source/libads/kerberos_verify.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    kerberos utility library
   4    Copyright (C) Andrew Tridgell 2001
   5    Copyright (C) Remus Koos 2001
   6    Copyright (C) Luke Howard 2003
   7    Copyright (C) Guenther Deschner 2003
   8    Copyright (C) Jim McDonough (jmcd@us.ibm.com) 2003
   9
  10    This program is free software; you can redistribute it and/or modify
  11    it under the terms of the GNU General Public License as published by
  12    the Free Software Foundation; either version 2 of the License, or
  13    (at your option) any later version.
  14
  15    This program is distributed in the hope that it will be useful,
  16    but WITHOUT ANY WARRANTY; without even the implied warranty of
  17    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18    GNU General Public License for more details.
  19
  20    You should have received a copy of the GNU General Public License
  21    along with this program; if not, write to the Free Software
  22    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  23 */
  24
  25 #include "includes.h"
  26
  27 #ifdef HAVE_KRB5
  28
  29 static void free_keytab(krb5_context context, krb5_keytab keytab)
  30 {
  31         int ret=0;
  32
  33         if (keytab)
  34                 ret = krb5_kt_close(context, keytab);
  35         if (ret) {
  36                 DEBUG(3, ("krb5_kt_close failed (%s)\n",
  37                           error_message(ret)));
  38         }
  39 }
  40
  41 #ifdef HAVE_MEMORY_KEYTAB
  42 static krb5_error_code create_keytab(krb5_context context,
  43                                      krb5_principal host_princ,
  44                                      char *host_princ_s,
  45                                      krb5_data password,
  46                                      krb5_enctype *enctypes,
  47                                      krb5_keytab *keytab,
  48                                      char *keytab_name)
  49 {
  50         krb5_keytab_entry entry;
  51         krb5_kvno kvno = 1;
  52         krb5_error_code ret;
  53         krb5_keyblock *key;
  54         int i;
  55
  56         DEBUG(10,("creating keytab: %s\n", keytab_name));
  57         ret = krb5_kt_resolve(context, keytab_name, keytab);
  58         if (ret)
  59                 return ret;
  60
  61         if (!(key = (krb5_keyblock *)malloc(sizeof(*key)))) {
  62                 return ENOMEM;
  63         }
  64
  65         /* add keytab entries for all encryption types */
  66         for ( i=0; enctypes[i]; i++ ) {
  67
  68                 if (create_kerberos_key_from_string(context, host_princ, &password, key, enctypes[i])) {
  69                         continue;
  70                 }
  71
  72                 entry.principal = host_princ;
  73                 entry.vno       = kvno;
  74                 /* this will have to be detected in configure...heimdal
  75                    calls it keyblock, MIT calls it key, but it does not
  76                    matter we are creating keytabs with MIT */
  77                 entry.keyblock  = *key;
  78
  79                 DEBUG(10,("adding keytab-entry for (%s) with encryption type (%d)\n",
  80                                 host_princ_s, enctypes[i]));
  81                 ret = krb5_kt_add_entry(context, *keytab, &entry);
  82                 if (ret) {
  83                         DEBUG(1,("adding entry to keytab failed (%s)\n",
  84                                  error_message(ret)));
  85                         free_keytab(context, *keytab);
  86                         return ret;
  87                 }
  88         }
  89         krb5_free_keyblock(context, key);
  90
  91         return 0;
  92 }
  93 #endif
  94
  95 static BOOL setup_keytab(krb5_context context,
  96                          krb5_principal host_princ,
  97                          char *host_princ_s,
  98                          krb5_data password,
  99                          krb5_enctype *enctypes,
 100                          krb5_keytab *keytab)
 101 {
 102         char *keytab_name = NULL;
 103         krb5_error_code ret;
 104
 105         /* check if we have to setup a keytab - not currently enabled
 106            I've put this in so that the else block below functions
 107            the same way that it will when this code is turned on */
 108         if (0 /* will later be *lp_keytab() */) {
 109
 110                 /* use a file-keytab */
 111                 asprintf(&keytab_name, "%s:%s",
 112                          ""
 113                          /* KRB5_KT_FILE_PREFIX, "FILE" or
 114                             "WRFILE" depending on HEeimdal or MIT */,
 115                          "" /* will later be lp_keytab() */);
 116
 117                 DEBUG(10,("will use filebased keytab: %s\n", keytab_name));
 118                 ret = krb5_kt_resolve(context, keytab_name, keytab);
 119                 if (ret) {
 120                         DEBUG(3,("cannot resolve keytab name %s (%s)\n",
 121                                  keytab_name,
 122                                  error_message(ret)));
 123                         SAFE_FREE(keytab_name);
 124                         return False;
 125                 }
 126
 127         }
 128
 129 #if defined(HAVE_MEMORY_KEYTAB)
 130         else {
 131
 132                 /* setup a in-memory-keytab */
 133                 asprintf(&keytab_name, "MEMORY:");
 134
 135                 ret = create_keytab(context, host_princ, host_princ_s, password, enctypes,
 136                         keytab, keytab_name);
 137                 if (ret) {
 138                         DEBUG(3,("unable to create MEMORY: keytab (%s)\n",
 139                                  error_message(ret)));
 140                         SAFE_FREE(keytab_name);
 141                         return False;
 142                 }
 143         }
 144 #endif
 145         SAFE_FREE(keytab_name);
 146         return True;
 147 }
 148
 149
 150 /*
 151   verify an incoming ticket and parse out the principal name and
 152   authorization_data if available
 153 */
 154 NTSTATUS ads_verify_ticket(const char *realm, const DATA_BLOB *ticket,
 155                            char **principal, DATA_BLOB *auth_data,
 156                            DATA_BLOB *ap_rep,
 157                            uint8 session_key[16])
 158 {
 159         NTSTATUS sret = NT_STATUS_LOGON_FAILURE;
 160         krb5_context context = NULL;
 161         krb5_auth_context auth_context = NULL;
 162         krb5_keytab keytab = NULL;
 163         krb5_data packet;
 164         krb5_ticket *tkt = NULL;
 165         krb5_rcache rcache = NULL;
 166         int ret, i;
 167         krb5_keyblock *key = NULL;
 168         krb5_principal host_princ;
 169         char *host_princ_s = NULL;
 170         fstring myname;
 171         char *password_s = NULL;
 172         krb5_data password;
 173         krb5_enctype *enctypes = NULL;
 174 #if 0
 175         krb5_address local_addr;
 176         krb5_address remote_addr;
 177 #endif
 178         BOOL auth_ok = False;
 179
 180         ZERO_STRUCT(packet);
 181         ZERO_STRUCT(password);
 182         ZERO_STRUCTP(auth_data);
 183         ZERO_STRUCTP(ap_rep);
 184
 185         if (!secrets_init()) {
 186                 DEBUG(1,("ads_verify_ticket: secrets_init failed\n"));
 187                 return NT_STATUS_LOGON_FAILURE;
 188         }
 189
 190         password_s = secrets_fetch_machine_password(lp_workgroup(), NULL, NULL);
 191         if (!password_s) {
 192                 DEBUG(1,("ads_verify_ticket: failed to fetch machine password\n"));
 193                 return NT_STATUS_LOGON_FAILURE;
 194         }
 195
 196         password.data = password_s;
 197         password.length = strlen(password_s);
 198
 199         ret = krb5_init_context(&context);
 200         if (ret) {
 201                 DEBUG(1,("ads_verify_ticket: krb5_init_context failed (%s)\n", error_message(ret)));
 202                 return NT_STATUS_LOGON_FAILURE;
 203         }
 204
 205         ret = krb5_set_default_realm(context, realm);
 206         if (ret) {
 207                 DEBUG(1,("ads_verify_ticket: krb5_set_default_realm failed (%s)\n", error_message(ret)));
 208                 sret = NT_STATUS_LOGON_FAILURE;
 209                 goto out;
 210         }
 211
 212         /* This whole process is far more complex than I would
 213            like. We have to go through all this to allow us to store
 214            the secret internally, instead of using /etc/krb5.keytab */
 215
 216         ret = krb5_auth_con_init(context, &auth_context);
 217         if (ret) {
 218                 DEBUG(1,("ads_verify_ticket: krb5_auth_con_init failed (%s)\n", error_message(ret)));
 219                 sret = NT_STATUS_LOGON_FAILURE;
 220                 goto out;
 221         }
 222
 223         fstrcpy(myname, global_myname());
 224         strlower_m(myname);
 225         asprintf(&host_princ_s, "HOST/%s@%s", myname, lp_realm());
 226         ret = krb5_parse_name(context, host_princ_s, &host_princ);
 227         if (ret) {
 228                 DEBUG(1,("ads_verify_ticket: krb5_parse_name(%s) failed (%s)\n",
 229                                         host_princ_s, error_message(ret)));
 230                 sret = NT_STATUS_LOGON_FAILURE;
 231                 goto out;
 232         }
 233
 234         /*
 235          * JRA. We must set the rcache here. This will prevent replay attacks.
 236          */
 237
 238         ret = krb5_get_server_rcache(context, krb5_princ_component(context, host_princ, 0), &rcache);
 239         if (ret) {
 240                 DEBUG(1,("ads_verify_ticket: krb5_get_server_rcache failed (%s)\n", error_message(ret)));
 241                 sret = NT_STATUS_LOGON_FAILURE;
 242                 goto out;
 243         }
 244
 245         ret = krb5_auth_con_setrcache(context, auth_context, rcache);
 246         if (ret) {
 247                 DEBUG(1,("ads_verify_ticket: krb5_auth_con_setrcache failed (%s)\n", error_message(ret)));
 248                 sret = NT_STATUS_LOGON_FAILURE;
 249                 goto out;
 250         }
 251
 252         /* CIFS doesn't use addresses in tickets. This would breat NAT. JRA */
 253
 254         if ((ret = get_kerberos_allowed_etypes(context, &enctypes))) {
 255                 DEBUG(1,("ads_verify_ticket: krb5_get_permitted_enctypes failed (%s)\n",
 256                          error_message(ret)));
 257                 sret = NT_STATUS_LOGON_FAILURE;
 258                 goto out;
 259         }
 260
 261         /* Lock a mutex surrounding the replay as there is no locking in the MIT krb5
 262          * code surrounding the replay cache... */
 263
 264         if (!grab_server_mutex("replay cache mutex")) {
 265                 DEBUG(1,("ads_verify_ticket: unable to protect replay cache with mutex.\n"));
 266                 sret = NT_STATUS_LOGON_FAILURE;
 267                 goto out;
 268         }
 269
 270         if (!setup_keytab(context, host_princ, host_princ_s, password,
 271                           enctypes, &keytab)) {
 272                 DEBUG(3,("ads_verify_ticket: unable to setup keytab\n"));
 273                 sret = NT_STATUS_LOGON_FAILURE;
 274                 goto out;
 275         }
 276
 277         /* We need to setup a auth context with each possible encoding type in turn. */
 278         for (i=0;enctypes[i];i++) {
 279                 if (!(key = (krb5_keyblock *)malloc(sizeof(*key)))) {
 280                         sret = NT_STATUS_NO_MEMORY;
 281                         goto out;
 282                 }
 283
 284                 if (create_kerberos_key_from_string(context, host_princ, &password, key, enctypes[i])) {
 285                         continue;
 286                 }
 287
 288                 krb5_auth_con_setuseruserkey(context, auth_context, key);
 289
 290                 krb5_free_keyblock(context, key);
 291
 292                 packet.length = ticket->length;
 293                 packet.data = (krb5_pointer)ticket->data;
 294
 295                 if (!(ret = krb5_rd_req(context, &auth_context, &packet,
 296 #ifdef HAVE_MEMORY_KEYTAB
 297                                         host_princ,
 298 #else
 299                                         NULL,
 300 #endif
 301                                         keytab, NULL, &tkt))) {
 302                         DEBUG(10,("ads_verify_ticket: enc type [%u] decrypted message !\n",
 303                                 (unsigned int)enctypes[i] ));
 304                         auth_ok = True;
 305                         break;
 306                 }
 307
 308                 DEBUG((ret != KRB5_BAD_ENCTYPE) ? 3 : 10,
 309                                 ("ads_verify_ticket: enc type [%u] failed to decrypt with error %s\n",
 310                                 (unsigned int)enctypes[i], error_message(ret)));
 311         }
 312
 313         release_server_mutex();
 314
 315         if (!auth_ok) {
 316                 DEBUG(3,("ads_verify_ticket: krb5_rd_req with auth failed (%s)\n",
 317                          error_message(ret)));
 318                 sret = NT_STATUS_LOGON_FAILURE;
 319                 goto out;
 320         }
 321
 322         ret = krb5_mk_rep(context, auth_context, &packet);
 323         if (ret) {
 324                 DEBUG(3,("ads_verify_ticket: Failed to generate mutual authentication reply (%s)\n",
 325                         error_message(ret)));
 326                 sret = NT_STATUS_LOGON_FAILURE;
 327                 goto out;
 328         }
 329
 330         *ap_rep = data_blob(packet.data, packet.length);
 331         free(packet.data);
 332
 333         get_krb5_smb_session_key(context, auth_context, session_key, True);
 334 #ifdef DEBUG_PASSWORD
 335         DEBUG(10,("SMB session key (from ticket) follows:\n"));
 336         dump_data(10, session_key, 16);
 337 #endif
 338
 339 #if 0
 340         file_save("/tmp/ticket.dat", ticket->data, ticket->length);
 341 #endif
 342
 343         get_auth_data_from_tkt(auth_data, tkt);
 344
 345         {
 346                 TALLOC_CTX *ctx = talloc_init("pac data");
 347                 decode_pac_data(auth_data, ctx);
 348                 talloc_destroy(ctx);
 349         }
 350
 351 #if 0
 352         if (tkt->enc_part2) {
 353                 file_save("/tmp/authdata.dat",
 354                           tkt->enc_part2->authorization_data[0]->contents,
 355                           tkt->enc_part2->authorization_data[0]->length);
 356         }
 357 #endif
 358
 359
 360         /* get rid of all resources associated with the keytab */
 361         if (keytab) free_keytab(context, keytab);
 362
 363         if ((ret = krb5_unparse_name(context, get_principal_from_tkt(tkt),
 364                                      principal))) {
 365                 DEBUG(3,("ads_verify_ticket: krb5_unparse_name failed (%s)\n",
 366                          error_message(ret)));
 367                 sret = NT_STATUS_LOGON_FAILURE;
 368                 goto out;
 369         }
 370
 371         sret = NT_STATUS_OK;
 372
 373  out:
 374
 375         if (!NT_STATUS_IS_OK(sret))
 376                 data_blob_free(auth_data);
 377
 378         if (!NT_STATUS_IS_OK(sret))
 379                 data_blob_free(ap_rep);
 380
 381         krb5_free_principal(context, host_princ);
 382         if (tkt != NULL)
 383                 krb5_free_ticket(context, tkt);
 384         free_kerberos_etypes(context, enctypes);
 385         SAFE_FREE(password_s);
 386         SAFE_FREE(host_princ_s);
 387
 388         if (auth_context)
 389                 krb5_auth_con_free(context, auth_context);
 390
 391         if (context)
 392                 krb5_free_context(context);
 393
 394         return sret;
 395 }
 396
 397 #endif /* HAVE_KRB5 */