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 1.6 2004/12/19 21:10:48 cpressey Exp $
  37  */
  38
  39 #include <sys/cdefs.h>
  40 #include <sys/param.h>
  41 #include <sys/time.h>
  42 #include <sys/resource.h>
  43
  44 #include <err.h>
  45 #include <errno.h>
  46 #include <grp.h>
  47 #include <paths.h>
  48 #include <pwd.h>
  49 #include <stdio.h>
  50 #include <stdlib.h>
  51 #include <string.h>
  52 #include <syslog.h>
  53 #include <unistd.h>
  54 #include <libutil.h>
  55
  56 #ifdef LOGIN_CAP
  57 #include <login_cap.h>
  58 #endif
  59
  60 #ifdef  SKEY
  61 #include <skey.h>
  62 #endif
  63
  64 #ifdef KERBEROS5
  65 #include <krb5.h>
  66
  67 static long get_su_principal(krb5_context context, const char *target_user,
  68     const char *current_user, char **su_principal_name,
  69     krb5_principal *su_principal);
  70 static long kerberos5(krb5_context context, const char *current_user,
  71     const char *target_user, krb5_principal su_principal,
  72     const char *pass);
  73
  74 int use_kerberos5 = 1;
  75 #endif
  76
  77 #ifdef LOGIN_CAP
  78 #define LOGIN_CAP_ARG(x) x
  79 #else
  80 #define LOGIN_CAP_ARG(x)
  81 #endif
  82 #if defined(KERBEROS5)
  83 #define KERBEROS_ARG(x) x
  84 #else
  85 #define KERBEROS_ARG(x)
  86 #endif
  87 #define COMMON_ARG(x) x
  88 #define ARGSTR  "-" COMMON_ARG("flm") LOGIN_CAP_ARG("c:") KERBEROS_ARG("K")
  89
  90 char   *ontty(void);
  91 int     chshell(char *);
  92 static void usage(void);
  93
  94 extern char **environ;
  95
  96 int
  97 main(int argc, char **argv)
  98 {
  99         struct passwd *pwd;
 100 #ifdef WHEELSU
 101         char *targetpass;
 102         int iswheelsu;
 103 #endif /* WHEELSU */
 104         const char *p, *user, *shell = NULL;
 105         const char **nargv, **np;
 106         char **g, **cleanenv, *username, *entered_pass;
 107         struct group *gr;
 108         uid_t ruid;
 109         gid_t gid;
 110         int asme, ch, asthem, fastlogin, prio, i;
 111         enum { UNSET, YES, NO } iscsh = UNSET;
 112 #ifdef LOGIN_CAP
 113         login_cap_t *lc;
 114         char *class=NULL;
 115         int setwhat;
 116 #endif
 117 #if defined(KERBEROS5)
 118         char *k;
 119 #endif
 120 #ifdef KERBEROS5
 121         char *su_principal_name, *ccname;
 122         krb5_context context;
 123         krb5_principal su_principal;
 124 #endif
 125         char shellbuf[MAXPATHLEN];
 126
 127 #ifdef WHEELSU
 128         iswheelsu =
 129 #endif /* WHEELSU */
 130         asme = asthem = fastlogin = 0;
 131         user = "root";
 132         while((ch = getopt(argc, argv, ARGSTR)) != -1)
 133                 switch((char)ch) {
 134 #if defined(KERBEROS5)
 135                 case 'K':
 136                         use_kerberos5 = 0;
 137                         break;
 138 #endif
 139                 case 'f':
 140                         fastlogin = 1;
 141                         break;
 142                 case '-':
 143                 case 'l':
 144                         asme = 0;
 145                         asthem = 1;
 146                         break;
 147                 case 'm':
 148                         asme = 1;
 149                         asthem = 0;
 150                         break;
 151 #ifdef LOGIN_CAP
 152                 case 'c':
 153                         class = optarg;
 154                         break;
 155 #endif
 156                 case '?':
 157                 default:
 158                         usage();
 159                 }
 160
 161         if (optind < argc)
 162                 user = argv[optind++];
 163
 164         if (strlen(user) > MAXLOGNAME - 1) {
 165                 (void)fprintf(stderr, "su: username too long.\n");
 166                 exit(1);
 167         }
 168
 169         if (user == NULL)
 170                 usage();
 171
 172         if ((nargv = malloc (sizeof (char *) * (argc + 4))) == NULL) {
 173             errx(1, "malloc failure");
 174         }
 175
 176         nargv[argc + 3] = NULL;
 177         for (i = argc; i >= optind; i--)
 178             nargv[i + 3] = argv[i];
 179         np = &nargv[i + 3];
 180
 181         argv += optind;
 182
 183 #if defined(KERBEROS5)
 184         k = auth_getval("auth_list");
 185         if (k && !strstr(k, "kerberos")) {
 186             use_kerberos5 = 0;
 187         }
 188         su_principal_name = NULL;
 189         su_principal = NULL;
 190         if (krb5_init_context(&context) != 0)
 191                 use_kerberos5 = 0;
 192 #endif
 193         errno = 0;
 194         prio = getpriority(PRIO_PROCESS, 0);
 195         if (errno)
 196                 prio = 0;
 197         (void)setpriority(PRIO_PROCESS, 0, -2);
 198         openlog("su", LOG_CONS, 0);
 199
 200         /* get current login name and shell */
 201         ruid = getuid();
 202         username = getlogin();
 203         if (username == NULL || (pwd = getpwnam(username)) == NULL ||
 204             pwd->pw_uid != ruid)
 205                 pwd = getpwuid(ruid);
 206         if (pwd == NULL)
 207                 errx(1, "who are you?");
 208         username = strdup(pwd->pw_name);
 209         gid = pwd->pw_gid;
 210         if (username == NULL)
 211                 err(1, NULL);
 212         if (asme) {
 213                 if (pwd->pw_shell != NULL && *pwd->pw_shell != '\0') {
 214                         /* copy: pwd memory is recycled */
 215                         shell = strncpy(shellbuf,  pwd->pw_shell, sizeof shellbuf);
 216                         shellbuf[sizeof shellbuf - 1] = '\0';
 217                 } else {
 218                         shell = _PATH_BSHELL;
 219                         iscsh = NO;
 220                 }
 221         }
 222
 223         /* get target login information, default to root */
 224         if ((pwd = getpwnam(user)) == NULL) {
 225                 errx(1, "unknown login: %s", user);
 226         }
 227 #ifdef LOGIN_CAP
 228         if (class==NULL) {
 229                 lc = login_getpwclass(pwd);
 230         } else {
 231                 if (ruid)
 232                         errx(1, "only root may use -c");
 233                 lc = login_getclass(class);
 234                 if (lc == NULL)
 235                         errx(1, "unknown class: %s", class);
 236         }
 237 #endif
 238
 239 #ifdef WHEELSU
 240         targetpass = strdup(pwd->pw_passwd);
 241 #endif /* WHEELSU */
 242
 243         if (ruid) {
 244 #ifdef KERBEROS5
 245                 if (use_kerberos5) {
 246                         if (get_su_principal(context, user, username,
 247                             &su_principal_name, &su_principal) != 0 ||
 248                             !krb5_kuserok(context, su_principal, user)) {
 249                                 warnx("kerberos5: not in %s's ACL.", user);
 250                                 use_kerberos5 = 0;
 251                         }
 252                 }
 253 #endif
 254                 {
 255                         /*
 256                          * Only allow those with pw_gid==0 or those listed in
 257                          * group zero to su to root.  If group zero entry is
 258                          * missing or empty, then allow anyone to su to root.
 259                          * iswheelsu will only be set if the user is EXPLICITLY
 260                          * listed in group zero.
 261                          */
 262                         if (pwd->pw_uid == 0 && (gr = getgrgid((gid_t)0)) &&
 263                             gr->gr_mem && *(gr->gr_mem))
 264                                 for (g = gr->gr_mem;; ++g) {
 265                                         if (!*g) {
 266                                                 if (gid == 0)
 267                                                         break;
 268                                                 else
 269                                                         errx(1,
 270                              "you are not in the correct group (%s) to su %s.",
 271                                                             gr->gr_name,
 272                                                             user);
 273                                         }
 274                                         if (strcmp(username, *g) == 0) {
 275 #ifdef WHEELSU
 276                                                 iswheelsu = 1;
 277 #endif /* WHEELSU */
 278                                                 break;
 279                                         }
 280                                 }
 281                 }
 282                 /* if target requires a password, verify it */
 283                 if (*pwd->pw_passwd) {
 284 #ifdef  SKEY
 285 #ifdef WHEELSU
 286                         if (iswheelsu) {
 287                                 pwd = getpwnam(username);
 288                         }
 289 #endif /* WHEELSU */
 290                         entered_pass = skey_getpass("Password:", pwd, 1);
 291                         if (!(!strcmp(pwd->pw_passwd, skey_crypt(entered_pass,
 292                             pwd->pw_passwd, pwd, 1))
 293 #ifdef WHEELSU
 294                               || (iswheelsu && !strcmp(targetpass,
 295                                   crypt(entered_pass, targetpass)))
 296 #endif /* WHEELSU */
 297                               )) {
 298 #else
 299                         entered_pass = getpass("Password:");
 300                         if (strcmp(pwd->pw_passwd, crypt(entered_pass,
 301                             pwd->pw_passwd))) {
 302 #endif
 303 #ifdef KERBEROS5
 304                                 if (use_kerberos5 && kerberos5(context,
 305                                     username, user, su_principal,
 306                                     entered_pass) == 0)
 307                                         goto authok;
 308 #endif
 309                                 fprintf(stderr, "Sorry\n");
 310                                 syslog(LOG_AUTH|LOG_WARNING,
 311                                     "BAD SU %s to %s%s", username, user,
 312                                     ontty());
 313                                 exit(1);
 314                         }
 315 #if defined(KERBEROS5)
 316                 authok:
 317                         ;
 318 #endif
 319 #ifdef WHEELSU
 320                         if (iswheelsu) {
 321                                 pwd = getpwnam(user);
 322                         }
 323 #endif /* WHEELSU */
 324                 }
 325                 if (pwd->pw_expire && time(NULL) >= pwd->pw_expire) {
 326                         fprintf(stderr, "Sorry - account expired\n");
 327                         syslog(LOG_AUTH|LOG_WARNING,
 328                                 "BAD SU %s to %s%s", username,
 329                                 user, ontty());
 330                         exit(1);
 331                 }
 332         }
 333
 334         if (asme) {
 335                 /* if asme and non-standard target shell, must be root */
 336                 if (!chshell(pwd->pw_shell) && ruid)
 337                         errx(1, "permission denied (shell).");
 338         } else if (pwd->pw_shell && *pwd->pw_shell) {
 339                 shell = pwd->pw_shell;
 340                 iscsh = UNSET;
 341         } else {
 342                 shell = _PATH_BSHELL;
 343                 iscsh = NO;
 344         }
 345
 346         /* if we're forking a csh, we want to slightly muck the args */
 347         if (iscsh == UNSET) {
 348                 p = strrchr(shell, '/');
 349                 if (p)
 350                         ++p;
 351                 else
 352                         p = shell;
 353                 if ((iscsh = strcmp(p, "csh") ? NO : YES) == NO)
 354                     iscsh = strcmp(p, "tcsh") ? NO : YES;
 355         }
 356
 357         (void)setpriority(PRIO_PROCESS, 0, prio);
 358
 359 #ifdef LOGIN_CAP
 360         /* Set everything now except the environment & umask */
 361         setwhat = LOGIN_SETUSER|LOGIN_SETGROUP|LOGIN_SETRESOURCES|LOGIN_SETPRIORITY;
 362         /*
 363          * Don't touch resource/priority settings if -m has been
 364          * used or -l and -c hasn't, and we're not su'ing to root.
 365          */
 366         if ((asme || (!asthem && class == NULL)) && pwd->pw_uid)
 367                 setwhat &= ~(LOGIN_SETPRIORITY|LOGIN_SETRESOURCES);
 368         if (setusercontext(lc, pwd, pwd->pw_uid, setwhat) < 0)
 369                 err(1, "setusercontext");
 370 #else
 371         /* set permissions */
 372         if (setgid(pwd->pw_gid) < 0)
 373                 err(1, "setgid");
 374         if (initgroups(user, pwd->pw_gid))
 375                 errx(1, "initgroups failed");
 376         if (setuid(pwd->pw_uid) < 0)
 377                 err(1, "setuid");
 378 #endif
 379
 380         if (!asme) {
 381                 if (asthem) {
 382                         p = getenv("TERM");
 383 #ifdef KERBEROS5
 384                         ccname = getenv("KRB5CCNAME");
 385 #endif
 386                         if ((cleanenv = calloc(20, sizeof(char*))) == NULL)
 387                                 errx(1, "calloc");
 388                         cleanenv[0] = NULL;
 389                         environ = cleanenv;
 390 #ifdef LOGIN_CAP
 391                         /* set the su'd user's environment & umask */
 392                         setusercontext(lc, pwd, pwd->pw_uid, LOGIN_SETPATH|LOGIN_SETUMASK|LOGIN_SETENV);
 393 #else
 394                         (void)setenv("PATH", _PATH_DEFPATH, 1);
 395 #endif
 396                         if (p)
 397                                 (void)setenv("TERM", p, 1);
 398 #ifdef KERBEROS5
 399                         if (ccname)
 400                                 (void)setenv("KRB5CCNAME", ccname, 1);
 401 #endif
 402                         if (chdir(pwd->pw_dir) < 0)
 403                                 errx(1, "no directory");
 404                 }
 405                 if (asthem || pwd->pw_uid)
 406                         (void)setenv("USER", pwd->pw_name, 1);
 407                 (void)setenv("HOME", pwd->pw_dir, 1);
 408                 (void)setenv("SHELL", shell, 1);
 409         }
 410         if (iscsh == YES) {
 411                 if (fastlogin)
 412                         *np-- = "-f";
 413                 if (asme)
 414                         *np-- = "-m";
 415         }
 416
 417         /* csh strips the first character... */
 418         *np = asthem ? "-su" : iscsh == YES ? "_su" : "su";
 419
 420         if (ruid != 0)
 421                 syslog(LOG_NOTICE|LOG_AUTH, "%s to %s%s",
 422                     username, user, ontty());
 423
 424 #ifdef LOGIN_CAP
 425         login_close(lc);
 426 #endif
 427
 428         execv(shell, __DECONST(char * const *, np));
 429         err(1, "%s", shell);
 430 }
 431
 432 static void
 433 usage(void)
 434 {
 435         (void)fprintf(stderr, "usage: su [-] [-%s] %s[login [args]]\n",
 436             KERBEROS_ARG("K") COMMON_ARG("flm"),
 437 #ifdef LOGIN_CAP
 438             "[-c class] "
 439 #else
 440             ""
 441 #endif
 442             );
 443         exit(1);
 444 }
 445
 446 int
 447 chshell(char *sh)
 448 {
 449         int  r = 0;
 450         char *cp;
 451
 452         setusershell();
 453         while (!r && (cp = getusershell()) != NULL)
 454                 r = strcmp(cp, sh) == 0;
 455         endusershell();
 456         return r;
 457 }
 458
 459 char *
 460 ontty(void)
 461 {
 462         char *p;
 463         static char buf[MAXPATHLEN + 4];
 464
 465         buf[0] = 0;
 466         p = ttyname(STDERR_FILENO);
 467         if (p)
 468                 snprintf(buf, sizeof(buf), " on %s", p);
 469         return (buf);
 470 }
 471
 472 #ifdef KERBEROS5
 473 const char superuser[] = "root";
 474
 475 /* Authenticate using Kerberos 5.
 476  *   context           -- An initialized krb5_context.
 477  *   current_user      -- The current username.
 478  *   target_user       -- The target account name.
 479  *   su_principal      -- The target krb5_principal.
 480  *   pass              -- The user's password.
 481  * Note that a valid keytab in the default location with a host entry
 482  * must be available.
 483  * Returns 0 if authentication was successful, or a com_err error code if
 484  * it was not.
 485  */
 486 static long
 487 kerberos5(krb5_context context, const char *current_user,
 488     const char *target_user, krb5_principal su_principal,
 489     const char *pass)
 490 {
 491         krb5_creds       creds;
 492         krb5_get_init_creds_opt gic_opt;
 493         krb5_verify_init_creds_opt vic_opt;
 494         long             rv;
 495
 496         krb5_get_init_creds_opt_init(&gic_opt);
 497         krb5_verify_init_creds_opt_init(&vic_opt);
 498         rv = krb5_get_init_creds_password(context, &creds, su_principal,
 499             pass, NULL, NULL, 0, NULL, &gic_opt);
 500         if (rv != 0) {
 501                 syslog(LOG_NOTICE|LOG_AUTH, "BAD Kerberos5 SU: %s to %s%s: %s",
 502                     current_user, target_user, ontty(),
 503                     krb5_get_err_text(context, rv));
 504                 return (rv);
 505         }
 506         krb5_verify_init_creds_opt_set_ap_req_nofail(&vic_opt, 1);
 507         rv = krb5_verify_init_creds(context, &creds, NULL, NULL, NULL,
 508             &vic_opt);
 509         krb5_free_cred_contents(context, &creds);
 510         if (rv != 0) {
 511                 syslog(LOG_NOTICE|LOG_AUTH, "BAD Kerberos5 SU: %s to %s%s: %s",
 512                     current_user, target_user, ontty(),
 513                     krb5_get_err_text(context, rv));
 514                 return (rv);
 515         }
 516         return (0);
 517 }
 518
 519 /* Determine the target principal given the current user and the target user.
 520  *   context           -- An initialized krb5_context.
 521  *   target_user       -- The target username.
 522  *   current_user      -- The current username.
 523  *   su_principal_name -- (out) The target principal name.
 524  *   su_principal      -- (out) The target krb5_principal.
 525  *
 526  * When target_user is `root', the su_principal will be a `root
 527  * instance', e.g. `luser/root@REA.LM'.  Otherwise, the su_principal
 528  * will simply be the current user's default principal name.  Note that
 529  * in any case, if KRB5CCNAME is set and a credentials cache exists, the
 530  * principal name found there will be the `starting point', rather than
 531  * the current_user parameter.
 532  *
 533  * Returns 0 for success, or a com_err error code on failure.
 534  */
 535 static long
 536 get_su_principal(krb5_context context, const char *target_user,
 537     const char *current_user, char **su_principal_name,
 538     krb5_principal *su_principal)
 539 {
 540         krb5_principal   default_principal;
 541         krb5_ccache      ccache;
 542         char            *principal_name, *ccname, *p;
 543         long             rv;
 544         uid_t            euid, ruid;
 545
 546         *su_principal = NULL;
 547         default_principal = NULL;
 548         /* Lower privs while messing about with the credentials
 549          * cache.
 550          */
 551         ruid = getuid();
 552         euid = geteuid();
 553         rv = seteuid(getuid());
 554         if (rv != 0)
 555                 return (errno);
 556         p = getenv("KRB5CCNAME");
 557         if (p != NULL)
 558                 ccname = strdup(p);
 559         else
 560                 (void)asprintf(&ccname, "%s%lu", KRB5_DEFAULT_CCROOT,
 561                     (unsigned long)ruid);
 562         if (ccname == NULL)
 563                 return (errno);
 564         rv = krb5_cc_resolve(context, ccname, &ccache);
 565         free(ccname);
 566         if (rv == 0) {
 567                 rv = krb5_cc_get_principal(context, ccache,
 568                     &default_principal);
 569                 krb5_cc_close(context, ccache);
 570                 if (rv != 0)
 571                         default_principal = NULL; /* just to be safe */
 572         }
 573         rv = seteuid(euid);
 574         if (rv != 0)
 575                 return (errno);
 576         if (default_principal == NULL) {
 577                 rv = krb5_make_principal(context, &default_principal, NULL,
 578                     current_user, NULL);
 579                 if (rv != 0) {
 580                         warnx("Could not determine default principal name.");
 581                         return (rv);
 582                 }
 583         }
 584         /* Now that we have some principal, if the target account is
 585          * `root', then transform it into a `root' instance, e.g.
 586          * `user@REA.LM' -> `user/root@REA.LM'.
 587          */
 588         rv = krb5_unparse_name(context, default_principal, &principal_name);
 589         krb5_free_principal(context, default_principal);
 590         if (rv != 0) {
 591                 warnx("krb5_unparse_name: %s", krb5_get_err_text(context, rv));
 592                 return (rv);
 593         }
 594         if (strcmp(target_user, superuser) == 0) {
 595                 p = strrchr(principal_name, '@');
 596                 if (p == NULL) {
 597                         warnx("malformed principal name `%s'", principal_name);
 598                         free(principal_name);
 599                         return (rv);
 600                 }
 601                 *p++ = '\0';
 602                 (void)asprintf(su_principal_name, "%s/%s@%s", principal_name,
 603                     superuser, p);
 604                 free(principal_name);
 605         } else
 606                 *su_principal_name = principal_name;
 607         if (*su_principal_name == NULL)
 608                 return errno;
 609         rv = krb5_parse_name(context, *su_principal_name, &default_principal);
 610         if (rv != 0) {
 611                 warnx("krb5_parse_name `%s': %s", *su_principal_name,
 612                     krb5_get_err_text(context, rv));
 613                 free(*su_principal_name);
 614                 return (rv);
 615         }
 616         *su_principal = default_principal;
 617         return 0;
 618 }
 619
 620 #endif