/* * SPDX-FileCopyrightText: 1990 - 1994, Julianne Frances Haugh * SPDX-FileCopyrightText: 1996 - 2000, Marek Michałkiewicz * SPDX-FileCopyrightText: 2001 - 2006, Tomasz Kłoczko * SPDX-FileCopyrightText: 2007 - 2008, Nicolas François * * SPDX-License-Identifier: BSD-3-Clause */ #include #ident "$Id$" #include #include #include #include #include #include "defines.h" #include "getdef.h" #include "prototypes.h" /*@-exitarg@*/ #include "exitcodes.h" #include "shadowlog.h" /* * Global variables */ const char *Prog; extern char **newenvp; extern char **environ; #ifdef HAVE_SETGROUPS static int ngroups; static /*@null@*/ /*@only@*/GETGROUPS_T *grouplist; #endif static bool is_newgrp; #ifdef WITH_AUDIT static char audit_buf[80]; #endif /* local function prototypes */ static void usage (void); static void check_perms (const struct group *grp, struct passwd *pwd, const char *groupname); static void syslog_sg (const char *name, const char *group); /* * usage - print command usage message */ static void usage (void) { if (is_newgrp) { (void) fputs (_("Usage: newgrp [-] [group]\n"), stderr); } else { (void) fputs (_("Usage: sg group [[-c] command]\n"), stderr); } } static bool ingroup(const char *name, struct group *gr) { char **look; bool notfound = true; look = gr->gr_mem; while (*look && notfound) notfound = strcmp (*look++, name); return !notfound; } /* * find_matching_group - search all groups of a gr's group id for * membership of a given username * but check gr itself first */ static /*@null@*/struct group *find_matching_group (const char *name, struct group *gr) { gid_t gid = gr->gr_gid; if (ingroup(name, gr)) return gr; setgrent (); while ((gr = getgrent ()) != NULL) { if (gr->gr_gid != gid) { continue; } /* * A group with matching GID was found. * Test for membership of 'name'. */ if (ingroup(name, gr)) break; } endgrent (); return gr; } /* * check_perms - check if the user is allowed to switch to this group * * If needed, the user will be authenticated. * * It will not return if the user could not be authenticated. */ static void check_perms (const struct group *grp, struct passwd *pwd, const char *groupname) { bool needspasswd = false; struct spwd *spwd; char *cp; const char *cpasswd; /* * see if she is a member of this group (i.e. in the list of * members of the group, or if the group is her primary group). * * If she isn't a member, she needs to provide the group password. * If there is no group password, she will be denied access * anyway. * */ if ( (grp->gr_gid != pwd->pw_gid) && !is_on_list (grp->gr_mem, pwd->pw_name)) { needspasswd = true; } /* * If she does not have either a shadowed password, or a regular * password, and the group has a password, she needs to give the * group password. */ spwd = xgetspnam (pwd->pw_name); if (NULL != spwd) { pwd->pw_passwd = xstrdup (spwd->sp_pwdp); spw_free (spwd); } if ((pwd->pw_passwd[0] == '\0') && (grp->gr_passwd[0] != '\0')) { needspasswd = true; } /* * Now I see about letting her into the group she requested. If she * is the root user, I'll let her in without having to prompt for * the password. Otherwise I ask for a password if she flunked one * of the tests above. */ if ((getuid () != 0) && needspasswd) { /* * get the password from her, and set the salt for * the decryption from the group file. */ cp = getpass (_("Password: ")); if (NULL == cp) { goto failure; } /* * encrypt the key she gave us using the salt from the * password in the group file. The result of this encryption * must match the previously encrypted value in the file. */ cpasswd = pw_encrypt (cp, grp->gr_passwd); strzero (cp); if (NULL == cpasswd) { fprintf (stderr, _("%s: failed to crypt password with previous salt: %s\n"), Prog, strerror (errno)); SYSLOG ((LOG_INFO, "Failed to crypt password with previous salt of group '%s'", groupname)); goto failure; } if (grp->gr_passwd[0] == '\0' || strcmp (cpasswd, grp->gr_passwd) != 0) { #ifdef WITH_AUDIT snprintf (audit_buf, sizeof(audit_buf), "authentication new-gid=%lu", (unsigned long) grp->gr_gid); audit_logger (AUDIT_GRP_AUTH, Prog, audit_buf, NULL, (unsigned int) getuid (), 0); #endif SYSLOG ((LOG_INFO, "Invalid password for group '%s' from '%s'", groupname, pwd->pw_name)); (void) sleep (1); (void) fputs (_("Invalid password.\n"), stderr); goto failure; } #ifdef WITH_AUDIT snprintf (audit_buf, sizeof(audit_buf), "authentication new-gid=%lu", (unsigned long) grp->gr_gid); audit_logger (AUDIT_GRP_AUTH, Prog, audit_buf, NULL, (unsigned int) getuid (), 1); #endif } return; failure: /* The closelog is probably unnecessary, but it does no * harm. -- JWP */ closelog (); #ifdef WITH_AUDIT if (groupname) { snprintf (audit_buf, sizeof(audit_buf), "changing new-group=%s", groupname); audit_logger (AUDIT_CHGRP_ID, Prog, audit_buf, NULL, (unsigned int) getuid (), 0); } else { audit_logger (AUDIT_CHGRP_ID, Prog, "changing", NULL, (unsigned int) getuid (), 0); } #endif exit (EXIT_FAILURE); } #ifdef USE_SYSLOG /* * syslog_sg - log the change of group to syslog * * The logout will also be logged when the user will quit the * sg/newgrp session. */ static void syslog_sg (const char *name, const char *group) { const char *loginname = getlogin (); const char *tty = ttyname (0); char *free_login = NULL, *free_tty = NULL; if (loginname != NULL) { free_login = xstrdup (loginname); loginname = free_login; } if (tty != NULL) { free_tty = xstrdup (tty); tty = free_tty; } if (loginname == NULL) { loginname = "???"; } if (tty == NULL) { tty = "???"; } else if (strncmp (tty, "/dev/", 5) == 0) { tty += 5; } SYSLOG ((LOG_INFO, "user '%s' (login '%s' on %s) switched to group '%s'", name, loginname, tty, group)); #ifdef USE_PAM /* * We want to fork and exec the new shell in the child, leaving the * parent waiting to log the session close. * * The parent must ignore signals generated from the console * (SIGINT, SIGQUIT, SIGHUP) which might make the parent terminate * before its child. When bash is exec'ed as the subshell, it * generates a new process group id for itself, and consequently * only SIGHUP, which is sent to all process groups in the session, * can reach the parent. However, since arbitrary programs can be * specified as login shells, there is no such guarantee in general. * For the same reason, we must also ignore stop signals generated * from the console (SIGTSTP, SIGTTIN, and SIGTTOU) in order to * avoid any possibility of the parent being stopped when it * receives SIGCHLD from the terminating subshell. -- JWP */ { pid_t child; /* Ignore these signals. The signal handlers will later be * restored to the default handlers. */ (void) signal (SIGINT, SIG_IGN); (void) signal (SIGQUIT, SIG_IGN); (void) signal (SIGHUP, SIG_IGN); (void) signal (SIGTSTP, SIG_IGN); (void) signal (SIGTTIN, SIG_IGN); (void) signal (SIGTTOU, SIG_IGN); child = fork (); if ((pid_t)-1 == child) { /* error in fork() */ fprintf (stderr, _("%s: failure forking: %s\n"), is_newgrp ? "newgrp" : "sg", strerror (errno)); #ifdef WITH_AUDIT if (group) { snprintf (audit_buf, sizeof(audit_buf), "changing new-group=%s", group); audit_logger (AUDIT_CHGRP_ID, Prog, audit_buf, NULL, (unsigned int) getuid (), 0); } else { audit_logger (AUDIT_CHGRP_ID, Prog, "changing", NULL, (unsigned int) getuid (), 0); } #endif exit (EXIT_FAILURE); } else if (child != 0) { /* parent - wait for child to finish, then log session close */ int cst = 0; gid_t gid = getgid(); struct group *grp = getgrgid (gid); pid_t pid; do { errno = 0; pid = waitpid (child, &cst, WUNTRACED); if ((pid == child) && (WIFSTOPPED (cst) != 0)) { /* The child (shell) was suspended. * Suspend sg/newgrp. */ kill (getpid (), SIGSTOP); /* wake child when resumed */ kill (child, SIGCONT); } } while ( ((pid == child) && (WIFSTOPPED (cst) != 0)) || ((pid != child) && (errno == EINTR))); /* local, no need for xgetgrgid */ if (NULL != grp) { SYSLOG ((LOG_INFO, "user '%s' (login '%s' on %s) returned to group '%s'", name, loginname, tty, grp->gr_name)); } else { SYSLOG ((LOG_INFO, "user '%s' (login '%s' on %s) returned to group '%lu'", name, loginname, tty, (unsigned long) gid)); /* Either the user's passwd entry has a * GID that does not match with any group, * or the group was deleted while the user * was in a newgrp session.*/ SYSLOG ((LOG_WARN, "unknown GID '%lu' used by user '%s'", (unsigned long) gid, name)); } closelog (); exit ((0 != WIFEXITED (cst)) ? WEXITSTATUS (cst) : WTERMSIG (cst) + 128); } /* child - restore signals to their default state */ (void) signal (SIGINT, SIG_DFL); (void) signal (SIGQUIT, SIG_DFL); (void) signal (SIGHUP, SIG_DFL); (void) signal (SIGTSTP, SIG_DFL); (void) signal (SIGTTIN, SIG_DFL); (void) signal (SIGTTOU, SIG_DFL); } #endif /* USE_PAM */ free(free_login); free(free_tty); } #endif /* USE_SYSLOG */ /* * newgrp - change the invokers current real and effective group id */ int main (int argc, char **argv) { bool initflag = false; int i; bool is_member = false; bool cflag = false; int err = 0; gid_t gid; char *cp; char *progbase; const char *name, *prog; char *group = NULL; char *command = NULL; char **envp = environ; struct passwd *pwd; /*@null@*/struct group *grp; #ifdef SHADOWGRP struct sgrp *sgrp; #endif #ifdef WITH_AUDIT audit_help_open (); #endif (void) setlocale (LC_ALL, ""); (void) bindtextdomain (PACKAGE, LOCALEDIR); (void) textdomain (PACKAGE); /* * Save my name for error messages and save my real gid incase of * errors. If there is an error i have to exec a new login shell for * the user since her old shell won't have fork'd to create the * process. Skip over the program name to the next command line * argument. * * This historical comment, and the code itself, suggest that the * behavior of the system/shell on which it was written differed * significantly from the one I am using. If this process was * started from a shell (including the login shell), it was fork'ed * and exec'ed as a child by that shell. In order to get the user * back to that shell, it is only necessary to exit from this * process which terminates the child of the fork. The parent shell, * which is blocked waiting for a signal, will then receive a * SIGCHLD and will continue; any changes made to the process * persona or the environment after the fork never occurred in the * parent process. * * Bottom line: we want to save the name and real gid for messages, * but we do not need to restore the previous process persona and we * don't need to re-exec anything. -- JWP */ Prog = Basename (argv[0]); log_set_progname(Prog); log_set_logfd(stderr); is_newgrp = (strcmp (Prog, "newgrp") == 0); OPENLOG (is_newgrp ? "newgrp" : "sg"); argc--; argv++; initenv (); pwd = get_my_pwent (); if (NULL == pwd) { fprintf (stderr, _("%s: Cannot determine your user name.\n"), Prog); #ifdef WITH_AUDIT audit_logger (AUDIT_CHGRP_ID, Prog, "changing", NULL, (unsigned int) getuid (), 0); #endif SYSLOG ((LOG_WARN, "Cannot determine the user name of the caller (UID %lu)", (unsigned long) getuid ())); closelog (); exit (EXIT_FAILURE); } name = pwd->pw_name; /* * Parse the command line. There are two accepted flags. The first * is "-", which for newgrp means to re-create the entire * environment as though a login had been performed, and "-c", which * for sg causes a command string to be executed. * * The next argument, if present, must be the new group name. Any * remaining remaining arguments will be used to execute a command * as the named group. If the group name isn't present, I just use * the login group ID of the current user. * * The valid syntax are * newgrp [-] [groupid] * newgrp [-l] [groupid] * sg [-] * sg [-] groupid [[-c command] */ if ( (argc > 0) && ( (strcmp (argv[0], "-") == 0) || (strcmp (argv[0], "-l") == 0))) { argc--; argv++; initflag = true; } if (!is_newgrp) { /* * Do the command line for everything that is * not "newgrp". */ if ((argc > 0) && (argv[0][0] != '-')) { group = argv[0]; argc--; argv++; } else { usage (); closelog (); exit (EXIT_FAILURE); } if (argc > 0) { /* * skip -c if specified so both forms work: * "sg group -c command" (as in the man page) or * "sg group command" (as in the usage message). */ if ((argc > 1) && (strcmp (argv[0], "-c") == 0)) { command = argv[1]; } else { command = argv[0]; } cflag = true; } } else { /* * Do the command line for "newgrp". It's just making sure * there aren't any flags and getting the new group name. */ if ((argc > 0) && (argv[0][0] == '-')) { usage (); goto failure; } else if (argv[0] != (char *) 0) { group = argv[0]; } else { /* * get the group file entry for her login group id. * the entry must exist, simply to be annoying. * * Perhaps in the past, but the default behavior now depends on the * group entry, so it had better exist. -- JWP */ grp = xgetgrgid (pwd->pw_gid); if (NULL == grp) { fprintf (stderr, _("%s: GID '%lu' does not exist\n"), Prog, (unsigned long) pwd->pw_gid); SYSLOG ((LOG_CRIT, "GID '%lu' does not exist", (unsigned long) pwd->pw_gid)); goto failure; } else { group = grp->gr_name; } } } #ifdef HAVE_SETGROUPS /* * get the current users groupset. The new group will be added to * the concurrent groupset if there is room, otherwise you get a * nasty message but at least your real and effective group id's are * set. */ /* don't use getgroups(0, 0) - it doesn't work on some systems */ i = 16; for (;;) { grouplist = (GETGROUPS_T *) xmalloc (i * sizeof (GETGROUPS_T)); ngroups = getgroups (i, grouplist); if (i > ngroups && !(ngroups == -1 && errno == EINVAL)) { break; } /* not enough room, so try allocating a larger buffer */ free (grouplist); i *= 2; } if (ngroups < 0) { perror ("getgroups"); #ifdef WITH_AUDIT if (group) { snprintf (audit_buf, sizeof(audit_buf), "changing new-group=%s", group); audit_logger (AUDIT_CHGRP_ID, Prog, audit_buf, NULL, (unsigned int) getuid (), 0); } else { audit_logger (AUDIT_CHGRP_ID, Prog, "changing", NULL, (unsigned int) getuid (), 0); } #endif exit (EXIT_FAILURE); } #endif /* HAVE_SETGROUPS */ /* * now we put her in the new group. The password file entry for her * current user id has been gotten. If there was no optional group * argument she will have her real and effective group id set to the * set to the value from her password file entry. * * If run as newgrp, or as sg with no command, this process exec's * an interactive subshell with the effective GID of the new group. * If run as sg with a command, that command is exec'ed in this * subshell. When this process terminates, either because the user * exits, or the command completes, the parent of this process * resumes with the current GID. * * If a group is explicitly specified on the command line, the * interactive shell or command is run with that effective GID. * Access will be denied if no entry for that group can be found in * /etc/group. If the current user name appears in the members list * for that group, access will be granted immediately; if not, the * user will be challenged for that group's password. If the * password response is incorrect, if the specified group does not * have a password, or if that group has been locked by gpasswd -R, * access will be denied. This is true even if the group specified * has the user's login GID (as shown in /etc/passwd). If no group * is explicitly specified on the command line, the effect is * exactly the same as if a group name matching the user's login GID * had been explicitly specified. Root, however, is never * challenged for passwords, and is always allowed access. * * The previous behavior was to allow access to the login group if * no explicit group was specified, irrespective of the group * control file(s). This behavior is usually not desirable. A user * wishing to return to the login group has only to exit back to the * login shell. Generating yet more shell levels in order to * provide a convenient "return" to the default group has the * undesirable side effects of confusing the user, scrambling the * history file, and consuming system resources. The default now is * to lock out such behavior. A sys admin can allow it by explicitly * including the user's name in the member list of the user's login * group. -- JWP */ grp = getgrnam (group); /* local, no need for xgetgrnam */ if (NULL == grp) { fprintf (stderr, _("%s: group '%s' does not exist\n"), Prog, group); goto failure; } #ifdef HAVE_SETGROUPS /* when using pam_group, she will not be listed in the groups * database. However getgroups() will return the group. So * if she is listed there already it is ok to grant membership. */ for (i = 0; i < ngroups; i++) { if (grp->gr_gid == grouplist[i]) { is_member = true; break; } } #endif /* HAVE_SETGROUPS */ /* * For splitted groups (due to limitations of NIS), check all * groups of the same GID like the requested group for * membership of the current user. */ if (!is_member) { grp = find_matching_group (name, grp); if (NULL == grp) { /* * No matching group found. As we already know that * the group exists, this happens only in the case * of a requested group where the user is not member. * * Re-read the group entry for further processing. */ grp = xgetgrnam (group); assert (NULL != grp); } } #ifdef SHADOWGRP sgrp = getsgnam (group); if (NULL != sgrp) { grp->gr_passwd = sgrp->sg_passwd; grp->gr_mem = sgrp->sg_mem; } #endif /* * Check if the user is allowed to access this group. */ if (!is_member) { check_perms (grp, pwd, group); } /* * all successful validations pass through this point. The group id * will be set, and the group added to the concurrent groupset. */ #ifdef USE_SYSLOG if (getdef_bool ("SYSLOG_SG_ENAB")) { syslog_sg (name, group); } #endif /* USE_SYSLOG */ gid = grp->gr_gid; #ifdef HAVE_SETGROUPS /* * I am going to try to add her new group id to her concurrent group * set. If the group id is already present i'll just skip this part. * If the group doesn't fit, i'll complain loudly and skip this * part. */ for (i = 0; i < ngroups; i++) { if (gid == grouplist[i]) { break; } } if (i == ngroups) { if (ngroups >= sysconf (_SC_NGROUPS_MAX)) { (void) fputs (_("too many groups\n"), stderr); } else { grouplist[ngroups++] = gid; if (setgroups (ngroups, grouplist) != 0) { perror ("setgroups"); } } } #endif /* * Close all files before changing the user/group IDs. * * The needed structure should have been copied before, or * permission to read the database will be required. */ endspent (); #ifdef SHADOWGRP endsgent (); #endif endpwent (); endgrent (); /* * Set the effective GID to the new group id and the effective UID * to the real UID. For root, this also sets the real GID to the * new group id. */ if (setgid (gid) != 0) { perror ("setgid"); #ifdef WITH_AUDIT snprintf (audit_buf, sizeof(audit_buf), "changing new-gid=%lu", (unsigned long) gid); audit_logger (AUDIT_CHGRP_ID, Prog, audit_buf, NULL, (unsigned int) getuid (), 0); #endif exit (EXIT_FAILURE); } if (setuid (getuid ()) != 0) { perror ("setuid"); #ifdef WITH_AUDIT snprintf (audit_buf, sizeof(audit_buf), "changing new-gid=%lu", (unsigned long) gid); audit_logger (AUDIT_CHGRP_ID, Prog, audit_buf, NULL, (unsigned int) getuid (), 0); #endif exit (EXIT_FAILURE); } /* * See if the "-c" flag was used. If it was, i just create a shell * command for her using the argument that followed the "-c" flag. */ if (cflag) { closelog (); execl (SHELL, "sh", "-c", command, (char *) 0); #ifdef WITH_AUDIT snprintf (audit_buf, sizeof(audit_buf), "changing new-gid=%lu", (unsigned long) gid); audit_logger (AUDIT_CHGRP_ID, Prog, audit_buf, NULL, (unsigned int) getuid (), 0); #endif perror (SHELL); exit ((errno == ENOENT) ? E_CMD_NOTFOUND : E_CMD_NOEXEC); } /* * I have to get the pathname of her login shell. As a favor, i'll * try her environment for a $SHELL value first, and then try the * password file entry. Obviously this shouldn't be in the * restricted command directory since it could be used to leave the * restricted environment. * * Note that the following assumes this user's entry in /etc/passwd * does not have a chroot * prefix. If it does, the * will be copied * verbatim into the exec path. This is probably not an issue * because if this user is operating in a chroot jail, her entry in * the version of /etc/passwd that is accessible here should * probably never have a chroot shell entry (but entries for other * users might). If I have missed something, and this causes you a * problem, try using $SHELL as a workaround; also please notify me * at jparmele@wildbear.com -- JWP */ cp = getenv ("SHELL"); if (!initflag && (NULL != cp)) { prog = cp; } else if ((NULL != pwd->pw_shell) && ('\0' != pwd->pw_shell[0])) { prog = pwd->pw_shell; } else { prog = SHELL; } /* * Now I try to find the basename of the login shell. This will * become argv[0] of the spawned command. */ progbase = (char *) Basename ((char *) prog); /* * Switch back to her home directory if i am doing login * initialization. */ if (initflag) { if (chdir (pwd->pw_dir) != 0) { perror ("chdir"); } while (NULL != *envp) { if (strncmp (*envp, "PATH=", 5) == 0 || strncmp (*envp, "HOME=", 5) == 0 || strncmp (*envp, "SHELL=", 6) == 0 || strncmp (*envp, "TERM=", 5) == 0) addenv (*envp, NULL); envp++; } } else { while (NULL != *envp) { addenv (*envp, NULL); envp++; } } #ifdef WITH_AUDIT snprintf (audit_buf, sizeof(audit_buf), "changing new-gid=%lu", (unsigned long) gid); audit_logger (AUDIT_CHGRP_ID, Prog, audit_buf, NULL, (unsigned int) getuid (), 1); #endif /* * Exec the login shell and go away. We are trying to get back to * the previous environment which should be the user's login shell. */ err = shell (prog, initflag ? (char *) 0 : progbase, newenvp); exit ((err == ENOENT) ? E_CMD_NOTFOUND : E_CMD_NOEXEC); /*@notreached@*/ failure: /* * The previous code, when run as newgrp, re-exec'ed the shell in * the current process with the original gid on error conditions. * See the comment above. This historical behavior now has the * effect of creating unlogged extraneous shell layers when the * command line has an error or there is an authentication failure. * We now just want to exit with error status back to the parent * process. The closelog is probably unnecessary, but it does no * harm. -- JWP */ closelog (); #ifdef WITH_AUDIT if (NULL != group) { snprintf (audit_buf, sizeof(audit_buf), "changing new-group=%s", group); audit_logger (AUDIT_CHGRP_ID, Prog, audit_buf, NULL, (unsigned int) getuid (), 0); } else { audit_logger (AUDIT_CHGRP_ID, Prog, "changing", NULL, (unsigned int) getuid (), 0); } #endif exit (EXIT_FAILURE); }