source3/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 3 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, see <http://www.gnu.org/licenses/>.
  18 */
  19
  20 #ifndef AUTOCONF_TEST
  21 #include "includes.h"
  22 #include "system/passwd.h" /* uid_wrapper */
  23 #include "../lib/util/setid.h"
  24
  25 #else
  26 /* we are running this code in autoconf test mode to see which type of setuid
  27    function works */
  28 #if defined(HAVE_UNISTD_H)
  29 #include <unistd.h>
  30 #endif
  31 #include <stdlib.h>
  32 #include <stdio.h>
  33 #include <sys/types.h>
  34 #include <errno.h>
  35
  36 #ifdef HAVE_SYS_PRIV_H
  37 #include <sys/priv.h>
  38 #endif
  39 #ifdef HAVE_SYS_ID_H
  40 #include <sys/id.h>
  41 #endif
  42
  43 #define DEBUG(x, y) printf y
  44 #define smb_panic(x) exit(1)
  45 #define bool int
  46 #endif
  47
  48 /* are we running as non-root? This is used by the regresison test code,
  49    and potentially also for sites that want non-root smbd */
  50 static uid_t initial_uid;
  51 static gid_t initial_gid;
  52
  53 /****************************************************************************
  54 remember what uid we got started as - this allows us to run correctly
  55 as non-root while catching trapdoor systems
  56 ****************************************************************************/
  57
  58 void sec_init(void)
  59 {
  60         static int initialized;
  61
  62         if (!initialized) {
  63                 initial_uid = geteuid();
  64                 initial_gid = getegid();
  65                 initialized = 1;
  66         }
  67 }
  68
  69 /****************************************************************************
  70 some code (eg. winbindd) needs to know what uid we started as
  71 ****************************************************************************/
  72 uid_t sec_initial_uid(void)
  73 {
  74         return initial_uid;
  75 }
  76
  77 /****************************************************************************
  78 some code (eg. winbindd, profiling shm) needs to know what gid we started as
  79 ****************************************************************************/
  80 gid_t sec_initial_gid(void)
  81 {
  82         return initial_gid;
  83 }
  84
  85 /****************************************************************************
  86 are we running in non-root mode?
  87 ****************************************************************************/
  88 bool non_root_mode(void)
  89 {
  90         return (initial_uid != (uid_t)0);
  91 }
  92
  93 /****************************************************************************
  94 abort if we haven't set the uid correctly
  95 ****************************************************************************/
  96 static void assert_uid(uid_t ruid, uid_t euid)
  97 {
  98         if ((euid != (uid_t)-1 && geteuid() != euid) ||
  99             (ruid != (uid_t)-1 && getuid() != ruid)) {
 100                 if (!non_root_mode()) {
 101                         DEBUG(0,("Failed to set uid privileges to (%d,%d) now set to (%d,%d)\n",
 102                                  (int)ruid, (int)euid,
 103                                  (int)getuid(), (int)geteuid()));
 104                         smb_panic("failed to set uid\n");
 105                         exit(1);
 106                 }
 107         }
 108 }
 109
 110 /****************************************************************************
 111 abort if we haven't set the gid correctly
 112 ****************************************************************************/
 113 static void assert_gid(gid_t rgid, gid_t egid)
 114 {
 115         if ((egid != (gid_t)-1 && getegid() != egid) ||
 116             (rgid != (gid_t)-1 && getgid() != rgid)) {
 117                 if (!non_root_mode()) {
 118                         DEBUG(0,("Failed to set gid privileges to (%d,%d) now set to (%d,%d) uid=(%d,%d)\n",
 119                                  (int)rgid, (int)egid,
 120                                  (int)getgid(), (int)getegid(),
 121                                  (int)getuid(), (int)geteuid()));
 122                         smb_panic("failed to set gid\n");
 123                         exit(1);
 124                 }
 125         }
 126 }
 127
 128 /****************************************************************************
 129  Gain root privilege before doing something.
 130  We want to end up with ruid==euid==0
 131 ****************************************************************************/
 132 void gain_root_privilege(void)
 133 {
 134 #if defined(USE_SETRESUID) || defined(USE_LINUX_THREAD_CREDENTIALS)
 135         samba_setresuid(0,0,0);
 136 #endif
 137
 138 #if USE_SETEUID
 139         samba_seteuid(0);
 140 #endif
 141
 142 #if USE_SETREUID
 143         samba_setreuid(0, 0);
 144 #endif
 145
 146 #if USE_SETUIDX
 147         samba_setuidx(ID_EFFECTIVE, 0);
 148         samba_setuidx(ID_REAL, 0);
 149 #endif
 150
 151         /* this is needed on some systems */
 152         samba_setuid(0);
 153
 154         assert_uid(0, 0);
 155 }
 156
 157
 158 /****************************************************************************
 159  Ensure our real and effective groups are zero.
 160  we want to end up with rgid==egid==0
 161 ****************************************************************************/
 162 void gain_root_group_privilege(void)
 163 {
 164 #if defined(USE_SETRESUID) || defined(USE_LINUX_THREAD_CREDENTIALS)
 165         samba_setresgid(0,0,0);
 166 #endif
 167
 168 #if USE_SETREUID
 169         samba_setregid(0,0);
 170 #endif
 171
 172 #if USE_SETEUID
 173         samba_setegid(0);
 174 #endif
 175
 176 #if USE_SETUIDX
 177         samba_setgidx(ID_EFFECTIVE, 0);
 178         samba_setgidx(ID_REAL, 0);
 179 #endif
 180
 181         samba_setgid(0);
 182
 183         assert_gid(0, 0);
 184 }
 185
 186
 187 /****************************************************************************
 188  Set effective uid, and possibly the real uid too.
 189  We want to end up with either:
 190
 191    ruid==uid and euid==uid
 192
 193  or
 194
 195    ruid==0 and euid==uid
 196
 197  depending on what the local OS will allow us to regain root from.
 198 ****************************************************************************/
 199 void set_effective_uid(uid_t uid)
 200 {
 201 #if defined(USE_SETRESUID) || defined(USE_LINUX_THREAD_CREDENTIALS)
 202         /* Set the effective as well as the real uid. */
 203         if (samba_setresuid(uid,uid,-1) == -1) {
 204                 if (errno == EAGAIN) {
 205                         DEBUG(0, ("samba_setresuid failed with EAGAIN. uid(%d) "
 206                                   "might be over its NPROC limit\n",
 207                                   (int)uid));
 208                 }
 209         }
 210 #endif
 211
 212 #if USE_SETREUID
 213         samba_setreuid(-1,uid);
 214 #endif
 215
 216 #if USE_SETEUID
 217         samba_seteuid(uid);
 218 #endif
 219
 220 #if USE_SETUIDX
 221         samba_setuidx(ID_EFFECTIVE, uid);
 222 #endif
 223
 224         assert_uid(-1, uid);
 225 }
 226
 227 /****************************************************************************
 228  Set *only* the effective gid.
 229  we want to end up with rgid==0 and egid==gid
 230 ****************************************************************************/
 231 void set_effective_gid(gid_t gid)
 232 {
 233 #if defined(USE_SETRESUID) || defined(USE_LINUX_THREAD_CREDENTIALS)
 234         samba_setresgid(-1,gid,-1);
 235 #endif
 236
 237 #if USE_SETREUID
 238         samba_setregid(-1,gid);
 239 #endif
 240
 241 #if USE_SETEUID
 242         samba_setegid(gid);
 243 #endif
 244
 245 #if USE_SETUIDX
 246         samba_setgidx(ID_EFFECTIVE, gid);
 247 #endif
 248
 249         assert_gid(-1, gid);
 250 }
 251
 252 static uid_t saved_euid, saved_ruid;
 253 static gid_t saved_egid, saved_rgid;
 254
 255 /****************************************************************************
 256  save the real and effective uid for later restoration. Used by the quotas
 257  code
 258 ****************************************************************************/
 259 void save_re_uid(void)
 260 {
 261         saved_ruid = getuid();
 262         saved_euid = geteuid();
 263 }
 264
 265
 266 /****************************************************************************
 267  and restore them!
 268 ****************************************************************************/
 269
 270 void restore_re_uid_fromroot(void)
 271 {
 272 #if defined(USE_SETRESUID) || defined(USE_LINUX_THREAD_CREDENTIALS)
 273         samba_setresuid(saved_ruid, saved_euid, -1);
 274 #elif USE_SETREUID
 275         samba_setreuid(saved_ruid, -1);
 276         samba_setreuid(-1,saved_euid);
 277 #elif USE_SETUIDX
 278         samba_setuidx(ID_REAL, saved_ruid);
 279         samba_setuidx(ID_EFFECTIVE, saved_euid);
 280 #else
 281         set_effective_uid(saved_euid);
 282         if (getuid() != saved_ruid)
 283                 samba_setuid(saved_ruid);
 284         set_effective_uid(saved_euid);
 285 #endif
 286
 287         assert_uid(saved_ruid, saved_euid);
 288 }
 289
 290 void restore_re_uid(void)
 291 {
 292         set_effective_uid(0);
 293         restore_re_uid_fromroot();
 294 }
 295
 296 /****************************************************************************
 297  save the real and effective gid for later restoration. Used by the
 298  getgroups code
 299 ****************************************************************************/
 300 void save_re_gid(void)
 301 {
 302         saved_rgid = getgid();
 303         saved_egid = getegid();
 304 }
 305
 306 /****************************************************************************
 307  and restore them!
 308 ****************************************************************************/
 309 void restore_re_gid(void)
 310 {
 311 #if defined(USE_SETRESUID) || defined(USE_LINUX_THREAD_CREDENTIALS)
 312         samba_setresgid(saved_rgid, saved_egid, -1);
 313 #elif USE_SETREUID
 314         samba_setregid(saved_rgid, -1);
 315         samba_setregid(-1,saved_egid);
 316 #elif USE_SETUIDX
 317         samba_setgidx(ID_REAL, saved_rgid);
 318         samba_setgidx(ID_EFFECTIVE, saved_egid);
 319 #else
 320         set_effective_gid(saved_egid);
 321         if (getgid() != saved_rgid)
 322                 samba_setgid(saved_rgid);
 323         set_effective_gid(saved_egid);
 324 #endif
 325
 326         assert_gid(saved_rgid, saved_egid);
 327 }
 328
 329
 330 /****************************************************************************
 331  set the real AND effective uid to the current effective uid in a way that
 332  allows root to be regained.
 333  This is only possible on some platforms.
 334 ****************************************************************************/
 335 int set_re_uid(void)
 336 {
 337         uid_t uid = geteuid();
 338
 339 #if defined(USE_SETRESUID) || defined(USE_LINUX_THREAD_CREDENTIALS)
 340         samba_setresuid(uid, uid, -1);
 341 #endif
 342
 343 #if USE_SETREUID
 344         samba_setreuid(0, 0);
 345         samba_setreuid(uid, -1);
 346         samba_setreuid(-1, uid);
 347 #endif
 348
 349 #if USE_SETEUID
 350         /* can't be done */
 351         return -1;
 352 #endif
 353
 354 #if USE_SETUIDX
 355         /* can't be done */
 356         return -1;
 357 #endif
 358
 359         assert_uid(uid, uid);
 360         return 0;
 361 }
 362
 363
 364 /****************************************************************************
 365  Become the specified uid and gid - permanently !
 366  there should be no way back if possible
 367 ****************************************************************************/
 368 void become_user_permanently(uid_t uid, gid_t gid)
 369 {
 370         /*
 371          * First - gain root privilege. We do this to ensure
 372          * we can lose it again.
 373          */
 374
 375         gain_root_privilege();
 376         gain_root_group_privilege();
 377
 378 #if defined(USE_SETRESUID) || defined(USE_LINUX_THREAD_CREDENTIALS)
 379         samba_setresgid(gid,gid,gid);
 380         samba_setgid(gid);
 381         samba_setresuid(uid,uid,uid);
 382         samba_setuid(uid);
 383 #endif
 384
 385 #if USE_SETREUID
 386         samba_setregid(gid,gid);
 387         samba_setgid(gid);
 388         samba_setreuid(uid,uid);
 389         samba_setuid(uid);
 390 #endif
 391
 392 #if USE_SETEUID
 393         samba_setegid(gid);
 394         samba_setgid(gid);
 395         samba_setuid(uid);
 396         samba_seteuid(uid);
 397         samba_setuid(uid);
 398 #endif
 399
 400 #if USE_SETUIDX
 401         samba_setgidx(ID_REAL, gid);
 402         samba_setgidx(ID_EFFECTIVE, gid);
 403         samba_setgid(gid);
 404         samba_setuidx(ID_REAL, uid);
 405         samba_setuidx(ID_EFFECTIVE, uid);
 406         samba_setuid(uid);
 407 #endif
 408
 409         assert_uid(uid, uid);
 410         assert_gid(gid, gid);
 411 }
 412
 413 /**********************************************************
 414  Function to set thread specific credentials in an
 415  irreversible way. Must be thread-safe code.
 416 **********************************************************/
 417
 418 int set_thread_credentials_permanently(uid_t uid,
 419                                 gid_t gid,
 420                                 size_t setlen,
 421                                 const gid_t *gidset)
 422 {
 423 #if defined(USE_LINUX_THREAD_CREDENTIALS)
 424         /*
 425          * With Linux thread-specific credentials
 426          * we know we have setresuid/setresgid
 427          * available.
 428          */
 429
 430         /* Become root. */
 431         /* Set ru=0, eu=0 */
 432         if (samba_setresuid(0, 0, -1) != 0) {
 433                 return -1;
 434         }
 435         /* Set our primary gid. */
 436         /* Set rg=gid, eg=gid, sg=gid */
 437         if (samba_setresgid(gid, gid, gid) != 0) {
 438                 return -1;
 439         }
 440         /* Set extra groups list. */
 441         if (samba_setgroups(setlen, gidset) != 0) {
 442                 return -1;
 443         }
 444         /* Become the requested user. No way back after this. */
 445         /* Set ru=uid, eu=uid, su=uid */
 446         if (samba_setresuid(uid, uid, uid) != 0) {
 447                 return -1;
 448         }
 449         if (geteuid() != uid || getuid() != uid ||
 450                         getegid() != gid || getgid() != gid) {
 451                 smb_panic("set_thread_credentials_permanently failed\n");
 452                 return -1;
 453         }
 454         return 0;
 455 #else
 456         errno = ENOSYS;
 457         return -1;
 458 #endif
 459 }
 460
 461 #ifdef AUTOCONF_TEST
 462
 463 /****************************************************************************
 464 this function just checks that we don't get ENOSYS back
 465 ****************************************************************************/
 466 static int have_syscall(void)
 467 {
 468         errno = 0;
 469
 470 #if defined(USE_SETRESUID) || defined(USE_LINUX_THREAD_CREDENTIALS)
 471         samba_setresuid(-1,-1,-1);
 472 #endif
 473
 474 #if USE_SETREUID
 475         samba_setreuid(-1,-1);
 476 #endif
 477
 478 #if USE_SETEUID
 479         samba_seteuid(-1);
 480 #endif
 481
 482 #if USE_SETUIDX
 483         samba_setuidx(ID_EFFECTIVE, -1);
 484 #endif
 485
 486         if (errno == ENOSYS) return -1;
 487
 488         return 0;
 489 }
 490
 491 main()
 492 {
 493         if (getuid() != 0) {
 494 #if (defined(AIX) && defined(USE_SETREUID))
 495                 /* setreuid is badly broken on AIX 4.1, we avoid it completely */
 496                 fprintf(stderr,"avoiding possibly broken setreuid\n");
 497                 exit(1);
 498 #endif
 499
 500                 /* if not running as root then at least check to see if we get ENOSYS - this
 501                    handles Linux 2.0.x with glibc 2.1 */
 502                 fprintf(stderr,"not running as root: checking for ENOSYS\n");
 503                 exit(have_syscall());
 504         }
 505
 506         gain_root_privilege();
 507         gain_root_group_privilege();
 508         set_effective_gid(1);
 509         set_effective_uid(1);
 510         save_re_uid();
 511         restore_re_uid();
 512         gain_root_privilege();
 513         gain_root_group_privilege();
 514         become_user_permanently(1, 1);
 515         samba_setuid(0);
 516         if (getuid() == 0) {
 517                 fprintf(stderr,"uid not set permanently\n");
 518                 exit(1);
 519         }
 520
 521         printf("OK\n");
 522
 523         exit(0);
 524 }
 525 #endif
 526
 527 /****************************************************************************
 528 Check if we are setuid root.  Used in libsmb and smbpasswd paranoia checks.
 529 ****************************************************************************/
 530 bool is_setuid_root(void)
 531 {
 532         return (geteuid() == (uid_t)0) && (getuid() != (uid_t)0);
 533 }