/*
* chsh.c -- change your login shell
* (c) 1994 by salvatore valente <svalente@athena.mit.edu>
*
* 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 Mi¶kiewicz <misiek@pld.ORG.PL>
* - added Native Language Support
*
*
*/
#include <err.h>
#include <sys/types.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <pwd.h>
#include <errno.h>
#include <ctype.h>
#include <getopt.h>
#include "c.h"
#include "my_crypt.h"
#include "islocal.h"
#include "setpwnam.h"
#include "nls.h"
#include "env.h"
#include "pathnames.h"
#include "xalloc.h"
#if defined(REQUIRE_PASSWORD) && defined(HAVE_SECURITY_PAM_MISC_H)
#include <security/pam_appl.h>
#include <security/pam_misc.h>
#define PAM_FAIL_CHECK(_ph, _rc) \
do { \
if ((_rc) != PAM_SUCCESS) { \
fprintf(stderr, "\n%s\n", pam_strerror((_ph), (_rc))); \
pam_end((_ph), (_rc)); \
exit(EXIT_FAILURE); \
} \
} while(0)
#endif /* PAM */
#ifdef HAVE_LIBSELINUX
#include <selinux/selinux.h>
#include <selinux/av_permissions.h>
#include "selinux_utils.h"
#endif
typedef unsigned char boolean;
#define false 0
#define true 1
/* Only root is allowed to assign a luser a non-listed shell, by default */
#define ONLY_LISTED_SHELLS 1
static char *whoami;
struct sinfo {
char *username;
char *shell;
};
static void parse_argv (int argc, char *argv[], struct sinfo *pinfo);
static char *prompt (char *question, char *def_val);
static int check_shell (char *shell);
static boolean get_shell_list (char *shell);
static int __attribute__((__noreturn__)) usage (FILE *fp)
{
fprintf (fp,
_("Usage: %s [ -s shell ] [ --list-shells ] "
"[ --help ] [ --version ]\n"
" [ username ]\n"), whoami);
exit(fp == stderr ? EXIT_FAILURE : EXIT_SUCCESS);
}
int
main (int argc, char *argv[]) {
char *cp, *shell, *oldshell;
uid_t uid;
struct sinfo info;
struct passwd *pw;
sanitize_env();
setlocale(LC_ALL, "");
bindtextdomain(PACKAGE, LOCALEDIR);
textdomain(PACKAGE);
/* whoami is the program name for error messages */
whoami = argv[0];
if (! whoami) whoami = "chsh";
for (cp = whoami; *cp; cp++)
if (*cp == '/') whoami = cp + 1;
uid = getuid ();
memset(&info, 0, sizeof(info));
parse_argv (argc, argv, &info);
pw = NULL;
if (! info.username) {
pw = getpwuid (uid);
if (! pw)
errx(EXIT_FAILURE, _("%s: you (user %d) don't exist."), whoami, uid);
}
else {
pw = getpwnam (info.username);
if (! pw)
errx(EXIT_FAILURE, _("%s: user \"%s\" does not exist."),
whoami, info.username);
}
if (!(is_local(pw->pw_name)))
errx(EXIT_FAILURE, _("%s: can only change local entries."), whoami);
#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: %s is not authorized to change the shell of %s"),
whoami, user_context ? : _("Unknown user context"),
pw->pw_name);
}
}
if (setupDefaultContext("/etc/passwd") != 0)
errx(EXIT_FAILURE, _("%s: can't set default context for /etc/passwd"),
whoami);
}
#endif
oldshell = pw->pw_shell;
if (oldshell == NULL || *oldshell == '\0')
oldshell = _PATH_BSHELL; /* default */
/* reality check */
if (uid != 0 && uid != pw->pw_uid) {
errno = EACCES;
err(EXIT_FAILURE, _("%s: running UID doesn't match UID of user we're "
"altering, shell change denied"), whoami);
}
if (uid != 0 && !get_shell_list(oldshell)) {
errno = EACCES;
err(EXIT_FAILURE, _("%s: your shell is not in /etc/shells, "
"shell change denied"), whoami);
}
shell = info.shell;
printf( _("Changing shell for %s.\n"), pw->pw_name );
#ifdef REQUIRE_PASSWORD
#ifdef HAVE_SECURITY_PAM_MISC_H
if (uid != 0) {
pam_handle_t *pamh = NULL;
struct pam_conv conv = { misc_conv, NULL };
int retcode;
retcode = pam_start("chsh", pw->pw_name, &conv, &pamh);
if(retcode != PAM_SUCCESS)
errx(EXIT_FAILURE, _("%s: PAM failure, aborting: %s"),
whoami, pam_strerror(pamh, retcode));
retcode = pam_authenticate(pamh, 0);
PAM_FAIL_CHECK(pamh, retcode);
retcode = pam_acct_mgmt(pamh, 0);
if (retcode == PAM_NEW_AUTHTOK_REQD)
retcode = pam_chauthtok(pamh, PAM_CHANGE_EXPIRED_AUTHTOK);
PAM_FAIL_CHECK(pamh, retcode);
retcode = pam_setcred(pamh, 0);
PAM_FAIL_CHECK(pamh, retcode);
pam_end(pamh, 0);
/* no need to establish a session; this isn't a session-oriented
* activity... */
}
#else /* HAVE_SECURITY_PAM_MISC_H */
/* require password, unless root */
if(uid != 0 && pw->pw_passwd && pw->pw_passwd[0]) {
char *pwdstr = getpass(_("Password: "));
if(strncmp(pw->pw_passwd,
crypt(pwdstr, pw->pw_passwd), 13)) {
puts(_("Incorrect password."));
return EXIT_FAILURE;
}
}
#endif /* HAVE_SECURITY_PAM_MISC_H */
#endif /* REQUIRE_PASSWORD */
if (! shell) {
shell = prompt (_("New shell"), oldshell);
if (! shell)
return EXIT_SUCCESS;
}
if (check_shell (shell) < 0)
return EXIT_FAILURE;
if (! strcmp (pw->pw_shell, shell)) {
printf (_("Shell not changed.\n"));
return EXIT_SUCCESS;
}
pw->pw_shell = shell;
if (setpwnam (pw) < 0) {
warn(_("setpwnam failed"));
printf( _("Shell *NOT* changed. Try again later.\n") );
return EXIT_FAILURE;
}
printf (_("Shell changed.\n"));
return EXIT_SUCCESS;
}
/*
* 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) {
int index, c;
static 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' },
};
optind = c = 0;
while (c != EOF) {
c = getopt_long (argc, argv, "s:luv", long_options, &index);
switch (c) {
case -1:
break;
case 'v':
printf ("%s\n", PACKAGE_STRING);
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];
}
}
/*
* prompt () --
* ask the user for a given field and return it.
*/
static char *
prompt (char *question, char *def_val) {
int len;
char *ans, *cp;
char buf[BUFSIZ];
if (! def_val) def_val = "";
printf("%s [%s]: ", question, def_val);
*buf = 0;
if (fgets (buf, sizeof (buf), stdin) == NULL) {
printf (_("\nAborted.\n"));
exit (EXIT_FAILURE);
}
/* remove the newline at the end of buf. */
ans = buf;
while (isspace (*ans)) ans++;
len = strlen (ans);
while (len > 0 && isspace (ans[len-1])) len--;
if (len <= 0) return NULL;
ans[len] = 0;
cp = (char *) xmalloc (len + 1);
strcpy (cp, ans);
return cp;
}
/*
* 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 (char *shell) {
int i, c;
if (!shell)
return -1;
if (*shell != '/') {
printf (_("%s: shell must be a full path name.\n"), whoami);
return -1;
}
if (access (shell, F_OK) < 0) {
printf (_("%s: \"%s\" does not exist.\n"), whoami, shell);
return -1;
}
if (access (shell, X_OK) < 0) {
printf (_("%s: \"%s\" is not executable.\n"), whoami, shell);
return -1;
}
/* keep /etc/passwd clean. */
for (i = 0; i < strlen (shell); i++) {
c = shell[i];
if (c == ',' || c == ':' || c == '=' || c == '"' || c == '\n') {
printf (_("%s: '%c' is not allowed.\n"), whoami, c);
return -1;
}
if (iscntrl (c)) {
printf (_("%s: Control characters are not allowed.\n"), whoami);
return -1;
}
}
#ifdef ONLY_LISTED_SHELLS
if (! get_shell_list (shell)) {
if (!getuid())
printf (_("Warning: \"%s\" is not listed in /etc/shells.\n"), shell);
else {
printf (_("%s: \"%s\" is not listed in /etc/shells.\n"),
whoami, shell);
printf( _("%s: Use -l option to see list.\n"), whoami );
exit(EXIT_FAILURE);
}
}
#else
if (! get_shell_list (shell)) {
printf (_("Warning: \"%s\" is not listed in /etc/shells.\n"), shell);
printf( _("Use %s -l to see list.\n"), whoami );
}
#endif
return 0;
}
/*
* 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 boolean
get_shell_list (char *shell_name) {
FILE *fp;
boolean found;
int len;
char buf[PATH_MAX];
found = false;
fp = fopen ("/etc/shells", "r");
if (! fp) {
if (! shell_name) printf (_("No known shells.\n"));
return true;
}
while (fgets (buf, sizeof (buf), fp) != NULL) {
/* ignore comments */
if (*buf == '#') continue;
len = strlen (buf);
/* strip the ending newline */
if (buf[len - 1] == '\n') buf[len - 1] = 0;
/* ignore lines that are too damn long */
else continue;
/* check or output the shell */
if (shell_name) {
if (! strcmp (shell_name, buf)) {
found = true;
break;
}
}
else printf ("%s\n", buf);
}
fclose (fp);
return found;
}
