source/lib/util_sec.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    Copyright (C) Jeremy Allison 1998.
   4    rewritten for version 2.0.6 by Tridge
   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 #ifndef AUTOCONF_TEST
  22 #include "includes.h"
  23 #else
  24 /* we are running this code in autoconf test mode to see which type of setuid
  25    function works */
  26 #if defined(HAVE_UNISTD_H)
  27 #include <unistd.h>
  28 #endif
  29 #include <stdlib.h>
  30 #include <stdio.h>
  31 #include <sys/types.h>
  32 #include <errno.h>
  33
  34 #ifdef HAVE_SYS_PRIV_H
  35 #include <sys/priv.h>
  36 #endif
  37 #ifdef HAVE_SYS_ID_H
  38 #include <sys/id.h>
  39 #endif
  40
  41 #define DEBUG(x, y) printf y
  42 #define smb_panic(x) exit(1)
  43 #define BOOL int
  44 #endif
  45
  46 /* are we running as non-root? This is used by the regresison test code,
  47    and potentially also for sites that want non-root smbd */
  48 static uid_t initial_uid;
  49 static gid_t initial_gid;
  50
  51 /****************************************************************************
  52 remember what uid we got started as - this allows us to run correctly
  53 as non-root while catching trapdoor systems
  54 ****************************************************************************/
  55
  56 void sec_init(void)
  57 {
  58         static int initialized;
  59
  60         if (!initialized) {
  61                 initial_uid = geteuid();
  62                 initial_gid = getegid();
  63                 initialized = 1;
  64         }
  65 }
  66
  67 /****************************************************************************
  68 some code (eg. winbindd) needs to know what uid we started as
  69 ****************************************************************************/
  70 uid_t sec_initial_uid(void)
  71 {
  72         return initial_uid;
  73 }
  74
  75 /****************************************************************************
  76 some code (eg. winbindd, profiling shm) needs to know what gid we started as
  77 ****************************************************************************/
  78 gid_t sec_initial_gid(void)
  79 {
  80         return initial_gid;
  81 }
  82
  83 /****************************************************************************
  84 are we running in non-root mode?
  85 ****************************************************************************/
  86 BOOL non_root_mode(void)
  87 {
  88         return (initial_uid != (uid_t)0);
  89 }
  90
  91 /****************************************************************************
  92 abort if we haven't set the uid correctly
  93 ****************************************************************************/
  94 static void assert_uid(uid_t ruid, uid_t euid)
  95 {
  96         if ((euid != (uid_t)-1 && geteuid() != euid) ||
  97             (ruid != (uid_t)-1 && getuid() != ruid)) {
  98                 if (!non_root_mode()) {
  99                         DEBUG(0,("Failed to set uid privileges to (%d,%d) now set to (%d,%d)\n",
 100                                  (int)ruid, (int)euid,
 101                                  (int)getuid(), (int)geteuid()));
 102                         smb_panic("failed to set uid\n");
 103                         exit(1);
 104                 }
 105         }
 106 }
 107
 108 /****************************************************************************
 109 abort if we haven't set the gid correctly
 110 ****************************************************************************/
 111 static void assert_gid(gid_t rgid, gid_t egid)
 112 {
 113         if ((egid != (gid_t)-1 && getegid() != egid) ||
 114             (rgid != (gid_t)-1 && getgid() != rgid)) {
 115                 if (!non_root_mode()) {
 116                         DEBUG(0,("Failed to set gid privileges to (%d,%d) now set to (%d,%d) uid=(%d,%d)\n",
 117                                  (int)rgid, (int)egid,
 118                                  (int)getgid(), (int)getegid(),
 119                                  (int)getuid(), (int)geteuid()));
 120                         smb_panic("failed to set gid\n");
 121                         exit(1);
 122                 }
 123         }
 124 }
 125
 126 /****************************************************************************
 127  Gain root privilege before doing something.
 128  We want to end up with ruid==euid==0
 129 ****************************************************************************/
 130 void gain_root_privilege(void)
 131 {
 132 #if USE_SETRESUID
 133         setresuid(0,0,0);
 134 #endif
 135
 136 #if USE_SETEUID
 137         seteuid(0);
 138 #endif
 139
 140 #if USE_SETREUID
 141         setreuid(0, 0);
 142 #endif
 143
 144 #if USE_SETUIDX
 145         setuidx(ID_EFFECTIVE, 0);
 146         setuidx(ID_REAL, 0);
 147 #endif
 148
 149         /* this is needed on some systems */
 150         setuid(0);
 151
 152         assert_uid(0, 0);
 153 }
 154
 155
 156 /****************************************************************************
 157  Ensure our real and effective groups are zero.
 158  we want to end up with rgid==egid==0
 159 ****************************************************************************/
 160 void gain_root_group_privilege(void)
 161 {
 162 #if USE_SETRESUID
 163         setresgid(0,0,0);
 164 #endif
 165
 166 #if USE_SETREUID
 167         setregid(0,0);
 168 #endif
 169
 170 #if USE_SETEUID
 171         setegid(0);
 172 #endif
 173
 174 #if USE_SETUIDX
 175         setgidx(ID_EFFECTIVE, 0);
 176         setgidx(ID_REAL, 0);
 177 #endif
 178
 179         setgid(0);
 180
 181         assert_gid(0, 0);
 182 }
 183
 184
 185 /****************************************************************************
 186  Set effective uid, and possibly the real uid too.
 187  We want to end up with either:
 188
 189    ruid==uid and euid==uid
 190
 191  or
 192
 193    ruid==0 and euid==uid
 194
 195  depending on what the local OS will allow us to regain root from.
 196 ****************************************************************************/
 197 void set_effective_uid(uid_t uid)
 198 {
 199 #if USE_SETRESUID
 200         /* Set the effective as well as the real uid. */
 201         setresuid(uid,uid,-1);
 202 #endif
 203
 204 #if USE_SETREUID
 205         setreuid(-1,uid);
 206 #endif
 207
 208 #if USE_SETEUID
 209         seteuid(uid);
 210 #endif
 211
 212 #if USE_SETUIDX
 213         setuidx(ID_EFFECTIVE, uid);
 214 #endif
 215
 216         assert_uid(-1, uid);
 217 }
 218
 219 /****************************************************************************
 220  Set *only* the effective gid.
 221  we want to end up with rgid==0 and egid==gid
 222 ****************************************************************************/
 223 void set_effective_gid(gid_t gid)
 224 {
 225 #if USE_SETRESUID
 226         setresgid(-1,gid,-1);
 227 #endif
 228
 229 #if USE_SETREUID
 230         setregid(-1,gid);
 231 #endif
 232
 233 #if USE_SETEUID
 234         setegid(gid);
 235 #endif
 236
 237 #if USE_SETUIDX
 238         setgidx(ID_EFFECTIVE, gid);
 239 #endif
 240
 241         assert_gid(-1, gid);
 242 }
 243
 244 static uid_t saved_euid, saved_ruid;
 245 static gid_t saved_egid, saved_rgid;
 246
 247 /****************************************************************************
 248  save the real and effective uid for later restoration. Used by the quotas
 249  code
 250 ****************************************************************************/
 251 void save_re_uid(void)
 252 {
 253         saved_ruid = getuid();
 254         saved_euid = geteuid();
 255 }
 256
 257
 258 /****************************************************************************
 259  and restore them!
 260 ****************************************************************************/
 261
 262 static void restore_re_uid_fromroot(void)
 263 {
 264 #if USE_SETRESUID
 265         setresuid(saved_ruid, saved_euid, -1);
 266 #elif USE_SETREUID
 267         setreuid(saved_ruid, -1);
 268         setreuid(-1,saved_euid);
 269 #elif USE_SETUIDX
 270         setuidx(ID_REAL, saved_ruid);
 271         setuidx(ID_EFFECTIVE, saved_euid);
 272 #else
 273         set_effective_uid(saved_euid);
 274         if (getuid() != saved_ruid)
 275                 setuid(saved_ruid);
 276         set_effective_uid(saved_euid);
 277 #endif
 278
 279         assert_uid(saved_ruid, saved_euid);
 280 }
 281
 282 void restore_re_uid(void)
 283 {
 284         set_effective_uid(0);
 285         restore_re_uid_fromroot();
 286 }
 287
 288 /****************************************************************************
 289  Lightweight become root - no group change.
 290 ****************************************************************************/
 291
 292 void become_root_uid_only(void)
 293 {
 294         save_re_uid();
 295         set_effective_uid(0);
 296 }
 297
 298 /****************************************************************************
 299  Lightweight unbecome root - no group change. Expects we are root already,
 300  saves errno across call boundary.
 301 ****************************************************************************/
 302
 303 void unbecome_root_uid_only(void)
 304 {
 305         int saved_errno = errno;
 306         restore_re_uid_fromroot();
 307         errno = saved_errno;
 308 }
 309
 310 /****************************************************************************
 311  save the real and effective gid for later restoration. Used by the
 312  getgroups code
 313 ****************************************************************************/
 314 void save_re_gid(void)
 315 {
 316         saved_rgid = getgid();
 317         saved_egid = getegid();
 318 }
 319
 320 /****************************************************************************
 321  and restore them!
 322 ****************************************************************************/
 323 void restore_re_gid(void)
 324 {
 325 #if USE_SETRESUID
 326         setresgid(saved_rgid, saved_egid, -1);
 327 #elif USE_SETREUID
 328         setregid(saved_rgid, -1);
 329         setregid(-1,saved_egid);
 330 #elif USE_SETUIDX
 331         setgidx(ID_REAL, saved_rgid);
 332         setgidx(ID_EFFECTIVE, saved_egid);
 333 #else
 334         set_effective_gid(saved_egid);
 335         if (getgid() != saved_rgid)
 336                 setgid(saved_rgid);
 337         set_effective_gid(saved_egid);
 338 #endif
 339
 340         assert_gid(saved_rgid, saved_egid);
 341 }
 342
 343
 344 /****************************************************************************
 345  set the real AND effective uid to the current effective uid in a way that
 346  allows root to be regained.
 347  This is only possible on some platforms.
 348 ****************************************************************************/
 349 int set_re_uid(void)
 350 {
 351         uid_t uid = geteuid();
 352
 353 #if USE_SETRESUID
 354         setresuid(geteuid(), -1, -1);
 355 #endif
 356
 357 #if USE_SETREUID
 358         setreuid(0, 0);
 359         setreuid(uid, -1);
 360         setreuid(-1, uid);
 361 #endif
 362
 363 #if USE_SETEUID
 364         /* can't be done */
 365         return -1;
 366 #endif
 367
 368 #if USE_SETUIDX
 369         /* can't be done */
 370         return -1;
 371 #endif
 372
 373         assert_uid(uid, uid);
 374         return 0;
 375 }
 376
 377
 378 /****************************************************************************
 379  Become the specified uid and gid - permanently !
 380  there should be no way back if possible
 381 ****************************************************************************/
 382 void become_user_permanently(uid_t uid, gid_t gid)
 383 {
 384         /*
 385          * First - gain root privilege. We do this to ensure
 386          * we can lose it again.
 387          */
 388
 389         gain_root_privilege();
 390         gain_root_group_privilege();
 391
 392 #if USE_SETRESUID
 393         setresgid(gid,gid,gid);
 394         setgid(gid);
 395         setresuid(uid,uid,uid);
 396         setuid(uid);
 397 #endif
 398
 399 #if USE_SETREUID
 400         setregid(gid,gid);
 401         setgid(gid);
 402         setreuid(uid,uid);
 403         setuid(uid);
 404 #endif
 405
 406 #if USE_SETEUID
 407         setegid(gid);
 408         setgid(gid);
 409         setuid(uid);
 410         seteuid(uid);
 411         setuid(uid);
 412 #endif
 413
 414 #if USE_SETUIDX
 415         setgidx(ID_REAL, gid);
 416         setgidx(ID_EFFECTIVE, gid);
 417         setgid(gid);
 418         setuidx(ID_REAL, uid);
 419         setuidx(ID_EFFECTIVE, uid);
 420         setuid(uid);
 421 #endif
 422
 423         assert_uid(uid, uid);
 424         assert_gid(gid, gid);
 425 }
 426
 427 #ifdef AUTOCONF_TEST
 428
 429 /****************************************************************************
 430 this function just checks that we don't get ENOSYS back
 431 ****************************************************************************/
 432 static int have_syscall(void)
 433 {
 434         errno = 0;
 435
 436 #if USE_SETRESUID
 437         setresuid(-1,-1,-1);
 438 #endif
 439
 440 #if USE_SETREUID
 441         setreuid(-1,-1);
 442 #endif
 443
 444 #if USE_SETEUID
 445         seteuid(-1);
 446 #endif
 447
 448 #if USE_SETUIDX
 449         setuidx(ID_EFFECTIVE, -1);
 450 #endif
 451
 452         if (errno == ENOSYS) return -1;
 453
 454         return 0;
 455 }
 456
 457 main()
 458 {
 459         if (getuid() != 0) {
 460 #if (defined(AIX) && defined(USE_SETREUID))
 461                 /* setreuid is badly broken on AIX 4.1, we avoid it completely */
 462                 fprintf(stderr,"avoiding possibly broken setreuid\n");
 463                 exit(1);
 464 #endif
 465
 466                 /* if not running as root then at least check to see if we get ENOSYS - this
 467                    handles Linux 2.0.x with glibc 2.1 */
 468                 fprintf(stderr,"not running as root: checking for ENOSYS\n");
 469                 exit(have_syscall());
 470         }
 471
 472         gain_root_privilege();
 473         gain_root_group_privilege();
 474         set_effective_gid(1);
 475         set_effective_uid(1);
 476         save_re_uid();
 477         restore_re_uid();
 478         gain_root_privilege();
 479         gain_root_group_privilege();
 480         become_user_permanently(1, 1);
 481         setuid(0);
 482         if (getuid() == 0) {
 483                 fprintf(stderr,"uid not set permanently\n");
 484                 exit(1);
 485         }
 486
 487         printf("OK\n");
 488
 489         exit(0);
 490 }
 491 #endif
 492
 493 /****************************************************************************
 494 Check if we are setuid root.  Used in libsmb and smbpasswd paranoia checks.
 495 ****************************************************************************/
 496 BOOL is_setuid_root(void)
 497 {
 498         return (geteuid() == (uid_t)0) && (getuid() != (uid_t)0);
 499 }