source3/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
  75 #if !defined(HAVE_KRB5_KEYTAB_ENTRY_KEY) && !defined(HAVE_KRB5_KEYTAB_ENTRY_KEYBLOCK)
  76 #error krb5_keytab_entry has no key or keyblock member
  77 #endif
  78
  79 #ifdef HAVE_KRB5_KEYTAB_ENTRY_KEY /* MIT */
  80                 entry.key = *key;
  81 #endif
  82
  83 #ifdef HAVE_KRB5_KEYTAB_ENTRY_KEYBLOCK /* Heimdal */
  84                 entry.keyblock = *key;
  85 #endif
  86
  87                 DEBUG(10,("adding keytab-entry for (%s) with encryption type (%d)\n",
  88                                 host_princ_s, enctypes[i]));
  89                 ret = krb5_kt_add_entry(context, *keytab, &entry);
  90                 if (ret) {
  91                         DEBUG(1,("adding entry to keytab failed (%s)\n",
  92                                  error_message(ret)));
  93                         free_keytab(context, *keytab);
  94                         return ret;
  95                 }
  96         }
  97         krb5_free_keyblock(context, key);
  98
  99         return 0;
 100 }
 101 #endif
 102
 103 static BOOL setup_keytab(krb5_context context,
 104                          krb5_principal host_princ,
 105                          char *host_princ_s,
 106                          krb5_data password,
 107                          krb5_enctype *enctypes,
 108                          krb5_keytab *keytab)
 109 {
 110         char *keytab_name = NULL;
 111         krb5_error_code ret;
 112
 113         /* check if we have to setup a keytab - not currently enabled
 114            I've put this in so that the else block below functions
 115            the same way that it will when this code is turned on */
 116         if (0 /* will later be *lp_keytab() */) {
 117
 118                 /* use a file-keytab */
 119                 asprintf(&keytab_name, "%s:%s",
 120                          ""
 121                          /* KRB5_KT_FILE_PREFIX, "FILE" or
 122                             "WRFILE" depending on HEeimdal or MIT */,
 123                          "" /* will later be lp_keytab() */);
 124
 125                 DEBUG(10,("will use filebased keytab: %s\n", keytab_name));
 126                 ret = krb5_kt_resolve(context, keytab_name, keytab);
 127                 if (ret) {
 128                         DEBUG(3,("cannot resolve keytab name %s (%s)\n",
 129                                  keytab_name,
 130                                  error_message(ret)));
 131                         SAFE_FREE(keytab_name);
 132                         return False;
 133                 }
 134
 135         }
 136
 137 #if defined(HAVE_MEMORY_KEYTAB)
 138         else {
 139
 140                 /* setup a in-memory-keytab */
 141                 asprintf(&keytab_name, "MEMORY:");
 142
 143                 ret = create_keytab(context, host_princ, host_princ_s, password, enctypes,
 144                         keytab, keytab_name);
 145                 if (ret) {
 146                         DEBUG(3,("unable to create MEMORY: keytab (%s)\n",
 147                                  error_message(ret)));
 148                         SAFE_FREE(keytab_name);
 149                         return False;
 150                 }
 151         }
 152 #endif
 153         SAFE_FREE(keytab_name);
 154         return True;
 155 }
 156
 157
 158 /*
 159   verify an incoming ticket and parse out the principal name and
 160   authorization_data if available
 161 */
 162 NTSTATUS ads_verify_ticket(const char *realm, const DATA_BLOB *ticket,
 163                            char **principal, DATA_BLOB *auth_data,
 164                            DATA_BLOB *ap_rep,
 165                            uint8 session_key[16])
 166 {
 167         NTSTATUS sret = NT_STATUS_LOGON_FAILURE;
 168         krb5_context context = NULL;
 169         krb5_auth_context auth_context = NULL;
 170         krb5_keytab keytab = NULL;
 171         krb5_data packet;
 172         krb5_ticket *tkt = NULL;
 173         krb5_rcache rcache = NULL;
 174         int ret, i;
 175         krb5_keyblock *key = NULL;
 176         krb5_principal host_princ;
 177         char *host_princ_s = NULL;
 178         fstring myname;
 179         char *password_s = NULL;
 180         krb5_data password;
 181         krb5_enctype *enctypes = NULL;
 182 #if 0
 183         krb5_address local_addr;
 184         krb5_address remote_addr;
 185 #endif
 186         BOOL auth_ok = False;
 187
 188         ZERO_STRUCT(packet);
 189         ZERO_STRUCT(password);
 190         ZERO_STRUCTP(auth_data);
 191         ZERO_STRUCTP(ap_rep);
 192
 193         if (!secrets_init()) {
 194                 DEBUG(1,("ads_verify_ticket: secrets_init failed\n"));
 195                 return NT_STATUS_LOGON_FAILURE;
 196         }
 197
 198         password_s = secrets_fetch_machine_password(lp_workgroup(), NULL, NULL);
 199         if (!password_s) {
 200                 DEBUG(1,("ads_verify_ticket: failed to fetch machine password\n"));
 201                 return NT_STATUS_LOGON_FAILURE;
 202         }
 203
 204         password.data = password_s;
 205         password.length = strlen(password_s);
 206
 207         ret = krb5_init_context(&context);
 208         if (ret) {
 209                 DEBUG(1,("ads_verify_ticket: krb5_init_context failed (%s)\n", error_message(ret)));
 210                 return NT_STATUS_LOGON_FAILURE;
 211         }
 212
 213         ret = krb5_set_default_realm(context, realm);
 214         if (ret) {
 215                 DEBUG(1,("ads_verify_ticket: krb5_set_default_realm failed (%s)\n", error_message(ret)));
 216                 sret = NT_STATUS_LOGON_FAILURE;
 217                 goto out;
 218         }
 219
 220         /* This whole process is far more complex than I would
 221            like. We have to go through all this to allow us to store
 222            the secret internally, instead of using /etc/krb5.keytab */
 223
 224         ret = krb5_auth_con_init(context, &auth_context);
 225         if (ret) {
 226                 DEBUG(1,("ads_verify_ticket: krb5_auth_con_init failed (%s)\n", error_message(ret)));
 227                 sret = NT_STATUS_LOGON_FAILURE;
 228                 goto out;
 229         }
 230
 231         fstrcpy(myname, global_myname());
 232         strlower_m(myname);
 233         asprintf(&host_princ_s, "HOST/%s@%s", myname, lp_realm());
 234         ret = krb5_parse_name(context, host_princ_s, &host_princ);
 235         if (ret) {
 236                 DEBUG(1,("ads_verify_ticket: krb5_parse_name(%s) failed (%s)\n",
 237                                         host_princ_s, error_message(ret)));
 238                 sret = NT_STATUS_LOGON_FAILURE;
 239                 goto out;
 240         }
 241
 242         /*
 243          * JRA. We must set the rcache here. This will prevent replay attacks.
 244          */
 245
 246         ret = krb5_get_server_rcache(context, krb5_princ_component(context, host_princ, 0), &rcache);
 247         if (ret) {
 248                 DEBUG(1,("ads_verify_ticket: krb5_get_server_rcache failed (%s)\n", error_message(ret)));
 249                 sret = NT_STATUS_LOGON_FAILURE;
 250                 goto out;
 251         }
 252
 253         ret = krb5_auth_con_setrcache(context, auth_context, rcache);
 254         if (ret) {
 255                 DEBUG(1,("ads_verify_ticket: krb5_auth_con_setrcache failed (%s)\n", error_message(ret)));
 256                 sret = NT_STATUS_LOGON_FAILURE;
 257                 goto out;
 258         }
 259
 260         /* CIFS doesn't use addresses in tickets. This would breat NAT. JRA */
 261
 262         if ((ret = get_kerberos_allowed_etypes(context, &enctypes))) {
 263                 DEBUG(1,("ads_verify_ticket: krb5_get_permitted_enctypes failed (%s)\n",
 264                          error_message(ret)));
 265                 sret = NT_STATUS_LOGON_FAILURE;
 266                 goto out;
 267         }
 268
 269         /* Lock a mutex surrounding the replay as there is no locking in the MIT krb5
 270          * code surrounding the replay cache... */
 271
 272         if (!grab_server_mutex("replay cache mutex")) {
 273                 DEBUG(1,("ads_verify_ticket: unable to protect replay cache with mutex.\n"));
 274                 sret = NT_STATUS_LOGON_FAILURE;
 275                 goto out;
 276         }
 277
 278         if (!setup_keytab(context, host_princ, host_princ_s, password,
 279                           enctypes, &keytab)) {
 280                 DEBUG(3,("ads_verify_ticket: unable to setup keytab\n"));
 281                 sret = NT_STATUS_LOGON_FAILURE;
 282                 goto out;
 283         }
 284
 285         /* We need to setup a auth context with each possible encoding type in turn. */
 286         for (i=0;enctypes[i];i++) {
 287                 if (!(key = (krb5_keyblock *)malloc(sizeof(*key)))) {
 288                         sret = NT_STATUS_NO_MEMORY;
 289                         goto out;
 290                 }
 291
 292                 if (create_kerberos_key_from_string(context, host_princ, &password, key, enctypes[i])) {
 293                         continue;
 294                 }
 295
 296                 krb5_auth_con_setuseruserkey(context, auth_context, key);
 297
 298                 krb5_free_keyblock(context, key);
 299
 300                 packet.length = ticket->length;
 301                 packet.data = (krb5_pointer)ticket->data;
 302
 303                 if (!(ret = krb5_rd_req(context, &auth_context, &packet,
 304 #ifdef HAVE_MEMORY_KEYTAB
 305                                         host_princ,
 306 #else
 307                                         NULL,
 308 #endif
 309                                         keytab, NULL, &tkt))) {
 310                         DEBUG(10,("ads_verify_ticket: enc type [%u] decrypted message !\n",
 311                                 (unsigned int)enctypes[i] ));
 312                         auth_ok = True;
 313                         break;
 314                 }
 315
 316                 DEBUG((ret != KRB5_BAD_ENCTYPE) ? 3 : 10,
 317                                 ("ads_verify_ticket: enc type [%u] failed to decrypt with error %s\n",
 318                                 (unsigned int)enctypes[i], error_message(ret)));
 319         }
 320
 321         release_server_mutex();
 322
 323         if (!auth_ok) {
 324                 DEBUG(3,("ads_verify_ticket: krb5_rd_req with auth failed (%s)\n",
 325                          error_message(ret)));
 326                 sret = NT_STATUS_LOGON_FAILURE;
 327                 goto out;
 328         }
 329
 330         ret = krb5_mk_rep(context, auth_context, &packet);
 331         if (ret) {
 332                 DEBUG(3,("ads_verify_ticket: Failed to generate mutual authentication reply (%s)\n",
 333                         error_message(ret)));
 334                 sret = NT_STATUS_LOGON_FAILURE;
 335                 goto out;
 336         }
 337
 338         *ap_rep = data_blob(packet.data, packet.length);
 339         free(packet.data);
 340
 341         get_krb5_smb_session_key(context, auth_context, session_key, True);
 342 #ifdef DEBUG_PASSWORD
 343         DEBUG(10,("SMB session key (from ticket) follows:\n"));
 344         dump_data(10, session_key, 16);
 345 #endif
 346
 347 #if 0
 348         file_save("/tmp/ticket.dat", ticket->data, ticket->length);
 349 #endif
 350
 351         get_auth_data_from_tkt(auth_data, tkt);
 352
 353         {
 354                 TALLOC_CTX *ctx = talloc_init("pac data");
 355                 decode_pac_data(auth_data, ctx);
 356                 talloc_destroy(ctx);
 357         }
 358
 359 #if 0
 360         if (tkt->enc_part2) {
 361                 file_save("/tmp/authdata.dat",
 362                           tkt->enc_part2->authorization_data[0]->contents,
 363                           tkt->enc_part2->authorization_data[0]->length);
 364         }
 365 #endif
 366
 367
 368         /* get rid of all resources associated with the keytab */
 369         if (keytab) free_keytab(context, keytab);
 370
 371         if ((ret = krb5_unparse_name(context, get_principal_from_tkt(tkt),
 372                                      principal))) {
 373                 DEBUG(3,("ads_verify_ticket: krb5_unparse_name failed (%s)\n",
 374                          error_message(ret)));
 375                 sret = NT_STATUS_LOGON_FAILURE;
 376                 goto out;
 377         }
 378
 379         sret = NT_STATUS_OK;
 380
 381  out:
 382
 383         if (!NT_STATUS_IS_OK(sret))
 384                 data_blob_free(auth_data);
 385
 386         if (!NT_STATUS_IS_OK(sret))
 387                 data_blob_free(ap_rep);
 388
 389         krb5_free_principal(context, host_princ);
 390         if (tkt != NULL)
 391                 krb5_free_ticket(context, tkt);
 392         free_kerberos_etypes(context, enctypes);
 393         SAFE_FREE(password_s);
 394         SAFE_FREE(host_princ_s);
 395
 396         if (auth_context)
 397                 krb5_auth_con_free(context, auth_context);
 398
 399         if (context)
 400                 krb5_free_context(context);
 401
 402         return sret;
 403 }
 404
 405 #endif /* HAVE_KRB5 */