c7302b61ef
Files with no license use the default 3-clauses BSD license. The copyright were mostly not recorded; they were updated according to the Changelog. "Julianne Frances Haugh and contributors" changed to "copyright holders and contributors".
553 lines
14 KiB
C
553 lines
14 KiB
C
/*
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* Copyright (c) 1989 - 1994, Julianne Frances Haugh
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* Copyright (c) 1996 - 2000, Marek Michałkiewicz
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* Copyright (c) 2001 - 2006, Tomasz Kłoczko
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* Copyright (c) 2007 - 2008, Nicolas François
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. The name of the copyright holders or contributors may not be used to
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* endorse or promote products derived from this software without
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* specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
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* PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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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 <signal.h>
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#include <stdio.h>
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#include <sys/types.h>
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#ifdef WITH_SELINUX
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#include <selinux/selinux.h>
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#include <selinux/av_permissions.h>
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#endif
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#include "defines.h"
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#include "exitcodes.h"
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#include "getdef.h"
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#include "nscd.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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#ifndef SHELLS_FILE
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#define SHELLS_FILE "/etc/shells"
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#endif
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/*
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* Global variables
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*/
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static char *Prog; /* Program name */
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static int 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 int sflg = 0; /* -s - set shell from command line */
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#ifdef USE_PAM
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static pam_handle_t *pamh = NULL;
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#endif
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/* external identifiers */
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/* local function prototypes */
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static void usage (void);
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static void new_fields (void);
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static int check_shell (const char *);
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static int 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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* usage - print command line syntax and exit
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*/
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static void usage (void)
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{
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fputs (_("Usage: chsh [options] [LOGIN]\n"
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"\n"
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"Options:\n"
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" -h, --help display this help message and exit\n"
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" -s, --shell SHELL new login shell for the user account\n"
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"\n"), stderr);
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exit (E_USAGE);
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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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* restricted_shell - return true if the named shell begins with 'r' or 'R'
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*
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* If the first letter of the filename is 'r' or 'R', the shell is
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* considered to be restricted.
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*/
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static int 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 !check_shell (sh);
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}
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/*
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* check_shell - 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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static int check_shell (const char *sh)
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{
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char *cp;
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int found = 0;
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#ifndef HAVE_GETUSERSHELL
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char buf[BUFSIZ];
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FILE *fp;
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#endif
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#ifdef HAVE_GETUSERSHELL
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setusershell ();
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while ((cp = getusershell ())) {
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if (*cp == '#') {
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continue;
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}
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if (strcmp (cp, sh) == 0) {
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found = 1;
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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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fp = fopen (SHELLS_FILE, "r");
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if (NULL == fp) {
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return 0;
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}
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while (fgets (buf, sizeof (buf), fp)) {
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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 = 1;
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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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/*
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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 option_index = 0;
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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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{"shell", required_argument, NULL, 's'},
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{NULL, 0, NULL, '\0'}
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};
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while ((c =
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getopt_long (argc, argv, "hs:", long_options,
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&option_index)) != -1) {
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switch (c) {
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case 'h':
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usage ();
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break;
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case 's':
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sflg++;
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STRFCPY (loginsh, optarg);
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break;
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default:
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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 ();
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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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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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closelog ();
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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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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 && 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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closelog ();
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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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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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&& (is_selinux_enabled () > 0)
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&& (selinux_check_passwd_access (PASSWD__CHSH) != 0)) {
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SYSLOG ((LOG_WARN, "can't change shell for `%s'", pw->pw_name));
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closelog ();
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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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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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retval = PAM_SUCCESS;
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pampw = getpwuid (getuid ()); /* local, no need for xgetpwuid */
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if (pampw == NULL) {
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retval = PAM_USER_UNKNOWN;
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}
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if (retval == PAM_SUCCESS) {
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retval = pam_start ("chsh", pampw->pw_name, &conv, &pamh);
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}
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if (retval == PAM_SUCCESS) {
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retval = pam_authenticate (pamh, 0);
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if (retval != PAM_SUCCESS) {
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pam_end (pamh, retval);
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}
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}
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if (retval == PAM_SUCCESS) {
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retval = pam_acct_mgmt (pamh, 0);
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if (retval != PAM_SUCCESS) {
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pam_end (pamh, retval);
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}
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}
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if (retval != PAM_SUCCESS) {
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fprintf (stderr, _("%s: PAM authentication failed\n"), Prog);
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exit (E_NOPERM);
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}
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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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closelog ();
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fputs (_("Cannot change ID to root.\n"), stderr);
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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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SYSLOG ((LOG_WARN, "can't lock /etc/passwd"));
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closelog ();
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fputs (_("Cannot lock the password file; try again later.\n"),
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stderr);
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exit (1);
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}
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if (pw_open (O_RDWR) == 0) {
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SYSLOG ((LOG_ERR, "can't open /etc/passwd"));
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closelog ();
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fputs (_("Cannot open the password file.\n"), stderr);
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pw_unlock ();
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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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pw_unlock ();
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fprintf (stderr,
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_("%s: %s not found in /etc/passwd\n"), Prog, user);
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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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SYSLOG ((LOG_ERR, "error updating passwd entry"));
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closelog ();
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fputs (_("Error updating the password entry.\n"), stderr);
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pw_unlock ();
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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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SYSLOG ((LOG_ERR, "can't rewrite /etc/passwd"));
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closelog ();
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fputs (_("Cannot commit password file changes.\n"), stderr);
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pw_unlock ();
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exit (1);
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}
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if (pw_unlock () == 0) {
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SYSLOG ((LOG_ERR, "can't unlock /etc/passwd"));
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closelog ();
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fputs (_("Cannot unlock the password file.\n"), stderr);
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exit (1);
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}
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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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setlocale (LC_ALL, "");
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bindtextdomain (PACKAGE, LOCALEDIR);
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textdomain (PACKAGE);
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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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/*
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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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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 (!pw) {
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fprintf (stderr,
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_("%s: unknown user %s\n"), Prog, user);
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exit (1);
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}
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} else {
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pw = get_my_pwent ();
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if (!pw) {
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fprintf (stderr,
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_
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("%s: Cannot determine your user name.\n"),
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Prog);
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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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_
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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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exit (1);
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}
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#endif
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check_perms (pw);
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/*
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* Now get the login shell. Either get it from the password
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* file, or use the value from the command line.
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*/
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if (!sflg) {
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STRFCPY (loginsh, pw->pw_shell);
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}
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/*
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* If the login shell was not set on the command line, let the user
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* interactively change it.
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*/
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if (!sflg) {
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printf (_("Changing the login shell for %s\n"), user);
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new_fields ();
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}
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/*
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* Check all of the fields for valid information. The shell
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* field may not contain any illegal characters. Non-privileged
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* users are restricted to using the shells in /etc/shells.
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* The shell must be executable by the user.
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*/
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if (valid_field (loginsh, ":,=")) {
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fprintf (stderr, _("%s: Invalid entry: %s\n"), Prog, loginsh);
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closelog ();
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exit (1);
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}
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if (!amroot && (!check_shell (loginsh) || access (loginsh, X_OK) != 0)) {
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fprintf (stderr, _("%s is an invalid shell.\n"), loginsh);
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closelog ();
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exit (1);
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}
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update_shell (user, loginsh);
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SYSLOG ((LOG_INFO, "changed user `%s' shell to `%s'", user, loginsh));
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nscd_flush_cache ("passwd");
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#ifdef USE_PAM
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pam_end (pamh, PAM_SUCCESS);
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#endif /* USE_PAM */
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closelog ();
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exit (E_SUCCESS);
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}
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