source/auth/kerberos/kerberos_util.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3
   4    Kerberos utility functions for GENSEC
   5
   6    Copyright (C) Andrew Bartlett <abartlet@samba.org> 2004-2005
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 2 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18
  19    You should have received a copy of the GNU General Public License
  20    along with this program; if not, write to the Free Software
  21    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  22 */
  23
  24 #include "includes.h"
  25 #include "system/kerberos.h"
  26 #include "system/time.h"
  27 #include "system/network.h"
  28 #include "auth/kerberos/kerberos.h"
  29 #include "auth/auth.h"
  30
  31 struct principal_container {
  32         struct smb_krb5_context *smb_krb5_context;
  33         krb5_principal principal;
  34 };
  35
  36 static int free_principal(void *ptr) {
  37         struct principal_container *pc = ptr;
  38         /* current heimdal - 0.6.3, which we need anyway, fixes segfaults here */
  39         krb5_free_principal(pc->smb_krb5_context->krb5_context, pc->principal);
  40
  41         return 0;
  42 }
  43
  44 krb5_error_code salt_principal_from_credentials(TALLOC_CTX *parent_ctx,
  45                                                 struct cli_credentials *machine_account,
  46                                                 struct smb_krb5_context *smb_krb5_context,
  47                                                 krb5_principal *salt_princ)
  48 {
  49         krb5_error_code ret;
  50         char *machine_username;
  51         char *salt_body;
  52         char *lower_realm;
  53         const char *salt_principal;
  54         struct principal_container *mem_ctx = talloc(parent_ctx, struct principal_container);
  55         if (!mem_ctx) {
  56                 return ENOMEM;
  57         }
  58
  59         salt_principal = cli_credentials_get_salt_principal(machine_account);
  60         if (salt_principal) {
  61                 ret = krb5_parse_name(smb_krb5_context->krb5_context, salt_principal, salt_princ);
  62         } else {
  63                 machine_username = talloc_strdup(mem_ctx, cli_credentials_get_username(machine_account));
  64
  65                 if (!machine_username) {
  66                         talloc_free(mem_ctx);
  67                         return ENOMEM;
  68                 }
  69
  70                 if (machine_username[strlen(machine_username)-1] == '$') {
  71                         machine_username[strlen(machine_username)-1] = '\0';
  72                 }
  73                 lower_realm = strlower_talloc(mem_ctx, cli_credentials_get_realm(machine_account));
  74                 if (!lower_realm) {
  75                         talloc_free(mem_ctx);
  76                         return ENOMEM;
  77                 }
  78
  79                 salt_body = talloc_asprintf(mem_ctx, "%s.%s", machine_username,
  80                                             lower_realm);
  81                 if (!salt_body) {
  82                         talloc_free(mem_ctx);
  83                 return ENOMEM;
  84                 }
  85
  86                 ret = krb5_make_principal(smb_krb5_context->krb5_context, salt_princ,
  87                                           cli_credentials_get_realm(machine_account),
  88                                           "host", salt_body, NULL);
  89         }
  90
  91         if (ret == 0) {
  92                 mem_ctx->smb_krb5_context = talloc_reference(mem_ctx, smb_krb5_context);
  93                 mem_ctx->principal = *salt_princ;
  94                 talloc_set_destructor(mem_ctx, free_principal);
  95         }
  96         return ret;
  97 }
  98
  99 /* Obtain the principal set on this context.  Requires a
 100  * smb_krb5_context because we are doing krb5 principal parsing with
 101  * the library routines.  The returned princ is placed in the talloc
 102  * system by means of a destructor (do *not* free). */
 103
 104 krb5_error_code principal_from_credentials(TALLOC_CTX *parent_ctx,
 105                                            struct cli_credentials *credentials,
 106                                            struct smb_krb5_context *smb_krb5_context,
 107                                            krb5_principal *princ)
 108 {
 109         krb5_error_code ret;
 110         const char *princ_string;
 111         struct principal_container *mem_ctx = talloc(parent_ctx, struct principal_container);
 112         if (!mem_ctx) {
 113                 return ENOMEM;
 114         }
 115
 116         princ_string = cli_credentials_get_principal(credentials, mem_ctx);
 117
 118         /* A NULL here has meaning, as the gssapi server case will then use the principal from the client */
 119         if (!princ_string) {
 120                 talloc_free(mem_ctx);
 121                 princ = NULL;
 122                 return 0;
 123         }
 124
 125         ret = krb5_parse_name(smb_krb5_context->krb5_context,
 126                               princ_string, princ);
 127
 128         if (ret == 0) {
 129                 /* This song-and-dance effectivly puts the principal
 130                  * into talloc, so we can't loose it. */
 131                 mem_ctx->smb_krb5_context = talloc_reference(mem_ctx, smb_krb5_context);
 132                 mem_ctx->principal = *princ;
 133                 talloc_set_destructor(mem_ctx, free_principal);
 134         }
 135         return ret;
 136 }
 137
 138 /**
 139  * Return a freshly allocated ccache (destroyed by destructor on child
 140  * of parent_ctx), for a given set of client credentials
 141  */
 142
 143  krb5_error_code kinit_to_ccache(TALLOC_CTX *parent_ctx,
 144                                  struct cli_credentials *credentials,
 145                                  struct smb_krb5_context *smb_krb5_context,
 146                                  krb5_ccache ccache)
 147 {
 148         krb5_error_code ret;
 149         const char *password;
 150         time_t kdc_time = 0;
 151         krb5_principal princ;
 152
 153         TALLOC_CTX *mem_ctx = talloc_new(parent_ctx);
 154
 155         if (!mem_ctx) {
 156                 return ENOMEM;
 157         }
 158
 159         ret = principal_from_credentials(mem_ctx, credentials, smb_krb5_context, &princ);
 160         if (ret) {
 161                 talloc_free(mem_ctx);
 162                 return ret;
 163         }
 164
 165         password = cli_credentials_get_password(credentials);
 166
 167         if (password) {
 168                 ret = kerberos_kinit_password_cc(smb_krb5_context->krb5_context, ccache,
 169                                                  princ,
 170                                                  password, NULL, &kdc_time);
 171         } else {
 172                 /* No password available, try to use a keyblock instead */
 173
 174                 krb5_keyblock keyblock;
 175                 const struct samr_Password *mach_pwd;
 176                 mach_pwd = cli_credentials_get_nt_hash(credentials, mem_ctx);
 177                 if (!mach_pwd) {
 178                         talloc_free(mem_ctx);
 179                         DEBUG(1, ("kinit_to_ccache: No password available for kinit\n"));
 180                         return EINVAL;
 181                 }
 182                 ret = krb5_keyblock_init(smb_krb5_context->krb5_context,
 183                                          ENCTYPE_ARCFOUR_HMAC,
 184                                          mach_pwd->hash, sizeof(mach_pwd->hash),
 185                                          &keyblock);
 186
 187                 if (ret == 0) {
 188                         ret = kerberos_kinit_keyblock_cc(smb_krb5_context->krb5_context, ccache,
 189                                                          princ,
 190                                                          &keyblock, NULL, &kdc_time);
 191                         krb5_free_keyblock_contents(smb_krb5_context->krb5_context, &keyblock);
 192                 }
 193         }
 194
 195         /* cope with ticket being in the future due to clock skew */
 196         if ((unsigned)kdc_time > time(NULL)) {
 197                 time_t t = time(NULL);
 198                 int time_offset =(unsigned)kdc_time-t;
 199                 DEBUG(4,("Advancing clock by %d seconds to cope with clock skew\n", time_offset));
 200                 krb5_set_real_time(smb_krb5_context->krb5_context, t + time_offset + 1, 0);
 201         }
 202
 203         if (ret == KRB5KRB_AP_ERR_SKEW || ret == KRB5_KDCREP_SKEW) {
 204                 DEBUG(1,("kinit for %s failed (%s)\n",
 205                          cli_credentials_get_principal(credentials, mem_ctx),
 206                          smb_get_krb5_error_message(smb_krb5_context->krb5_context,
 207                                                     ret, mem_ctx)));
 208                 talloc_free(mem_ctx);
 209                 return ret;
 210         }
 211         if (ret) {
 212                 DEBUG(1,("kinit for %s failed (%s)\n",
 213                          cli_credentials_get_principal(credentials, mem_ctx),
 214                          smb_get_krb5_error_message(smb_krb5_context->krb5_context,
 215                                                     ret, mem_ctx)));
 216                 talloc_free(mem_ctx);
 217                 return ret;
 218         }
 219         return 0;
 220 }
 221
 222 static int free_keytab(void *ptr) {
 223         struct keytab_container *ktc = ptr;
 224         krb5_kt_close(ktc->smb_krb5_context->krb5_context, ktc->keytab);
 225
 226         return 0;
 227 }
 228
 229 struct enctypes_container {
 230         struct smb_krb5_context *smb_krb5_context;
 231         krb5_enctype *enctypes;
 232 };
 233
 234 static int free_enctypes(void *ptr) {
 235         struct enctypes_container *etc = ptr;
 236         free_kerberos_etypes(etc->smb_krb5_context->krb5_context, etc->enctypes);
 237         return 0;
 238 }
 239
 240 static krb5_error_code keytab_add_keys(TALLOC_CTX *parent_ctx,
 241                                        const char *princ_string,
 242                                        krb5_principal princ,
 243                                        krb5_principal salt_princ,
 244                                        int kvno,
 245                                        const char *password_s,
 246                                        struct smb_krb5_context *smb_krb5_context,
 247                                        krb5_keytab keytab)
 248 {
 249         int i;
 250         krb5_error_code ret;
 251         krb5_enctype *enctypes;
 252         char *enctype_string;
 253         struct enctypes_container *etc;
 254         krb5_data password;
 255         TALLOC_CTX *mem_ctx = talloc_new(parent_ctx);
 256         if (!mem_ctx) {
 257                 return ENOMEM;
 258         }
 259
 260         etc = talloc(mem_ctx, struct enctypes_container);
 261         if (!etc) {
 262                 talloc_free(mem_ctx);
 263                 return ENOMEM;
 264         }
 265         ret = get_kerberos_allowed_etypes(smb_krb5_context->krb5_context,
 266                                           &enctypes);
 267         if (ret != 0) {
 268                 DEBUG(1,("keytab_add_keys: getting encrption types failed (%s)\n",
 269                          error_message(ret)));
 270                 talloc_free(mem_ctx);
 271                 return ret;
 272         }
 273
 274         etc->smb_krb5_context = talloc_reference(etc, smb_krb5_context);
 275         etc->enctypes = enctypes;
 276
 277         talloc_set_destructor(etc, free_enctypes);
 278
 279         password.data = discard_const_p(char *, password_s);
 280         password.length = strlen(password_s);
 281
 282         for (i=0; enctypes[i]; i++) {
 283                 krb5_keytab_entry entry;
 284                 ret = create_kerberos_key_from_string(smb_krb5_context->krb5_context,
 285                                                       salt_princ, &password, &entry.keyblock, enctypes[i]);
 286                 if (ret != 0) {
 287                         talloc_free(mem_ctx);
 288                         return ret;
 289                 }
 290
 291                 entry.principal = princ;
 292                 entry.vno       = kvno;
 293                 ret = krb5_kt_add_entry(smb_krb5_context->krb5_context, keytab, &entry);
 294                 enctype_string = NULL;
 295                 krb5_enctype_to_string(smb_krb5_context->krb5_context, enctypes[i], &enctype_string);
 296                 if (ret != 0) {
 297                         DEBUG(1, ("Failed to add %s entry for %s(kvno %d) to keytab: %s\n",
 298                                   enctype_string,
 299                                   princ_string,
 300                                   kvno,
 301                                   smb_get_krb5_error_message(smb_krb5_context->krb5_context,
 302                                                              ret, mem_ctx)));
 303                         talloc_free(mem_ctx);
 304                         free(enctype_string);
 305                         krb5_free_keyblock_contents(smb_krb5_context->krb5_context, &entry.keyblock);
 306                         return ret;
 307                 }
 308
 309                 DEBUG(5, ("Added %s(kvno %d) to keytab (%s)\n",
 310                           princ_string, kvno,
 311                           enctype_string));
 312                 free(enctype_string);
 313
 314                 krb5_free_keyblock_contents(smb_krb5_context->krb5_context, &entry.keyblock);
 315         }
 316         talloc_free(mem_ctx);
 317         return 0;
 318 }
 319
 320 static int create_keytab(TALLOC_CTX *parent_ctx,
 321                          struct cli_credentials *machine_account,
 322                          struct smb_krb5_context *smb_krb5_context,
 323                          krb5_keytab keytab,
 324                          BOOL add_old)
 325 {
 326         krb5_error_code ret;
 327         const char *password_s;
 328         char *enctype_string;
 329         const char *old_secret;
 330         int kvno;
 331         krb5_principal salt_princ;
 332         krb5_principal princ;
 333         const char *princ_string;
 334
 335         TALLOC_CTX *mem_ctx = talloc_new(parent_ctx);
 336         if (!mem_ctx) {
 337                 return ENOMEM;
 338         }
 339
 340         princ_string = cli_credentials_get_principal(machine_account, mem_ctx);
 341         /* Get the principal we will store the new keytab entries under */
 342         ret = principal_from_credentials(mem_ctx, machine_account, smb_krb5_context, &princ);
 343         if (ret) {
 344                 DEBUG(1,("create_keytab: makeing krb5 principal failed (%s)\n",
 345                          smb_get_krb5_error_message(smb_krb5_context->krb5_context,
 346                                                     ret, mem_ctx)));
 347                 talloc_free(mem_ctx);
 348                 return ret;
 349         }
 350
 351         /* The salt used to generate these entries may be different however, fetch that */
 352         ret = salt_principal_from_credentials(mem_ctx, machine_account,
 353                                               smb_krb5_context,
 354                                               &salt_princ);
 355         if (ret) {
 356                 DEBUG(1,("create_keytab: makeing salt principal failed (%s)\n",
 357                          smb_get_krb5_error_message(smb_krb5_context->krb5_context,
 358                                                     ret, mem_ctx)));
 359                 talloc_free(mem_ctx);
 360                 return ret;
 361         }
 362
 363         /* Finally, do the dance to get the password to put in the entry */
 364         password_s = cli_credentials_get_password(machine_account);
 365         if (!password_s) {
 366                 /* If we don't have the plaintext password, try for
 367                  * the MD4 password hash */
 368
 369                 krb5_keytab_entry entry;
 370                 const struct samr_Password *mach_pwd;
 371                 mach_pwd = cli_credentials_get_nt_hash(machine_account, mem_ctx);
 372                 if (!mach_pwd) {
 373                         talloc_free(mem_ctx);
 374                         DEBUG(1, ("create_keytab: Domain trust informaton for account %s not available\n",
 375                                   cli_credentials_get_principal(machine_account, mem_ctx)));
 376                         return EINVAL;
 377                 }
 378                 ret = krb5_keyblock_init(smb_krb5_context->krb5_context,
 379                                          ENCTYPE_ARCFOUR_HMAC,
 380                                          mach_pwd->hash, sizeof(mach_pwd->hash),
 381                                          &entry.keyblock);
 382                 if (ret) {
 383                         DEBUG(1, ("create_keytab: krb5_keyblock_init failed: %s\n",
 384                                   smb_get_krb5_error_message(smb_krb5_context->krb5_context,
 385                                                              ret, mem_ctx)));
 386                         return ret;
 387                 }
 388
 389                 entry.principal = princ;
 390                 entry.vno       = cli_credentials_get_kvno(machine_account);
 391                 ret = krb5_kt_add_entry(smb_krb5_context->krb5_context, keytab, &entry);
 392                 if (ret) {
 393                         DEBUG(1, ("Failed to add ARCFOUR_HMAC (only) entry for %s to keytab: %s",
 394                                   cli_credentials_get_principal(machine_account, mem_ctx),
 395                                   smb_get_krb5_error_message(smb_krb5_context->krb5_context,
 396                                                              ret, mem_ctx)));
 397                         talloc_free(mem_ctx);
 398                         krb5_free_keyblock_contents(smb_krb5_context->krb5_context, &entry.keyblock);
 399                         return ret;
 400                 }
 401
 402                 krb5_enctype_to_string(smb_krb5_context->krb5_context, ENCTYPE_ARCFOUR_HMAC, &enctype_string);
 403                 DEBUG(5, ("Added %s(kvno %d) to keytab (%s)\n",
 404                           cli_credentials_get_principal(machine_account, mem_ctx),
 405                           cli_credentials_get_kvno(machine_account),
 406                           enctype_string));
 407                 free(enctype_string);
 408
 409                 krb5_free_keyblock_contents(smb_krb5_context->krb5_context, &entry.keyblock);
 410
 411                 /* Can't go any further, we only have this one key */
 412                 talloc_free(mem_ctx);
 413                 return 0;
 414         }
 415
 416         kvno = cli_credentials_get_kvno(machine_account);
 417         /* good, we actually have the real plaintext */
 418         ret = keytab_add_keys(mem_ctx, princ_string, princ, salt_princ,
 419                               kvno, password_s, smb_krb5_context, keytab);
 420         if (!ret) {
 421                 talloc_free(mem_ctx);
 422                 return ret;
 423         }
 424
 425         if (!add_old || kvno == 0) {
 426                 talloc_free(mem_ctx);
 427                 return 0;
 428         }
 429
 430         old_secret = cli_credentials_get_old_password(machine_account);
 431         if (!old_secret) {
 432                 talloc_free(mem_ctx);
 433                 return 0;
 434         }
 435
 436         ret = keytab_add_keys(mem_ctx, princ_string, princ, salt_princ,
 437                               kvno - 1, old_secret, smb_krb5_context, keytab);
 438         if (!ret) {
 439                 talloc_free(mem_ctx);
 440                 return ret;
 441         }
 442
 443         talloc_free(mem_ctx);
 444         return 0;
 445 }
 446
 447
 448 /*
 449  * Walk the keytab, looking for entries of this principal name, with KVNO other than current kvno -1.
 450  *
 451  * These entries are now stale, we only keep the current, and previous entries around.
 452  *
 453  * Inspired by the code in Samba3 for 'use kerberos keytab'.
 454  *
 455  */
 456
 457 static krb5_error_code remove_old_entries(TALLOC_CTX *parent_ctx,
 458                                           struct cli_credentials *machine_account,
 459                                           struct smb_krb5_context *smb_krb5_context,
 460                                           krb5_keytab keytab, BOOL *found_previous)
 461 {
 462         krb5_error_code ret, ret2;
 463         krb5_kt_cursor cursor;
 464         krb5_principal princ;
 465         int kvno;
 466         TALLOC_CTX *mem_ctx = talloc_new(parent_ctx);
 467         const char *princ_string;
 468         if (!mem_ctx) {
 469                 return ENOMEM;
 470         }
 471
 472         *found_previous = False;
 473         princ_string = cli_credentials_get_principal(machine_account, mem_ctx);
 474
 475         /* Get the principal we will store the new keytab entries under */
 476         ret = principal_from_credentials(mem_ctx, machine_account, smb_krb5_context, &princ);
 477         if (ret) {
 478                 DEBUG(1,("update_keytab: makeing krb5 principal failed (%s)\n",
 479                          smb_get_krb5_error_message(smb_krb5_context->krb5_context,
 480                                                     ret, mem_ctx)));
 481                 talloc_free(mem_ctx);
 482                 return ret;
 483         }
 484
 485         kvno = cli_credentials_get_kvno(machine_account);
 486
 487         /* for each entry in the keytab */
 488         ret = krb5_kt_start_seq_get(smb_krb5_context->krb5_context, keytab, &cursor);
 489         switch (ret) {
 490         case 0:
 491                 break;
 492         case ENOENT:
 493         case KRB5_KT_END:
 494                 /* no point enumerating if there isn't anything here */
 495                 talloc_free(mem_ctx);
 496                 return 0;
 497         default:
 498                 DEBUG(1,("failed to open keytab for read of old entries: %s\n",
 499                          smb_get_krb5_error_message(smb_krb5_context->krb5_context,
 500                                                     ret, mem_ctx)));
 501                 talloc_free(mem_ctx);
 502                 return ret;
 503         }
 504
 505         while (!ret) {
 506                 krb5_keytab_entry entry;
 507                 ret = krb5_kt_next_entry(smb_krb5_context->krb5_context, keytab, &entry, &cursor);
 508                 if (ret) {
 509                         break;
 510                 }
 511                 /* if it matches our principal */
 512                 if (!krb5_kt_compare(smb_krb5_context->krb5_context, &entry, princ, 0, 0)) {
 513                         /* Free the entry, it wasn't the one we were looking for anyway */
 514                         krb5_kt_free_entry(smb_krb5_context->krb5_context, &entry);
 515                         continue;
 516                 }
 517
 518                 /* delete it, if it is not kvno -1 */
 519                 if (entry.vno != (kvno - 1 )) {
 520                         /* Release the enumeration.  We are going to
 521                          * have to start this from the top again,
 522                          * because deletes during enumeration may not
 523                          * always be consistant.
 524                          *
 525                          * Also, the enumeration locks the keytab
 526                          */
 527
 528                         krb5_kt_end_seq_get(smb_krb5_context->krb5_context, keytab, &cursor);
 529
 530                         ret = krb5_kt_remove_entry(smb_krb5_context->krb5_context, keytab, &entry);
 531                         krb5_kt_free_entry(smb_krb5_context->krb5_context, &entry);
 532
 533                         /* Deleted: Restart from the top */
 534                         ret2 = krb5_kt_start_seq_get(smb_krb5_context->krb5_context, keytab, &cursor);
 535                         if (ret2) {
 536                                 krb5_kt_free_entry(smb_krb5_context->krb5_context, &entry);
 537                                 DEBUG(1,("failed to restart enumeration of keytab: %s\n",
 538                                          smb_get_krb5_error_message(smb_krb5_context->krb5_context,
 539                                                                     ret, mem_ctx)));
 540
 541                                 talloc_free(mem_ctx);
 542                                 return ret2;
 543                         }
 544
 545                         if (ret) {
 546                                 break;
 547                         }
 548
 549                 } else {
 550                         *found_previous = True;
 551                 }
 552
 553                 /* Free the entry, we don't need it any more */
 554                 krb5_kt_free_entry(smb_krb5_context->krb5_context, &entry);
 555
 556
 557         }
 558         krb5_kt_end_seq_get(smb_krb5_context->krb5_context, keytab, &cursor);
 559
 560         switch (ret) {
 561         case 0:
 562                 break;
 563         case ENOENT:
 564         case KRB5_KT_END:
 565                 ret = 0;
 566                 break;
 567         default:
 568                 DEBUG(1,("failed in deleting old entries for principal: %s: %s\n",
 569                          princ_string,
 570                          smb_get_krb5_error_message(smb_krb5_context->krb5_context,
 571                                                     ret, mem_ctx)));
 572         }
 573         talloc_free(mem_ctx);
 574         return ret;
 575 }
 576
 577 int update_keytab(TALLOC_CTX *parent_ctx,
 578                   struct cli_credentials *machine_account,
 579                   struct smb_krb5_context *smb_krb5_context,
 580                   struct keytab_container *keytab_container)
 581 {
 582         krb5_error_code ret;
 583         BOOL found_previous;
 584         TALLOC_CTX *mem_ctx = talloc_new(parent_ctx);
 585         if (!mem_ctx) {
 586                 return ENOMEM;
 587         }
 588
 589         ret = remove_old_entries(mem_ctx, machine_account,
 590                                  smb_krb5_context, keytab_container->keytab, &found_previous);
 591         if (ret != 0) {
 592                 talloc_free(mem_ctx);
 593                 return ret;
 594         }
 595
 596         /* Create a new keytab.  If during the cleanout we found
 597          * entires for kvno -1, then don't try and duplicate them.
 598          * Otherwise, add kvno, and kvno -1 */
 599
 600         ret = create_keytab(mem_ctx, machine_account, smb_krb5_context,
 601                             keytab_container->keytab,
 602                             found_previous ? False : True);
 603         talloc_free(mem_ctx);
 604         return ret;
 605 }
 606
 607 int create_memory_keytab(TALLOC_CTX *parent_ctx,
 608                          struct cli_credentials *machine_account,
 609                          struct smb_krb5_context *smb_krb5_context,
 610                          struct keytab_container **keytab_container)
 611 {
 612         krb5_error_code ret;
 613         TALLOC_CTX *mem_ctx = talloc_new(parent_ctx);
 614         const char *keytab_name = "MEMORY:";
 615         krb5_keytab keytab;
 616         if (!mem_ctx) {
 617                 return ENOMEM;
 618         }
 619
 620         *keytab_container = talloc(mem_ctx, struct keytab_container);
 621
 622         /* Find the keytab */
 623         ret = krb5_kt_resolve(smb_krb5_context->krb5_context, keytab_name, &keytab);
 624         if (ret) {
 625                 DEBUG(1,("failed to resolve keytab: %s: %s\n",
 626                          keytab_name,
 627                          smb_get_krb5_error_message(smb_krb5_context->krb5_context,
 628                                                     ret, mem_ctx)));
 629                 talloc_free(mem_ctx);
 630                 return ret;
 631         }
 632
 633         (*keytab_container)->smb_krb5_context = talloc_reference(*keytab_container, smb_krb5_context);
 634         (*keytab_container)->keytab = keytab;
 635
 636         talloc_set_destructor(*keytab_container, free_keytab);
 637
 638         ret = update_keytab(mem_ctx, machine_account, smb_krb5_context, *keytab_container);
 639         if (ret == 0) {
 640                 talloc_steal(parent_ctx, *keytab_container);
 641         } else {
 642                 *keytab_container = NULL;
 643         }
 644         talloc_free(mem_ctx);
 645         return ret;
 646 }
 647