source/smbd/sec_ctx.c

   1 /*
   2    Unix SMB/Netbios implementation.
   3    Version 1.9.
   4    uid/user handling
   5    Copyright (C) Tim Potter 2000
   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 2 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, write to the Free Software
  19    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20 */
  21
  22 #include "includes.h"
  23
  24 extern struct current_user current_user;
  25
  26 struct sec_ctx {
  27         uid_t uid;
  28         uid_t gid;
  29         int ngroups;
  30         gid_t *groups;
  31         NT_USER_TOKEN *token;
  32 };
  33
  34 /* A stack of security contexts.  We include the current context as being
  35    the first one, so there is room for another MAX_SEC_CTX_DEPTH more. */
  36
  37 static struct sec_ctx sec_ctx_stack[MAX_SEC_CTX_DEPTH + 1];
  38 static int sec_ctx_stack_ndx;
  39
  40 /****************************************************************************
  41  Become the specified uid.
  42 ****************************************************************************/
  43
  44 static BOOL become_uid(uid_t uid)
  45 {
  46         /* Check for dodgy uid values */
  47
  48         if (uid == (uid_t)-1 ||
  49             ((sizeof(uid_t) == 2) && (uid == (uid_t)65535))) {
  50                 static int done;
  51
  52                 if (!done) {
  53                         DEBUG(1,("WARNING: using uid %d is a security risk\n",
  54                                  (int)uid));
  55                         done = 1;
  56                 }
  57         }
  58
  59         /* Set effective user id */
  60
  61         set_effective_uid(uid);
  62
  63         DO_PROFILE_INC(uid_changes);
  64         return True;
  65 }
  66
  67 /****************************************************************************
  68  Become the specified gid.
  69 ****************************************************************************/
  70
  71 static BOOL become_gid(gid_t gid)
  72 {
  73         /* Check for dodgy gid values */
  74
  75         if (gid == (gid_t)-1 || ((sizeof(gid_t) == 2) &&
  76                                  (gid == (gid_t)65535))) {
  77                 static int done;
  78
  79                 if (!done) {
  80                         DEBUG(1,("WARNING: using gid %d is a security risk\n",
  81                                  (int)gid));
  82                         done = 1;
  83                 }
  84         }
  85
  86         /* Set effective group id */
  87
  88         set_effective_gid(gid);
  89         return True;
  90 }
  91
  92 /****************************************************************************
  93  Become the specified uid and gid.
  94 ****************************************************************************/
  95
  96 static BOOL become_id(uid_t uid, gid_t gid)
  97 {
  98         return become_gid(gid) && become_uid(uid);
  99 }
 100
 101 /****************************************************************************
 102  Drop back to root privileges in order to change to another user.
 103 ****************************************************************************/
 104
 105 static void gain_root(void)
 106 {
 107         if (non_root_mode()) {
 108                 return;
 109         }
 110
 111         if (geteuid() != 0) {
 112                 set_effective_uid(0);
 113
 114                 if (geteuid() != 0) {
 115                         DEBUG(0,
 116                               ("Warning: You appear to have a trapdoor "
 117                                "uid system\n"));
 118                 }
 119         }
 120
 121         if (getegid() != 0) {
 122                 set_effective_gid(0);
 123
 124                 if (getegid() != 0) {
 125                         DEBUG(0,
 126                               ("Warning: You appear to have a trapdoor "
 127                                "gid system\n"));
 128                 }
 129         }
 130 }
 131
 132 /****************************************************************************
 133  Get the list of current groups.
 134 ****************************************************************************/
 135
 136 int get_current_groups(gid_t gid, int *p_ngroups, gid_t **p_groups)
 137 {
 138         int i;
 139         gid_t grp;
 140         int ngroups;
 141         gid_t *groups = NULL;
 142
 143         (*p_ngroups) = 0;
 144         (*p_groups) = NULL;
 145
 146         /* this looks a little strange, but is needed to cope with
 147            systems that put the current egid in the group list
 148            returned from getgroups() (tridge) */
 149         save_re_gid();
 150         set_effective_gid(gid);
 151         setgid(gid);
 152
 153         ngroups = sys_getgroups(0,&grp);
 154         if (ngroups <= 0) {
 155                 goto fail;
 156         }
 157
 158         if((groups = (gid_t *)malloc(sizeof(gid_t)*(ngroups+1))) == NULL) {
 159                 DEBUG(0,("setup_groups malloc fail !\n"));
 160                 goto fail;
 161         }
 162
 163         if ((ngroups = sys_getgroups(ngroups,groups)) == -1) {
 164                 goto fail;
 165         }
 166
 167         restore_re_gid();
 168
 169         (*p_ngroups) = ngroups;
 170         (*p_groups) = groups;
 171
 172         DEBUG( 3, ( "get_current_groups: user is in %u groups: ", ngroups ) );
 173         for (i = 0; i < ngroups; i++ ) {
 174                 DEBUG( 3, ( "%s%d", (i ? ", " : ""), (int)groups[i] ) );
 175         }
 176         DEBUG( 3, ( "\n" ) );
 177
 178         return ngroups;
 179
 180 fail:
 181         SAFE_FREE(groups);
 182         restore_re_gid();
 183         return -1;
 184 }
 185
 186 /****************************************************************************
 187  Delete a SID token.
 188 ****************************************************************************/
 189
 190 void delete_nt_token(NT_USER_TOKEN **pptoken)
 191 {
 192     if (*pptoken) {
 193                 NT_USER_TOKEN *ptoken = *pptoken;
 194         SAFE_FREE( ptoken->user_sids );
 195         ZERO_STRUCTP(ptoken);
 196     }
 197     SAFE_FREE(*pptoken);
 198 }
 199
 200 /****************************************************************************
 201  Duplicate a SID token.
 202 ****************************************************************************/
 203
 204 NT_USER_TOKEN *dup_nt_token(NT_USER_TOKEN *ptoken)
 205 {
 206         NT_USER_TOKEN *token;
 207
 208         if (!ptoken)
 209                 return NULL;
 210
 211     if ((token = (NT_USER_TOKEN *)malloc( sizeof(NT_USER_TOKEN) ) ) == NULL)
 212         return NULL;
 213
 214     ZERO_STRUCTP(token);
 215
 216     if ((token->user_sids = (DOM_SID *)memdup( ptoken->user_sids, sizeof(DOM_SID) * ptoken->num_sids )) == NULL) {
 217         SAFE_FREE(token);
 218         return NULL;
 219     }
 220
 221     token->num_sids = ptoken->num_sids;
 222
 223         return token;
 224 }
 225
 226 /****************************************************************************
 227  Initialize the groups a user belongs to.
 228 ****************************************************************************/
 229
 230 BOOL initialise_groups(char *user, uid_t uid, gid_t gid)
 231 {
 232         struct sec_ctx *prev_ctx_p;
 233         BOOL result = True;
 234
 235         if (non_root_mode()) {
 236                 return True;
 237         }
 238
 239         become_root();
 240
 241         /* Call initgroups() to get user groups */
 242
 243         if (winbind_initgroups(user,gid) == -1) {
 244                 DEBUG(0,("Unable to initgroups. Error was %s\n", strerror(errno) ));
 245                 if (getuid() == 0) {
 246                         if (gid < 0 || gid > 32767 || uid < 0 || uid > 32767) {
 247                                 DEBUG(0,("This is probably a problem with the account %s\n", user));
 248                         }
 249                 }
 250                 result = False;
 251                 goto done;
 252         }
 253
 254         /* Store groups in previous user's security context.  This will
 255            always work as the become_root() call increments the stack
 256            pointer. */
 257
 258         prev_ctx_p = &sec_ctx_stack[sec_ctx_stack_ndx - 1];
 259
 260         SAFE_FREE(prev_ctx_p->groups);
 261         prev_ctx_p->ngroups = 0;
 262
 263         get_current_groups(gid, &prev_ctx_p->ngroups, &prev_ctx_p->groups);
 264
 265  done:
 266         unbecome_root();
 267
 268         return result;
 269 }
 270
 271 /****************************************************************************
 272  Create a new security context on the stack.  It is the same as the old
 273  one.  User changes are done using the set_sec_ctx() function.
 274 ****************************************************************************/
 275
 276 BOOL push_sec_ctx(void)
 277 {
 278         struct sec_ctx *ctx_p;
 279
 280         /* Check we don't overflow our stack */
 281
 282         if (sec_ctx_stack_ndx == MAX_SEC_CTX_DEPTH) {
 283                 DEBUG(0, ("Security context stack overflow!\n"));
 284                 smb_panic("Security context stack overflow!\n");
 285         }
 286
 287         /* Store previous user context */
 288
 289         sec_ctx_stack_ndx++;
 290
 291         ctx_p = &sec_ctx_stack[sec_ctx_stack_ndx];
 292
 293         ctx_p->uid = geteuid();
 294         ctx_p->gid = getegid();
 295
 296         DEBUG(3, ("push_sec_ctx(%u, %u) : sec_ctx_stack_ndx = %d\n",
 297                   (unsigned int)ctx_p->uid, (unsigned int)ctx_p->gid, sec_ctx_stack_ndx ));
 298
 299         ctx_p->token = dup_nt_token(sec_ctx_stack[sec_ctx_stack_ndx-1].token);
 300
 301         ctx_p->ngroups = sys_getgroups(0, NULL);
 302
 303         if (ctx_p->ngroups != 0) {
 304                 if (!(ctx_p->groups = malloc(ctx_p->ngroups * sizeof(gid_t)))) {
 305                         DEBUG(0, ("Out of memory in push_sec_ctx()\n"));
 306                         delete_nt_token(&ctx_p->token);
 307                         return False;
 308                 }
 309
 310                 sys_getgroups(ctx_p->ngroups, ctx_p->groups);
 311         } else {
 312                 ctx_p->groups = NULL;
 313         }
 314
 315         return True;
 316 }
 317
 318 /****************************************************************************
 319  Set the current security context to a given user.
 320 ****************************************************************************/
 321
 322 void set_sec_ctx(uid_t uid, gid_t gid, int ngroups, gid_t *groups, NT_USER_TOKEN *token)
 323 {
 324         struct sec_ctx *ctx_p = &sec_ctx_stack[sec_ctx_stack_ndx];
 325
 326         /* Set the security context */
 327
 328         DEBUG(3, ("setting sec ctx (%u, %u) - sec_ctx_stack_ndx = %d\n",
 329                 (unsigned int)uid, (unsigned int)gid, sec_ctx_stack_ndx));
 330
 331         if (ngroups) {
 332                 int i;
 333
 334                 DEBUG(3, ("%d user groups: \n", ngroups));
 335                 for (i = 0; i < ngroups; i++) {
 336                         DEBUGADD(3, ("%u ", (unsigned int)groups[i]));
 337                 }
 338
 339                 DEBUG(3, ("\n"));
 340         }
 341
 342
 343         gain_root();
 344
 345 #ifdef HAVE_SETGROUPS
 346         sys_setgroups(ngroups, groups);
 347 #endif
 348
 349         ctx_p->ngroups = ngroups;
 350
 351         SAFE_FREE(ctx_p->groups);
 352         if (token && (token == ctx_p->token))
 353                 smb_panic("DUPLICATE_TOKEN");
 354
 355         delete_nt_token(&ctx_p->token);
 356
 357         ctx_p->groups = memdup(groups, sizeof(gid_t) * ngroups);
 358         ctx_p->token = dup_nt_token(token);
 359
 360         become_id(uid, gid);
 361
 362         ctx_p->uid = uid;
 363         ctx_p->gid = gid;
 364
 365         /* Update current_user stuff */
 366
 367         current_user.uid = uid;
 368         current_user.gid = gid;
 369         current_user.ngroups = ngroups;
 370         current_user.groups = groups;
 371         current_user.nt_user_token = ctx_p->token;
 372 }
 373
 374 /****************************************************************************
 375  Become root context.
 376 ****************************************************************************/
 377
 378 void set_root_sec_ctx(void)
 379 {
 380         /* May need to worry about supplementary groups at some stage */
 381
 382         set_sec_ctx(0, 0, 0, NULL, NULL);
 383 }
 384
 385 /****************************************************************************
 386  Pop a security context from the stack.
 387 ****************************************************************************/
 388
 389 BOOL pop_sec_ctx(void)
 390 {
 391         struct sec_ctx *ctx_p;
 392         struct sec_ctx *prev_ctx_p;
 393
 394         /* Check for stack underflow */
 395
 396         if (sec_ctx_stack_ndx == 0) {
 397                 DEBUG(0, ("Security context stack underflow!\n"));
 398                 smb_panic("Security context stack underflow!\n");
 399         }
 400
 401         ctx_p = &sec_ctx_stack[sec_ctx_stack_ndx];
 402
 403         /* Clear previous user info */
 404
 405         ctx_p->uid = (uid_t)-1;
 406         ctx_p->gid = (gid_t)-1;
 407
 408         SAFE_FREE(ctx_p->groups);
 409         ctx_p->ngroups = 0;
 410
 411         delete_nt_token(&ctx_p->token);
 412
 413         /* Pop back previous user */
 414
 415         sec_ctx_stack_ndx--;
 416
 417         gain_root();
 418
 419         prev_ctx_p = &sec_ctx_stack[sec_ctx_stack_ndx];
 420
 421 #ifdef HAVE_SETGROUPS
 422         sys_setgroups(prev_ctx_p->ngroups, prev_ctx_p->groups);
 423 #endif
 424
 425         become_id(prev_ctx_p->uid, prev_ctx_p->gid);
 426
 427         /* Update current_user stuff */
 428
 429         current_user.uid = prev_ctx_p->uid;
 430         current_user.gid = prev_ctx_p->gid;
 431         current_user.ngroups = prev_ctx_p->ngroups;
 432         current_user.groups = prev_ctx_p->groups;
 433         current_user.nt_user_token = prev_ctx_p->token;
 434
 435         DEBUG(3, ("pop_sec_ctx (%u, %u) - sec_ctx_stack_ndx = %d\n",
 436                 (unsigned int)geteuid(), (unsigned int)getegid(), sec_ctx_stack_ndx));
 437
 438         return True;
 439 }
 440
 441 /* Initialise the security context system */
 442
 443 void init_sec_ctx(void)
 444 {
 445         int i;
 446         struct sec_ctx *ctx_p;
 447
 448         /* Initialise security context stack */
 449
 450         memset(sec_ctx_stack, 0, sizeof(struct sec_ctx) * MAX_SEC_CTX_DEPTH);
 451
 452         for (i = 0; i < MAX_SEC_CTX_DEPTH; i++) {
 453                 sec_ctx_stack[i].uid = (uid_t)-1;
 454                 sec_ctx_stack[i].gid = (gid_t)-1;
 455         }
 456
 457         /* Initialise first level of stack.  It is the current context */
 458         ctx_p = &sec_ctx_stack[0];
 459
 460         ctx_p->uid = geteuid();
 461         ctx_p->gid = getegid();
 462
 463         get_current_groups(ctx_p->gid, &ctx_p->ngroups, &ctx_p->groups);
 464
 465         ctx_p->token = NULL; /* Maps to guest user. */
 466
 467         /* Initialise current_user global */
 468
 469         current_user.uid = ctx_p->uid;
 470         current_user.gid = ctx_p->gid;
 471         current_user.ngroups = ctx_p->ngroups;
 472         current_user.groups = ctx_p->groups;
 473
 474         /* The conn and vuid are usually taken care of by other modules.
 475            We initialise them here. */
 476
 477         current_user.conn = NULL;
 478         current_user.vuid = UID_FIELD_INVALID;
 479         current_user.nt_user_token = NULL;
 480 }