1 /* 2 * Copyright (c) 1997 - 2001 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,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 } 221