usr.bin/su/su.c

   1 /*
   2  * Copyright (c) 1988, 1993, 1994
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by the University of
  16  *      California, Berkeley and its contributors.
  17  * 4. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  *
  33  * @(#) Copyright (c) 1988, 1993, 1994 The Regents of the University of California.  All rights reserved.
  34  * @(#)su.c     8.3 (Berkeley) 4/2/94
  35  * $FreeBSD: src/usr.bin/su/su.c,v 1.34.2.4 2002/06/16 21:04:15 nectar Exp $
  36  * $DragonFly: src/usr.bin/su/su.c,v 1.4 2003/10/04 20:36:51 hmp Exp $
  37  */
  38
  39 #include <sys/param.h>
  40 #include <sys/time.h>
  41 #include <sys/resource.h>
  42
  43 #include <err.h>
  44 #include <errno.h>
  45 #include <grp.h>
  46 #include <paths.h>
  47 #include <pwd.h>
  48 #include <stdio.h>
  49 #include <stdlib.h>
  50 #include <string.h>
  51 #include <syslog.h>
  52 #include <unistd.h>
  53 #include <libutil.h>
  54
  55 #ifdef LOGIN_CAP
  56 #include <login_cap.h>
  57 #endif
  58
  59 #ifdef  SKEY
  60 #include <skey.h>
  61 #endif
  62
  63 #ifdef KERBEROS5
  64 #include <krb5.h>
  65
  66 static long get_su_principal(krb5_context context, const char *target_user,
  67     const char *current_user, char **su_principal_name,
  68     krb5_principal *su_principal);
  69 static long kerberos5(krb5_context context, const char *current_user,
  70     const char *target_user, krb5_principal su_principal,
  71     const char *pass);
  72
  73 int use_kerberos5 = 1;
  74 #endif
  75
  76 #ifdef LOGIN_CAP
  77 #define LOGIN_CAP_ARG(x) x
  78 #else
  79 #define LOGIN_CAP_ARG(x)
  80 #endif
  81 #if defined(KERBEROS5)
  82 #define KERBEROS_ARG(x) x
  83 #else
  84 #define KERBEROS_ARG(x)
  85 #endif
  86 #define COMMON_ARG(x) x
  87 #define ARGSTR  "-" COMMON_ARG("flm") LOGIN_CAP_ARG("c:") KERBEROS_ARG("K")
  88
  89 char   *ontty(void);
  90 int     chshell(char *);
  91 static void usage(void);
  92
  93 int
  94 main(int argc, char **argv)
  95 {
  96         extern char **environ;
  97         struct passwd *pwd;
  98 #ifdef WHEELSU
  99         char *targetpass;
 100         int iswheelsu;
 101 #endif /* WHEELSU */
 102         char *p, **g, *user, *shell=NULL, *username, **cleanenv, **nargv, **np;
 103         struct group *gr;
 104         uid_t ruid;
 105         gid_t gid;
 106         int asme, ch, asthem, fastlogin, prio, i;
 107         enum { UNSET, YES, NO } iscsh = UNSET;
 108 #ifdef LOGIN_CAP
 109         login_cap_t *lc;
 110         char *class=NULL;
 111         int setwhat;
 112 #endif
 113 #if defined(KERBEROS5)
 114         char *k;
 115 #endif
 116 #ifdef KERBEROS5
 117         char *su_principal_name, *ccname;
 118         krb5_context context;
 119         krb5_principal su_principal;
 120 #endif
 121         char shellbuf[MAXPATHLEN];
 122
 123 #ifdef WHEELSU
 124         iswheelsu =
 125 #endif /* WHEELSU */
 126         asme = asthem = fastlogin = 0;
 127         user = "root";
 128         while((ch = getopt(argc, argv, ARGSTR)) != -1)
 129                 switch((char)ch) {
 130 #if defined(KERBEROS5)
 131                 case 'K':
 132                         use_kerberos5 = 0;
 133                         break;
 134 #endif
 135                 case 'f':
 136                         fastlogin = 1;
 137                         break;
 138                 case '-':
 139                 case 'l':
 140                         asme = 0;
 141                         asthem = 1;
 142                         break;
 143                 case 'm':
 144                         asme = 1;
 145                         asthem = 0;
 146                         break;
 147 #ifdef LOGIN_CAP
 148                 case 'c':
 149                         class = optarg;
 150                         break;
 151 #endif
 152                 case '?':
 153                 default:
 154                         usage();
 155                 }
 156
 157         if (optind < argc)
 158                 user = argv[optind++];
 159
 160         if (strlen(user) > MAXLOGNAME - 1) {
 161                 (void)fprintf(stderr, "su: username too long.\n");
 162                 exit(1);
 163         }
 164
 165         if (user == NULL)
 166                 usage();
 167
 168         if ((nargv = malloc (sizeof (char *) * (argc + 4))) == NULL) {
 169             errx(1, "malloc failure");
 170         }
 171
 172         nargv[argc + 3] = NULL;
 173         for (i = argc; i >= optind; i--)
 174             nargv[i + 3] = argv[i];
 175         np = &nargv[i + 3];
 176
 177         argv += optind;
 178
 179 #if defined(KERBEROS5)
 180         k = auth_getval("auth_list");
 181         if (k && !strstr(k, "kerberos")) {
 182             use_kerberos5 = 0;
 183         }
 184         su_principal_name = NULL;
 185         su_principal = NULL;
 186         if (krb5_init_context(&context) != 0)
 187                 use_kerberos5 = 0;
 188 #endif
 189         errno = 0;
 190         prio = getpriority(PRIO_PROCESS, 0);
 191         if (errno)
 192                 prio = 0;
 193         (void)setpriority(PRIO_PROCESS, 0, -2);
 194         openlog("su", LOG_CONS, 0);
 195
 196         /* get current login name and shell */
 197         ruid = getuid();
 198         username = getlogin();
 199         if (username == NULL || (pwd = getpwnam(username)) == NULL ||
 200             pwd->pw_uid != ruid)
 201                 pwd = getpwuid(ruid);
 202         if (pwd == NULL)
 203                 errx(1, "who are you?");
 204         username = strdup(pwd->pw_name);
 205         gid = pwd->pw_gid;
 206         if (username == NULL)
 207                 err(1, NULL);
 208         if (asme) {
 209                 if (pwd->pw_shell != NULL && *pwd->pw_shell != '\0') {
 210                         /* copy: pwd memory is recycled */
 211                         shell = strncpy(shellbuf,  pwd->pw_shell, sizeof shellbuf);
 212                         shellbuf[sizeof shellbuf - 1] = '\0';
 213                 } else {
 214                         shell = _PATH_BSHELL;
 215                         iscsh = NO;
 216                 }
 217         }
 218
 219         /* get target login information, default to root */
 220         if ((pwd = getpwnam(user)) == NULL) {
 221                 errx(1, "unknown login: %s", user);
 222         }
 223 #ifdef LOGIN_CAP
 224         if (class==NULL) {
 225                 lc = login_getpwclass(pwd);
 226         } else {
 227                 if (ruid)
 228                         errx(1, "only root may use -c");
 229                 lc = login_getclass(class);
 230                 if (lc == NULL)
 231                         errx(1, "unknown class: %s", class);
 232         }
 233 #endif
 234
 235 #ifdef WHEELSU
 236         targetpass = strdup(pwd->pw_passwd);
 237 #endif /* WHEELSU */
 238
 239         if (ruid) {
 240 #ifdef KERBEROS5
 241                 if (use_kerberos5) {
 242                         if (get_su_principal(context, user, username,
 243                             &su_principal_name, &su_principal) != 0 ||
 244                             !krb5_kuserok(context, su_principal, user)) {
 245                                 warnx("kerberos5: not in %s's ACL.", user);
 246                                 use_kerberos5 = 0;
 247                         }
 248                 }
 249 #endif
 250                 {
 251                         /*
 252                          * Only allow those with pw_gid==0 or those listed in
 253                          * group zero to su to root.  If group zero entry is
 254                          * missing or empty, then allow anyone to su to root.
 255                          * iswheelsu will only be set if the user is EXPLICITLY
 256                          * listed in group zero.
 257                          */
 258                         if (pwd->pw_uid == 0 && (gr = getgrgid((gid_t)0)) &&
 259                             gr->gr_mem && *(gr->gr_mem))
 260                                 for (g = gr->gr_mem;; ++g) {
 261                                         if (!*g) {
 262                                                 if (gid == 0)
 263                                                         break;
 264                                                 else
 265                                                         errx(1,
 266                              "you are not in the correct group (%s) to su %s.",
 267                                                             gr->gr_name,
 268                                                             user);
 269                                         }
 270                                         if (strcmp(username, *g) == 0) {
 271 #ifdef WHEELSU
 272                                                 iswheelsu = 1;
 273 #endif /* WHEELSU */
 274                                                 break;
 275                                         }
 276                                 }
 277                 }
 278                 /* if target requires a password, verify it */
 279                 if (*pwd->pw_passwd) {
 280 #ifdef  SKEY
 281 #ifdef WHEELSU
 282                         if (iswheelsu) {
 283                                 pwd = getpwnam(username);
 284                         }
 285 #endif /* WHEELSU */
 286                         p = skey_getpass("Password:", pwd, 1);
 287                         if (!(!strcmp(pwd->pw_passwd, skey_crypt(p, pwd->pw_passwd, pwd, 1))
 288 #ifdef WHEELSU
 289                               || (iswheelsu && !strcmp(targetpass, crypt(p,targetpass)))
 290 #endif /* WHEELSU */
 291                               )) {
 292 #else
 293                         p = getpass("Password:");
 294                         if (strcmp(pwd->pw_passwd, crypt(p, pwd->pw_passwd))) {
 295 #endif
 296 #ifdef KERBEROS5
 297                                 if (use_kerberos5 && kerberos5(context,
 298                                     username, user, su_principal, p) == 0)
 299                                         goto authok;
 300 #endif
 301                                 fprintf(stderr, "Sorry\n");
 302                                 syslog(LOG_AUTH|LOG_WARNING,
 303                                     "BAD SU %s to %s%s", username, user,
 304                                     ontty());
 305                                 exit(1);
 306                         }
 307 #if defined(KERBEROS5)
 308                 authok:
 309 #endif
 310 #ifdef WHEELSU
 311                         if (iswheelsu) {
 312                                 pwd = getpwnam(user);
 313                         }
 314 #endif /* WHEELSU */
 315                 }
 316                 if (pwd->pw_expire && time(NULL) >= pwd->pw_expire) {
 317                         fprintf(stderr, "Sorry - account expired\n");
 318                         syslog(LOG_AUTH|LOG_WARNING,
 319                                 "BAD SU %s to %s%s", username,
 320                                 user, ontty());
 321                         exit(1);
 322                 }
 323         }
 324
 325         if (asme) {
 326                 /* if asme and non-standard target shell, must be root */
 327                 if (!chshell(pwd->pw_shell) && ruid)
 328                         errx(1, "permission denied (shell).");
 329         } else if (pwd->pw_shell && *pwd->pw_shell) {
 330                 shell = pwd->pw_shell;
 331                 iscsh = UNSET;
 332         } else {
 333                 shell = _PATH_BSHELL;
 334                 iscsh = NO;
 335         }
 336
 337         /* if we're forking a csh, we want to slightly muck the args */
 338         if (iscsh == UNSET) {
 339                 p = strrchr(shell, '/');
 340                 if (p)
 341                         ++p;
 342                 else
 343                         p = shell;
 344                 if ((iscsh = strcmp(p, "csh") ? NO : YES) == NO)
 345                     iscsh = strcmp(p, "tcsh") ? NO : YES;
 346         }
 347
 348         (void)setpriority(PRIO_PROCESS, 0, prio);
 349
 350 #ifdef LOGIN_CAP
 351         /* Set everything now except the environment & umask */
 352         setwhat = LOGIN_SETUSER|LOGIN_SETGROUP|LOGIN_SETRESOURCES|LOGIN_SETPRIORITY;
 353         /*
 354          * Don't touch resource/priority settings if -m has been
 355          * used or -l and -c hasn't, and we're not su'ing to root.
 356          */
 357         if ((asme || (!asthem && class == NULL)) && pwd->pw_uid)
 358                 setwhat &= ~(LOGIN_SETPRIORITY|LOGIN_SETRESOURCES);
 359         if (setusercontext(lc, pwd, pwd->pw_uid, setwhat) < 0)
 360                 err(1, "setusercontext");
 361 #else
 362         /* set permissions */
 363         if (setgid(pwd->pw_gid) < 0)
 364                 err(1, "setgid");
 365         if (initgroups(user, pwd->pw_gid))
 366                 errx(1, "initgroups failed");
 367         if (setuid(pwd->pw_uid) < 0)
 368                 err(1, "setuid");
 369 #endif
 370
 371         if (!asme) {
 372                 if (asthem) {
 373                         p = getenv("TERM");
 374 #ifdef KERBEROS5
 375                         ccname = getenv("KRB5CCNAME");
 376 #endif
 377                         if ((cleanenv = calloc(20, sizeof(char*))) == NULL)
 378                                 errx(1, "calloc");
 379                         cleanenv[0] = NULL;
 380                         environ = cleanenv;
 381 #ifdef LOGIN_CAP
 382                         /* set the su'd user's environment & umask */
 383                         setusercontext(lc, pwd, pwd->pw_uid, LOGIN_SETPATH|LOGIN_SETUMASK|LOGIN_SETENV);
 384 #else
 385                         (void)setenv("PATH", _PATH_DEFPATH, 1);
 386 #endif
 387                         if (p)
 388                                 (void)setenv("TERM", p, 1);
 389 #ifdef KERBEROS5
 390                         if (ccname)
 391                                 (void)setenv("KRB5CCNAME", ccname, 1);
 392 #endif
 393                         if (chdir(pwd->pw_dir) < 0)
 394                                 errx(1, "no directory");
 395                 }
 396                 if (asthem || pwd->pw_uid)
 397                         (void)setenv("USER", pwd->pw_name, 1);
 398                 (void)setenv("HOME", pwd->pw_dir, 1);
 399                 (void)setenv("SHELL", shell, 1);
 400         }
 401         if (iscsh == YES) {
 402                 if (fastlogin)
 403                         *np-- = "-f";
 404                 if (asme)
 405                         *np-- = "-m";
 406         }
 407
 408         /* csh strips the first character... */
 409         *np = asthem ? "-su" : iscsh == YES ? "_su" : "su";
 410
 411         if (ruid != 0)
 412                 syslog(LOG_NOTICE|LOG_AUTH, "%s to %s%s",
 413                     username, user, ontty());
 414
 415 #ifdef LOGIN_CAP
 416         login_close(lc);
 417 #endif
 418
 419         execv(shell, np);
 420         err(1, "%s", shell);
 421 }
 422
 423 static void
 424 usage(void)
 425 {
 426         (void)fprintf(stderr, "usage: su [-] [-%s] %s[login [args]]\n",
 427             KERBEROS_ARG("K") COMMON_ARG("flm"),
 428 #ifdef LOGIN_CAP
 429             "[-c class] "
 430 #else
 431             ""
 432 #endif
 433             );
 434         exit(1);
 435 }
 436
 437 int
 438 chshell(char *sh)
 439 {
 440         int  r = 0;
 441         char *cp;
 442
 443         setusershell();
 444         while (!r && (cp = getusershell()) != NULL)
 445                 r = strcmp(cp, sh) == 0;
 446         endusershell();
 447         return r;
 448 }
 449
 450 char *
 451 ontty(void)
 452 {
 453         char *p;
 454         static char buf[MAXPATHLEN + 4];
 455
 456         buf[0] = 0;
 457         p = ttyname(STDERR_FILENO);
 458         if (p)
 459                 snprintf(buf, sizeof(buf), " on %s", p);
 460         return (buf);
 461 }
 462
 463 #ifdef KERBEROS5
 464 const char superuser[] = "root";
 465
 466 /* Authenticate using Kerberos 5.
 467  *   context           -- An initialized krb5_context.
 468  *   current_user      -- The current username.
 469  *   target_user       -- The target account name.
 470  *   su_principal      -- The target krb5_principal.
 471  *   pass              -- The user's password.
 472  * Note that a valid keytab in the default location with a host entry
 473  * must be available.
 474  * Returns 0 if authentication was successful, or a com_err error code if
 475  * it was not.
 476  */
 477 static long
 478 kerberos5(krb5_context context, const char *current_user,
 479     const char *target_user, krb5_principal su_principal,
 480     const char *pass)
 481 {
 482         krb5_creds       creds;
 483         krb5_get_init_creds_opt gic_opt;
 484         krb5_verify_init_creds_opt vic_opt;
 485         long             rv;
 486
 487         krb5_get_init_creds_opt_init(&gic_opt);
 488         krb5_verify_init_creds_opt_init(&vic_opt);
 489         rv = krb5_get_init_creds_password(context, &creds, su_principal,
 490             pass, NULL, NULL, 0, NULL, &gic_opt);
 491         if (rv != 0) {
 492                 syslog(LOG_NOTICE|LOG_AUTH, "BAD Kerberos5 SU: %s to %s%s: %s",
 493                     current_user, target_user, ontty(),
 494                     krb5_get_err_text(context, rv));
 495                 return (rv);
 496         }
 497         krb5_verify_init_creds_opt_set_ap_req_nofail(&vic_opt, 1);
 498         rv = krb5_verify_init_creds(context, &creds, NULL, NULL, NULL,
 499             &vic_opt);
 500         krb5_free_cred_contents(context, &creds);
 501         if (rv != 0) {
 502                 syslog(LOG_NOTICE|LOG_AUTH, "BAD Kerberos5 SU: %s to %s%s: %s",
 503                     current_user, target_user, ontty(),
 504                     krb5_get_err_text(context, rv));
 505                 return (rv);
 506         }
 507         return (0);
 508 }
 509
 510 /* Determine the target principal given the current user and the target user.
 511  *   context           -- An initialized krb5_context.
 512  *   target_user       -- The target username.
 513  *   current_user      -- The current username.
 514  *   su_principal_name -- (out) The target principal name.
 515  *   su_principal      -- (out) The target krb5_principal.
 516  *
 517  * When target_user is `root', the su_principal will be a `root
 518  * instance', e.g. `luser/root@REA.LM'.  Otherwise, the su_principal
 519  * will simply be the current user's default principal name.  Note that
 520  * in any case, if KRB5CCNAME is set and a credentials cache exists, the
 521  * principal name found there will be the `starting point', rather than
 522  * the current_user parameter.
 523  *
 524  * Returns 0 for success, or a com_err error code on failure.
 525  */
 526 static long
 527 get_su_principal(krb5_context context, const char *target_user,
 528     const char *current_user, char **su_principal_name,
 529     krb5_principal *su_principal)
 530 {
 531         krb5_principal   default_principal;
 532         krb5_ccache      ccache;
 533         char            *principal_name, *ccname, *p;
 534         long             rv;
 535         uid_t            euid, ruid;
 536
 537         *su_principal = NULL;
 538         default_principal = NULL;
 539         /* Lower privs while messing about with the credentials
 540          * cache.
 541          */
 542         ruid = getuid();
 543         euid = geteuid();
 544         rv = seteuid(getuid());
 545         if (rv != 0)
 546                 return (errno);
 547         p = getenv("KRB5CCNAME");
 548         if (p != NULL)
 549                 ccname = strdup(p);
 550         else
 551                 (void)asprintf(&ccname, "%s%lu", KRB5_DEFAULT_CCROOT,
 552                     (unsigned long)ruid);
 553         if (ccname == NULL)
 554                 return (errno);
 555         rv = krb5_cc_resolve(context, ccname, &ccache);
 556         free(ccname);
 557         if (rv == 0) {
 558                 rv = krb5_cc_get_principal(context, ccache,
 559                     &default_principal);
 560                 krb5_cc_close(context, ccache);
 561                 if (rv != 0)
 562                         default_principal = NULL; /* just to be safe */
 563         }
 564         rv = seteuid(euid);
 565         if (rv != 0)
 566                 return (errno);
 567         if (default_principal == NULL) {
 568                 rv = krb5_make_principal(context, &default_principal, NULL,
 569                     current_user, NULL);
 570                 if (rv != 0) {
 571                         warnx("Could not determine default principal name.");
 572                         return (rv);
 573                 }
 574         }
 575         /* Now that we have some principal, if the target account is
 576          * `root', then transform it into a `root' instance, e.g.
 577          * `user@REA.LM' -> `user/root@REA.LM'.
 578          */
 579         rv = krb5_unparse_name(context, default_principal, &principal_name);
 580         krb5_free_principal(context, default_principal);
 581         if (rv != 0) {
 582                 warnx("krb5_unparse_name: %s", krb5_get_err_text(context, rv));
 583                 return (rv);
 584         }
 585         if (strcmp(target_user, superuser) == 0) {
 586                 p = strrchr(principal_name, '@');
 587                 if (p == NULL) {
 588                         warnx("malformed principal name `%s'", principal_name);
 589                         free(principal_name);
 590                         return (rv);
 591                 }
 592                 *p++ = '\0';
 593                 (void)asprintf(su_principal_name, "%s/%s@%s", principal_name,
 594                     superuser, p);
 595                 free(principal_name);
 596         } else
 597                 *su_principal_name = principal_name;
 598         if (*su_principal_name == NULL)
 599                 return errno;
 600         rv = krb5_parse_name(context, *su_principal_name, &default_principal);
 601         if (rv != 0) {
 602                 warnx("krb5_parse_name `%s': %s", *su_principal_name,
 603                     krb5_get_err_text(context, rv));
 604                 free(*su_principal_name);
 605                 return (rv);
 606         }
 607         *su_principal = default_principal;
 608         return 0;
 609 }
 610
 611 #endif