source/auth/auth_server.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    Authenticate to a remote server
   4    Copyright (C) Andrew Tridgell 1992-1998
   5    Copyright (C) Andrew Bartlett 2001
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  19 */
  20
  21 #include "includes.h"
  22
  23 #undef DBGC_CLASS
  24 #define DBGC_CLASS DBGC_AUTH
  25
  26 extern userdom_struct current_user_info;
  27
  28 /****************************************************************************
  29  Support for server level security.
  30 ****************************************************************************/
  31
  32 static struct cli_state *server_cryptkey(TALLOC_CTX *mem_ctx)
  33 {
  34         struct cli_state *cli = NULL;
  35         char *desthost = NULL;
  36         struct sockaddr_storage dest_ss;
  37         const char *p;
  38         char *pserver = NULL;
  39         bool connected_ok = False;
  40         struct named_mutex *mutex;
  41
  42         if (!(cli = cli_initialise()))
  43                 return NULL;
  44
  45         /* security = server just can't function with spnego */
  46         cli->use_spnego = False;
  47
  48         pserver = talloc_strdup(mem_ctx, lp_passwordserver());
  49         p = pserver;
  50
  51         while(next_token_talloc(mem_ctx, &p, &desthost, LIST_SEP)) {
  52                 NTSTATUS status;
  53
  54                 desthost = talloc_sub_basic(mem_ctx,
  55                                 current_user_info.smb_name,
  56                                 current_user_info.domain,
  57                                 desthost);
  58                 if (!desthost) {
  59                         return NULL;
  60                 }
  61                 strupper_m(desthost);
  62
  63                 if(!resolve_name( desthost, &dest_ss, 0x20)) {
  64                         DEBUG(1,("server_cryptkey: Can't resolve address for %s\n",desthost));
  65                         continue;
  66                 }
  67
  68                 if (ismyaddr(&dest_ss)) {
  69                         DEBUG(1,("Password server loop - disabling password server %s\n",desthost));
  70                         continue;
  71                 }
  72
  73                 /* we use a mutex to prevent two connections at once - when a
  74                    Win2k PDC get two connections where one hasn't completed a
  75                    session setup yet it will send a TCP reset to the first
  76                    connection (tridge) */
  77
  78                 mutex = grab_named_mutex(talloc_tos(), desthost, 10);
  79                 if (mutex == NULL) {
  80                         cli_shutdown(cli);
  81                         return NULL;
  82                 }
  83
  84                 status = cli_connect(cli, desthost, &dest_ss);
  85                 if (NT_STATUS_IS_OK(status)) {
  86                         DEBUG(3,("connected to password server %s\n",desthost));
  87                         connected_ok = True;
  88                         break;
  89                 }
  90                 DEBUG(10,("server_cryptkey: failed to connect to server %s. Error %s\n",
  91                         desthost, nt_errstr(status) ));
  92                 TALLOC_FREE(mutex);
  93         }
  94
  95         if (!connected_ok) {
  96                 DEBUG(0,("password server not available\n"));
  97                 cli_shutdown(cli);
  98                 return NULL;
  99         }
 100
 101         if (!attempt_netbios_session_request(&cli, global_myname(),
 102                                              desthost, &dest_ss)) {
 103                 TALLOC_FREE(mutex);
 104                 DEBUG(1,("password server fails session request\n"));
 105                 cli_shutdown(cli);
 106                 return NULL;
 107         }
 108
 109         if (strequal(desthost,myhostname())) {
 110                 exit_server_cleanly("Password server loop!");
 111         }
 112
 113         DEBUG(3,("got session\n"));
 114
 115         if (!cli_negprot(cli)) {
 116                 TALLOC_FREE(mutex);
 117                 DEBUG(1,("%s rejected the negprot\n",desthost));
 118                 cli_shutdown(cli);
 119                 return NULL;
 120         }
 121
 122         if (cli->protocol < PROTOCOL_LANMAN2 ||
 123             !(cli->sec_mode & NEGOTIATE_SECURITY_USER_LEVEL)) {
 124                 TALLOC_FREE(mutex);
 125                 DEBUG(1,("%s isn't in user level security mode\n",desthost));
 126                 cli_shutdown(cli);
 127                 return NULL;
 128         }
 129
 130         /* Get the first session setup done quickly, to avoid silly
 131            Win2k bugs.  (The next connection to the server will kill
 132            this one...
 133         */
 134
 135         if (!NT_STATUS_IS_OK(cli_session_setup(cli, "", "", 0, "", 0,
 136                                                ""))) {
 137                 TALLOC_FREE(mutex);
 138                 DEBUG(0,("%s rejected the initial session setup (%s)\n",
 139                          desthost, cli_errstr(cli)));
 140                 cli_shutdown(cli);
 141                 return NULL;
 142         }
 143
 144         TALLOC_FREE(mutex);
 145
 146         DEBUG(3,("password server OK\n"));
 147
 148         return cli;
 149 }
 150
 151 struct server_security_state {
 152         struct cli_state *cli;
 153 };
 154
 155 /****************************************************************************
 156  Send a 'keepalive' packet down the cli pipe.
 157 ****************************************************************************/
 158
 159 static bool send_server_keepalive(const struct timeval *now,
 160                                   void *private_data)
 161 {
 162         struct server_security_state *state = talloc_get_type_abort(
 163                 private_data, struct server_security_state);
 164
 165         if (!state->cli || !state->cli->initialised) {
 166                 return False;
 167         }
 168
 169         if (send_keepalive(state->cli->fd)) {
 170                 return True;
 171         }
 172
 173         DEBUG( 2, ( "send_server_keepalive: password server keepalive "
 174                     "failed.\n"));
 175         cli_shutdown(state->cli);
 176         state->cli = NULL;
 177         return False;
 178 }
 179
 180 static int destroy_server_security(struct server_security_state *state)
 181 {
 182         if (state->cli) {
 183                 cli_shutdown(state->cli);
 184         }
 185         return 0;
 186 }
 187
 188 static struct server_security_state *make_server_security_state(struct cli_state *cli)
 189 {
 190         struct server_security_state *result;
 191
 192         if (!(result = talloc(NULL, struct server_security_state))) {
 193                 DEBUG(0, ("talloc failed\n"));
 194                 cli_shutdown(cli);
 195                 return NULL;
 196         }
 197
 198         result->cli = cli;
 199         talloc_set_destructor(result, destroy_server_security);
 200
 201         if (lp_keepalive() != 0) {
 202                 struct timeval interval;
 203                 interval.tv_sec = lp_keepalive();
 204                 interval.tv_usec = 0;
 205
 206                 if (event_add_idle(smbd_event_context(), result, interval,
 207                                    "server_security_keepalive",
 208                                    send_server_keepalive,
 209                                    result) == NULL) {
 210                         DEBUG(0, ("event_add_idle failed\n"));
 211                         TALLOC_FREE(result);
 212                         return NULL;
 213                 }
 214         }
 215
 216         return result;
 217 }
 218
 219 /****************************************************************************
 220  Get the challenge out of a password server.
 221 ****************************************************************************/
 222
 223 static DATA_BLOB auth_get_challenge_server(const struct auth_context *auth_context,
 224                                            void **my_private_data,
 225                                            TALLOC_CTX *mem_ctx)
 226 {
 227         struct cli_state *cli = server_cryptkey(mem_ctx);
 228
 229         if (cli) {
 230                 DEBUG(3,("using password server validation\n"));
 231
 232                 if ((cli->sec_mode & NEGOTIATE_SECURITY_CHALLENGE_RESPONSE) == 0) {
 233                         /* We can't work with unencrypted password servers
 234                            unless 'encrypt passwords = no' */
 235                         DEBUG(5,("make_auth_info_server: Server is unencrypted, no challenge available..\n"));
 236
 237                         /* However, it is still a perfectly fine connection
 238                            to pass that unencrypted password over */
 239                         *my_private_data =
 240                                 (void *)make_server_security_state(cli);
 241                         return data_blob_null;
 242                 } else if (cli->secblob.length < 8) {
 243                         /* We can't do much if we don't get a full challenge */
 244                         DEBUG(2,("make_auth_info_server: Didn't receive a full challenge from server\n"));
 245                         cli_shutdown(cli);
 246                         return data_blob_null;
 247                 }
 248
 249                 if (!(*my_private_data = (void *)make_server_security_state(cli))) {
 250                         return data_blob(NULL,0);
 251                 }
 252
 253                 /* The return must be allocated on the caller's mem_ctx, as our own will be
 254                    destoyed just after the call. */
 255                 return data_blob_talloc(auth_context->mem_ctx, cli->secblob.data,8);
 256         } else {
 257                 return data_blob_null;
 258         }
 259 }
 260
 261
 262 /****************************************************************************
 263  Check for a valid username and password in security=server mode.
 264   - Validate a password with the password server.
 265 ****************************************************************************/
 266
 267 static NTSTATUS check_smbserver_security(const struct auth_context *auth_context,
 268                                          void *my_private_data,
 269                                          TALLOC_CTX *mem_ctx,
 270                                          const auth_usersupplied_info *user_info,
 271                                          auth_serversupplied_info **server_info)
 272 {
 273         struct cli_state *cli;
 274         static bool tested_password_server = False;
 275         static bool bad_password_server = False;
 276         NTSTATUS nt_status = NT_STATUS_NOT_IMPLEMENTED;
 277         bool locally_made_cli = False;
 278
 279         cli = (struct cli_state *)my_private_data;
 280
 281         if (cli) {
 282         } else {
 283                 cli = server_cryptkey(mem_ctx);
 284                 locally_made_cli = True;
 285         }
 286
 287         if (!cli || !cli->initialised) {
 288                 DEBUG(1,("password server is not connected (cli not initilised)\n"));
 289                 return NT_STATUS_LOGON_FAILURE;
 290         }
 291
 292         if ((cli->sec_mode & NEGOTIATE_SECURITY_CHALLENGE_RESPONSE) == 0) {
 293                 if (user_info->encrypted) {
 294                         DEBUG(1,("password server %s is plaintext, but we are encrypted. This just can't work :-(\n", cli->desthost));
 295                         return NT_STATUS_LOGON_FAILURE;
 296                 }
 297         } else {
 298                 if (memcmp(cli->secblob.data, auth_context->challenge.data, 8) != 0) {
 299                         DEBUG(1,("the challenge that the password server (%s) supplied us is not the one we gave our client. This just can't work :-(\n", cli->desthost));
 300                         return NT_STATUS_LOGON_FAILURE;
 301                 }
 302         }
 303
 304         /*
 305          * Attempt a session setup with a totally incorrect password.
 306          * If this succeeds with the guest bit *NOT* set then the password
 307          * server is broken and is not correctly setting the guest bit. We
 308          * need to detect this as some versions of NT4.x are broken. JRA.
 309          */
 310
 311         /* I sure as hell hope that there aren't servers out there that take
 312          * NTLMv2 and have this bug, as we don't test for that...
 313          *  - abartlet@samba.org
 314          */
 315
 316         if ((!tested_password_server) && (lp_paranoid_server_security())) {
 317                 unsigned char badpass[24];
 318                 char *baduser = NULL;
 319
 320                 memset(badpass, 0x1f, sizeof(badpass));
 321
 322                 if((user_info->nt_resp.length == sizeof(badpass)) &&
 323                    !memcmp(badpass, user_info->nt_resp.data, sizeof(badpass))) {
 324                         /*
 325                          * Very unlikely, our random bad password is the same as the users
 326                          * password.
 327                          */
 328                         memset(badpass, badpass[0]+1, sizeof(badpass));
 329                 }
 330
 331                 baduser = talloc_asprintf(mem_ctx,
 332                                         "%s%s",
 333                                         INVALID_USER_PREFIX,
 334                                         global_myname());
 335                 if (!baduser) {
 336                         return NT_STATUS_NO_MEMORY;
 337                 }
 338
 339                 if (NT_STATUS_IS_OK(cli_session_setup(cli, baduser,
 340                                                       (char *)badpass,
 341                                                       sizeof(badpass),
 342                                                       (char *)badpass,
 343                                                       sizeof(badpass),
 344                                                       user_info->domain))) {
 345
 346                         /*
 347                          * We connected to the password server so we
 348                          * can say we've tested it.
 349                          */
 350                         tested_password_server = True;
 351
 352                         if ((SVAL(cli->inbuf,smb_vwv2) & 1) == 0) {
 353                                 DEBUG(0,("server_validate: password server %s allows users as non-guest \
 354 with a bad password.\n", cli->desthost));
 355                                 DEBUG(0,("server_validate: This is broken (and insecure) behaviour. Please do not \
 356 use this machine as the password server.\n"));
 357                                 cli_ulogoff(cli);
 358
 359                                 /*
 360                                  * Password server has the bug.
 361                                  */
 362                                 bad_password_server = True;
 363                                 return NT_STATUS_LOGON_FAILURE;
 364                         }
 365                         cli_ulogoff(cli);
 366                 }
 367         } else {
 368
 369                 /*
 370                  * We have already tested the password server.
 371                  * Fail immediately if it has the bug.
 372                  */
 373
 374                 if(bad_password_server) {
 375                         DEBUG(0,("server_validate: [1] password server %s allows users as non-guest \
 376 with a bad password.\n", cli->desthost));
 377                         DEBUG(0,("server_validate: [1] This is broken (and insecure) behaviour. Please do not \
 378 use this machine as the password server.\n"));
 379                         return NT_STATUS_LOGON_FAILURE;
 380                 }
 381         }
 382
 383         /*
 384          * Now we know the password server will correctly set the guest bit, or is
 385          * not guest enabled, we can try with the real password.
 386          */
 387
 388         if (!user_info->encrypted) {
 389                 /* Plaintext available */
 390                 nt_status = cli_session_setup(
 391                         cli, user_info->smb_name,
 392                         (char *)user_info->plaintext_password.data,
 393                         user_info->plaintext_password.length,
 394                         NULL, 0, user_info->domain);
 395
 396         } else {
 397                 nt_status = cli_session_setup(
 398                         cli, user_info->smb_name,
 399                         (char *)user_info->lm_resp.data,
 400                         user_info->lm_resp.length,
 401                         (char *)user_info->nt_resp.data,
 402                         user_info->nt_resp.length,
 403                         user_info->domain);
 404         }
 405
 406         if (!NT_STATUS_IS_OK(nt_status)) {
 407                 DEBUG(1,("password server %s rejected the password: %s\n",
 408                          cli->desthost, nt_errstr(nt_status)));
 409         }
 410
 411         /* if logged in as guest then reject */
 412         if ((SVAL(cli->inbuf,smb_vwv2) & 1) != 0) {
 413                 DEBUG(1,("password server %s gave us guest only\n", cli->desthost));
 414                 nt_status = NT_STATUS_LOGON_FAILURE;
 415         }
 416
 417         cli_ulogoff(cli);
 418
 419         if (NT_STATUS_IS_OK(nt_status)) {
 420                 fstring real_username;
 421                 struct passwd *pass;
 422
 423                 if ( (pass = smb_getpwnam( NULL, user_info->internal_username,
 424                         real_username, True )) != NULL )
 425                 {
 426                         /* if a real user check pam account restrictions */
 427                         /* only really perfomed if "obey pam restriction" is true */
 428                         nt_status = smb_pam_accountcheck(pass->pw_name);
 429                         if (  !NT_STATUS_IS_OK(nt_status)) {
 430                                 DEBUG(1, ("PAM account restriction prevents user login\n"));
 431                         } else {
 432
 433                                 nt_status = make_server_info_pw(server_info, pass->pw_name, pass);
 434                         }
 435                         TALLOC_FREE(pass);
 436                 }
 437                 else
 438                 {
 439                         nt_status = NT_STATUS_NO_SUCH_USER;
 440                 }
 441         }
 442
 443         if (locally_made_cli) {
 444                 cli_shutdown(cli);
 445         }
 446
 447         return(nt_status);
 448 }
 449
 450 static NTSTATUS auth_init_smbserver(struct auth_context *auth_context, const char* param, auth_methods **auth_method)
 451 {
 452         if (!make_auth_methods(auth_context, auth_method)) {
 453                 return NT_STATUS_NO_MEMORY;
 454         }
 455         (*auth_method)->name = "smbserver";
 456         (*auth_method)->auth = check_smbserver_security;
 457         (*auth_method)->get_chal = auth_get_challenge_server;
 458         return NT_STATUS_OK;
 459 }
 460
 461 NTSTATUS auth_server_init(void)
 462 {
 463         return smb_register_auth(AUTH_INTERFACE_VERSION, "smbserver", auth_init_smbserver);
 464 }