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