/* * Copyright 1990 - 1994, Julianne Frances Haugh * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of Julianne F. Haugh nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY JULIE HAUGH AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL JULIE HAUGH OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ #include #include "rcsid.h" RCSID (PKG_VER "$Id: newgrp.c,v 1.32 2005/06/20 10:17:08 kloczek Exp $") #include #include #include #include #include "prototypes.h" #include "defines.h" #include "getdef.h" extern char **environ; #ifdef HAVE_SETGROUPS static int ngroups; static GETGROUPS_T *grouplist; #endif static char *Prog; static int is_newgrp; /* local function prototypes */ static void usage (void); /* * usage - print command usage message */ static void usage (void) { if (is_newgrp) fprintf (stderr, _("Usage: newgrp [-] [group]\n")); else fprintf (stderr, _("Usage: sg group [[-c] command]\n")); } /* * newgrp - change the invokers current real and effective group id */ int main (int argc, char **argv) { int initflag = 0; int needspasswd = 0; int i; int cflag = 0; gid_t gid; char *cp; const char *cpasswd, *name, *prog; char *group = NULL; char *command = NULL; char **envp = environ; struct passwd *pwd; struct group *grp; struct spwd *spwd; #ifdef SHADOWGRP struct sgrp *sgrp; #endif setlocale (LC_ALL, ""); bindtextdomain (PACKAGE, LOCALEDIR); 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]); is_newgrp = (strcmp (Prog, "newgrp") == 0); OPENLOG (is_newgrp ? "newgrp" : "sg"); gid = getgid (); argc--; argv++; initenv (); pwd = get_my_pwent (); if (!pwd) { fprintf (stderr, _("unknown UID: %u\n"), getuid ()); SYSLOG ((LOG_WARN, "unknown UID %u", getuid ())); closelog (); exit (1); } 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], "-") || !strcmp (argv[0], "-l"))) { argc--; argv++; initflag = 1; } 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 (1); } 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++; } } 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 */ if (!(grp = getgrgid (pwd->pw_gid))) { fprintf (stderr, _("unknown GID: %lu\n"), (unsigned long) pwd->pw_gid); SYSLOG ((LOG_CRIT, "unknown GID: %lu", (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"); exit (1); } #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 */ if (!(grp = getgrnam (group))) { fprintf (stderr, _("unknown group: %s\n"), group); goto failure; } #ifdef SHADOWGRP if ((sgrp = getsgnam (group))) { grp->gr_passwd = sgrp->sg_passwd; grp->gr_mem = sgrp->sg_mem; } #endif /* * see if she is a member of this 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 (!is_on_list (grp->gr_mem, name)) needspasswd = 1; /* * 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. */ if ((spwd = getspnam (name))) pwd->pw_passwd = spwd->sp_pwdp; if (pwd->pw_passwd[0] == '\0' && grp->gr_passwd[0]) needspasswd = 1; /* * 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. * * Note that she now has to provide the password to her own group, * unless she is listed as a member. -- JWP */ if (getuid () != 0 && needspasswd) { /* * get the password from her, and set the salt for * the decryption from the group file. */ if (!(cp = getpass (_("Password: ")))) 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 (grp->gr_passwd[0] == '\0') { /* * there is no password, print out "Sorry" and give up */ sleep (1); fputs (_("Sorry.\n"), stderr); goto failure; } if (strcmp (cpasswd, grp->gr_passwd) != 0) { SYSLOG ((LOG_INFO, "Invalid password for group `%s' from `%s'", group, name)); sleep (1); fputs (_("Sorry.\n"), stderr); goto failure; } } /* * 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 ((LOG_INFO, "user `%s' switched to group `%s'", name, group)); if (getdef_bool ("SYSLOG_SG_ENAB")) { char *loginname = getlogin (); char *tty = ttyname (0); if (loginname != NULL) loginname = xstrdup (loginname); if (tty != NULL) tty = xstrdup (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 if (getdef_bool ("CLOSE_SESSIONS")) { /* * 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, pid; signal (SIGINT, SIG_IGN); signal (SIGQUIT, SIG_IGN); signal (SIGHUP, SIG_IGN); signal (SIGTSTP, SIG_IGN); signal (SIGTTIN, SIG_IGN); signal (SIGTTOU, SIG_IGN); child = fork (); if (child < 0) { /* error in fork() */ fprintf (stderr, "%s: failure forking: %s", is_newgrp ? "newgrp" : "sg", strerror (errno)); exit (1); } else if (child) { /* parent - wait for child to finish, then log session close */ do { pid = waitpid (child, NULL, 0); } while (pid != child); SYSLOG ((LOG_INFO, "user `%s' (login `%s' on %s) returned to group `%s'", name, loginname, tty, getgrgid (gid)->gr_name)); closelog (); exit (0); } /* child - restore signals to their default state */ signal (SIGINT, SIG_DFL); signal (SIGQUIT, SIG_DFL); signal (SIGHUP, SIG_DFL); signal (SIGTSTP, SIG_DFL); signal (SIGTTIN, SIG_DFL); signal (SIGTTOU, SIG_DFL); } #endif /* USE_PAM */ } #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)) { fprintf (stderr, _("too many groups\n")); } else { grouplist[ngroups++] = gid; if (setgroups (ngroups, grouplist)) { perror ("setgroups"); } } } #endif /* * 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)) perror ("setgid"); if (setuid (getuid ())) { perror ("setuid"); exit (1); } /* * 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 ("/bin/sh", "sh", "-c", command, (char *) 0); if (errno == ENOENT) { perror ("/bin/sh"); exit (127); } else { perror ("/bin/sh"); exit (126); } } /* * 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 */ if (!initflag && (cp = getenv ("SHELL"))) prog = cp; else if (pwd->pw_shell && pwd->pw_shell[0]) prog = pwd->pw_shell; else prog = "/bin/sh"; /* * Now i try to find the basename of the login shell. This will * become argv[0] of the spawned command. */ cp = Basename ((char *) prog); endspent (); #ifdef SHADOWGRP endsgent (); #endif endpwent (); endgrent (); /* * Switch back to her home directory if i am doing login * initialization. */ if (initflag) { if (chdir (pwd->pw_dir)) perror ("chdir"); while (*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 (*envp) addenv (*envp++, NULL); } /* * 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. */ shell (prog, initflag ? (char *) 0 : cp); /* 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 (); exit (1); }