2 * Copyright (c) 1990 - 1994, Julianne Frances Haugh
3 * Copyright (c) 1996 - 2000, Marek Michałkiewicz
4 * Copyright (c) 2001 - 2006, Tomasz Kłoczko
5 * Copyright (c) 2007 - 2008, Nicolas François
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. The name of the copyright holders or contributors may not be used to
17 * endorse or promote products derived from this software without
18 * specific prior written permission.
20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
23 * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
24 * HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
25 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
26 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
27 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
28 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
29 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
30 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
44 #include "prototypes.h"
45 #include "exitcodes.h"
51 extern char **newenvp;
52 extern char **environ;
56 static /*@null@*/ /*@only@*/GETGROUPS_T *grouplist;
59 static bool is_newgrp;
62 static char audit_buf[80];
65 /* local function prototypes */
66 static void usage (void);
67 static void check_perms (const struct group *grp,
69 const char *groupname);
70 static void syslog_sg (const char *name, const char *group);
73 * usage - print command usage message
75 static void usage (void)
78 (void) fputs (_("Usage: newgrp [-] [group]\n"), stderr);
80 (void) fputs (_("Usage: sg group [[-c] command]\n"), stderr);
85 * find_matching_group - search all groups of a given group id for
86 * membership of a given username
88 static /*@null@*/struct group *find_matching_group (const char *name, gid_t gid)
95 while ((gr = getgrent ()) != NULL) {
96 if (gr->gr_gid != gid) {
101 * A group with matching GID was found.
102 * Test for membership of 'name'.
105 while ((NULL != *look) && notfound) {
106 notfound = (strcmp (*look, name) != 0);
118 * check_perms - check if the user is allowed to switch to this group
120 * If needed, the user will be authenticated.
122 * It will not return if the user could not be authenticated.
124 static void check_perms (const struct group *grp,
126 const char *groupname)
128 bool needspasswd = false;
134 * see if she is a member of this group (i.e. in the list of
135 * members of the group, or if the group is her primary group).
137 * If she isn't a member, she needs to provide the group password.
138 * If there is no group password, she will be denied access
142 if ( (grp->gr_gid != pwd->pw_gid)
143 && !is_on_list (grp->gr_mem, pwd->pw_name)) {
148 * If she does not have either a shadowed password, or a regular
149 * password, and the group has a password, she needs to give the
152 spwd = xgetspnam (pwd->pw_name);
154 pwd->pw_passwd = spwd->sp_pwdp;
157 if ((pwd->pw_passwd[0] == '\0') && (grp->gr_passwd[0] != '\0')) {
162 * Now I see about letting her into the group she requested. If she
163 * is the root user, I'll let her in without having to prompt for
164 * the password. Otherwise I ask for a password if she flunked one
165 * of the tests above.
167 if ((getuid () != 0) && needspasswd) {
169 * get the password from her, and set the salt for
170 * the decryption from the group file.
172 cp = getpass (_("Password: "));
178 * encrypt the key she gave us using the salt from the
179 * password in the group file. The result of this encryption
180 * must match the previously encrypted value in the file.
182 cpasswd = pw_encrypt (cp, grp->gr_passwd);
185 if (grp->gr_passwd[0] == '\0' ||
186 strcmp (cpasswd, grp->gr_passwd) != 0) {
188 snprintf (audit_buf, sizeof(audit_buf),
189 "authentication new-gid=%lu",
190 (unsigned long) grp->gr_gid);
191 audit_logger (AUDIT_GRP_AUTH, Prog,
193 (unsigned int) getuid (), 0);
196 "Invalid password for group '%s' from '%s'",
197 groupname, pwd->pw_name));
199 (void) fputs (_("Invalid password.\n"), stderr);
203 snprintf (audit_buf, sizeof(audit_buf),
204 "authentication new-gid=%lu",
205 (unsigned long) grp->gr_gid);
206 audit_logger (AUDIT_GRP_AUTH, Prog,
208 (unsigned int) getuid (), 1);
215 /* The closelog is probably unnecessary, but it does no
221 snprintf (audit_buf, sizeof(audit_buf),
222 "changing new-group=%s", groupname);
223 audit_logger (AUDIT_CHGRP_ID, Prog,
225 (unsigned int) getuid (), 0);
227 audit_logger (AUDIT_CHGRP_ID, Prog,
229 (unsigned int) getuid (), 0);
237 * syslog_sg - log the change of group to syslog
239 * The loggout will also be logged when the user will quit the
242 static void syslog_sg (const char *name, const char *group)
244 const char *loginname = getlogin ();
245 const char *tty = ttyname (0);
247 if (loginname != NULL) {
248 loginname = xstrdup (loginname);
254 if (loginname == NULL) {
259 } else if (strncmp (tty, "/dev/", 5) == 0) {
263 "user '%s' (login '%s' on %s) switched to group '%s'",
264 name, loginname, tty, group));
267 * We want to fork and exec the new shell in the child, leaving the
268 * parent waiting to log the session close.
270 * The parent must ignore signals generated from the console
271 * (SIGINT, SIGQUIT, SIGHUP) which might make the parent terminate
272 * before its child. When bash is exec'ed as the subshell, it
273 * generates a new process group id for itself, and consequently
274 * only SIGHUP, which is sent to all process groups in the session,
275 * can reach the parent. However, since arbitrary programs can be
276 * specified as login shells, there is no such guarantee in general.
277 * For the same reason, we must also ignore stop signals generated
278 * from the console (SIGTSTP, SIGTTIN, and SIGTTOU) in order to
279 * avoid any possibility of the parent being stopped when it
280 * receives SIGCHLD from the terminating subshell. -- JWP
285 /* Ignore these signals. The signal handlers will later be
286 * restored to the default handlers. */
287 (void) signal (SIGINT, SIG_IGN);
288 (void) signal (SIGQUIT, SIG_IGN);
289 (void) signal (SIGHUP, SIG_IGN);
290 (void) signal (SIGTSTP, SIG_IGN);
291 (void) signal (SIGTTIN, SIG_IGN);
292 (void) signal (SIGTTOU, SIG_IGN);
294 if ((pid_t)-1 == child) {
295 /* error in fork() */
296 fprintf (stderr, _("%s: failure forking: %s\n"),
297 is_newgrp ? "newgrp" : "sg", strerror (errno));
300 snprintf (audit_buf, sizeof(audit_buf),
301 "changing new-group=%s", group);
302 audit_logger (AUDIT_CHGRP_ID, Prog,
304 (unsigned int) getuid (), 0);
306 audit_logger (AUDIT_CHGRP_ID, Prog,
308 (unsigned int) getuid (), 0);
312 } else if (child != 0) {
313 /* parent - wait for child to finish, then log session close */
315 gid_t gid = getgid();
316 struct group *grp = getgrgid (gid);
320 pid = waitpid (child, &cst, WUNTRACED);
321 if ((pid == child) && (WIFSTOPPED (cst) != 0)) {
322 /* stop when child stops */
323 kill (getpid (), WSTOPSIG(cst));
324 /* wake child when resumed */
325 kill (child, SIGCONT);
327 } while ( ((pid == child) && (WIFSTOPPED (cst) != 0))
328 || ((pid != child) && (errno == EINTR)));
329 /* local, no need for xgetgrgid */
332 "user '%s' (login '%s' on %s) returned to group '%s'",
333 name, loginname, tty, grp->gr_name));
336 "user '%s' (login '%s' on %s) returned to group '%lu'",
337 name, loginname, tty,
338 (unsigned long) gid));
339 /* Either the user's passwd entry has a
340 * GID that does not match with any group,
341 * or the group was deleted while the user
342 * was in a newgrp session.*/
344 "unknown GID '%lu' used by user '%s'",
345 (unsigned long) gid, name));
351 /* child - restore signals to their default state */
352 (void) signal (SIGINT, SIG_DFL);
353 (void) signal (SIGQUIT, SIG_DFL);
354 (void) signal (SIGHUP, SIG_DFL);
355 (void) signal (SIGTSTP, SIG_DFL);
356 (void) signal (SIGTTIN, SIG_DFL);
357 (void) signal (SIGTTOU, SIG_DFL);
361 #endif /* USE_SYSLOG */
364 * newgrp - change the invokers current real and effective group id
366 int main (int argc, char **argv)
368 bool initflag = false;
374 const char *name, *prog;
376 char *command = NULL;
377 char **envp = environ;
379 /*@null@*/struct group *grp;
388 (void) setlocale (LC_ALL, "");
389 (void) bindtextdomain (PACKAGE, LOCALEDIR);
390 (void) textdomain (PACKAGE);
393 * Save my name for error messages and save my real gid incase of
394 * errors. If there is an error i have to exec a new login shell for
395 * the user since her old shell won't have fork'd to create the
396 * process. Skip over the program name to the next command line
399 * This historical comment, and the code itself, suggest that the
400 * behavior of the system/shell on which it was written differed
401 * significantly from the one I am using. If this process was
402 * started from a shell (including the login shell), it was fork'ed
403 * and exec'ed as a child by that shell. In order to get the user
404 * back to that shell, it is only necessary to exit from this
405 * process which terminates the child of the fork. The parent shell,
406 * which is blocked waiting for a signal, will then receive a
407 * SIGCHLD and will continue; any changes made to the process
408 * persona or the environment after the fork never occurred in the
411 * Bottom line: we want to save the name and real gid for messages,
412 * but we do not need to restore the previous process persona and we
413 * don't need to re-exec anything. -- JWP
415 Prog = Basename (argv[0]);
416 is_newgrp = (strcmp (Prog, "newgrp") == 0);
417 OPENLOG (is_newgrp ? "newgrp" : "sg");
424 pwd = get_my_pwent ();
426 fprintf (stderr, _("%s: Cannot determine your user name.\n"),
429 audit_logger (AUDIT_CHGRP_ID, Prog,
431 (unsigned int) getuid (), 0);
433 SYSLOG ((LOG_WARN, "Cannot determine the user name of the caller (UID %lu)",
434 (unsigned long) getuid ()));
441 * Parse the command line. There are two accepted flags. The first
442 * is "-", which for newgrp means to re-create the entire
443 * environment as though a login had been performed, and "-c", which
444 * for sg causes a command string to be executed.
446 * The next argument, if present, must be the new group name. Any
447 * remaining remaining arguments will be used to execute a command
448 * as the named group. If the group name isn't present, I just use
449 * the login group ID of the current user.
451 * The valid syntax are
452 * newgrp [-] [groupid]
453 * newgrp [-l] [groupid]
455 * sg [-] groupid [[-c command]
458 && ( (strcmp (argv[0], "-") == 0)
459 || (strcmp (argv[0], "-l") == 0))) {
466 * Do the command line for everything that is
469 if ((argc > 0) && (argv[0][0] != '-')) {
481 * skip -c if specified so both forms work:
482 * "sg group -c command" (as in the man page) or
483 * "sg group command" (as in the usage message).
485 if ((argc > 1) && (strcmp (argv[0], "-c") == 0)) {
494 * Do the command line for "newgrp". It's just making sure
495 * there aren't any flags and getting the new group name.
497 if ((argc > 0) && (argv[0][0] == '-')) {
500 } else if (argv[0] != (char *) 0) {
504 * get the group file entry for her login group id.
505 * the entry must exist, simply to be annoying.
507 * Perhaps in the past, but the default behavior now depends on the
508 * group entry, so it had better exist. -- JWP
510 grp = xgetgrgid (pwd->pw_gid);
513 _("%s: GID '%lu' does not exist\n"),
514 Prog, (unsigned long) pwd->pw_gid);
515 SYSLOG ((LOG_CRIT, "GID '%lu' does not exist",
516 (unsigned long) pwd->pw_gid));
519 group = grp->gr_name;
524 #ifdef HAVE_SETGROUPS
526 * get the current users groupset. The new group will be added to
527 * the concurrent groupset if there is room, otherwise you get a
528 * nasty message but at least your real and effective group id's are
531 /* don't use getgroups(0, 0) - it doesn't work on some systems */
534 grouplist = (GETGROUPS_T *) xmalloc (i * sizeof (GETGROUPS_T));
535 ngroups = getgroups (i, grouplist);
536 if (i > ngroups && !(ngroups == -1 && errno == EINVAL)) {
539 /* not enough room, so try allocating a larger buffer */
544 perror ("getgroups");
547 snprintf (audit_buf, sizeof(audit_buf),
548 "changing new-group=%s", group);
549 audit_logger (AUDIT_CHGRP_ID, Prog,
551 (unsigned int) getuid (), 0);
553 audit_logger (AUDIT_CHGRP_ID, Prog,
555 (unsigned int) getuid (), 0);
560 #endif /* HAVE_SETGROUPS */
563 * now we put her in the new group. The password file entry for her
564 * current user id has been gotten. If there was no optional group
565 * argument she will have her real and effective group id set to the
566 * set to the value from her password file entry.
568 * If run as newgrp, or as sg with no command, this process exec's
569 * an interactive subshell with the effective GID of the new group.
570 * If run as sg with a command, that command is exec'ed in this
571 * subshell. When this process terminates, either because the user
572 * exits, or the command completes, the parent of this process
573 * resumes with the current GID.
575 * If a group is explicitly specified on the command line, the
576 * interactive shell or command is run with that effective GID.
577 * Access will be denied if no entry for that group can be found in
578 * /etc/group. If the current user name appears in the members list
579 * for that group, access will be granted immediately; if not, the
580 * user will be challenged for that group's password. If the
581 * password response is incorrect, if the specified group does not
582 * have a password, or if that group has been locked by gpasswd -R,
583 * access will be denied. This is true even if the group specified
584 * has the user's login GID (as shown in /etc/passwd). If no group
585 * is explicitly specified on the command line, the effect is
586 * exactly the same as if a group name matching the user's login GID
587 * had been explicitly specified. Root, however, is never
588 * challenged for passwords, and is always allowed access.
590 * The previous behavior was to allow access to the login group if
591 * no explicit group was specified, irrespective of the group
592 * control file(s). This behavior is usually not desirable. A user
593 * wishing to return to the login group has only to exit back to the
594 * login shell. Generating yet more shell levels in order to
595 * provide a convenient "return" to the default group has the
596 * undesirable side effects of confusing the user, scrambling the
597 * history file, and consuming system resources. The default now is
598 * to lock out such behavior. A sys admin can allow it by explicitly
599 * including the user's name in the member list of the user's login
602 grp = getgrnam (group); /* local, no need for xgetgrnam */
604 fprintf (stderr, _("%s: group '%s' does not exist\n"), Prog, group);
609 * For splitted groups (due to limitations of NIS), check all
610 * groups of the same GID like the requested group for
611 * membership of the current user.
613 grp = find_matching_group (name, grp->gr_gid);
616 * No matching group found. As we already know that
617 * the group exists, this happens only in the case
618 * of a requested group where the user is not member.
620 * Re-read the group entry for further processing.
622 grp = xgetgrnam (group);
623 assert (NULL != grp);
626 sgrp = getsgnam (group);
628 grp->gr_passwd = sgrp->sg_passwd;
629 grp->gr_mem = sgrp->sg_mem;
634 * Check if the user is allowed to access this group.
636 check_perms (grp, pwd, group);
639 * all successful validations pass through this point. The group id
640 * will be set, and the group added to the concurrent groupset.
643 if (getdef_bool ("SYSLOG_SG_ENAB")) {
644 syslog_sg (name, group);
646 #endif /* USE_SYSLOG */
650 #ifdef HAVE_SETGROUPS
652 * I am going to try to add her new group id to her concurrent group
653 * set. If the group id is already present i'll just skip this part.
654 * If the group doesn't fit, i'll complain loudly and skip this
657 for (i = 0; i < ngroups; i++) {
658 if (gid == grouplist[i]) {
663 if (ngroups >= sysconf (_SC_NGROUPS_MAX)) {
664 (void) fputs (_("too many groups\n"), stderr);
666 grouplist[ngroups++] = gid;
667 if (setgroups (ngroups, grouplist) != 0) {
668 perror ("setgroups");
675 * Set the effective GID to the new group id and the effective UID
676 * to the real UID. For root, this also sets the real GID to the
679 if (setgid (gid) != 0) {
682 snprintf (audit_buf, sizeof(audit_buf),
683 "changing new-gid=%lu", (unsigned long) gid);
684 audit_logger (AUDIT_CHGRP_ID, Prog,
686 (unsigned int) getuid (), 0);
691 if (setuid (getuid ()) != 0) {
694 snprintf (audit_buf, sizeof(audit_buf),
695 "changing new-gid=%lu", (unsigned long) gid);
696 audit_logger (AUDIT_CHGRP_ID, Prog,
698 (unsigned int) getuid (), 0);
704 * See if the "-c" flag was used. If it was, i just create a shell
705 * command for her using the argument that followed the "-c" flag.
709 execl ("/bin/sh", "sh", "-c", command, (char *) 0);
711 snprintf (audit_buf, sizeof(audit_buf),
712 "changing new-gid=%lu", (unsigned long) gid);
713 audit_logger (AUDIT_CHGRP_ID, Prog,
715 (unsigned int) getuid (), 0);
718 exit (errno == ENOENT ? E_CMD_NOTFOUND : E_CMD_NOEXEC);
722 * I have to get the pathname of her login shell. As a favor, i'll
723 * try her environment for a $SHELL value first, and then try the
724 * password file entry. Obviously this shouldn't be in the
725 * restricted command directory since it could be used to leave the
726 * restricted environment.
728 * Note that the following assumes this user's entry in /etc/passwd
729 * does not have a chroot * prefix. If it does, the * will be copied
730 * verbatim into the exec path. This is probably not an issue
731 * because if this user is operating in a chroot jail, her entry in
732 * the version of /etc/passwd that is accessible here should
733 * probably never have a chroot shell entry (but entries for other
734 * users might). If I have missed something, and this causes you a
735 * problem, try using $SHELL as a workaround; also please notify me
736 * at jparmele@wildbear.com -- JWP
738 cp = getenv ("SHELL");
739 if (!initflag && (NULL != cp)) {
741 } else if ((NULL != pwd->pw_shell) && ('\0' != pwd->pw_shell[0])) {
742 prog = pwd->pw_shell;
748 * Now I try to find the basename of the login shell. This will
749 * become argv[0] of the spawned command.
751 cp = Basename ((char *) prog);
761 * Switch back to her home directory if i am doing login
765 if (chdir (pwd->pw_dir) != 0) {
769 while (NULL != *envp) {
770 if (strncmp (*envp, "PATH=", 5) == 0 ||
771 strncmp (*envp, "HOME=", 5) == 0 ||
772 strncmp (*envp, "SHELL=", 6) == 0 ||
773 strncmp (*envp, "TERM=", 5) == 0)
774 addenv (*envp, NULL);
779 while (NULL != *envp) {
780 addenv (*envp, NULL);
786 snprintf (audit_buf, sizeof(audit_buf), "changing new-gid=%lu",
787 (unsigned long) gid);
788 audit_logger (AUDIT_CHGRP_ID, Prog,
790 (unsigned int) getuid (), 1);
793 * Exec the login shell and go away. We are trying to get back to
794 * the previous environment which should be the user's login shell.
796 err = shell (prog, initflag ? (char *) 0 : cp, newenvp);
797 exit (err == ENOENT ? E_CMD_NOTFOUND : E_CMD_NOEXEC);
802 * The previous code, when run as newgrp, re-exec'ed the shell in
803 * the current process with the original gid on error conditions.
804 * See the comment above. This historical behavior now has the
805 * effect of creating unlogged extraneous shell layers when the
806 * command line has an error or there is an authentication failure.
807 * We now just want to exit with error status back to the parent
808 * process. The closelog is probably unnecessary, but it does no
814 snprintf (audit_buf, sizeof(audit_buf),
815 "changing new-group=%s", group);
816 audit_logger (AUDIT_CHGRP_ID, Prog,
818 (unsigned int) getuid (), 0);
820 audit_logger (AUDIT_CHGRP_ID, Prog,
822 (unsigned int) getuid (), 0);