source3/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
  41         if (!(cli = cli_initialise()))
  42                 return NULL;
  43
  44         /* security = server just can't function with spnego */
  45         cli->use_spnego = False;
  46
  47         pserver = talloc_strdup(mem_ctx, lp_passwordserver());
  48         p = pserver;
  49
  50         while(next_token_talloc(mem_ctx, &p, &desthost, LIST_SEP)) {
  51                 NTSTATUS status;
  52
  53                 desthost = talloc_sub_basic(mem_ctx,
  54                                 current_user_info.smb_name,
  55                                 current_user_info.domain,
  56                                 desthost);
  57                 if (!desthost) {
  58                         return NULL;
  59                 }
  60                 strupper_m(desthost);
  61
  62                 if(!resolve_name( desthost, &dest_ss, 0x20)) {
  63                         DEBUG(1,("server_cryptkey: Can't resolve address for %s\n",desthost));
  64                         continue;
  65                 }
  66
  67                 if (ismyaddr(&dest_ss)) {
  68                         DEBUG(1,("Password server loop - disabling password server %s\n",desthost));
  69                         continue;
  70                 }
  71
  72                 /* we use a mutex to prevent two connections at once - when a
  73                    Win2k PDC get two connections where one hasn't completed a
  74                    session setup yet it will send a TCP reset to the first
  75                    connection (tridge) */
  76
  77                 if (!grab_server_mutex(desthost)) {
  78                         return NULL;
  79                 }
  80
  81                 status = cli_connect(cli, desthost, &dest_ss);
  82                 if (NT_STATUS_IS_OK(status)) {
  83                         DEBUG(3,("connected to password server %s\n",desthost));
  84                         connected_ok = True;
  85                         break;
  86                 }
  87                 DEBUG(10,("server_cryptkey: failed to connect to server %s. Error %s\n",
  88                         desthost, nt_errstr(status) ));
  89                 release_server_mutex();
  90         }
  91
  92         if (!connected_ok) {
  93                 DEBUG(0,("password server not available\n"));
  94                 cli_shutdown(cli);
  95                 return NULL;
  96         }
  97
  98         if (!attempt_netbios_session_request(&cli, global_myname(),
  99                                              desthost, &dest_ss)) {
 100                 release_server_mutex();
 101                 DEBUG(1,("password server fails session request\n"));
 102                 cli_shutdown(cli);
 103                 return NULL;
 104         }
 105
 106         if (strequal(desthost,myhostname())) {
 107                 exit_server_cleanly("Password server loop!");
 108         }
 109
 110         DEBUG(3,("got session\n"));
 111
 112         if (!cli_negprot(cli)) {
 113                 DEBUG(1,("%s rejected the negprot\n",desthost));
 114                 release_server_mutex();
 115                 cli_shutdown(cli);
 116                 return NULL;
 117         }
 118
 119         if (cli->protocol < PROTOCOL_LANMAN2 ||
 120             !(cli->sec_mode & NEGOTIATE_SECURITY_USER_LEVEL)) {
 121                 DEBUG(1,("%s isn't in user level security mode\n",desthost));
 122                 release_server_mutex();
 123                 cli_shutdown(cli);
 124                 return NULL;
 125         }
 126
 127         /* Get the first session setup done quickly, to avoid silly
 128            Win2k bugs.  (The next connection to the server will kill
 129            this one...
 130         */
 131
 132         if (!NT_STATUS_IS_OK(cli_session_setup(cli, "", "", 0, "", 0,
 133                                                ""))) {
 134                 DEBUG(0,("%s rejected the initial session setup (%s)\n",
 135                          desthost, cli_errstr(cli)));
 136                 release_server_mutex();
 137                 cli_shutdown(cli);
 138                 return NULL;
 139         }
 140
 141         release_server_mutex();
 142
 143         DEBUG(3,("password server OK\n"));
 144
 145         return cli;
 146 }
 147
 148 struct server_security_state {
 149         struct cli_state *cli;
 150 };
 151
 152 /****************************************************************************
 153  Send a 'keepalive' packet down the cli pipe.
 154 ****************************************************************************/
 155
 156 static bool send_server_keepalive(const struct timeval *now,
 157                                   void *private_data)
 158 {
 159         struct server_security_state *state = talloc_get_type_abort(
 160                 private_data, struct server_security_state);
 161
 162         if (!state->cli || !state->cli->initialised) {
 163                 return False;
 164         }
 165
 166         if (send_keepalive(state->cli->fd)) {
 167                 return True;
 168         }
 169
 170         DEBUG( 2, ( "send_server_keepalive: password server keepalive "
 171                     "failed.\n"));
 172         cli_shutdown(state->cli);
 173         state->cli = NULL;
 174         return False;
 175 }
 176
 177 static int destroy_server_security(struct server_security_state *state)
 178 {
 179         if (state->cli) {
 180                 cli_shutdown(state->cli);
 181         }
 182         return 0;
 183 }
 184
 185 static struct server_security_state *make_server_security_state(struct cli_state *cli)
 186 {
 187         struct server_security_state *result;
 188
 189         if (!(result = talloc(NULL, struct server_security_state))) {
 190                 DEBUG(0, ("talloc failed\n"));
 191                 cli_shutdown(cli);
 192                 return NULL;
 193         }
 194
 195         result->cli = cli;
 196         talloc_set_destructor(result, destroy_server_security);
 197
 198         if (lp_keepalive() != 0) {
 199                 struct timeval interval;
 200                 interval.tv_sec = lp_keepalive();
 201                 interval.tv_usec = 0;
 202
 203                 if (event_add_idle(smbd_event_context(), result, interval,
 204                                    "server_security_keepalive",
 205                                    send_server_keepalive,
 206                                    result) == NULL) {
 207                         DEBUG(0, ("event_add_idle failed\n"));
 208                         TALLOC_FREE(result);
 209                         return NULL;
 210                 }
 211         }
 212
 213         return result;
 214 }
 215
 216 /****************************************************************************
 217  Get the challenge out of a password server.
 218 ****************************************************************************/
 219
 220 static DATA_BLOB auth_get_challenge_server(const struct auth_context *auth_context,
 221                                            void **my_private_data,
 222                                            TALLOC_CTX *mem_ctx)
 223 {
 224         struct cli_state *cli = server_cryptkey(mem_ctx);
 225
 226         if (cli) {
 227                 DEBUG(3,("using password server validation\n"));
 228
 229                 if ((cli->sec_mode & NEGOTIATE_SECURITY_CHALLENGE_RESPONSE) == 0) {
 230                         /* We can't work with unencrypted password servers
 231                            unless 'encrypt passwords = no' */
 232                         DEBUG(5,("make_auth_info_server: Server is unencrypted, no challenge available..\n"));
 233
 234                         /* However, it is still a perfectly fine connection
 235                            to pass that unencrypted password over */
 236                         *my_private_data =
 237                                 (void *)make_server_security_state(cli);
 238                         return data_blob_null;
 239                 } else if (cli->secblob.length < 8) {
 240                         /* We can't do much if we don't get a full challenge */
 241                         DEBUG(2,("make_auth_info_server: Didn't receive a full challenge from server\n"));
 242                         cli_shutdown(cli);
 243                         return data_blob_null;
 244                 }
 245
 246                 if (!(*my_private_data = (void *)make_server_security_state(cli))) {
 247                         return data_blob(NULL,0);
 248                 }
 249
 250                 /* The return must be allocated on the caller's mem_ctx, as our own will be
 251                    destoyed just after the call. */
 252                 return data_blob_talloc(auth_context->mem_ctx, cli->secblob.data,8);
 253         } else {
 254                 return data_blob_null;
 255         }
 256 }
 257
 258
 259 /****************************************************************************
 260  Check for a valid username and password in security=server mode.
 261   - Validate a password with the password server.
 262 ****************************************************************************/
 263
 264 static NTSTATUS check_smbserver_security(const struct auth_context *auth_context,
 265                                          void *my_private_data,
 266                                          TALLOC_CTX *mem_ctx,
 267                                          const auth_usersupplied_info *user_info,
 268                                          auth_serversupplied_info **server_info)
 269 {
 270         struct cli_state *cli;
 271         static bool tested_password_server = False;
 272         static bool bad_password_server = False;
 273         NTSTATUS nt_status = NT_STATUS_NOT_IMPLEMENTED;
 274         bool locally_made_cli = False;
 275
 276         cli = (struct cli_state *)my_private_data;
 277
 278         if (cli) {
 279         } else {
 280                 cli = server_cryptkey(mem_ctx);
 281                 locally_made_cli = True;
 282         }
 283
 284         if (!cli || !cli->initialised) {
 285                 DEBUG(1,("password server is not connected (cli not initilised)\n"));
 286                 return NT_STATUS_LOGON_FAILURE;
 287         }
 288
 289         if ((cli->sec_mode & NEGOTIATE_SECURITY_CHALLENGE_RESPONSE) == 0) {
 290                 if (user_info->encrypted) {
 291                         DEBUG(1,("password server %s is plaintext, but we are encrypted. This just can't work :-(\n", cli->desthost));
 292                         return NT_STATUS_LOGON_FAILURE;
 293                 }
 294         } else {
 295                 if (memcmp(cli->secblob.data, auth_context->challenge.data, 8) != 0) {
 296                         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));
 297                         return NT_STATUS_LOGON_FAILURE;
 298                 }
 299         }
 300
 301         /*
 302          * Attempt a session setup with a totally incorrect password.
 303          * If this succeeds with the guest bit *NOT* set then the password
 304          * server is broken and is not correctly setting the guest bit. We
 305          * need to detect this as some versions of NT4.x are broken. JRA.
 306          */
 307
 308         /* I sure as hell hope that there aren't servers out there that take
 309          * NTLMv2 and have this bug, as we don't test for that...
 310          *  - abartlet@samba.org
 311          */
 312
 313         if ((!tested_password_server) && (lp_paranoid_server_security())) {
 314                 unsigned char badpass[24];
 315                 char *baduser = NULL;
 316
 317                 memset(badpass, 0x1f, sizeof(badpass));
 318
 319                 if((user_info->nt_resp.length == sizeof(badpass)) &&
 320                    !memcmp(badpass, user_info->nt_resp.data, sizeof(badpass))) {
 321                         /*
 322                          * Very unlikely, our random bad password is the same as the users
 323                          * password.
 324                          */
 325                         memset(badpass, badpass[0]+1, sizeof(badpass));
 326                 }
 327
 328                 baduser = talloc_asprintf(mem_ctx,
 329                                         "%s%s",
 330                                         INVALID_USER_PREFIX,
 331                                         global_myname());
 332                 if (!baduser) {
 333                         return NT_STATUS_NO_MEMORY;
 334                 }
 335
 336                 if (NT_STATUS_IS_OK(cli_session_setup(cli, baduser,
 337                                                       (char *)badpass,
 338                                                       sizeof(badpass),
 339                                                       (char *)badpass,
 340                                                       sizeof(badpass),
 341                                                       user_info->domain))) {
 342
 343                         /*
 344                          * We connected to the password server so we
 345                          * can say we've tested it.
 346                          */
 347                         tested_password_server = True;
 348
 349                         if ((SVAL(cli->inbuf,smb_vwv2) & 1) == 0) {
 350                                 DEBUG(0,("server_validate: password server %s allows users as non-guest \
 351 with a bad password.\n", cli->desthost));
 352                                 DEBUG(0,("server_validate: This is broken (and insecure) behaviour. Please do not \
 353 use this machine as the password server.\n"));
 354                                 cli_ulogoff(cli);
 355
 356                                 /*
 357                                  * Password server has the bug.
 358                                  */
 359                                 bad_password_server = True;
 360                                 return NT_STATUS_LOGON_FAILURE;
 361                         }
 362                         cli_ulogoff(cli);
 363                 }
 364         } else {
 365
 366                 /*
 367                  * We have already tested the password server.
 368                  * Fail immediately if it has the bug.
 369                  */
 370
 371                 if(bad_password_server) {
 372                         DEBUG(0,("server_validate: [1] password server %s allows users as non-guest \
 373 with a bad password.\n", cli->desthost));
 374                         DEBUG(0,("server_validate: [1] This is broken (and insecure) behaviour. Please do not \
 375 use this machine as the password server.\n"));
 376                         return NT_STATUS_LOGON_FAILURE;
 377                 }
 378         }
 379
 380         /*
 381          * Now we know the password server will correctly set the guest bit, or is
 382          * not guest enabled, we can try with the real password.
 383          */
 384
 385         if (!user_info->encrypted) {
 386                 /* Plaintext available */
 387                 nt_status = cli_session_setup(
 388                         cli, user_info->smb_name,
 389                         (char *)user_info->plaintext_password.data,
 390                         user_info->plaintext_password.length,
 391                         NULL, 0, user_info->domain);
 392
 393         } else {
 394                 nt_status = cli_session_setup(
 395                         cli, user_info->smb_name,
 396                         (char *)user_info->lm_resp.data,
 397                         user_info->lm_resp.length,
 398                         (char *)user_info->nt_resp.data,
 399                         user_info->nt_resp.length,
 400                         user_info->domain);
 401         }
 402
 403         if (!NT_STATUS_IS_OK(nt_status)) {
 404                 DEBUG(1,("password server %s rejected the password: %s\n",
 405                          cli->desthost, nt_errstr(nt_status)));
 406         }
 407
 408         /* if logged in as guest then reject */
 409         if ((SVAL(cli->inbuf,smb_vwv2) & 1) != 0) {
 410                 DEBUG(1,("password server %s gave us guest only\n", cli->desthost));
 411                 nt_status = NT_STATUS_LOGON_FAILURE;
 412         }
 413
 414         cli_ulogoff(cli);
 415
 416         if (NT_STATUS_IS_OK(nt_status)) {
 417                 fstring real_username;
 418                 struct passwd *pass;
 419
 420                 if ( (pass = smb_getpwnam( NULL, user_info->internal_username,
 421                         real_username, True )) != NULL )
 422                 {
 423                         /* if a real user check pam account restrictions */
 424                         /* only really perfomed if "obey pam restriction" is true */
 425                         nt_status = smb_pam_accountcheck(pass->pw_name);
 426                         if (  !NT_STATUS_IS_OK(nt_status)) {
 427                                 DEBUG(1, ("PAM account restriction prevents user login\n"));
 428                         } else {
 429
 430                                 nt_status = make_server_info_pw(server_info, pass->pw_name, pass);
 431                         }
 432                         TALLOC_FREE(pass);
 433                 }
 434                 else
 435                 {
 436                         nt_status = NT_STATUS_NO_SUCH_USER;
 437                 }
 438         }
 439
 440         if (locally_made_cli) {
 441                 cli_shutdown(cli);
 442         }
 443
 444         return(nt_status);
 445 }
 446
 447 static NTSTATUS auth_init_smbserver(struct auth_context *auth_context, const char* param, auth_methods **auth_method)
 448 {
 449         if (!make_auth_methods(auth_context, auth_method)) {
 450                 return NT_STATUS_NO_MEMORY;
 451         }
 452         (*auth_method)->name = "smbserver";
 453         (*auth_method)->auth = check_smbserver_security;
 454         (*auth_method)->get_chal = auth_get_challenge_server;
 455         return NT_STATUS_OK;
 456 }
 457
 458 NTSTATUS auth_server_init(void)
 459 {
 460         return smb_register_auth(AUTH_INTERFACE_VERSION, "smbserver", auth_init_smbserver);
 461 }