/*
* chsh.c -- change your login shell
* (c) 1994 by salvatore valente <svalente@athena.mit.edu>
* (c) 2012 by Cody Maloney <cmaloney@theoreticalchaos.com>
*
* this program is free software. you can redistribute it and
* modify it under the terms of the gnu general public license.
* there is no warranty.
*
* $Author: aebr $
* $Revision: 1.19 $
* $Date: 1998/06/11 22:30:14 $
*
* Updated Thu Oct 12 09:33:15 1995 by faith@cs.unc.edu with security
* patches from Zefram <A.Main@dcs.warwick.ac.uk>
*
* Updated Mon Jul 1 18:46:22 1996 by janl@math.uio.no with security
* suggestion from Zefram. Disallowing users with shells not in /etc/shells
* from changing their shell.
*
* 1999-02-22 Arkadiusz Miśkiewicz <misiek@pld.ORG.PL>
* - added Native Language Support
*/
#include <ctype.h>
#include <errno.h>
#include <getopt.h>
#include <pwd.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>
#include "c.h"
#include "env.h"
#include "closestream.h"
#include "islocal.h"
#include "nls.h"
#include "pathnames.h"
#include "setpwnam.h"
#include "strutils.h"
#include "xalloc.h"
#include "ch-common.h"
#ifdef HAVE_LIBSELINUX
# include <selinux/selinux.h>
# include <selinux/av_permissions.h>
# include "selinux_utils.h"
#endif
#ifdef HAVE_LIBUSER
# include <libuser/user.h>
# include "libuser.h"
#elif CHFN_CHSH_PASSWORD
# include "auth.h"
#endif
struct sinfo {
char *username;
char *shell;
};
static void __attribute__((__noreturn__)) usage (FILE *fp)
{
fputs(USAGE_HEADER, fp);
fprintf(fp, _(" %s [options] [<username>]\n"), program_invocation_short_name);
fputs(USAGE_OPTIONS, fp);
fputs(_(" -s, --shell <shell> specify login shell\n"), fp);
fputs(_(" -l, --list-shells print list of shells and exit\n"), fp);
fputs(USAGE_SEPARATOR, fp);
fputs(_(" -u, --help display this help and exit\n"), fp);
fputs(_(" -v, --version output version information and exit\n"), fp);
fprintf(fp, USAGE_MAN_TAIL("chsh(1)"));
exit(fp == stderr ? EXIT_FAILURE : EXIT_SUCCESS);
}
/*
* get_shell_list () -- if the given shell appears in /etc/shells,
* return true. if not, return false.
* if the given shell is NULL, /etc/shells is outputted to stdout.
*/
static int get_shell_list(const char *shell_name)
{
FILE *fp;
int found;
char *buf = NULL;
size_t sz = 0, len;
found = false;
fp = fopen(_PATH_SHELLS, "r");
if (!fp) {
if (!shell_name)
warnx(_("No known shells."));
return true;
}
while (getline(&buf, &sz, fp) != -1) {
len = strlen(buf);
/* ignore comments */
if (*buf == '#')
continue;
/* skip blank lines*/
if (len < 2)
continue;
/* strip the ending newline */
if (buf[len - 1] == '\n')
buf[len - 1] = 0;
/* check or output the shell */
if (shell_name) {
if (!strcmp(shell_name, buf)) {
found = true;
break;
}
} else
printf("%s\n", buf);
}
fclose(fp);
free(buf);
return found;
}
/*
* parse_argv () --
* parse the command line arguments, and fill in "pinfo" with any
* information from the command line.
*/
static void parse_argv(int argc, char **argv, struct sinfo *pinfo)
{
const struct option long_options[] = {
{"shell", required_argument, 0, 's'},
{"list-shells", no_argument, 0, 'l'},
{"help", no_argument, 0, 'u'},
{"version", no_argument, 0, 'v'},
{NULL, no_argument, 0, '0'},
};
int c;
while ((c = getopt_long(argc, argv, "s:luv", long_options, NULL)) != -1) {
switch (c) {
case 'v':
printf(UTIL_LINUX_VERSION);
exit(EXIT_SUCCESS);
case 'u':
usage(stdout);
case 'l':
get_shell_list(NULL);
exit(EXIT_SUCCESS);
case 's':
if (!optarg)
usage(stderr);
pinfo->shell = optarg;
break;
default:
usage(stderr);
}
}
/* done parsing arguments. check for a username. */
if (optind < argc) {
if (optind + 1 < argc)
usage(stderr);
pinfo->username = argv[optind];
}
}
/*
* ask_new_shell () --
* ask the user for a shell and return it.
*/
static char *ask_new_shell(char *question, char *oldshell)
{
int len;
char *ans = NULL;
size_t dummy = 0;
ssize_t sz;
if (!oldshell)
oldshell = "";
printf("%s [%s]: ", question, oldshell);
sz = getline(&ans, &dummy, stdin);
if (sz == -1)
return NULL;
/* remove the newline at the end of ans. */
ltrim_whitespace((unsigned char *) ans);
len = rtrim_whitespace((unsigned char *) ans);
if (len == 0)
return NULL;
return ans;
}
/*
* check_shell () -- if the shell is completely invalid, print
* an error and return (-1).
* if the shell is a bad idea, print a warning.
*/
static int check_shell(const char *shell)
{
if (!shell)
return -1;
if (*shell != '/') {
warnx(_("shell must be a full path name"));
return -1;
}
if (access(shell, F_OK) < 0) {
warnx(_("\"%s\" does not exist"), shell);
return -1;
}
if (access(shell, X_OK) < 0) {
printf(_("\"%s\" is not executable"), shell);
return -1;
}
if (illegal_passwd_chars(shell)) {
warnx(_("%s: has illegal characters"), shell);
return -1;
}
#ifdef ONLY_LISTED_SHELLS
if (!get_shell_list(shell)) {
if (!getuid())
warnx(_
("Warning: \"%s\" is not listed in %s."),
shell, _PATH_SHELLS);
else
errx(EXIT_FAILURE,
_("\"%s\" is not listed in %s.\n"
"Use %s -l to see list."), shell, _PATH_SHELLS,
program_invocation_short_name);
}
#else
if (!get_shell_list(shell)) {
warnx(_("\"%s\" is not listed in %s.\n"
"Use %s -l to see list."), shell, _PATH_SHELLS,
program_invocation_short_name);
}
#endif
return 0;
}
int main(int argc, char **argv)
{
char *oldshell;
int nullshell = 0;
const uid_t uid = getuid();
struct sinfo info = { 0 };
struct passwd *pw;
sanitize_env();
setlocale(LC_ALL, "");
bindtextdomain(PACKAGE, LOCALEDIR);
textdomain(PACKAGE);
atexit(close_stdout);
parse_argv(argc, argv, &info);
if (!info.username) {
pw = getpwuid(uid);
if (!pw)
errx(EXIT_FAILURE, _("you (user %d) don't exist."),
uid);
} else {
pw = getpwnam(info.username);
if (!pw)
errx(EXIT_FAILURE, _("user \"%s\" does not exist."),
info.username);
}
#ifndef HAVE_LIBUSER
if (!(is_local(pw->pw_name)))
errx(EXIT_FAILURE, _("can only change local entries"));
#endif
#ifdef HAVE_LIBSELINUX
if (is_selinux_enabled() > 0) {
if (uid == 0) {
if (checkAccess(pw->pw_name, PASSWD__CHSH) != 0) {
security_context_t user_context;
if (getprevcon(&user_context) < 0)
user_context =
(security_context_t) NULL;
errx(EXIT_FAILURE,
_("%s is not authorized to change the shell of %s"),
user_context ? : _("Unknown user context"),
pw->pw_name);
}
}
if (setupDefaultContext(_PATH_PASSWD) != 0)
errx(EXIT_FAILURE,
_("can't set default context for %s"), _PATH_PASSWD);
}
#endif
oldshell = pw->pw_shell;
if (oldshell == NULL || *oldshell == '\0') {
oldshell = _PATH_BSHELL; /* default */
nullshell = 1;
}
/* reality check */
#ifdef HAVE_LIBUSER
/* If we're setuid and not really root, disallow the password change. */
if (geteuid() != getuid() && uid != pw->pw_uid) {
#else
if (uid != 0 && uid != pw->pw_uid) {
#endif
errno = EACCES;
err(EXIT_FAILURE,
_("running UID doesn't match UID of user we're "
"altering, shell change denied"));
}
if (uid != 0 && !get_shell_list(oldshell)) {
errno = EACCES;
err(EXIT_FAILURE, _("your shell is not in %s, "
"shell change denied"), _PATH_SHELLS);
}
printf(_("Changing shell for %s.\n"), pw->pw_name);
#if !defined(HAVE_LIBUSER) && defined(CHFN_CHSH_PASSWORD)
if (!auth_pam("chsh", uid, pw->pw_name)) {
return EXIT_FAILURE;
}
#endif
if (!info.shell) {
info.shell = ask_new_shell(_("New shell"), oldshell);
if (!info.shell)
return EXIT_SUCCESS;
}
if (check_shell(info.shell) < 0)
return EXIT_FAILURE;
if (!nullshell && strcmp(oldshell, info.shell) == 0)
errx(EXIT_SUCCESS, _("Shell not changed."));
#ifdef HAVE_LIBUSER
if (set_value_libuser("chsh", pw->pw_name, uid,
LU_LOGINSHELL, info.shell) < 0)
errx(EXIT_FAILURE, _("Shell *NOT* changed. Try again later."));
#else
pw->pw_shell = info.shell;
if (setpwnam(pw) < 0)
err(EXIT_FAILURE, _("setpwnam failed\n"
"Shell *NOT* changed. Try again later."));
#endif
printf(_("Shell changed.\n"));
return EXIT_SUCCESS;
}
