603 lines
14 KiB
C
603 lines
14 KiB
C
/*
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* SPDX-FileCopyrightText: 1989 - 1994, Julianne Frances Haugh
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* SPDX-FileCopyrightText: 1996 - 2000, Marek Michałkiewicz
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* SPDX-FileCopyrightText: 2001 - 2006, Tomasz Kłoczko
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* SPDX-FileCopyrightText: 2007 - 2011, Nicolas François
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*
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* SPDX-License-Identifier: BSD-3-Clause
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*/
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#include <config.h>
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#ident "$Id$"
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#include <fcntl.h>
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#include <getopt.h>
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#include <pwd.h>
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#include <stdio.h>
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#include <sys/types.h>
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#include "alloc.h"
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#include "defines.h"
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#include "getdef.h"
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#include "nscd.h"
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#include "sssd.h"
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#include "prototypes.h"
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#include "pwauth.h"
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#include "pwio.h"
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#ifdef USE_PAM
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#include "pam_defs.h"
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#endif
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/*@-exitarg@*/
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#include "exitcodes.h"
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#include "shadowlog.h"
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#ifndef SHELLS_FILE
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#define SHELLS_FILE "/etc/shells"
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#endif
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#ifdef HAVE_VENDORDIR
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#include <libeconf.h>
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#define SHELLS "shells"
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#define ETCDIR "/etc"
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#endif
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/*
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* Global variables
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*/
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const char *Prog; /* Program name */
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static bool amroot; /* Real UID is root */
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static char loginsh[BUFSIZ]; /* Name of new login shell */
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/* command line options */
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static bool sflg = false; /* -s - set shell from command line */
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static bool pw_locked = false;
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/* external identifiers */
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/* local function prototypes */
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NORETURN static void fail_exit (int code);
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NORETURN static void usage (int status);
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static void new_fields (void);
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static bool shell_is_listed (const char *);
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static bool is_restricted_shell (const char *);
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static void process_flags (int argc, char **argv);
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static void check_perms (const struct passwd *pw);
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static void update_shell (const char *user, char *loginsh);
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/*
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* fail_exit - do some cleanup and exit with the given error code
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*/
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NORETURN
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static void
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fail_exit (int code)
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{
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if (pw_locked) {
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if (pw_unlock () == 0) {
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fprintf (stderr, _("%s: failed to unlock %s\n"), Prog, pw_dbname ());
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SYSLOG ((LOG_ERR, "failed to unlock %s", pw_dbname ()));
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/* continue */
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}
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}
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closelog ();
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exit (code);
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}
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/*
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* usage - print command line syntax and exit
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*/
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NORETURN
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static void
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usage (int status)
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{
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FILE *usageout = (E_SUCCESS != status) ? stderr : stdout;
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(void) fprintf (usageout,
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_("Usage: %s [options] [LOGIN]\n"
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"\n"
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"Options:\n"),
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Prog);
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(void) fputs (_(" -h, --help display this help message and exit\n"), usageout);
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(void) fputs (_(" -R, --root CHROOT_DIR directory to chroot into\n"), usageout);
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(void) fputs (_(" -s, --shell SHELL new login shell for the user account\n"), usageout);
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(void) fputs ("\n", usageout);
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exit (status);
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}
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/*
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* new_fields - change the user's login shell information interactively
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*
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* prompt the user for the login shell and change it according to the
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* response, or leave it alone if nothing was entered.
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*/
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static void new_fields (void)
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{
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puts (_("Enter the new value, or press ENTER for the default"));
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change_field (loginsh, sizeof loginsh, _("Login Shell"));
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}
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/*
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* is_restricted_shell - return true if the shell is restricted
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*
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*/
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static bool is_restricted_shell (const char *sh)
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{
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/*
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* Shells not listed in /etc/shells are considered to be restricted.
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* Changed this to avoid confusion with "rc" (the plan9 shell - not
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* restricted despite the name starting with 'r'). --marekm
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*/
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return !shell_is_listed (sh);
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}
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/*
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* shell_is_listed - see if the user's login shell is listed in /etc/shells
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*
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* The /etc/shells file is read for valid names of login shells. If the
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* /etc/shells file does not exist the user cannot set any shell unless
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* they are root.
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*
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* If getusershell() is available (Linux, *BSD, possibly others), use it
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* instead of re-implementing it.
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*/
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#ifdef HAVE_VENDORDIR
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static bool shell_is_listed (const char *sh)
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{
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bool found = false;
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size_t size = 0;
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econf_err error;
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char **keys;
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econf_file *key_file;
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error = econf_readDirs(&key_file,
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VENDORDIR,
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ETCDIR,
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SHELLS,
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NULL,
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"", /* key only */
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"#" /* comment */);
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if (error) {
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fprintf (stderr,
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_("Cannot parse shell files: %s"),
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econf_errString(error));
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fail_exit (1);
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}
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error = econf_getKeys(key_file, NULL, &size, &keys);
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if (error) {
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fprintf (stderr,
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_("Cannot evaluate entries in shell files: %s"),
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econf_errString(error));
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econf_free (key_file);
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fail_exit (1);
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}
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for (size_t i = 0; i < size; i++) {
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if (strcmp (keys[i], sh) == 0) {
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found = true;
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break;
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}
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}
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econf_free (keys);
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econf_free (key_file);
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return found;
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}
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#else /* without HAVE_VENDORDIR */
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static bool shell_is_listed (const char *sh)
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{
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bool found = false;
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#ifdef HAVE_GETUSERSHELL
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char *cp;
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setusershell ();
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while ((cp = getusershell ())) {
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if (strcmp (cp, sh) == 0) {
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found = true;
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break;
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}
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}
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endusershell ();
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#else
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char buf[BUFSIZ];
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FILE *fp;
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fp = fopen (SHELLS_FILE, "r");
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if (NULL == fp) {
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return false;
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}
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while (fgets (buf, sizeof (buf), fp) == buf) {
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cp = strrchr (buf, '\n');
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if (NULL != cp) {
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*cp = '\0';
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}
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if (buf[0] == '#') {
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continue;
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}
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if (strcmp (buf, sh) == 0) {
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found = true;
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break;
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}
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}
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fclose (fp);
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#endif
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return found;
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}
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#endif /* with HAVE_VENDORDIR */
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/*
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* process_flags - parse the command line options
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*
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* It will not return if an error is encountered.
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*/
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static void process_flags (int argc, char **argv)
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{
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int c;
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static struct option long_options[] = {
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{"help", no_argument, NULL, 'h'},
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{"root", required_argument, NULL, 'R'},
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{"shell", required_argument, NULL, 's'},
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{NULL, 0, NULL, '\0'}
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};
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while ((c = getopt_long (argc, argv, "hR:s:",
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long_options, NULL)) != -1) {
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switch (c) {
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case 'h':
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usage (E_SUCCESS);
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/*@notreached@*/break;
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case 'R': /* no-op, handled in process_root_flag () */
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break;
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case 's':
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sflg = true;
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STRFCPY (loginsh, optarg);
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break;
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default:
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usage (E_USAGE);
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}
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}
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/*
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* There should be only one remaining argument at most and it should
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* be the user's name.
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*/
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if (argc > (optind + 1)) {
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usage (E_USAGE);
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}
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}
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/*
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* check_perms - check if the caller is allowed to add a group
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*
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* Non-root users are only allowed to change their shell, if their current
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* shell is not a restricted shell.
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*
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* Non-root users must be authenticated.
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*
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* It will not return if the user is not allowed.
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*/
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static void check_perms (const struct passwd *pw)
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{
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#ifdef USE_PAM
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pam_handle_t *pamh = NULL;
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int retval;
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struct passwd *pampw;
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#endif
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/*
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* Non-privileged users are only allowed to change the shell if the
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* UID of the user matches the current real UID.
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*/
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if (!amroot && pw->pw_uid != getuid ()) {
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SYSLOG ((LOG_WARN, "can't change shell for '%s'", pw->pw_name));
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fprintf (stderr,
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_("You may not change the shell for '%s'.\n"),
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pw->pw_name);
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fail_exit (1);
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}
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/*
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* Non-privileged users are only allowed to change the shell if it
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* is not a restricted one.
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*/
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if (!amroot && is_restricted_shell (pw->pw_shell)) {
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SYSLOG ((LOG_WARN, "can't change shell for '%s'", pw->pw_name));
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fprintf (stderr,
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_("You may not change the shell for '%s'.\n"),
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pw->pw_name);
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fail_exit (1);
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}
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#ifdef WITH_SELINUX
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/*
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* If the UID of the user does not match the current real UID,
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* check if the change is allowed by SELinux policy.
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*/
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if ((pw->pw_uid != getuid ())
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&& (check_selinux_permit("chsh") != 0)) {
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SYSLOG ((LOG_WARN, "can't change shell for '%s'", pw->pw_name));
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fprintf (stderr,
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_("You may not change the shell for '%s'.\n"),
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pw->pw_name);
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fail_exit (1);
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}
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#endif
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#ifndef USE_PAM
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/*
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* Non-privileged users are optionally authenticated (must enter
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* the password of the user whose information is being changed)
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* before any changes can be made. Idea from util-linux
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* chfn/chsh. --marekm
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*/
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if (!amroot && getdef_bool ("CHSH_AUTH")) {
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passwd_check (pw->pw_name, pw->pw_passwd, "chsh");
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}
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#else /* !USE_PAM */
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pampw = getpwuid (getuid ()); /* local, no need for xgetpwuid */
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if (NULL == pampw) {
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fprintf (stderr,
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_("%s: Cannot determine your user name.\n"),
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Prog);
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exit (E_NOPERM);
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}
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retval = pam_start ("chsh", pampw->pw_name, &conv, &pamh);
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if (PAM_SUCCESS == retval) {
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retval = pam_authenticate (pamh, 0);
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}
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if (PAM_SUCCESS == retval) {
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retval = pam_acct_mgmt (pamh, 0);
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}
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if (PAM_SUCCESS != retval) {
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fprintf (stderr, _("%s: PAM: %s\n"),
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Prog, pam_strerror (pamh, retval));
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SYSLOG((LOG_ERR, "%s", pam_strerror (pamh, retval)));
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if (NULL != pamh) {
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(void) pam_end (pamh, retval);
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}
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exit (E_NOPERM);
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}
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(void) pam_end (pamh, retval);
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#endif /* USE_PAM */
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}
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/*
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* update_shell - update the user's shell in the passwd database
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*
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* Commit the user's entry after changing her shell field.
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*
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* It will not return in case of error.
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*/
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static void update_shell (const char *user, char *newshell)
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{
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const struct passwd *pw; /* Password entry from /etc/passwd */
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struct passwd pwent; /* New password entry */
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/*
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* Before going any further, raise the ulimit to prevent
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* colliding into a lowered ulimit, and set the real UID
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* to root to protect against unexpected signals. Any
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* keyboard signals are set to be ignored.
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*/
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if (setuid (0) != 0) {
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SYSLOG ((LOG_ERR, "can't setuid(0)"));
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fputs (_("Cannot change ID to root.\n"), stderr);
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fail_exit (1);
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}
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pwd_init ();
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/*
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* The passwd entry is now ready to be committed back to
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* the password file. Get a lock on the file and open it.
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*/
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if (pw_lock () == 0) {
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fprintf (stderr, _("%s: cannot lock %s; try again later.\n"),
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Prog, pw_dbname ());
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fail_exit (1);
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}
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pw_locked = true;
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if (pw_open (O_CREAT | O_RDWR) == 0) {
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fprintf (stderr, _("%s: cannot open %s\n"), Prog, pw_dbname ());
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SYSLOG ((LOG_WARN, "cannot open %s", pw_dbname ()));
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fail_exit (1);
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}
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/*
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* Get the entry to update using pw_locate() - we want the real
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* one from /etc/passwd, not the one from getpwnam() which could
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* contain the shadow password if (despite the warnings) someone
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* enables AUTOSHADOW (or SHADOW_COMPAT in libc). --marekm
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*/
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pw = pw_locate (user);
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if (NULL == pw) {
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fprintf (stderr,
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_("%s: user '%s' does not exist in %s\n"),
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Prog, user, pw_dbname ());
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fail_exit (1);
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}
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/*
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* Make a copy of the entry, then change the shell field. The other
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* fields remain unchanged.
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*/
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pwent = *pw;
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pwent.pw_shell = newshell;
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/*
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* Update the passwd file entry. If there is a DBM file, update
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* that entry as well.
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*/
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if (pw_update (&pwent) == 0) {
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fprintf (stderr,
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_("%s: failed to prepare the new %s entry '%s'\n"),
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Prog, pw_dbname (), pwent.pw_name);
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fail_exit (1);
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}
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/*
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* Changes have all been made, so commit them and unlock the file.
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*/
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if (pw_close () == 0) {
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fprintf (stderr, _("%s: failure while writing changes to %s\n"), Prog, pw_dbname ());
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SYSLOG ((LOG_ERR, "failure while writing changes to %s", pw_dbname ()));
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fail_exit (1);
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}
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if (pw_unlock () == 0) {
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fprintf (stderr, _("%s: failed to unlock %s\n"), Prog, pw_dbname ());
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SYSLOG ((LOG_ERR, "failed to unlock %s", pw_dbname ()));
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/* continue */
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}
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pw_locked= false;
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}
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/*
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* chsh - this command controls changes to the user's shell
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*
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* The only supported option is -s which permits the the login shell to
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* be set from the command line.
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*/
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int main (int argc, char **argv)
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{
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char *user; /* User name */
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const struct passwd *pw; /* Password entry from /etc/passwd */
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sanitize_env ();
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/*
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* Get the program name. The program name is used as a prefix to
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* most error messages.
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*/
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Prog = Basename (argv[0]);
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log_set_progname(Prog);
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log_set_logfd(stderr);
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(void) setlocale (LC_ALL, "");
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(void) bindtextdomain (PACKAGE, LOCALEDIR);
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(void) textdomain (PACKAGE);
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process_root_flag ("-R", argc, argv);
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/*
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* This command behaves different for root and non-root users.
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*/
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amroot = (getuid () == 0);
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OPENLOG ("chsh");
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/* parse the command line options */
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process_flags (argc, argv);
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/*
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* Get the name of the user to check. It is either the command line
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* name, or the name getlogin() returns.
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*/
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if (optind < argc) {
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user = argv[optind];
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pw = xgetpwnam (user);
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if (NULL == pw) {
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fprintf (stderr,
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_("%s: user '%s' does not exist\n"), Prog, user);
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fail_exit (1);
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}
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} else {
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pw = get_my_pwent ();
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if (NULL == pw) {
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fprintf (stderr,
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_("%s: Cannot determine your user name.\n"),
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Prog);
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SYSLOG ((LOG_WARN, "Cannot determine the user name of the caller (UID %lu)",
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(unsigned long) getuid ()));
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fail_exit (1);
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}
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user = xstrdup (pw->pw_name);
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}
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#ifdef USE_NIS
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/*
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* Now we make sure this is a LOCAL password entry for this user ...
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*/
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if (__ispwNIS ()) {
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char *nis_domain;
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char *nis_master;
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fprintf (stderr,
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_("%s: cannot change user '%s' on NIS client.\n"),
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Prog, user);
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if (!yp_get_default_domain (&nis_domain) &&
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!yp_master (nis_domain, "passwd.byname", &nis_master)) {
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fprintf (stderr,
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_("%s: '%s' is the NIS master for this client.\n"),
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Prog, nis_master);
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}
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fail_exit (1);
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}
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#endif
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check_perms (pw);
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|
|
|
/*
|
|
* Now get the login shell. Either get it from the password
|
|
* file, or use the value from the command line.
|
|
*/
|
|
if (!sflg) {
|
|
STRFCPY (loginsh, pw->pw_shell);
|
|
}
|
|
|
|
/*
|
|
* If the login shell was not set on the command line, let the user
|
|
* interactively change it.
|
|
*/
|
|
if (!sflg) {
|
|
printf (_("Changing the login shell for %s\n"), user);
|
|
new_fields ();
|
|
}
|
|
|
|
/*
|
|
* Check all of the fields for valid information. The shell
|
|
* field may not contain any illegal characters. Non-privileged
|
|
* users are restricted to using the shells in /etc/shells.
|
|
* The shell must be executable by the user.
|
|
*/
|
|
if (valid_field (loginsh, ":,=\n") != 0) {
|
|
fprintf (stderr, _("%s: Invalid entry: %s\n"), Prog, loginsh);
|
|
fail_exit (1);
|
|
}
|
|
if ( !amroot
|
|
&& ( loginsh[0] != '/'
|
|
|| is_restricted_shell (loginsh)
|
|
|| (access (loginsh, X_OK) != 0))) {
|
|
fprintf (stderr, _("%s: %s is an invalid shell\n"), Prog, loginsh);
|
|
fail_exit (1);
|
|
}
|
|
|
|
/* Even for root, warn if an invalid shell is specified. */
|
|
if (access (loginsh, F_OK) != 0) {
|
|
fprintf (stderr, _("%s: Warning: %s does not exist\n"), Prog, loginsh);
|
|
} else if (access (loginsh, X_OK) != 0) {
|
|
fprintf (stderr, _("%s: Warning: %s is not executable\n"), Prog, loginsh);
|
|
}
|
|
|
|
update_shell (user, loginsh);
|
|
|
|
SYSLOG ((LOG_INFO, "changed user '%s' shell to '%s'", user, loginsh));
|
|
|
|
nscd_flush_cache ("passwd");
|
|
sssd_flush_cache (SSSD_DB_PASSWD);
|
|
|
|
closelog ();
|
|
exit (E_SUCCESS);
|
|
}
|
|
|