source/smbd/sec_ctx.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    uid/user handling
   4    Copyright (C) Tim Potter 2000
   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 2 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, write to the Free Software
  18    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19 */
  20
  21 #include "includes.h"
  22
  23 extern struct current_user current_user;
  24
  25 struct sec_ctx {
  26         uid_t uid;
  27         uid_t gid;
  28         int ngroups;
  29         gid_t *groups;
  30         NT_USER_TOKEN *token;
  31         PRIVILEGE_SET *privs;
  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  Initialize the groups a user belongs to.
 188 ****************************************************************************/
 189
 190 BOOL initialise_groups(char *user, uid_t uid, gid_t gid)
 191 {
 192         struct sec_ctx *prev_ctx_p;
 193         BOOL result = True;
 194
 195         if (non_root_mode()) {
 196                 return True;
 197         }
 198
 199         become_root();
 200
 201         /* Call initgroups() to get user groups */
 202
 203         if (winbind_initgroups(user,gid) == -1) {
 204                 DEBUG(0,("Unable to initgroups. Error was %s\n", strerror(errno) ));
 205                 if (getuid() == 0) {
 206                         if (gid < 0 || gid > 32767 || uid < 0 || uid > 32767) {
 207                                 DEBUG(0,("This is probably a problem with the account %s\n", user));
 208                         }
 209                 }
 210                 result = False;
 211                 goto done;
 212         }
 213
 214         /* Store groups in previous user's security context.  This will
 215            always work as the become_root() call increments the stack
 216            pointer. */
 217
 218         prev_ctx_p = &sec_ctx_stack[sec_ctx_stack_ndx - 1];
 219
 220         SAFE_FREE(prev_ctx_p->groups);
 221         prev_ctx_p->ngroups = 0;
 222
 223         get_current_groups(gid, &prev_ctx_p->ngroups, &prev_ctx_p->groups);
 224
 225  done:
 226         unbecome_root();
 227
 228         return result;
 229 }
 230
 231 /****************************************************************************
 232  Create a new security context on the stack.  It is the same as the old
 233  one.  User changes are done using the set_sec_ctx() function.
 234 ****************************************************************************/
 235
 236 BOOL push_sec_ctx(void)
 237 {
 238         struct sec_ctx *ctx_p;
 239
 240         /* Check we don't overflow our stack */
 241
 242         if (sec_ctx_stack_ndx == MAX_SEC_CTX_DEPTH) {
 243                 DEBUG(0, ("Security context stack overflow!\n"));
 244                 smb_panic("Security context stack overflow!\n");
 245         }
 246
 247         /* Store previous user context */
 248
 249         sec_ctx_stack_ndx++;
 250
 251         ctx_p = &sec_ctx_stack[sec_ctx_stack_ndx];
 252
 253         ctx_p->uid = geteuid();
 254         ctx_p->gid = getegid();
 255
 256         DEBUG(3, ("push_sec_ctx(%u, %u) : sec_ctx_stack_ndx = %d\n",
 257                   (unsigned int)ctx_p->uid, (unsigned int)ctx_p->gid, sec_ctx_stack_ndx ));
 258
 259         ctx_p->token = dup_nt_token(sec_ctx_stack[sec_ctx_stack_ndx-1].token);
 260         if (! ctx_p->token) {
 261                 DEBUG(0, ("Out of memory in push_sec_ctx()\n"));
 262                 return False;
 263         }
 264
 265         ctx_p->ngroups = sys_getgroups(0, NULL);
 266
 267         if (ctx_p->ngroups != 0) {
 268                 if (!(ctx_p->groups = malloc(ctx_p->ngroups * sizeof(gid_t)))) {
 269                         DEBUG(0, ("Out of memory in push_sec_ctx()\n"));
 270                         delete_nt_token(&ctx_p->token);
 271                         return False;
 272                 }
 273
 274                 sys_getgroups(ctx_p->ngroups, ctx_p->groups);
 275         } else {
 276                 ctx_p->groups = NULL;
 277         }
 278
 279         init_privilege(&ctx_p->privs);
 280         if (! NT_STATUS_IS_OK(dup_priv_set(ctx_p->privs, sec_ctx_stack[sec_ctx_stack_ndx-1].privs))) {
 281                 DEBUG(0, ("Out of memory in push_sec_ctx()\n"));
 282                 delete_nt_token(&ctx_p->token);
 283                 destroy_privilege(&ctx_p->privs);
 284                 return False;
 285         }
 286
 287         return True;
 288 }
 289
 290 /****************************************************************************
 291  Set the current security context to a given user.
 292 ****************************************************************************/
 293
 294 void set_sec_ctx(uid_t uid, gid_t gid, int ngroups, gid_t *groups, NT_USER_TOKEN *token, PRIVILEGE_SET *privs)
 295 {
 296         struct sec_ctx *ctx_p = &sec_ctx_stack[sec_ctx_stack_ndx];
 297
 298         /* Set the security context */
 299
 300         DEBUG(3, ("setting sec ctx (%u, %u) - sec_ctx_stack_ndx = %d\n",
 301                 (unsigned int)uid, (unsigned int)gid, sec_ctx_stack_ndx));
 302
 303         debug_nt_user_token(DBGC_CLASS, 5, token);
 304         debug_unix_user_token(DBGC_CLASS, 5, uid, gid, ngroups, groups);
 305
 306         gain_root();
 307
 308 #ifdef HAVE_SETGROUPS
 309         sys_setgroups(ngroups, groups);
 310 #endif
 311
 312         ctx_p->ngroups = ngroups;
 313
 314         SAFE_FREE(ctx_p->groups);
 315         if (token && (token == ctx_p->token))
 316                 smb_panic("DUPLICATE_TOKEN");
 317
 318         delete_nt_token(&ctx_p->token);
 319         if (ctx_p->privs)
 320                 reset_privilege(ctx_p->privs);
 321         else
 322                 init_privilege(&ctx_p->privs);
 323
 324         ctx_p->groups = memdup(groups, sizeof(gid_t) * ngroups);
 325         ctx_p->token = dup_nt_token(token);
 326         dup_priv_set(ctx_p->privs, privs);
 327
 328         become_id(uid, gid);
 329
 330         ctx_p->uid = uid;
 331         ctx_p->gid = gid;
 332
 333         /* Update current_user stuff */
 334
 335         current_user.uid = uid;
 336         current_user.gid = gid;
 337         current_user.ngroups = ngroups;
 338         current_user.groups = groups;
 339         current_user.nt_user_token = ctx_p->token;
 340         current_user.privs = ctx_p->privs;
 341 }
 342
 343 /****************************************************************************
 344  Become root context.
 345 ****************************************************************************/
 346
 347 void set_root_sec_ctx(void)
 348 {
 349         /* May need to worry about supplementary groups at some stage */
 350
 351         set_sec_ctx(0, 0, 0, NULL, NULL, NULL);
 352 }
 353
 354 /****************************************************************************
 355  Pop a security context from the stack.
 356 ****************************************************************************/
 357
 358 BOOL pop_sec_ctx(void)
 359 {
 360         struct sec_ctx *ctx_p;
 361         struct sec_ctx *prev_ctx_p;
 362
 363         /* Check for stack underflow */
 364
 365         if (sec_ctx_stack_ndx == 0) {
 366                 DEBUG(0, ("Security context stack underflow!\n"));
 367                 smb_panic("Security context stack underflow!\n");
 368         }
 369
 370         ctx_p = &sec_ctx_stack[sec_ctx_stack_ndx];
 371
 372         /* Clear previous user info */
 373
 374         ctx_p->uid = (uid_t)-1;
 375         ctx_p->gid = (gid_t)-1;
 376
 377         SAFE_FREE(ctx_p->groups);
 378         ctx_p->ngroups = 0;
 379
 380         delete_nt_token(&ctx_p->token);
 381         destroy_privilege(&ctx_p->privs);
 382
 383         /* Pop back previous user */
 384
 385         sec_ctx_stack_ndx--;
 386
 387         gain_root();
 388
 389         prev_ctx_p = &sec_ctx_stack[sec_ctx_stack_ndx];
 390
 391 #ifdef HAVE_SETGROUPS
 392         sys_setgroups(prev_ctx_p->ngroups, prev_ctx_p->groups);
 393 #endif
 394
 395         become_id(prev_ctx_p->uid, prev_ctx_p->gid);
 396
 397         /* Update current_user stuff */
 398
 399         current_user.uid = prev_ctx_p->uid;
 400         current_user.gid = prev_ctx_p->gid;
 401         current_user.ngroups = prev_ctx_p->ngroups;
 402         current_user.groups = prev_ctx_p->groups;
 403         current_user.nt_user_token = prev_ctx_p->token;
 404         current_user.privs = prev_ctx_p->privs;
 405
 406         DEBUG(3, ("pop_sec_ctx (%u, %u) - sec_ctx_stack_ndx = %d\n",
 407                 (unsigned int)geteuid(), (unsigned int)getegid(), sec_ctx_stack_ndx));
 408
 409         return True;
 410 }
 411
 412 /* Initialise the security context system */
 413
 414 void init_sec_ctx(void)
 415 {
 416         int i;
 417         struct sec_ctx *ctx_p;
 418
 419         /* Initialise security context stack */
 420
 421         memset(sec_ctx_stack, 0, sizeof(struct sec_ctx) * MAX_SEC_CTX_DEPTH);
 422
 423         for (i = 0; i < MAX_SEC_CTX_DEPTH; i++) {
 424                 sec_ctx_stack[i].uid = (uid_t)-1;
 425                 sec_ctx_stack[i].gid = (gid_t)-1;
 426         }
 427
 428         /* Initialise first level of stack.  It is the current context */
 429         ctx_p = &sec_ctx_stack[0];
 430
 431         ctx_p->uid = geteuid();
 432         ctx_p->gid = getegid();
 433
 434         get_current_groups(ctx_p->gid, &ctx_p->ngroups, &ctx_p->groups);
 435
 436         ctx_p->token = NULL; /* Maps to guest user. */
 437         ctx_p->privs = NULL;
 438
 439         /* Initialise current_user global */
 440
 441         current_user.uid = ctx_p->uid;
 442         current_user.gid = ctx_p->gid;
 443         current_user.ngroups = ctx_p->ngroups;
 444         current_user.groups = ctx_p->groups;
 445
 446         /* The conn and vuid are usually taken care of by other modules.
 447            We initialise them here. */
 448
 449         current_user.conn = NULL;
 450         current_user.vuid = UID_FIELD_INVALID;
 451         current_user.nt_user_token = NULL;
 452         current_user.privs = NULL;
 453 }