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 #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         if (setresuid(uid,uid,-1) == -1) {
 202                 if (errno == EAGAIN) {
 203                         DEBUG(0, ("setresuid failed with EAGAIN. uid(%d) "
 204                                   "might be over its NPROC limit\n",
 205                                   (int)uid));
 206                 }
 207         }
 208 #endif
 209
 210 #if USE_SETREUID
 211         setreuid(-1,uid);
 212 #endif
 213
 214 #if USE_SETEUID
 215         seteuid(uid);
 216 #endif
 217
 218 #if USE_SETUIDX
 219         setuidx(ID_EFFECTIVE, uid);
 220 #endif
 221
 222         assert_uid(-1, uid);
 223 }
 224
 225 /****************************************************************************
 226  Set *only* the effective gid.
 227  we want to end up with rgid==0 and egid==gid
 228 ****************************************************************************/
 229 void set_effective_gid(gid_t gid)
 230 {
 231 #if USE_SETRESUID
 232         setresgid(-1,gid,-1);
 233 #endif
 234
 235 #if USE_SETREUID
 236         setregid(-1,gid);
 237 #endif
 238
 239 #if USE_SETEUID
 240         setegid(gid);
 241 #endif
 242
 243 #if USE_SETUIDX
 244         setgidx(ID_EFFECTIVE, gid);
 245 #endif
 246
 247         assert_gid(-1, gid);
 248 }
 249
 250 static uid_t saved_euid, saved_ruid;
 251 static gid_t saved_egid, saved_rgid;
 252
 253 /****************************************************************************
 254  save the real and effective uid for later restoration. Used by the quotas
 255  code
 256 ****************************************************************************/
 257 void save_re_uid(void)
 258 {
 259         saved_ruid = getuid();
 260         saved_euid = geteuid();
 261 }
 262
 263
 264 /****************************************************************************
 265  and restore them!
 266 ****************************************************************************/
 267
 268 void restore_re_uid_fromroot(void)
 269 {
 270 #if USE_SETRESUID
 271         setresuid(saved_ruid, saved_euid, -1);
 272 #elif USE_SETREUID
 273         setreuid(saved_ruid, -1);
 274         setreuid(-1,saved_euid);
 275 #elif USE_SETUIDX
 276         setuidx(ID_REAL, saved_ruid);
 277         setuidx(ID_EFFECTIVE, saved_euid);
 278 #else
 279         set_effective_uid(saved_euid);
 280         if (getuid() != saved_ruid)
 281                 setuid(saved_ruid);
 282         set_effective_uid(saved_euid);
 283 #endif
 284
 285         assert_uid(saved_ruid, saved_euid);
 286 }
 287
 288 void restore_re_uid(void)
 289 {
 290         set_effective_uid(0);
 291         restore_re_uid_fromroot();
 292 }
 293
 294 /****************************************************************************
 295  save the real and effective gid for later restoration. Used by the
 296  getgroups code
 297 ****************************************************************************/
 298 void save_re_gid(void)
 299 {
 300         saved_rgid = getgid();
 301         saved_egid = getegid();
 302 }
 303
 304 /****************************************************************************
 305  and restore them!
 306 ****************************************************************************/
 307 void restore_re_gid(void)
 308 {
 309 #if USE_SETRESUID
 310         setresgid(saved_rgid, saved_egid, -1);
 311 #elif USE_SETREUID
 312         setregid(saved_rgid, -1);
 313         setregid(-1,saved_egid);
 314 #elif USE_SETUIDX
 315         setgidx(ID_REAL, saved_rgid);
 316         setgidx(ID_EFFECTIVE, saved_egid);
 317 #else
 318         set_effective_gid(saved_egid);
 319         if (getgid() != saved_rgid)
 320                 setgid(saved_rgid);
 321         set_effective_gid(saved_egid);
 322 #endif
 323
 324         assert_gid(saved_rgid, saved_egid);
 325 }
 326
 327
 328 /****************************************************************************
 329  set the real AND effective uid to the current effective uid in a way that
 330  allows root to be regained.
 331  This is only possible on some platforms.
 332 ****************************************************************************/
 333 int set_re_uid(void)
 334 {
 335         uid_t uid = geteuid();
 336
 337 #if USE_SETRESUID
 338         setresuid(geteuid(), -1, -1);
 339 #endif
 340
 341 #if USE_SETREUID
 342         setreuid(0, 0);
 343         setreuid(uid, -1);
 344         setreuid(-1, uid);
 345 #endif
 346
 347 #if USE_SETEUID
 348         /* can't be done */
 349         return -1;
 350 #endif
 351
 352 #if USE_SETUIDX
 353         /* can't be done */
 354         return -1;
 355 #endif
 356
 357         assert_uid(uid, uid);
 358         return 0;
 359 }
 360
 361
 362 /****************************************************************************
 363  Become the specified uid and gid - permanently !
 364  there should be no way back if possible
 365 ****************************************************************************/
 366 void become_user_permanently(uid_t uid, gid_t gid)
 367 {
 368         /*
 369          * First - gain root privilege. We do this to ensure
 370          * we can lose it again.
 371          */
 372
 373         gain_root_privilege();
 374         gain_root_group_privilege();
 375
 376 #if USE_SETRESUID
 377         setresgid(gid,gid,gid);
 378         setgid(gid);
 379         setresuid(uid,uid,uid);
 380         setuid(uid);
 381 #endif
 382
 383 #if USE_SETREUID
 384         setregid(gid,gid);
 385         setgid(gid);
 386         setreuid(uid,uid);
 387         setuid(uid);
 388 #endif
 389
 390 #if USE_SETEUID
 391         setegid(gid);
 392         setgid(gid);
 393         setuid(uid);
 394         seteuid(uid);
 395         setuid(uid);
 396 #endif
 397
 398 #if USE_SETUIDX
 399         setgidx(ID_REAL, gid);
 400         setgidx(ID_EFFECTIVE, gid);
 401         setgid(gid);
 402         setuidx(ID_REAL, uid);
 403         setuidx(ID_EFFECTIVE, uid);
 404         setuid(uid);
 405 #endif
 406
 407         assert_uid(uid, uid);
 408         assert_gid(gid, gid);
 409 }
 410
 411 #ifdef AUTOCONF_TEST
 412
 413 /****************************************************************************
 414 this function just checks that we don't get ENOSYS back
 415 ****************************************************************************/
 416 static int have_syscall(void)
 417 {
 418         errno = 0;
 419
 420 #if USE_SETRESUID
 421         setresuid(-1,-1,-1);
 422 #endif
 423
 424 #if USE_SETREUID
 425         setreuid(-1,-1);
 426 #endif
 427
 428 #if USE_SETEUID
 429         seteuid(-1);
 430 #endif
 431
 432 #if USE_SETUIDX
 433         setuidx(ID_EFFECTIVE, -1);
 434 #endif
 435
 436         if (errno == ENOSYS) return -1;
 437
 438         return 0;
 439 }
 440
 441 main()
 442 {
 443         if (getuid() != 0) {
 444 #if (defined(AIX) && defined(USE_SETREUID))
 445                 /* setreuid is badly broken on AIX 4.1, we avoid it completely */
 446                 fprintf(stderr,"avoiding possibly broken setreuid\n");
 447                 exit(1);
 448 #endif
 449
 450                 /* if not running as root then at least check to see if we get ENOSYS - this
 451                    handles Linux 2.0.x with glibc 2.1 */
 452                 fprintf(stderr,"not running as root: checking for ENOSYS\n");
 453                 exit(have_syscall());
 454         }
 455
 456         gain_root_privilege();
 457         gain_root_group_privilege();
 458         set_effective_gid(1);
 459         set_effective_uid(1);
 460         save_re_uid();
 461         restore_re_uid();
 462         gain_root_privilege();
 463         gain_root_group_privilege();
 464         become_user_permanently(1, 1);
 465         setuid(0);
 466         if (getuid() == 0) {
 467                 fprintf(stderr,"uid not set permanently\n");
 468                 exit(1);
 469         }
 470
 471         printf("OK\n");
 472
 473         exit(0);
 474 }
 475 #endif
 476
 477 /****************************************************************************
 478 Check if we are setuid root.  Used in libsmb and smbpasswd paranoia checks.
 479 ****************************************************************************/
 480 bool is_setuid_root(void)
 481 {
 482         return (geteuid() == (uid_t)0) && (getuid() != (uid_t)0);
 483 }