source3/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 };
  32
  33 /* A stack of security contexts.  We include the current context as being
  34    the first one, so there is room for another MAX_SEC_CTX_DEPTH more. */
  35
  36 static struct sec_ctx sec_ctx_stack[MAX_SEC_CTX_DEPTH + 1];
  37 static int sec_ctx_stack_ndx;
  38
  39 /****************************************************************************
  40  Become the specified uid.
  41 ****************************************************************************/
  42
  43 static BOOL become_uid(uid_t uid)
  44 {
  45         /* Check for dodgy uid values */
  46
  47         if (uid == (uid_t)-1 ||
  48             ((sizeof(uid_t) == 2) && (uid == (uid_t)65535))) {
  49                 static int done;
  50
  51                 if (!done) {
  52                         DEBUG(1,("WARNING: using uid %d is a security risk\n",
  53                                  (int)uid));
  54                         done = 1;
  55                 }
  56         }
  57
  58         /* Set effective user id */
  59
  60         set_effective_uid(uid);
  61
  62         DO_PROFILE_INC(uid_changes);
  63         return True;
  64 }
  65
  66 /****************************************************************************
  67  Become the specified gid.
  68 ****************************************************************************/
  69
  70 static BOOL become_gid(gid_t gid)
  71 {
  72         /* Check for dodgy gid values */
  73
  74         if (gid == (gid_t)-1 || ((sizeof(gid_t) == 2) &&
  75                                  (gid == (gid_t)65535))) {
  76                 static int done;
  77
  78                 if (!done) {
  79                         DEBUG(1,("WARNING: using gid %d is a security risk\n",
  80                                  (int)gid));
  81                         done = 1;
  82                 }
  83         }
  84
  85         /* Set effective group id */
  86
  87         set_effective_gid(gid);
  88         return True;
  89 }
  90
  91 /****************************************************************************
  92  Become the specified uid and gid.
  93 ****************************************************************************/
  94
  95 static BOOL become_id(uid_t uid, gid_t gid)
  96 {
  97         return become_gid(gid) && become_uid(uid);
  98 }
  99
 100 /****************************************************************************
 101  Drop back to root privileges in order to change to another user.
 102 ****************************************************************************/
 103
 104 static void gain_root(void)
 105 {
 106         if (non_root_mode()) {
 107                 return;
 108         }
 109
 110         if (geteuid() != 0) {
 111                 set_effective_uid(0);
 112
 113                 if (geteuid() != 0) {
 114                         DEBUG(0,
 115                               ("Warning: You appear to have a trapdoor "
 116                                "uid system\n"));
 117                 }
 118         }
 119
 120         if (getegid() != 0) {
 121                 set_effective_gid(0);
 122
 123                 if (getegid() != 0) {
 124                         DEBUG(0,
 125                               ("Warning: You appear to have a trapdoor "
 126                                "gid system\n"));
 127                 }
 128         }
 129 }
 130
 131 /****************************************************************************
 132  Get the list of current groups.
 133 ****************************************************************************/
 134
 135 int get_current_groups(gid_t gid, int *p_ngroups, gid_t **p_groups)
 136 {
 137         int i;
 138         gid_t grp;
 139         int ngroups;
 140         gid_t *groups = NULL;
 141
 142         (*p_ngroups) = 0;
 143         (*p_groups) = NULL;
 144
 145         /* this looks a little strange, but is needed to cope with
 146            systems that put the current egid in the group list
 147            returned from getgroups() (tridge) */
 148         save_re_gid();
 149         set_effective_gid(gid);
 150         setgid(gid);
 151
 152         ngroups = sys_getgroups(0,&grp);
 153         if (ngroups <= 0) {
 154                 goto fail;
 155         }
 156
 157         if((groups = (gid_t *)malloc(sizeof(gid_t)*(ngroups+1))) == NULL) {
 158                 DEBUG(0,("setup_groups malloc fail !\n"));
 159                 goto fail;
 160         }
 161
 162         if ((ngroups = sys_getgroups(ngroups,groups)) == -1) {
 163                 goto fail;
 164         }
 165
 166         restore_re_gid();
 167
 168         (*p_ngroups) = ngroups;
 169         (*p_groups) = groups;
 170
 171         DEBUG( 3, ( "get_current_groups: user is in %u groups: ", ngroups));
 172         for (i = 0; i < ngroups; i++ ) {
 173                 DEBUG( 3, ( "%s%d", (i ? ", " : ""), (int)groups[i] ) );
 174         }
 175         DEBUG( 3, ( "\n" ) );
 176
 177         return ngroups;
 178
 179 fail:
 180         SAFE_FREE(groups);
 181         restore_re_gid();
 182         return -1;
 183 }
 184
 185 /****************************************************************************
 186  Initialize the groups a user belongs to.
 187 ****************************************************************************/
 188
 189 BOOL initialise_groups(char *user, uid_t uid, gid_t gid)
 190 {
 191         struct sec_ctx *prev_ctx_p;
 192         BOOL result = True;
 193
 194         if (non_root_mode()) {
 195                 return True;
 196         }
 197
 198         become_root();
 199
 200         /* Call initgroups() to get user groups */
 201
 202         if (initgroups(user,gid) == -1) {
 203                 DEBUG(0,("Unable to initgroups. Error was %s\n", strerror(errno) ));
 204                 if (getuid() == 0) {
 205                         if (gid < 0 || gid > 32767 || uid < 0 || uid > 32767) {
 206                                 DEBUG(0,("This is probably a problem with the account %s\n", user));
 207                         }
 208                 }
 209                 result = False;
 210                 goto done;
 211         }
 212
 213         /* Store groups in previous user's security context.  This will
 214            always work as the become_root() call increments the stack
 215            pointer. */
 216
 217         prev_ctx_p = &sec_ctx_stack[sec_ctx_stack_ndx - 1];
 218
 219         SAFE_FREE(prev_ctx_p->groups);
 220         prev_ctx_p->ngroups = 0;
 221
 222         get_current_groups(gid, &prev_ctx_p->ngroups, &prev_ctx_p->groups);
 223
 224  done:
 225         unbecome_root();
 226
 227         return result;
 228 }
 229
 230 /****************************************************************************
 231  Create a new security context on the stack.  It is the same as the old
 232  one.  User changes are done using the set_sec_ctx() function.
 233 ****************************************************************************/
 234
 235 BOOL push_sec_ctx(void)
 236 {
 237         struct sec_ctx *ctx_p;
 238
 239         /* Check we don't overflow our stack */
 240
 241         if (sec_ctx_stack_ndx == MAX_SEC_CTX_DEPTH) {
 242                 DEBUG(0, ("Security context stack overflow!\n"));
 243                 smb_panic("Security context stack overflow!\n");
 244         }
 245
 246         /* Store previous user context */
 247
 248         sec_ctx_stack_ndx++;
 249
 250         ctx_p = &sec_ctx_stack[sec_ctx_stack_ndx];
 251
 252         ctx_p->uid = geteuid();
 253         ctx_p->gid = getegid();
 254
 255         DEBUG(3, ("push_sec_ctx(%u, %u) : sec_ctx_stack_ndx = %d\n",
 256                   (unsigned int)ctx_p->uid, (unsigned int)ctx_p->gid, sec_ctx_stack_ndx ));
 257
 258         ctx_p->token = dup_nt_token(sec_ctx_stack[sec_ctx_stack_ndx-1].token);
 259
 260         ctx_p->ngroups = sys_getgroups(0, NULL);
 261
 262         if (ctx_p->ngroups != 0) {
 263                 if (!(ctx_p->groups = malloc(ctx_p->ngroups * sizeof(gid_t)))) {
 264                         DEBUG(0, ("Out of memory in push_sec_ctx()\n"));
 265                         delete_nt_token(&ctx_p->token);
 266                         return False;
 267                 }
 268
 269                 sys_getgroups(ctx_p->ngroups, ctx_p->groups);
 270         } else {
 271                 ctx_p->groups = NULL;
 272         }
 273
 274         return True;
 275 }
 276
 277 /****************************************************************************
 278  Set the current security context to a given user.
 279 ****************************************************************************/
 280
 281 void set_sec_ctx(uid_t uid, gid_t gid, int ngroups, gid_t *groups, NT_USER_TOKEN *token)
 282 {
 283         struct sec_ctx *ctx_p = &sec_ctx_stack[sec_ctx_stack_ndx];
 284
 285         /* Set the security context */
 286
 287         DEBUG(3, ("setting sec ctx (%u, %u) - sec_ctx_stack_ndx = %d\n",
 288                 (unsigned int)uid, (unsigned int)gid, sec_ctx_stack_ndx));
 289
 290         debug_nt_user_token(DBGC_CLASS, 5, token);
 291         debug_unix_user_token(DBGC_CLASS, 5, uid, gid, ngroups, groups);
 292
 293         gain_root();
 294
 295 #ifdef HAVE_SETGROUPS
 296         sys_setgroups(ngroups, groups);
 297 #endif
 298
 299         ctx_p->ngroups = ngroups;
 300
 301         SAFE_FREE(ctx_p->groups);
 302         if (token && (token == ctx_p->token))
 303                 smb_panic("DUPLICATE_TOKEN");
 304
 305         delete_nt_token(&ctx_p->token);
 306
 307         ctx_p->groups = memdup(groups, sizeof(gid_t) * ngroups);
 308         ctx_p->token = dup_nt_token(token);
 309
 310         become_id(uid, gid);
 311
 312         ctx_p->uid = uid;
 313         ctx_p->gid = gid;
 314
 315         /* Update current_user stuff */
 316
 317         current_user.uid = uid;
 318         current_user.gid = gid;
 319         current_user.ngroups = ngroups;
 320         current_user.groups = groups;
 321         current_user.nt_user_token = ctx_p->token;
 322 }
 323
 324 /****************************************************************************
 325  Become root context.
 326 ****************************************************************************/
 327
 328 void set_root_sec_ctx(void)
 329 {
 330         /* May need to worry about supplementary groups at some stage */
 331
 332         set_sec_ctx(0, 0, 0, NULL, NULL);
 333 }
 334
 335 /****************************************************************************
 336  Pop a security context from the stack.
 337 ****************************************************************************/
 338
 339 BOOL pop_sec_ctx(void)
 340 {
 341         struct sec_ctx *ctx_p;
 342         struct sec_ctx *prev_ctx_p;
 343
 344         /* Check for stack underflow */
 345
 346         if (sec_ctx_stack_ndx == 0) {
 347                 DEBUG(0, ("Security context stack underflow!\n"));
 348                 smb_panic("Security context stack underflow!\n");
 349         }
 350
 351         ctx_p = &sec_ctx_stack[sec_ctx_stack_ndx];
 352
 353         /* Clear previous user info */
 354
 355         ctx_p->uid = (uid_t)-1;
 356         ctx_p->gid = (gid_t)-1;
 357
 358         SAFE_FREE(ctx_p->groups);
 359         ctx_p->ngroups = 0;
 360
 361         delete_nt_token(&ctx_p->token);
 362
 363         /* Pop back previous user */
 364
 365         sec_ctx_stack_ndx--;
 366
 367         gain_root();
 368
 369         prev_ctx_p = &sec_ctx_stack[sec_ctx_stack_ndx];
 370
 371 #ifdef HAVE_SETGROUPS
 372         sys_setgroups(prev_ctx_p->ngroups, prev_ctx_p->groups);
 373 #endif
 374
 375         become_id(prev_ctx_p->uid, prev_ctx_p->gid);
 376
 377         /* Update current_user stuff */
 378
 379         current_user.uid = prev_ctx_p->uid;
 380         current_user.gid = prev_ctx_p->gid;
 381         current_user.ngroups = prev_ctx_p->ngroups;
 382         current_user.groups = prev_ctx_p->groups;
 383         current_user.nt_user_token = prev_ctx_p->token;
 384
 385         DEBUG(3, ("pop_sec_ctx (%u, %u) - sec_ctx_stack_ndx = %d\n",
 386                 (unsigned int)geteuid(), (unsigned int)getegid(), sec_ctx_stack_ndx));
 387
 388         return True;
 389 }
 390
 391 /* Initialise the security context system */
 392
 393 void init_sec_ctx(void)
 394 {
 395         int i;
 396         struct sec_ctx *ctx_p;
 397
 398         /* Initialise security context stack */
 399
 400         memset(sec_ctx_stack, 0, sizeof(struct sec_ctx) * MAX_SEC_CTX_DEPTH);
 401
 402         for (i = 0; i < MAX_SEC_CTX_DEPTH; i++) {
 403                 sec_ctx_stack[i].uid = (uid_t)-1;
 404                 sec_ctx_stack[i].gid = (gid_t)-1;
 405         }
 406
 407         /* Initialise first level of stack.  It is the current context */
 408         ctx_p = &sec_ctx_stack[0];
 409
 410         ctx_p->uid = geteuid();
 411         ctx_p->gid = getegid();
 412
 413         get_current_groups(ctx_p->gid, &ctx_p->ngroups, &ctx_p->groups);
 414
 415         ctx_p->token = NULL; /* Maps to guest user. */
 416
 417         /* Initialise current_user global */
 418
 419         current_user.uid = ctx_p->uid;
 420         current_user.gid = ctx_p->gid;
 421         current_user.ngroups = ctx_p->ngroups;
 422         current_user.groups = ctx_p->groups;
 423
 424         /* The conn and vuid are usually taken care of by other modules.
 425            We initialise them here. */
 426
 427         current_user.conn = NULL;
 428         current_user.vuid = UID_FIELD_INVALID;
 429         current_user.nt_user_token = NULL;
 430 }