get_host_realm.c revision 178825
154359Sroberto/* 2182007Sroberto * Copyright (c) 1997 - 2005 Kungliga Tekniska H�gskolan 3182007Sroberto * (Royal Institute of Technology, Stockholm, Sweden). 454359Sroberto * All rights reserved. 5280849Scy * 654359Sroberto * Redistribution and use in source and binary forms, with or without 754359Sroberto * modification, are permitted provided that the following conditions 854359Sroberto * are met: 954359Sroberto * 1054359Sroberto * 1. Redistributions of source code must retain the above copyright 1154359Sroberto * notice, this list of conditions and the following disclaimer. 1254359Sroberto * 1354359Sroberto * 2. Redistributions in binary form must reproduce the above copyright 1454359Sroberto * notice, this list of conditions and the following disclaimer in the 1554359Sroberto * documentation and/or other materials provided with the distribution. 1654359Sroberto * 1754359Sroberto * 3. Neither the name of the Institute nor the names of its contributors 1854359Sroberto * may be used to endorse or promote products derived from this software 1954359Sroberto * without specific prior written permission. 2054359Sroberto * 2154359Sroberto * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND 2254359Sroberto * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 2354359Sroberto * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 2454359Sroberto * ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE 2554359Sroberto * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 2654359Sroberto * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 2754359Sroberto * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 2854359Sroberto * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 2954359Sroberto * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 3054359Sroberto * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 3154359Sroberto * SUCH DAMAGE. 3254359Sroberto */ 3354359Sroberto 3454359Sroberto#include "krb5_locl.h" 3554359Sroberto#include <resolve.h> 3654359Sroberto 3754359SrobertoRCSID("$Id: get_host_realm.c 18541 2006-10-17 19:28:36Z lha $"); 3854359Sroberto 3954359Sroberto/* To automagically find the correct realm of a host (without 4054359Sroberto * [domain_realm] in krb5.conf) add a text record for your domain with 4154359Sroberto * the name of your realm, like this: 4254359Sroberto * 4354359Sroberto * _kerberos IN TXT "FOO.SE" 4454359Sroberto * 4554359Sroberto * The search is recursive, so you can add entries for specific 4654359Sroberto * hosts. To find the realm of host a.b.c, it first tries 4754359Sroberto * _kerberos.a.b.c, then _kerberos.b.c and so on. 4854359Sroberto * 4954359Sroberto * This method is described in draft-ietf-cat-krb-dns-locate-03.txt. 5054359Sroberto * 51280849Scy */ 5254359Sroberto 5354359Srobertostatic int 5454359Srobertocopy_txt_to_realms (struct resource_record *head, 5554359Sroberto krb5_realm **realms) 5654359Sroberto{ 5754359Sroberto struct resource_record *rr; 5854359Sroberto int n, i; 5954359Sroberto 6054359Sroberto for(n = 0, rr = head; rr; rr = rr->next) 6154359Sroberto if (rr->type == T_TXT) 6254359Sroberto ++n; 6354359Sroberto 6454359Sroberto if (n == 0) 6554359Sroberto return -1; 6654359Sroberto 6754359Sroberto *realms = malloc ((n + 1) * sizeof(krb5_realm)); 6854359Sroberto if (*realms == NULL) 6954359Sroberto return -1; 7054359Sroberto 7154359Sroberto for (i = 0; i < n + 1; ++i) 7254359Sroberto (*realms)[i] = NULL; 7354359Sroberto 7454359Sroberto for (i = 0, rr = head; rr; rr = rr->next) { 7554359Sroberto if (rr->type == T_TXT) { 7654359Sroberto char *tmp; 7754359Sroberto 7854359Sroberto tmp = strdup(rr->u.txt); 7954359Sroberto if (tmp == NULL) { 8054359Sroberto for (i = 0; i < n; ++i) 8154359Sroberto free ((*realms)[i]); 8254359Sroberto free (*realms); 8354359Sroberto return -1; 8454359Sroberto } 8554359Sroberto (*realms)[i] = tmp; 8654359Sroberto ++i; 8754359Sroberto } 8854359Sroberto } 8954359Sroberto return 0; 9054359Sroberto} 9154359Sroberto 9254359Srobertostatic int 93280849Scydns_find_realm(krb5_context context, 9454359Sroberto 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 140static int 141config_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 163krb5_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 218krb5_error_code KRB5_LIB_FUNCTION 219krb5_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