source3/smbd/uid.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    uid/user handling
   4    Copyright (C) Andrew Tridgell 1992-1998
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18 */
  19
  20 #include "includes.h"
  21 #include "system/passwd.h"
  22 #include "smbd/smbd.h"
  23 #include "smbd/globals.h"
  24 #include "../librpc/gen_ndr/netlogon.h"
  25 #include "libcli/security/security.h"
  26 #include "passdb/lookup_sid.h"
  27 #include "auth.h"
  28
  29 /* what user is current? */
  30 extern struct current_user current_user;
  31
  32 /****************************************************************************
  33  Become the guest user without changing the security context stack.
  34 ****************************************************************************/
  35
  36 bool change_to_guest(void)
  37 {
  38         struct passwd *pass;
  39
  40         pass = Get_Pwnam_alloc(talloc_tos(), lp_guestaccount());
  41         if (!pass) {
  42                 return false;
  43         }
  44
  45 #ifdef AIX
  46         /* MWW: From AIX FAQ patch to WU-ftpd: call initgroups before
  47            setting IDs */
  48         initgroups(pass->pw_name, pass->pw_gid);
  49 #endif
  50
  51         set_sec_ctx(pass->pw_uid, pass->pw_gid, 0, NULL, NULL);
  52
  53         current_user.conn = NULL;
  54         current_user.vuid = UID_FIELD_INVALID;
  55
  56         TALLOC_FREE(pass);
  57
  58         return true;
  59 }
  60
  61 /****************************************************************************
  62  talloc free the conn->session_info if not used in the vuid cache.
  63 ****************************************************************************/
  64
  65 static void free_conn_session_info_if_unused(connection_struct *conn)
  66 {
  67         unsigned int i;
  68
  69         for (i = 0; i < VUID_CACHE_SIZE; i++) {
  70                 struct vuid_cache_entry *ent;
  71                 ent = &conn->vuid_cache.array[i];
  72                 if (ent->vuid != UID_FIELD_INVALID &&
  73                                 conn->session_info == ent->session_info) {
  74                         return;
  75                 }
  76         }
  77         /* Not used, safe to free. */
  78         TALLOC_FREE(conn->session_info);
  79 }
  80
  81 /*******************************************************************
  82  Check if a username is OK.
  83
  84  This sets up conn->session_info with a copy related to this vuser that
  85  later code can then mess with.
  86 ********************************************************************/
  87
  88 static bool check_user_ok(connection_struct *conn,
  89                         uint16_t vuid,
  90                         const struct auth_session_info *session_info,
  91                         int snum)
  92 {
  93         bool valid_vuid = (vuid != UID_FIELD_INVALID);
  94         unsigned int i;
  95         bool readonly_share;
  96         bool admin_user;
  97
  98         if (valid_vuid) {
  99                 struct vuid_cache_entry *ent;
 100
 101                 for (i=0; i<VUID_CACHE_SIZE; i++) {
 102                         ent = &conn->vuid_cache.array[i];
 103                         if (ent->vuid == vuid) {
 104                                 free_conn_session_info_if_unused(conn);
 105                                 conn->session_info = ent->session_info;
 106                                 conn->read_only = ent->read_only;
 107                                 return(True);
 108                         }
 109                 }
 110         }
 111
 112         if (!user_ok_token(session_info->unix_info->unix_name,
 113                            session_info->info->domain_name,
 114                            session_info->security_token, snum))
 115                 return(False);
 116
 117         readonly_share = is_share_read_only_for_token(
 118                 session_info->unix_info->unix_name,
 119                 session_info->info->domain_name,
 120                 session_info->security_token,
 121                 conn);
 122
 123         if (!readonly_share &&
 124             !share_access_check(session_info->security_token,
 125                                 lp_servicename(snum), FILE_WRITE_DATA,
 126                                 NULL)) {
 127                 /* smb.conf allows r/w, but the security descriptor denies
 128                  * write. Fall back to looking at readonly. */
 129                 readonly_share = True;
 130                 DEBUG(5,("falling back to read-only access-evaluation due to "
 131                          "security descriptor\n"));
 132         }
 133
 134         if (!share_access_check(session_info->security_token,
 135                                 lp_servicename(snum),
 136                                 readonly_share ?
 137                                 FILE_READ_DATA : FILE_WRITE_DATA,
 138                                 NULL)) {
 139                 return False;
 140         }
 141
 142         admin_user = token_contains_name_in_list(
 143                 session_info->unix_info->unix_name,
 144                 session_info->info->domain_name,
 145                 NULL, session_info->security_token, lp_admin_users(snum));
 146
 147         if (valid_vuid) {
 148                 struct vuid_cache_entry *ent =
 149                         &conn->vuid_cache.array[conn->vuid_cache.next_entry];
 150
 151                 conn->vuid_cache.next_entry =
 152                         (conn->vuid_cache.next_entry + 1) % VUID_CACHE_SIZE;
 153
 154                 TALLOC_FREE(ent->session_info);
 155
 156                 /*
 157                  * If force_user was set, all session_info's are based on the same
 158                  * username-based faked one.
 159                  */
 160
 161                 ent->session_info = copy_session_info(
 162                         conn, conn->force_user ? conn->session_info : session_info);
 163
 164                 if (ent->session_info == NULL) {
 165                         ent->vuid = UID_FIELD_INVALID;
 166                         return false;
 167                 }
 168
 169                 ent->vuid = vuid;
 170                 ent->read_only = readonly_share;
 171                 free_conn_session_info_if_unused(conn);
 172                 conn->session_info = ent->session_info;
 173         }
 174
 175         conn->read_only = readonly_share;
 176         if (admin_user) {
 177                 DEBUG(2,("check_user_ok: user %s is an admin user. "
 178                         "Setting uid as %d\n",
 179                         conn->session_info->unix_info->unix_name,
 180                         sec_initial_uid() ));
 181                 conn->session_info->unix_token->uid = sec_initial_uid();
 182         }
 183
 184         return(True);
 185 }
 186
 187 /****************************************************************************
 188  Become the user of a connection number without changing the security context
 189  stack, but modify the current_user entries.
 190 ****************************************************************************/
 191
 192 static bool change_to_user_internal(connection_struct *conn,
 193                                     const struct auth_session_info *session_info,
 194                                     uint16_t vuid)
 195 {
 196         int snum;
 197         gid_t gid;
 198         uid_t uid;
 199         char group_c;
 200         int num_groups = 0;
 201         gid_t *group_list = NULL;
 202         bool ok;
 203
 204         snum = SNUM(conn);
 205
 206         ok = check_user_ok(conn, vuid, session_info, snum);
 207         if (!ok) {
 208                 DEBUG(2,("SMB user %s (unix user %s) "
 209                          "not permitted access to share %s.\n",
 210                          session_info->unix_info->sanitized_username,
 211                          session_info->unix_info->unix_name,
 212                          lp_servicename(snum)));
 213                 return false;
 214         }
 215
 216         uid = conn->session_info->unix_token->uid;
 217         gid = conn->session_info->unix_token->gid;
 218         num_groups = conn->session_info->unix_token->ngroups;
 219         group_list  = conn->session_info->unix_token->groups;
 220
 221         /*
 222          * See if we should force group for this service. If so this overrides
 223          * any group set in the force user code.
 224          */
 225         if((group_c = *lp_force_group(snum))) {
 226
 227                 SMB_ASSERT(conn->force_group_gid != (gid_t)-1);
 228
 229                 if (group_c == '+') {
 230                         int i;
 231
 232                         /*
 233                          * Only force group if the user is a member of the
 234                          * service group. Check the group memberships for this
 235                          * user (we already have this) to see if we should force
 236                          * the group.
 237                          */
 238                         for (i = 0; i < num_groups; i++) {
 239                                 if (group_list[i] == conn->force_group_gid) {
 240                                         conn->session_info->unix_token->gid =
 241                                                 conn->force_group_gid;
 242                                         gid = conn->force_group_gid;
 243                                         gid_to_sid(&conn->session_info->security_token
 244                                                    ->sids[1], gid);
 245                                         break;
 246                                 }
 247                         }
 248                 } else {
 249                         conn->session_info->unix_token->gid = conn->force_group_gid;
 250                         gid = conn->force_group_gid;
 251                         gid_to_sid(&conn->session_info->security_token->sids[1],
 252                                    gid);
 253                 }
 254         }
 255
 256         /*Set current_user since we will immediately also call set_sec_ctx() */
 257         current_user.ut.ngroups = num_groups;
 258         current_user.ut.groups  = group_list;
 259
 260         set_sec_ctx(uid,
 261                     gid,
 262                     current_user.ut.ngroups,
 263                     current_user.ut.groups,
 264                     conn->session_info->security_token);
 265
 266         current_user.conn = conn;
 267         current_user.vuid = vuid;
 268
 269         DEBUG(5, ("Impersonated user: uid=(%d,%d), gid=(%d,%d)\n",
 270                  (int)getuid(),
 271                  (int)geteuid(),
 272                  (int)getgid(),
 273                  (int)getegid()));
 274
 275         return true;
 276 }
 277
 278 bool change_to_user(connection_struct *conn, uint16_t vuid)
 279 {
 280         const struct auth_session_info *session_info = NULL;
 281         user_struct *vuser;
 282         int snum = SNUM(conn);
 283
 284         if (!conn) {
 285                 DEBUG(2,("Connection not open\n"));
 286                 return(False);
 287         }
 288
 289         vuser = get_valid_user_struct(conn->sconn, vuid);
 290
 291         if ((current_user.conn == conn) &&
 292                    (vuser != NULL) && (current_user.vuid == vuid) &&
 293                    (current_user.ut.uid == vuser->session_info->unix_token->uid)) {
 294                 DEBUG(4,("Skipping user change - already "
 295                          "user\n"));
 296                 return(True);
 297         }
 298
 299         if (vuser == NULL) {
 300                 /* Invalid vuid sent */
 301                 DEBUG(2,("Invalid vuid %d used on "
 302                          "share %s.\n", vuid, lp_servicename(snum) ));
 303                 return false;
 304         }
 305
 306         session_info = vuser->session_info;
 307
 308         if (!conn->force_user && vuser == NULL) {
 309                 DEBUG(2,("Invalid vuid used %d in accessing "
 310                         "share %s.\n", vuid, lp_servicename(snum) ));
 311                 return False;
 312         }
 313
 314         return change_to_user_internal(conn, session_info, vuid);
 315 }
 316
 317 bool change_to_user_by_session(connection_struct *conn,
 318                                const struct auth_session_info *session_info)
 319 {
 320         SMB_ASSERT(conn != NULL);
 321         SMB_ASSERT(session_info != NULL);
 322
 323         if ((current_user.conn == conn) &&
 324             (current_user.ut.uid == session_info->unix_token->uid)) {
 325                 DEBUG(7, ("Skipping user change - already user\n"));
 326
 327                 return true;
 328         }
 329
 330         return change_to_user_internal(conn, session_info, UID_FIELD_INVALID);
 331 }
 332
 333 /****************************************************************************
 334  Go back to being root without changing the security context stack,
 335  but modify the current_user entries.
 336 ****************************************************************************/
 337
 338 bool smbd_change_to_root_user(void)
 339 {
 340         set_root_sec_ctx();
 341
 342         DEBUG(5,("change_to_root_user: now uid=(%d,%d) gid=(%d,%d)\n",
 343                 (int)getuid(),(int)geteuid(),(int)getgid(),(int)getegid()));
 344
 345         current_user.conn = NULL;
 346         current_user.vuid = UID_FIELD_INVALID;
 347
 348         return(True);
 349 }
 350
 351 /****************************************************************************
 352  Become the user of an authenticated connected named pipe.
 353  When this is called we are currently running as the connection
 354  user. Doesn't modify current_user.
 355 ****************************************************************************/
 356
 357 bool become_authenticated_pipe_user(struct auth_session_info *session_info)
 358 {
 359         if (!push_sec_ctx())
 360                 return False;
 361
 362         set_sec_ctx(session_info->unix_token->uid, session_info->unix_token->gid,
 363                     session_info->unix_token->ngroups, session_info->unix_token->groups,
 364                     session_info->security_token);
 365
 366         return True;
 367 }
 368
 369 /****************************************************************************
 370  Unbecome the user of an authenticated connected named pipe.
 371  When this is called we are running as the authenticated pipe
 372  user and need to go back to being the connection user. Doesn't modify
 373  current_user.
 374 ****************************************************************************/
 375
 376 bool unbecome_authenticated_pipe_user(void)
 377 {
 378         return pop_sec_ctx();
 379 }
 380
 381 /****************************************************************************
 382  Utility functions used by become_xxx/unbecome_xxx.
 383 ****************************************************************************/
 384
 385 static void push_conn_ctx(void)
 386 {
 387         struct conn_ctx *ctx_p;
 388
 389         /* Check we don't overflow our stack */
 390
 391         if (conn_ctx_stack_ndx == MAX_SEC_CTX_DEPTH) {
 392                 DEBUG(0, ("Connection context stack overflow!\n"));
 393                 smb_panic("Connection context stack overflow!\n");
 394         }
 395
 396         /* Store previous user context */
 397         ctx_p = &conn_ctx_stack[conn_ctx_stack_ndx];
 398
 399         ctx_p->conn = current_user.conn;
 400         ctx_p->vuid = current_user.vuid;
 401
 402         DEBUG(4, ("push_conn_ctx(%u) : conn_ctx_stack_ndx = %d\n",
 403                 (unsigned int)ctx_p->vuid, conn_ctx_stack_ndx ));
 404
 405         conn_ctx_stack_ndx++;
 406 }
 407
 408 static void pop_conn_ctx(void)
 409 {
 410         struct conn_ctx *ctx_p;
 411
 412         /* Check for stack underflow. */
 413
 414         if (conn_ctx_stack_ndx == 0) {
 415                 DEBUG(0, ("Connection context stack underflow!\n"));
 416                 smb_panic("Connection context stack underflow!\n");
 417         }
 418
 419         conn_ctx_stack_ndx--;
 420         ctx_p = &conn_ctx_stack[conn_ctx_stack_ndx];
 421
 422         current_user.conn = ctx_p->conn;
 423         current_user.vuid = ctx_p->vuid;
 424
 425         ctx_p->conn = NULL;
 426         ctx_p->vuid = UID_FIELD_INVALID;
 427 }
 428
 429 /****************************************************************************
 430  Temporarily become a root user.  Must match with unbecome_root(). Saves and
 431  restores the connection context.
 432 ****************************************************************************/
 433
 434 void smbd_become_root(void)
 435 {
 436          /*
 437           * no good way to handle push_sec_ctx() failing without changing
 438           * the prototype of become_root()
 439           */
 440         if (!push_sec_ctx()) {
 441                 smb_panic("become_root: push_sec_ctx failed");
 442         }
 443         push_conn_ctx();
 444         set_root_sec_ctx();
 445 }
 446
 447 /* Unbecome the root user */
 448
 449 void smbd_unbecome_root(void)
 450 {
 451         pop_sec_ctx();
 452         pop_conn_ctx();
 453 }
 454
 455 /****************************************************************************
 456  Push the current security context then force a change via change_to_user().
 457  Saves and restores the connection context.
 458 ****************************************************************************/
 459
 460 bool become_user(connection_struct *conn, uint16 vuid)
 461 {
 462         if (!push_sec_ctx())
 463                 return False;
 464
 465         push_conn_ctx();
 466
 467         if (!change_to_user(conn, vuid)) {
 468                 pop_sec_ctx();
 469                 pop_conn_ctx();
 470                 return False;
 471         }
 472
 473         return True;
 474 }
 475
 476 bool become_user_by_session(connection_struct *conn,
 477                             const struct auth_session_info *session_info)
 478 {
 479         if (!push_sec_ctx())
 480                 return false;
 481
 482         push_conn_ctx();
 483
 484         if (!change_to_user_by_session(conn, session_info)) {
 485                 pop_sec_ctx();
 486                 pop_conn_ctx();
 487                 return false;
 488         }
 489
 490         return true;
 491 }
 492
 493 bool unbecome_user(void)
 494 {
 495         pop_sec_ctx();
 496         pop_conn_ctx();
 497         return True;
 498 }
 499
 500 /****************************************************************************
 501  Return the current user we are running effectively as on this connection.
 502  I'd like to make this return conn->session_info->unix_token->uid, but become_root()
 503  doesn't alter this value.
 504 ****************************************************************************/
 505
 506 uid_t get_current_uid(connection_struct *conn)
 507 {
 508         return current_user.ut.uid;
 509 }
 510
 511 /****************************************************************************
 512  Return the current group we are running effectively as on this connection.
 513  I'd like to make this return conn->session_info->unix_token->gid, but become_root()
 514  doesn't alter this value.
 515 ****************************************************************************/
 516
 517 gid_t get_current_gid(connection_struct *conn)
 518 {
 519         return current_user.ut.gid;
 520 }
 521
 522 /****************************************************************************
 523  Return the UNIX token we are running effectively as on this connection.
 524  I'd like to make this return &conn->session_info->unix_token-> but become_root()
 525  doesn't alter this value.
 526 ****************************************************************************/
 527
 528 const struct security_unix_token *get_current_utok(connection_struct *conn)
 529 {
 530         return &current_user.ut;
 531 }
 532
 533 const struct security_token *get_current_nttok(connection_struct *conn)
 534 {
 535         return current_user.nt_user_token;
 536 }
 537
 538 uint16_t get_current_vuid(connection_struct *conn)
 539 {
 540         return current_user.vuid;
 541 }