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                         uint64_t vuid,
  90                         const struct auth_session_info *session_info,
  91                         int snum)
  92 {
  93         unsigned int i;
  94         bool readonly_share;
  95         bool admin_user;
  96
  97         {
  98                 struct vuid_cache_entry *ent;
  99
 100                 for (i=0; i<VUID_CACHE_SIZE; i++) {
 101                         ent = &conn->vuid_cache.array[i];
 102                         if (ent->vuid == vuid) {
 103                                 free_conn_session_info_if_unused(conn);
 104                                 conn->session_info = ent->session_info;
 105                                 conn->read_only = ent->read_only;
 106                                 return(True);
 107                         }
 108                 }
 109         }
 110
 111         if (!user_ok_token(session_info->unix_info->unix_name,
 112                            session_info->info->domain_name,
 113                            session_info->security_token, snum))
 114                 return(False);
 115
 116         readonly_share = is_share_read_only_for_token(
 117                 session_info->unix_info->unix_name,
 118                 session_info->info->domain_name,
 119                 session_info->security_token,
 120                 conn);
 121
 122         if (!readonly_share &&
 123             !share_access_check(session_info->security_token,
 124                                 lp_servicename(talloc_tos(), snum),
 125                                 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(talloc_tos(), 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         {
 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                                     uint64_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(talloc_tos(), 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(talloc_tos(), 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, uint64_t vuid)
 279 {
 280         const struct auth_session_info *session_info = NULL;
 281         struct 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 %llu used on share %s.\n",
 302                          (unsigned long long)vuid, lp_servicename(talloc_tos(),
 303                                                                   snum)));
 304                 return false;
 305         }
 306
 307         session_info = vuser->session_info;
 308
 309         if (!conn->force_user && vuser == NULL) {
 310                 DEBUG(2,("Invalid vuid used %llu in accessing share %s.\n",
 311                          (unsigned long long)vuid,
 312                          lp_servicename(talloc_tos(), snum)));
 313                 return False;
 314         }
 315
 316         return change_to_user_internal(conn, session_info, vuid);
 317 }
 318
 319 static bool change_to_user_by_session(connection_struct *conn,
 320                                       const struct auth_session_info *session_info)
 321 {
 322         SMB_ASSERT(conn != NULL);
 323         SMB_ASSERT(session_info != NULL);
 324
 325         if ((current_user.conn == conn) &&
 326             (current_user.ut.uid == session_info->unix_token->uid)) {
 327                 DEBUG(7, ("Skipping user change - already user\n"));
 328
 329                 return true;
 330         }
 331
 332         return change_to_user_internal(conn, session_info, UID_FIELD_INVALID);
 333 }
 334
 335 /****************************************************************************
 336  Go back to being root without changing the security context stack,
 337  but modify the current_user entries.
 338 ****************************************************************************/
 339
 340 bool smbd_change_to_root_user(void)
 341 {
 342         set_root_sec_ctx();
 343
 344         DEBUG(5,("change_to_root_user: now uid=(%d,%d) gid=(%d,%d)\n",
 345                 (int)getuid(),(int)geteuid(),(int)getgid(),(int)getegid()));
 346
 347         current_user.conn = NULL;
 348         current_user.vuid = UID_FIELD_INVALID;
 349
 350         return(True);
 351 }
 352
 353 /****************************************************************************
 354  Become the user of an authenticated connected named pipe.
 355  When this is called we are currently running as the connection
 356  user. Doesn't modify current_user.
 357 ****************************************************************************/
 358
 359 bool become_authenticated_pipe_user(struct auth_session_info *session_info)
 360 {
 361         if (!push_sec_ctx())
 362                 return False;
 363
 364         set_sec_ctx(session_info->unix_token->uid, session_info->unix_token->gid,
 365                     session_info->unix_token->ngroups, session_info->unix_token->groups,
 366                     session_info->security_token);
 367
 368         return True;
 369 }
 370
 371 /****************************************************************************
 372  Unbecome the user of an authenticated connected named pipe.
 373  When this is called we are running as the authenticated pipe
 374  user and need to go back to being the connection user. Doesn't modify
 375  current_user.
 376 ****************************************************************************/
 377
 378 bool unbecome_authenticated_pipe_user(void)
 379 {
 380         return pop_sec_ctx();
 381 }
 382
 383 /****************************************************************************
 384  Utility functions used by become_xxx/unbecome_xxx.
 385 ****************************************************************************/
 386
 387 static void push_conn_ctx(void)
 388 {
 389         struct conn_ctx *ctx_p;
 390
 391         /* Check we don't overflow our stack */
 392
 393         if (conn_ctx_stack_ndx == MAX_SEC_CTX_DEPTH) {
 394                 DEBUG(0, ("Connection context stack overflow!\n"));
 395                 smb_panic("Connection context stack overflow!\n");
 396         }
 397
 398         /* Store previous user context */
 399         ctx_p = &conn_ctx_stack[conn_ctx_stack_ndx];
 400
 401         ctx_p->conn = current_user.conn;
 402         ctx_p->vuid = current_user.vuid;
 403
 404         DEBUG(4, ("push_conn_ctx(%llu) : conn_ctx_stack_ndx = %d\n",
 405                 (unsigned long long)ctx_p->vuid, conn_ctx_stack_ndx));
 406
 407         conn_ctx_stack_ndx++;
 408 }
 409
 410 static void pop_conn_ctx(void)
 411 {
 412         struct conn_ctx *ctx_p;
 413
 414         /* Check for stack underflow. */
 415
 416         if (conn_ctx_stack_ndx == 0) {
 417                 DEBUG(0, ("Connection context stack underflow!\n"));
 418                 smb_panic("Connection context stack underflow!\n");
 419         }
 420
 421         conn_ctx_stack_ndx--;
 422         ctx_p = &conn_ctx_stack[conn_ctx_stack_ndx];
 423
 424         current_user.conn = ctx_p->conn;
 425         current_user.vuid = ctx_p->vuid;
 426
 427         ctx_p->conn = NULL;
 428         ctx_p->vuid = UID_FIELD_INVALID;
 429 }
 430
 431 /****************************************************************************
 432  Temporarily become a root user.  Must match with unbecome_root(). Saves and
 433  restores the connection context.
 434 ****************************************************************************/
 435
 436 void smbd_become_root(void)
 437 {
 438          /*
 439           * no good way to handle push_sec_ctx() failing without changing
 440           * the prototype of become_root()
 441           */
 442         if (!push_sec_ctx()) {
 443                 smb_panic("become_root: push_sec_ctx failed");
 444         }
 445         push_conn_ctx();
 446         set_root_sec_ctx();
 447 }
 448
 449 /* Unbecome the root user */
 450
 451 void smbd_unbecome_root(void)
 452 {
 453         pop_sec_ctx();
 454         pop_conn_ctx();
 455 }
 456
 457 /****************************************************************************
 458  Push the current security context then force a change via change_to_user().
 459  Saves and restores the connection context.
 460 ****************************************************************************/
 461
 462 bool become_user(connection_struct *conn, uint64_t vuid)
 463 {
 464         if (!push_sec_ctx())
 465                 return False;
 466
 467         push_conn_ctx();
 468
 469         if (!change_to_user(conn, vuid)) {
 470                 pop_sec_ctx();
 471                 pop_conn_ctx();
 472                 return False;
 473         }
 474
 475         return True;
 476 }
 477
 478 bool become_user_by_session(connection_struct *conn,
 479                             const struct auth_session_info *session_info)
 480 {
 481         if (!push_sec_ctx())
 482                 return false;
 483
 484         push_conn_ctx();
 485
 486         if (!change_to_user_by_session(conn, session_info)) {
 487                 pop_sec_ctx();
 488                 pop_conn_ctx();
 489                 return false;
 490         }
 491
 492         return true;
 493 }
 494
 495 bool unbecome_user(void)
 496 {
 497         pop_sec_ctx();
 498         pop_conn_ctx();
 499         return True;
 500 }
 501
 502 /****************************************************************************
 503  Return the current user we are running effectively as on this connection.
 504  I'd like to make this return conn->session_info->unix_token->uid, but become_root()
 505  doesn't alter this value.
 506 ****************************************************************************/
 507
 508 uid_t get_current_uid(connection_struct *conn)
 509 {
 510         return current_user.ut.uid;
 511 }
 512
 513 /****************************************************************************
 514  Return the current group we are running effectively as on this connection.
 515  I'd like to make this return conn->session_info->unix_token->gid, but become_root()
 516  doesn't alter this value.
 517 ****************************************************************************/
 518
 519 gid_t get_current_gid(connection_struct *conn)
 520 {
 521         return current_user.ut.gid;
 522 }
 523
 524 /****************************************************************************
 525  Return the UNIX token we are running effectively as on this connection.
 526  I'd like to make this return &conn->session_info->unix_token-> but become_root()
 527  doesn't alter this value.
 528 ****************************************************************************/
 529
 530 const struct security_unix_token *get_current_utok(connection_struct *conn)
 531 {
 532         return &current_user.ut;
 533 }
 534
 535 /****************************************************************************
 536  Return the Windows token we are running effectively as on this connection.
 537  If this is currently a NULL token as we're inside become_root() - a temporary
 538  UNIX security override, then we search up the stack for the previous active
 539  token.
 540 ****************************************************************************/
 541
 542 const struct security_token *get_current_nttok(connection_struct *conn)
 543 {
 544         if (current_user.nt_user_token) {
 545                 return current_user.nt_user_token;
 546         }
 547         return sec_ctx_active_token();
 548 }
 549
 550 uint64_t get_current_vuid(connection_struct *conn)
 551 {
 552         return current_user.vuid;
 553 }