL, TRUE,
 174         "libdefaults", "dns_lookup_realm", NULL);
 175     for (p = host; p != NULL; p = strchr (p + 1, '.')) {
 176         if(config_find_realm(context, p, realms) == 0) {
 177             if(strcasecmp(*realms[0], "dns_locate") == 0) {
 178                 if(use_dns)
 179                     for (q = host; q != NULL; q = strchr(q + 1, '.'))
 180                         if(dns_find_realm(context, q, realms) == 0)
 181                             return 0;
 182                 continue;
 183             } else
 184                 return 0;
 185         }
 186         else if(use_dns && dns_locate_enable) {
 187             if(dns_find_realm(context, p, realms) == 0)
 188                 return 0;
 189         }
 190     }
 191     p = strchr(host, '.');
 192     if(p != NULL) {
 193         p++;
 194         *realms = malloc(2 * sizeof(krb5_realm));
 195         if (*realms == NULL) {
 196             krb5_set_error_string(context, "malloc: out of memory");
 197             return ENOMEM;
 198         }
 199
 200         (*realms)[0] = strdup(p);
 201         if((*realms)[0] == NULL) {
 202             free(*realms);
 203             krb5_set_error_string(context, "malloc: out of memory");
 204             return ENOMEM;
 205         }
 206         strupr((*realms)[0]);
 207         (*realms)[1] = NULL;
 208         return 0;
 209     }
 210     krb5_set_error_string(context, "unable to find realm of host %s", host);
 211     return KRB5_ERR_HOST_REALM_UNKNOWN;
 212 }
 213
 214 /*
 215  * Return the realm(s) of `host' as a NULL-terminated list in
 216  * `realms'. Free `realms' with krb5_free_host_realm().
 217  */
 218
 219 krb5_error_code KRB5_LIB_FUNCTION
 220 krb5_get_host_realm(krb5_context context,
 221                     const char *targethost,
 222                     krb5_realm **realms)
 223 {
 224     const char *host = targethost;
 225     char hostname[MAXHOSTNAMELEN];
 226     krb5_error_code ret;
 227     int use_dns;
 228
 229     if (host == NULL) {
 230         if (gethostname (hostname, sizeof(hostname))) {
 231             *realms = NULL;
 232             return errno;
 233         }
 234         host = hostname;
 235     }
 236
 237     /*
 238      * If our local hostname is without components, don't even try to dns.
 239      */
 240
 241     use_dns = (strchr(host, '.') != NULL);
 242
 243     ret = _krb5_get_host_realm_int (context, host, use_dns, realms);
 244     if (ret && targethost != NULL) {
 245         /*
 246          * If there was no realm mapping for the host (and we wasn't
 247          * looking for ourself), guess at the local realm, maybe our
 248          * KDC knows better then we do and we get a referral back.
 249          */
 250         ret = krb5_get_default_realms(context, realms);
 251         if (ret) {
 252             krb5_set_error_string(context, "Unable to find realm of host %s",
 253                                   host);
 254             return KRB5_ERR_HOST_REALM_UNKNOWN;
 255         }
 256     }
 257     return ret;
 258 }