1 /* 2 * Copyright (c) 1997 - 2005 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 18541 2006-10-17 19:28:36Z lha $"); 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 const char *default_labels[] = { "_kerberos", NULL }; 98 char dom[MAXHOSTNAMELEN]; 99 struct dns_reply *r; 100 const char **labels; 101 char **config_labels; 102 int i, ret; 103 104 config_labels = krb5_config_get_strings(context, NULL, "libdefaults", 105 "dns_lookup_realm_labels", NULL); 106 if(config_labels != NULL) 107 labels = (const char **)config_labels; 108 else 109 labels = default_labels; 110 if(*domain == '.') 111 domain++; 112 for (i = 0; labels[i] != NULL; i++) { 113 ret = snprintf(dom, sizeof(dom), "%s.%s.", labels[i], domain); 114 if(ret < 0 || ret >= sizeof(dom)) { 115 if (config_labels) 116 krb5_config_free_strings(config_labels); 117 return -1; 118 } 119 r = dns_lookup(dom, "TXT"); 120 if(r != NULL) { 121 ret = copy_txt_to_realms (r->head, realms); 122 dns_free_data(r); 123 if(ret == 0) { 124 if (config_labels) 125 krb5_config_free_strings(config_labels); 126 return 0; 127 } 128 } 129 } 130 if (config_labels) 131 krb5_config_free_strings(config_labels); 132 return -1; 133 } 134 135 /* 136 * Try to figure out what realms host in `domain' belong to from the 137 * configuration file. 138 */ 139 140 static int 141 config_find_realm(krb5_context context, 142 const char *domain, 143 krb5_realm **realms) 144 { 145 char **tmp = krb5_config_get_strings (context, NULL, 146 "domain_realm", 147 domain, 148 NULL); 149 150 if (tmp == NULL) 151 return -1; 152 *realms = tmp; 153 return 0; 154 } 155 156 /* 157 * This function assumes that `host' is a FQDN (and doesn't handle the 158 * special case of host == NULL either). 159 * Try to find mapping in the config file or DNS and it that fails, 160 * fall back to guessing 161 */ 162 163 krb5_error_code KRB5_LIB_FUNCTION 164 _krb5_get_host_realm_int (krb5_context context, 165 const char *host, 166 krb5_boolean use_dns, 167 krb5_realm **realms) 168 { 169 const char *p, *q; 170 krb5_boolean dns_locate_enable; 171 172 dns_locate_enable = krb5_config_get_bool_default(context, NULL, TRUE, 173 "libdefaults", "dns_lookup_realm", NULL); 174 for (p = host; p != NULL; p = strchr (p + 1, '.')) { 175 if(config_find_realm(context, p, realms) == 0) { 176 if(strcasecmp(*realms[0], "dns_locate") == 0) { 177 if(use_dns) 178 for (q = host; q != NULL; q = strchr(q + 1, '.')) 179 if(dns_find_realm(context, q, realms) == 0) 180 return 0; 181 continue; 182 } else 183 return 0; 184 } 185 else if(use_dns && dns_locate_enable) { 186 if(dns_find_realm(context, p, realms) == 0) 187 return 0; 188 } 189 } 190 p = strchr(host, '.'); 191 if(p != NULL) { 192 p++; 193 *realms = malloc(2 * sizeof(krb5_realm)); 194 if (*realms == NULL) { 195 krb5_set_error_string(context, "malloc: out of memory"); 196 return ENOMEM; 197 } 198 199 (*realms)[0] = strdup(p); 200 if((*realms)[0] == NULL) { 201 free(*realms); 202 krb5_set_error_string(context, "malloc: out of memory"); 203 return ENOMEM; 204 } 205 strupr((*realms)[0]); 206 (*realms)[1] = NULL; 207 return 0; 208 } 209 krb5_set_error_string(context, "unable to find realm of host %s", host); 210 return KRB5_ERR_HOST_REALM_UNKNOWN; 211 } 212 213 /* 214 * Return the realm(s) of `host' as a NULL-terminated list in 215 * `realms'. Free `realms' with krb5_free_host_realm(). 216 */ 217 218 krb5_error_code KRB5_LIB_FUNCTION 219 krb5_get_host_realm(krb5_context context, 220 const char *targethost, 221 krb5_realm **realms) 222 { 223 const char *host = targethost; 224 char hostname[MAXHOSTNAMELEN]; 225 krb5_error_code ret; 226 int use_dns; 227 228 if (host == NULL) { 229 if (gethostname (hostname, sizeof(hostname))) { 230 *realms = NULL; 231 return errno; 232 } 233 host = hostname; 234 } 235 236 /* 237 * If our local hostname is without components, don't even try to dns. 238 */ 239 240 use_dns = (strchr(host, '.') != NULL); 241 242 ret = _krb5_get_host_realm_int (context, host, use_dns, realms); 243 if (ret && targethost != NULL) { 244 /* 245 * If there was no realm mapping for the host (and we wasn't 246 * looking for ourself), guess at the local realm, maybe our 247 * KDC knows better then we do and we get a referral back. 248 */ 249 ret = krb5_get_default_realms(context, realms); 250 if (ret) { 251 krb5_set_error_string(context, "Unable to find realm of host %s", 252 host); 253 return KRB5_ERR_HOST_REALM_UNKNOWN; 254 } 255 } 256 return ret; 257 } 258