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/* To automagically find the correct realm of a host (without 38 * [domain_realm] in krb5.conf) add a text record for your domain with 39 * the name of your realm, like this: 40 * 41 * _kerberos IN TXT "FOO.SE" 42 * 43 * The search is recursive, so you can add entries for specific 44 * hosts. To find the realm of host a.b.c, it first tries 45 * _kerberos.a.b.c, then _kerberos.b.c and so on. 46 * 47 * This method is described in draft-ietf-cat-krb-dns-locate-03.txt. 48 * 49 */ 50 51static int 52copy_txt_to_realms (struct rk_resource_record *head, 53 krb5_realm **realms) 54{ 55 struct rk_resource_record *rr; 56 unsigned int n, i; 57 58 for(n = 0, rr = head; rr; rr = rr->next) 59 if (rr->type == rk_ns_t_txt) 60 ++n; 61 62 if (n == 0) 63 return -1; 64 65 *realms = malloc ((n + 1) * sizeof(krb5_realm)); 66 if (*realms == NULL) 67 return -1; 68 69 for (i = 0; i < n + 1; ++i) 70 (*realms)[i] = NULL; 71 72 for (i = 0, rr = head; rr; rr = rr->next) { 73 if (rr->type == rk_ns_t_txt) { 74 char *tmp; 75 76 tmp = strdup(rr->u.txt); 77 if (tmp == NULL) { 78 for (i = 0; i < n; ++i) 79 free ((*realms)[i]); 80 free (*realms); 81 return -1; 82 } 83 (*realms)[i] = tmp; 84 ++i; 85 } 86 } 87 return 0; 88} 89 90static int 91dns_find_realm(krb5_context context, 92 const char *domain, 93 krb5_realm **realms) 94{ 95 static const char *default_labels[] = { "_kerberos", NULL }; 96 char dom[MAXHOSTNAMELEN]; 97 struct rk_dns_reply *r; 98 const char **labels; 99 char **config_labels; 100 int i, ret; 101 102 config_labels = krb5_config_get_strings(context, NULL, "libdefaults", 103 "dns_lookup_realm_labels", NULL); 104 if(config_labels != NULL) 105 labels = (const char **)config_labels; 106 else 107 labels = default_labels; 108 if(*domain == '.') 109 domain++; 110 for (i = 0; labels[i] != NULL; i++) { 111 ret = snprintf(dom, sizeof(dom), "%s.%s.", labels[i], domain); 112 if(ret < 0 || (size_t)ret >= sizeof(dom)) { 113 if (config_labels) 114 krb5_config_free_strings(config_labels); 115 return -1; 116 } 117 r = rk_dns_lookup(dom, "TXT"); 118 if(r != NULL) { 119 ret = copy_txt_to_realms (r->head, realms); 120 rk_dns_free_data(r); 121 if(ret == 0) { 122 if (config_labels) 123 krb5_config_free_strings(config_labels); 124 return 0; 125 } 126 } 127 } 128 if (config_labels) 129 krb5_config_free_strings(config_labels); 130 return -1; 131} 132 133/* 134 * Try to figure out what realms host in `domain' belong to from the 135 * configuration file. 136 */ 137 138static int 139config_find_realm(krb5_context context, 140 const char *domain, 141 krb5_realm **realms) 142{ 143 char **tmp = krb5_config_get_strings (context, NULL, 144 "domain_realm", 145 domain, 146 NULL); 147 148 if (tmp == NULL) 149 return -1; 150 *realms = tmp; 151 return 0; 152} 153 154/* 155 * This function assumes that `host' is a FQDN (and doesn't handle the 156 * special case of host == NULL either). 157 * Try to find mapping in the config file or DNS and it that fails, 158 * fall back to guessing 159 */ 160 161KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL 162_krb5_get_host_realm_int (krb5_context context, 163 const char *host, 164 krb5_boolean use_dns, 165 krb5_realm **realms) 166{ 167 const char *p, *q; 168 krb5_boolean dns_locate_enable; 169 170 dns_locate_enable = krb5_config_get_bool_default(context, NULL, TRUE, 171 "libdefaults", "dns_lookup_realm", NULL); 172 for (p = host; p != NULL; p = strchr (p + 1, '.')) { 173 if(config_find_realm(context, p, realms) == 0) { 174 if(strcasecmp(*realms[0], "dns_locate") == 0) { 175 if(use_dns) 176 for (q = host; q != NULL; q = strchr(q + 1, '.')) 177 if(dns_find_realm(context, q, realms) == 0) 178 return 0; 179 continue; 180 } else 181 return 0; 182 } 183 else if(use_dns && dns_locate_enable) { 184 if(dns_find_realm(context, p, realms) == 0) 185 return 0; 186 } 187 } 188 p = strchr(host, '.'); 189 if(p != NULL) { 190 p++; 191 *realms = malloc(2 * sizeof(krb5_realm)); 192 if (*realms == NULL) { 193 krb5_set_error_message(context, ENOMEM, N_("malloc: out of memory", "")); 194 return ENOMEM; 195 } 196 197 (*realms)[0] = strdup(p); 198 if((*realms)[0] == NULL) { 199 free(*realms); 200 krb5_set_error_message(context, ENOMEM, N_("malloc: out of memory", "")); 201 return ENOMEM; 202 } 203 strupr((*realms)[0]); 204 (*realms)[1] = NULL; 205 return 0; 206 } 207 krb5_set_error_message(context, KRB5_ERR_HOST_REALM_UNKNOWN, 208 N_("unable to find realm of host %s", ""), 209 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_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL 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_message(context, KRB5_ERR_HOST_REALM_UNKNOWN, 252 N_("Unable to find realm of host %s", ""), 253 host); 254 return KRB5_ERR_HOST_REALM_UNKNOWN; 255 } 256 } 257 return ret; 258} 259