shadow/src/chsh.c

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/*
* Copyright (c) 1989 - 1994, Julianne Frances Haugh
* Copyright (c) 1996 - 2000, Marek Michałkiewicz
* Copyright (c) 2001 - 2006, Tomasz Kłoczko
* Copyright (c) 2007 - 2008, Nicolas François
* 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. The name of the copyright holders or contributors may not be used to
* endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 THE COPYRIGHT
* HOLDERS 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 <config.h>
#ident "$Id$"
#include <fcntl.h>
#include <getopt.h>
#include <pwd.h>
#include <signal.h>
#include <stdio.h>
#include <sys/types.h>
#ifdef WITH_SELINUX
#include <selinux/selinux.h>
#include <selinux/av_permissions.h>
#endif
#include "defines.h"
#include "exitcodes.h"
#include "getdef.h"
#include "nscd.h"
#include "prototypes.h"
#include "pwauth.h"
#include "pwio.h"
#ifdef USE_PAM
#include "pam_defs.h"
#endif
#ifndef SHELLS_FILE
#define SHELLS_FILE "/etc/shells"
#endif
/*
* Global variables
*/
static char *Prog; /* Program name */
static bool amroot; /* Real UID is root */
static char loginsh[BUFSIZ]; /* Name of new login shell */
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/* command line options */
static bool sflg = false; /* -s - set shell from command line */
#ifdef USE_PAM
static pam_handle_t *pamh = NULL;
#endif
/* external identifiers */
/* local function prototypes */
static void usage (void);
static void new_fields (void);
static bool shell_is_listed (const char *);
static bool is_restricted_shell (const char *);
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static void process_flags (int argc, char **argv);
static void check_perms (const struct passwd *pw);
static void update_shell (const char *user, char *loginsh);
/*
* usage - print command line syntax and exit
*/
static void usage (void)
{
fputs (_("Usage: chsh [options] [LOGIN]\n"
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"\n"
"Options:\n"
" -h, --help display this help message and exit\n"
" -s, --shell SHELL new login shell for the user account\n"
"\n"), stderr);
exit (E_USAGE);
}
/*
* new_fields - change the user's login shell information interactively
*
* prompt the user for the login shell and change it according to the
* response, or leave it alone if nothing was entered.
*/
static void new_fields (void)
{
puts (_("Enter the new value, or press ENTER for the default"));
change_field (loginsh, sizeof loginsh, _("Login Shell"));
}
/*
* is_restricted_shell - return true if the shell is restricted
*
*/
static bool is_restricted_shell (const char *sh)
{
/*
* Shells not listed in /etc/shells are considered to be restricted.
* Changed this to avoid confusion with "rc" (the plan9 shell - not
* restricted despite the name starting with 'r'). --marekm
*/
return !shell_is_listed (sh);
}
/*
* shell_is_listed - see if the user's login shell is listed in /etc/shells
*
* The /etc/shells file is read for valid names of login shells. If the
* /etc/shells file does not exist the user cannot set any shell unless
* they are root.
*
* If getusershell() is available (Linux, *BSD, possibly others), use it
* instead of re-implementing it.
*/
static bool shell_is_listed (const char *sh)
{
char *cp;
bool found = false;
#ifndef HAVE_GETUSERSHELL
char buf[BUFSIZ];
FILE *fp;
#endif
#ifdef HAVE_GETUSERSHELL
setusershell ();
while ((cp = getusershell ())) {
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if (*cp == '#') {
continue;
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}
if (strcmp (cp, sh) == 0) {
found = true;
break;
}
}
endusershell ();
#else
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fp = fopen (SHELLS_FILE, "r");
if (NULL == fp) {
return false;
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}
while (fgets (buf, sizeof (buf), fp)) {
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cp = strrchr (buf, '\n');
if (NULL != cp) {
*cp = '\0';
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}
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if (buf[0] == '#') {
continue;
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}
if (strcmp (buf, sh) == 0) {
found = true;
break;
}
}
fclose (fp);
#endif
return found;
}
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/*
* * process_flags - parse the command line options
*
* It will not return if an error is encountered.
*/
static void process_flags (int argc, char **argv)
{
int option_index = 0;
int c;
static struct option long_options[] = {
{"help", no_argument, NULL, 'h'},
{"shell", required_argument, NULL, 's'},
{NULL, 0, NULL, '\0'}
};
while ((c =
getopt_long (argc, argv, "hs:", long_options,
&option_index)) != -1) {
switch (c) {
case 'h':
usage ();
break;
case 's':
sflg = true;
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STRFCPY (loginsh, optarg);
break;
default:
usage ();
}
}
/*
* There should be only one remaining argument at most and it should
* be the user's name.
*/
if (argc > (optind + 1)) {
usage ();
}
}
/*
* check_perms - check if the caller is allowed to add a group
*
* Non-root users are only allowed to change their shell, if their current
* shell is not a restricted shell.
*
* Non-root users must be authenticated.
*
* It will not return if the user is not allowed.
*/
static void check_perms (const struct passwd *pw)
{
#ifdef USE_PAM
int retval;
struct passwd *pampw;
#endif
/*
* Non-privileged users are only allowed to change the shell if the
* UID of the user matches the current real UID.
*/
if (!amroot && pw->pw_uid != getuid ()) {
SYSLOG ((LOG_WARN, "can't change shell for `%s'", pw->pw_name));
closelog ();
fprintf (stderr,
_("You may not change the shell for %s.\n"),
pw->pw_name);
exit (1);
}
/*
* Non-privileged users are only allowed to change the shell if it
* is not a restricted one.
*/
if (!amroot && is_restricted_shell (pw->pw_shell)) {
SYSLOG ((LOG_WARN, "can't change shell for `%s'", pw->pw_name));
closelog ();
fprintf (stderr,
_("You may not change the shell for %s.\n"),
pw->pw_name);
exit (1);
}
#ifdef WITH_SELINUX
/*
* If the UID of the user does not match the current real UID,
* check if the change is allowed by SELinux policy.
*/
if ((pw->pw_uid != getuid ())
&& (is_selinux_enabled () > 0)
&& (selinux_check_passwd_access (PASSWD__CHSH) != 0)) {
SYSLOG ((LOG_WARN, "can't change shell for `%s'", pw->pw_name));
closelog ();
fprintf (stderr,
_("You may not change the shell for %s.\n"),
pw->pw_name);
exit (1);
}
#endif
#ifndef USE_PAM
/*
* Non-privileged users are optionally authenticated (must enter
* the password of the user whose information is being changed)
* before any changes can be made. Idea from util-linux
* chfn/chsh. --marekm
*/
if (!amroot && getdef_bool ("CHSH_AUTH")) {
passwd_check (pw->pw_name, pw->pw_passwd, "chsh");
}
#else /* !USE_PAM */
retval = PAM_SUCCESS;
pampw = getpwuid (getuid ()); /* local, no need for xgetpwuid */
if (pampw == NULL) {
retval = PAM_USER_UNKNOWN;
}
if (retval == PAM_SUCCESS) {
retval = pam_start ("chsh", pampw->pw_name, &conv, &pamh);
}
if (retval == PAM_SUCCESS) {
retval = pam_authenticate (pamh, 0);
if (retval != PAM_SUCCESS) {
pam_end (pamh, retval);
}
}
if (retval == PAM_SUCCESS) {
retval = pam_acct_mgmt (pamh, 0);
if (retval != PAM_SUCCESS) {
pam_end (pamh, retval);
}
}
if (retval != PAM_SUCCESS) {
fprintf (stderr, _("%s: PAM authentication failed\n"), Prog);
exit (E_NOPERM);
}
#endif /* USE_PAM */
}
/*
* update_shell - update the user's shell in the passwd database
*
* Commit the user's entry after changing her shell field.
*
* It will not return in case of error.
*/
static void update_shell (const char *user, char *newshell)
{
const struct passwd *pw; /* Password entry from /etc/passwd */
struct passwd pwent; /* New password entry */
/*
* Before going any further, raise the ulimit to prevent
* colliding into a lowered ulimit, and set the real UID
* to root to protect against unexpected signals. Any
* keyboard signals are set to be ignored.
*/
if (setuid (0) != 0) {
SYSLOG ((LOG_ERR, "can't setuid(0)"));
closelog ();
fputs (_("Cannot change ID to root.\n"), stderr);
exit (1);
}
pwd_init ();
/*
* The passwd entry is now ready to be committed back to
* the password file. Get a lock on the file and open it.
*/
if (pw_lock () == 0) {
SYSLOG ((LOG_WARN, "can't lock /etc/passwd"));
closelog ();
fputs (_("Cannot lock the password file; try again later.\n"),
stderr);
exit (1);
}
if (pw_open (O_RDWR) == 0) {
SYSLOG ((LOG_ERR, "can't open /etc/passwd"));
closelog ();
fputs (_("Cannot open the password file.\n"), stderr);
pw_unlock ();
exit (1);
}
/*
* Get the entry to update using pw_locate() - we want the real
* one from /etc/passwd, not the one from getpwnam() which could
* contain the shadow password if (despite the warnings) someone
* enables AUTOSHADOW (or SHADOW_COMPAT in libc). --marekm
*/
pw = pw_locate (user);
if (NULL == pw) {
pw_unlock ();
fprintf (stderr,
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_("%s: %s not found in /etc/passwd\n"), Prog, user);
exit (1);
}
/*
* Make a copy of the entry, then change the shell field. The other
* fields remain unchanged.
*/
pwent = *pw;
pwent.pw_shell = newshell;
/*
* Update the passwd file entry. If there is a DBM file, update
* that entry as well.
*/
if (pw_update (&pwent) == 0) {
SYSLOG ((LOG_ERR, "error updating passwd entry"));
closelog ();
fputs (_("Error updating the password entry.\n"), stderr);
pw_unlock ();
exit (1);
}
/*
* Changes have all been made, so commit them and unlock the file.
*/
if (pw_close () == 0) {
SYSLOG ((LOG_ERR, "can't rewrite /etc/passwd"));
closelog ();
fputs (_("Cannot commit password file changes.\n"), stderr);
pw_unlock ();
exit (1);
}
if (pw_unlock () == 0) {
SYSLOG ((LOG_ERR, "can't unlock /etc/passwd"));
closelog ();
fputs (_("Cannot unlock the password file.\n"), stderr);
exit (1);
}
}
/*
* chsh - this command controls changes to the user's shell
*
* The only supported option is -s which permits the the login shell to
* be set from the command line.
*/
int main (int argc, char **argv)
{
char *user; /* User name */
const struct passwd *pw; /* Password entry from /etc/passwd */
sanitize_env ();
(void) setlocale (LC_ALL, "");
(void) bindtextdomain (PACKAGE, LOCALEDIR);
(void) textdomain (PACKAGE);
/*
* This command behaves different for root and non-root users.
*/
amroot = (getuid () == 0);
/*
* Get the program name. The program name is used as a prefix to
* most error messages.
*/
Prog = Basename (argv[0]);
OPENLOG ("chsh");
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/* parse the command line options */
process_flags (argc, argv);
/*
* Get the name of the user to check. It is either the command line
* name, or the name getlogin() returns.
*/
if (optind < argc) {
user = argv[optind];
* lib/prototypes.h, configure.in, libmisc/Makefile.am, libmisc/xgetXXbyYY.c, libmisc/xgetpwnam.c, libmisc/xgetpwuid.c, libmisc/xgetgrnam.c, libmisc/xgetgrgid.c, libmisc/xgetspnam.c: Added functions xgetpwnam(), xgetpwuid(), xgetgrnam(), xgetgrgid(), and xgetspnam(). They allocate memory for the returned structure and are more robust to successive calls. They are implemented with the libc's getxxyyy_r() functions if available. * libmisc/limits.c, libmisc/entry.c, libmisc/chowntty.c, libmisc/addgrps.c, libmisc/myname.c, libmisc/rlogin.c, libmisc/pwdcheck.c, src/newgrp.c, src/login_nopam.c, src/userdel.c, src/lastlog.c, src/grpck.c, src/gpasswd.c, src/newusers.c, src/chpasswd.c, src/chfn.c, src/groupmems.c, src/usermod.c, src/expiry.c, src/groupdel.c, src/chgpasswd.c, src/su.c, src/useradd.c, src/groupmod.c, src/passwd.c, src/pwck.c, src/groupadd.c, src/chage.c, src/login.c, src/suauth.c, src/faillog.c, src/groups.c, src/chsh.c, src/id.c: Review all the usage of one of the getpwnam(), getpwuid(), getgrnam(), getgrgid(), and getspnam() functions. It was noticed on http://bugs.debian.org/341230 that chfn and chsh use a passwd structure after calling a pam function, which result in using information from the passwd structure requested by pam, not the original one. It is much easier to use the new xget... functions to avoid these issues. I've checked which call to the original get... functions could be left (reducing the scope of the structure if possible), and I've left comments to ease future reviews (e.g. /* local, no need for xgetpwnam */). Note: the getpwent/getgrent calls should probably be checked also. * src/groupdel.c, src/expiry.c: Fix typos in comments. * src/groupmod.c: Re-indent. * libmisc/Makefile.am, lib/groupmem.c, lib/groupio.c, lib/pwmem.c, lib/pwio.c, lib/shadowmem.c, lib/shadowio.c: Move the __<xx>_dup functions (used by the xget... functions) from the <xx>io.c files to the new <xx>mem.c files. This avoid linking some utils against the SELinux library.
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pw = xgetpwnam (user);
if (NULL == pw) {
fprintf (stderr,
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_("%s: unknown user %s\n"), Prog, user);
exit (1);
}
} else {
pw = get_my_pwent ();
if (NULL == pw) {
fprintf (stderr,
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_
("%s: Cannot determine your user name.\n"),
Prog);
exit (1);
}
user = xstrdup (pw->pw_name);
}
#ifdef USE_NIS
/*
* Now we make sure this is a LOCAL password entry for this user ...
*/
if (__ispwNIS ()) {
char *nis_domain;
char *nis_master;
fprintf (stderr,
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_("%s: cannot change user '%s' on NIS client.\n"),
Prog, user);
if (!yp_get_default_domain (&nis_domain) &&
!yp_master (nis_domain, "passwd.byname", &nis_master)) {
fprintf (stderr,
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_
("%s: '%s' is the NIS master for this client.\n"),
Prog, nis_master);
}
exit (1);
}
#endif
check_perms (pw);
/*
* Now get the login shell. Either get it from the password
* file, or use the value from the command line.
*/
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if (!sflg) {
STRFCPY (loginsh, pw->pw_shell);
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}
/*
* 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, ":,=") != 0) {
fprintf (stderr, _("%s: Invalid entry: %s\n"), Prog, loginsh);
closelog ();
exit (1);
}
if ( !amroot
&& ( is_restricted_shell (loginsh)
|| (access (loginsh, X_OK) != 0))) {
fprintf (stderr, _("%s is an invalid shell.\n"), loginsh);
closelog ();
exit (1);
}
update_shell (user, loginsh);
SYSLOG ((LOG_INFO, "changed user `%s' shell to `%s'", user, loginsh));
nscd_flush_cache ("passwd");
#ifdef USE_PAM
(void) pam_end (pamh, PAM_SUCCESS);
#endif /* USE_PAM */
closelog ();
exit (E_SUCCESS);
}
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