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 /**********************************************************************************
  30  Try to verify a ticket using the system keytab... the system keytab has kvno -1 entries, so
  31  it's more like what microsoft does... see comment in utils/net_ads.c in the
  32  ads_keytab_add_entry function for details.
  33 ***********************************************************************************/
  34
  35 static BOOL ads_keytab_verify_ticket(krb5_context context, krb5_auth_context auth_context,
  36                         const DATA_BLOB *ticket, krb5_data *p_packet, krb5_ticket **pp_tkt)
  37 {
  38         krb5_error_code ret = 0;
  39         BOOL auth_ok = False;
  40
  41         krb5_keytab keytab = NULL;
  42         krb5_kt_cursor cursor;
  43         krb5_keytab_entry kt_entry;
  44         char *princ_name = NULL;
  45
  46         ZERO_STRUCT(kt_entry);
  47         ZERO_STRUCT(cursor);
  48
  49         ret = krb5_kt_default(context, &keytab);
  50         if (ret) {
  51                 DEBUG(1, ("ads_keytab_verify_ticket: krb5_kt_default failed (%s)\n", error_message(ret)));
  52                 goto out;
  53         }
  54
  55         ret = krb5_kt_start_seq_get(context, keytab, &cursor);
  56         if (ret) {
  57                 DEBUG(1, ("ads_keytab_verify_ticket: krb5_kt_start_seq_get failed (%s)\n", error_message(ret)));
  58                 goto out;
  59         }
  60
  61         while (!krb5_kt_next_entry(context, keytab, &kt_entry, &cursor)) {
  62                 ret = krb5_unparse_name(context, kt_entry.principal, &princ_name);
  63                 if (ret) {
  64                         DEBUG(1, ("ads_keytab_verify_ticket: krb5_unparse_name failed (%s)\n", error_message(ret)));
  65                         goto out;
  66                 }
  67                 /* Look for a CIFS ticket */
  68                 if (!StrnCaseCmp(princ_name, "cifs/", 5)) {
  69 #ifdef HAVE_KRB5_KEYTAB_ENTRY_KEYBLOCK
  70                         krb5_auth_con_setuseruserkey(context, auth_context, &kt_entry.keyblock);
  71 #else
  72                         krb5_auth_con_setuseruserkey(context, auth_context, &kt_entry.key);
  73 #endif
  74
  75                         p_packet->length = ticket->length;
  76                         p_packet->data = (krb5_pointer)ticket->data;
  77
  78                         if (!(ret = krb5_rd_req(context, &auth_context, p_packet, NULL, NULL, NULL, pp_tkt))) {
  79                                 unsigned int keytype;
  80                                 krb5_free_unparsed_name(context, princ_name);
  81                                 princ_name = NULL;
  82 #ifdef HAVE_KRB5_KEYTAB_ENTRY_KEYBLOCK
  83                                 keytype = (unsigned int) kt_entry.keyblock.keytype;
  84 #else
  85                                 keytype = (unsigned int) kt_entry.key.enctype;
  86 #endif
  87                                 DEBUG(10,("ads_keytab_verify_ticket: enc type [%u] decrypted message !\n",
  88                                           keytype));
  89                                 auth_ok = True;
  90                                 break;
  91                         }
  92                 }
  93                 krb5_free_unparsed_name(context, princ_name);
  94                 princ_name = NULL;
  95         }
  96         if (ret && ret != KRB5_KT_END) {
  97                 /* This failed because something went wrong, not because the keytab file was empty. */
  98                 DEBUG(1, ("ads_keytab_verify_ticket: krb5_kt_next_entry failed (%s)\n", error_message(ret)));
  99                 goto out;
 100         }
 101
 102   out:
 103
 104         if (princ_name) {
 105                 krb5_free_unparsed_name(context, princ_name);
 106         }
 107         {
 108                 krb5_kt_cursor zero_csr;
 109                 ZERO_STRUCT(zero_csr);
 110                 if ((memcmp(&cursor, &zero_csr, sizeof(krb5_kt_cursor)) != 0) && keytab) {
 111                         krb5_kt_end_seq_get(context, keytab, &cursor);
 112                 }
 113         }
 114         if (keytab) {
 115                 krb5_kt_close(context, keytab);
 116         }
 117
 118         return auth_ok;
 119 }
 120
 121 /**********************************************************************************
 122  Try to verify a ticket using the secrets.tdb.
 123 ***********************************************************************************/
 124
 125 static BOOL ads_secrets_verify_ticket(krb5_context context, krb5_auth_context auth_context,
 126                         krb5_principal host_princ,
 127                         const DATA_BLOB *ticket, krb5_data *p_packet, krb5_ticket **pp_tkt)
 128 {
 129         krb5_error_code ret = 0;
 130         BOOL auth_ok = False;
 131         char *password_s = NULL;
 132         krb5_data password;
 133         krb5_enctype *enctypes = NULL;
 134         int i;
 135
 136         if (!secrets_init()) {
 137                 DEBUG(1,("ads_secrets_verify_ticket: secrets_init failed\n"));
 138                 return False;
 139         }
 140
 141         password_s = secrets_fetch_machine_password(lp_workgroup(), NULL, NULL);
 142         if (!password_s) {
 143                 DEBUG(1,("ads_secrets_verify_ticket: failed to fetch machine password\n"));
 144                 return False;
 145         }
 146
 147         password.data = password_s;
 148         password.length = strlen(password_s);
 149
 150         /* CIFS doesn't use addresses in tickets. This would break NAT. JRA */
 151
 152         if ((ret = get_kerberos_allowed_etypes(context, &enctypes))) {
 153                 DEBUG(1,("ads_secrets_verify_ticket: krb5_get_permitted_enctypes failed (%s)\n",
 154                          error_message(ret)));
 155                 goto out;
 156         }
 157
 158         p_packet->length = ticket->length;
 159         p_packet->data = (krb5_pointer)ticket->data;
 160
 161         /* We need to setup a auth context with each possible encoding type in turn. */
 162         for (i=0;enctypes[i];i++) {
 163                 krb5_keyblock *key = NULL;
 164
 165                 if (!(key = (krb5_keyblock *)malloc(sizeof(*key)))) {
 166                         goto out;
 167                 }
 168
 169                 if (create_kerberos_key_from_string(context, host_princ, &password, key, enctypes[i])) {
 170                         SAFE_FREE(key);
 171                         continue;
 172                 }
 173
 174                 krb5_auth_con_setuseruserkey(context, auth_context, key);
 175
 176                 krb5_free_keyblock(context, key);
 177
 178                 if (!(ret = krb5_rd_req(context, &auth_context, p_packet,
 179                                         NULL,
 180                                         NULL, NULL, pp_tkt))) {
 181                         DEBUG(10,("ads_secrets_verify_ticket: enc type [%u] decrypted message !\n",
 182                                 (unsigned int)enctypes[i] ));
 183                         auth_ok = True;
 184                         break;
 185                 }
 186
 187                 DEBUG((ret != KRB5_BAD_ENCTYPE) ? 3 : 10,
 188                                 ("ads_secrets_verify_ticket: enc type [%u] failed to decrypt with error %s\n",
 189                                 (unsigned int)enctypes[i], error_message(ret)));
 190         }
 191
 192  out:
 193
 194         free_kerberos_etypes(context, enctypes);
 195         SAFE_FREE(password_s);
 196
 197         return auth_ok;
 198 }
 199
 200 /**********************************************************************************
 201  Verify an incoming ticket and parse out the principal name and
 202  authorization_data if available.
 203 ***********************************************************************************/
 204
 205 NTSTATUS ads_verify_ticket(const char *realm, const DATA_BLOB *ticket,
 206                            char **principal, DATA_BLOB *auth_data,
 207                            DATA_BLOB *ap_rep,
 208                            DATA_BLOB *session_key)
 209 {
 210         NTSTATUS sret = NT_STATUS_LOGON_FAILURE;
 211         krb5_context context = NULL;
 212         krb5_auth_context auth_context = NULL;
 213         krb5_data packet;
 214         krb5_ticket *tkt = NULL;
 215         krb5_rcache rcache = NULL;
 216         int ret;
 217
 218         krb5_principal host_princ = NULL;
 219         char *host_princ_s = NULL;
 220         BOOL got_replay_mutex = False;
 221
 222         fstring myname;
 223         BOOL auth_ok = False;
 224
 225         ZERO_STRUCT(packet);
 226         ZERO_STRUCTP(auth_data);
 227         ZERO_STRUCTP(ap_rep);
 228         ZERO_STRUCTP(session_key);
 229
 230         initialize_krb5_error_table();
 231         ret = krb5_init_context(&context);
 232         if (ret) {
 233                 DEBUG(1,("ads_verify_ticket: krb5_init_context failed (%s)\n", error_message(ret)));
 234                 return NT_STATUS_LOGON_FAILURE;
 235         }
 236
 237         ret = krb5_set_default_realm(context, realm);
 238         if (ret) {
 239                 DEBUG(1,("ads_verify_ticket: krb5_set_default_realm failed (%s)\n", error_message(ret)));
 240                 goto out;
 241         }
 242
 243         /* This whole process is far more complex than I would
 244            like. We have to go through all this to allow us to store
 245            the secret internally, instead of using /etc/krb5.keytab */
 246
 247         ret = krb5_auth_con_init(context, &auth_context);
 248         if (ret) {
 249                 DEBUG(1,("ads_verify_ticket: krb5_auth_con_init failed (%s)\n", error_message(ret)));
 250                 goto out;
 251         }
 252
 253         name_to_fqdn(myname, global_myname());
 254         strlower_m(myname);
 255         asprintf(&host_princ_s, "host/%s@%s", myname, lp_realm());
 256         ret = krb5_parse_name(context, host_princ_s, &host_princ);
 257         if (ret) {
 258                 DEBUG(1,("ads_verify_ticket: krb5_parse_name(%s) failed (%s)\n",
 259                                         host_princ_s, error_message(ret)));
 260                 goto out;
 261         }
 262
 263
 264         /* Lock a mutex surrounding the replay as there is no locking in the MIT krb5
 265          * code surrounding the replay cache... */
 266
 267         if (!grab_server_mutex("replay cache mutex")) {
 268                 DEBUG(1,("ads_verify_ticket: unable to protect replay cache with mutex.\n"));
 269                 goto out;
 270         }
 271
 272         got_replay_mutex = True;
 273
 274         /*
 275          * JRA. We must set the rcache here. This will prevent replay attacks.
 276          */
 277
 278         ret = krb5_get_server_rcache(context, krb5_princ_component(context, host_princ, 0), &rcache);
 279         if (ret) {
 280                 DEBUG(1,("ads_verify_ticket: krb5_get_server_rcache failed (%s)\n", error_message(ret)));
 281                 goto out;
 282         }
 283
 284         ret = krb5_auth_con_setrcache(context, auth_context, rcache);
 285         if (ret) {
 286                 DEBUG(1,("ads_verify_ticket: krb5_auth_con_setrcache failed (%s)\n", error_message(ret)));
 287                 goto out;
 288         }
 289
 290         if (lp_use_kerberos_keytab()) {
 291                 auth_ok = ads_keytab_verify_ticket(context, auth_context, ticket, &packet, &tkt);
 292         }
 293         if (!auth_ok) {
 294                 auth_ok = ads_secrets_verify_ticket(context, auth_context, host_princ,
 295                                                         ticket, &packet, &tkt);
 296         }
 297
 298         release_server_mutex();
 299         got_replay_mutex = False;
 300
 301         if (!auth_ok) {
 302                 DEBUG(3,("ads_verify_ticket: krb5_rd_req with auth failed (%s)\n",
 303                          error_message(ret)));
 304                 goto out;
 305         }
 306
 307         ret = krb5_mk_rep(context, auth_context, &packet);
 308         if (ret) {
 309                 DEBUG(3,("ads_verify_ticket: Failed to generate mutual authentication reply (%s)\n",
 310                         error_message(ret)));
 311                 goto out;
 312         }
 313
 314         *ap_rep = data_blob(packet.data, packet.length);
 315         SAFE_FREE(packet.data);
 316         packet.length = 0;
 317
 318         get_krb5_smb_session_key(context, auth_context, session_key, True);
 319         dump_data_pw("SMB session key (from ticket)\n", session_key->data, session_key->length);
 320
 321 #if 0
 322         file_save("/tmp/ticket.dat", ticket->data, ticket->length);
 323 #endif
 324
 325         get_auth_data_from_tkt(auth_data, tkt);
 326
 327         {
 328                 TALLOC_CTX *ctx = talloc_init("pac data");
 329                 decode_pac_data(auth_data, ctx);
 330                 talloc_destroy(ctx);
 331         }
 332
 333 #if 0
 334         if (tkt->enc_part2) {
 335                 file_save("/tmp/authdata.dat",
 336                           tkt->enc_part2->authorization_data[0]->contents,
 337                           tkt->enc_part2->authorization_data[0]->length);
 338         }
 339 #endif
 340
 341         if ((ret = krb5_unparse_name(context, get_principal_from_tkt(tkt),
 342                                      principal))) {
 343                 DEBUG(3,("ads_verify_ticket: krb5_unparse_name failed (%s)\n",
 344                          error_message(ret)));
 345                 sret = NT_STATUS_LOGON_FAILURE;
 346                 goto out;
 347         }
 348
 349         sret = NT_STATUS_OK;
 350
 351  out:
 352
 353         if (got_replay_mutex) {
 354                 release_server_mutex();
 355         }
 356
 357         if (!NT_STATUS_IS_OK(sret)) {
 358                 data_blob_free(auth_data);
 359         }
 360
 361         if (!NT_STATUS_IS_OK(sret)) {
 362                 data_blob_free(ap_rep);
 363         }
 364
 365         if (host_princ) {
 366                 krb5_free_principal(context, host_princ);
 367         }
 368
 369         if (tkt != NULL) {
 370                 krb5_free_ticket(context, tkt);
 371         }
 372
 373         SAFE_FREE(host_princ_s);
 374
 375         if (auth_context) {
 376                 krb5_auth_con_free(context, auth_context);
 377         }
 378
 379         if (context) {
 380                 krb5_free_context(context);
 381         }
 382
 383         return sret;
 384 }
 385
 386 #endif /* HAVE_KRB5 */