shadow/src/chsh.c

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/*
* Copyright 1989 - 1994, Julianne Frances Haugh
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of Julianne F. Haugh nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY JULIE HAUGH AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL JULIE HAUGH OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <config.h>
#ident "$Id: chsh.c,v 1.35 2005/10/04 21:02:22 kloczek Exp $"
#include <fcntl.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
#ifdef HAVE_SHADOW_H
#include <shadow.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 int amroot; /* Real UID is root */
static char loginsh[BUFSIZ]; /* Name of new login shell */
/* external identifiers */
/* local function prototypes */
static void usage (void);
static void new_fields (void);
static int restricted_shell (const char *);
/*
* usage - print command line syntax and exit
*/
static void usage (void)
{
fprintf (stderr, _("Usage: %s [-s shell] [name]\n"), Prog);
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)
{
printf (_("Enter the new value, or press ENTER for the default\n"));
change_field (loginsh, sizeof loginsh, _("Login Shell"));
}
/*
* restricted_shell - return true if the named shell begins with 'r' or 'R'
*
* If the first letter of the filename is 'r' or 'R', the shell is
* considered to be restricted.
*/
static int 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 !check_shell (sh);
}
#ifdef USE_PAM
static struct pam_conv conv = {
misc_conv,
NULL
};
#endif /* USE_PAM */
/*
* 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 */
int flag; /* Current command line flag */
int sflg = 0; /* -s - set shell from command line */
const struct passwd *pw; /* Password entry from /etc/passwd */
struct passwd pwent; /* New password entry */
#ifdef USE_PAM
pam_handle_t *pamh = NULL;
struct passwd *pampw;
int retval;
#endif
sanitize_env ();
setlocale (LC_ALL, "");
bindtextdomain (PACKAGE, LOCALEDIR);
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");
/*
* There is only one option, but use getopt() anyway to
* keep things consistent.
*/
while ((flag = getopt (argc, argv, "s:")) != EOF) {
switch (flag) {
case 's':
sflg++;
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 ();
/*
* 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];
pw = getpwnam (user);
if (!pw) {
fprintf (stderr,
_("%s: unknown user %s\n"), Prog, user);
exit (1);
}
} else {
pw = get_my_pwent ();
if (!pw) {
fprintf (stderr,
_
("%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,
_("%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,
_
("%s: `%s' is the NIS master for this client.\n"),
Prog, nis_master);
}
exit (1);
}
#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'", user));
closelog ();
fprintf (stderr,
_("You may not change the shell for %s.\n"), user);
exit (1);
}
/*
* Non-privileged users are only allowed to change the shell if it
* is not a restricted one.
*/
if (!amroot && restricted_shell (pw->pw_shell)) {
SYSLOG ((LOG_WARN, "can't change shell for `%s'", user));
closelog ();
fprintf (stderr,
_("You may not change the shell for %s.\n"), user);
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 ())
&& (selinux_check_passwd_access (PASSWD__CHSH) != 0)) {
SYSLOG ((LOG_WARN, "can't change shell for `%s'", user));
closelog ();
fprintf (stderr,
_("You may not change the shell for %s.\n"), user);
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 ());
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 */
/*
* 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, ":,=")) {
fprintf (stderr, _("%s: Invalid entry: %s\n"), Prog, loginsh);
closelog ();
exit (1);
}
if (!amroot && (!check_shell (loginsh) || access (loginsh, X_OK) != 0)) {
fprintf (stderr, _("%s is an invalid shell.\n"), loginsh);
closelog ();
exit (1);
}
/*
* 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)) {
SYSLOG ((LOG_ERR, "can't setuid(0)"));
closelog ();
fprintf (stderr, _("Cannot change ID to root.\n"));
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 ()) {
SYSLOG ((LOG_WARN, "can't lock /etc/passwd"));
closelog ();
fprintf (stderr,
_
("Cannot lock the password file; try again later.\n"));
exit (1);
}
if (!pw_open (O_RDWR)) {
SYSLOG ((LOG_ERR, "can't open /etc/passwd"));
closelog ();
fprintf (stderr, _("Cannot open the password file.\n"));
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 (!pw) {
pw_unlock ();
fprintf (stderr,
_("%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 = loginsh;
/*
* Update the passwd file entry. If there is a DBM file, update
* that entry as well.
*/
if (!pw_update (&pwent)) {
SYSLOG ((LOG_ERR, "error updating passwd entry"));
closelog ();
fprintf (stderr, _("Error updating the password entry.\n"));
pw_unlock ();
exit (1);
}
/*
* Changes have all been made, so commit them and unlock the file.
*/
if (!pw_close ()) {
SYSLOG ((LOG_ERR, "can't rewrite /etc/passwd"));
closelog ();
fprintf (stderr, _("Cannot commit password file changes.\n"));
pw_unlock ();
exit (1);
}
if (!pw_unlock ()) {
SYSLOG ((LOG_ERR, "can't unlock /etc/passwd"));
closelog ();
fprintf (stderr, _("Cannot unlock the password file.\n"));
exit (1);
}
SYSLOG ((LOG_INFO, "changed user `%s' shell to `%s'", user, loginsh));
nscd_flush_cache ("passwd");
#ifdef USE_PAM
if (retval == PAM_SUCCESS)
pam_end (pamh, PAM_SUCCESS);
#endif /* USE_PAM */
closelog ();
exit (E_SUCCESS);
}