/* vi: set sw=4 ts=4: */
-
-#include "busybox.h"
-
-#include <fcntl.h>
-#include <signal.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
+/*
+ * Mini su implementation for busybox
+ *
+ * Licensed under GPLv2 or later, see file LICENSE in this source tree.
+ */
+//config:config SU
+//config: bool "su"
+//config: default y
+//config: select FEATURE_SYSLOG
+//config: help
+//config: su is used to become another user during a login session.
+//config: Invoked without a username, su defaults to becoming the super user.
+//config: Note that busybox binary must be setuid root for this applet to
+//config: work properly.
+//config:
+//config:config FEATURE_SU_SYSLOG
+//config: bool "Log to syslog all attempts to use su"
+//config: default y
+//config: depends on SU
+//config:
+//config:config FEATURE_SU_CHECKS_SHELLS
+//config: bool "If user's shell is not in /etc/shells, disallow -s PROG"
+//config: default y
+//config: depends on SU
+
+//applet:/* Needs to be run by root or be suid root - needs to change uid and gid: */
+//applet:IF_SU(APPLET(su, BB_DIR_BIN, BB_SUID_REQUIRE))
+
+//kbuild:lib-$(CONFIG_SU) += su.o
+
+//usage:#define su_trivial_usage
+//usage: "[-lmp] [-] [-s SH] [USER [SCRIPT ARGS / -c 'CMD' ARG0 ARGS]]"
+//usage:#define su_full_usage "\n\n"
+//usage: "Run shell under USER (by default, root)\n"
+//usage: "\n -,-l Clear environment, go to home dir, run shell as login shell"
+//usage: "\n -p,-m Do not set new $HOME, $SHELL, $USER, $LOGNAME"
+//usage: "\n -c CMD Command to pass to 'sh -c'"
+//usage: "\n -s SH Shell to use instead of user's default"
+
+#include "libbb.h"
#include <syslog.h>
-#include <termios.h>
-#include <unistd.h>
-#include <utmp.h>
-#include <sys/resource.h>
-#include <sys/stat.h>
-#include <sys/time.h>
-#include <sys/types.h>
-#include <ctype.h>
-#include <time.h>
-
-#include "pwd.h"
-#include "grp.h"
-
-#include "tinylogin.h"
-
+#if ENABLE_FEATURE_SU_CHECKS_SHELLS
+/* Return 1 if SHELL is a restricted shell (one not returned by
+ * getusershell), else 0, meaning it is a standard shell. */
+static int restricted_shell(const char *shell)
+{
+ char *line;
+ int result = 1;
-/* The shell to run if none is given in the user's passwd entry. */
-#define DEFAULT_SHELL "/bin/sh"
-#define DEFAULT_USER "root"
-
-//#define SYSLOG_SUCCESS
-#define SYSLOG_FAILURE
-
+ /*setusershell(); - getusershell does it itself*/
+ while ((line = getusershell()) != NULL) {
+ if (/* *line != '#' && */ strcmp(line, shell) == 0) {
+ result = 0;
+ break;
+ }
+ }
+ if (ENABLE_FEATURE_CLEAN_UP)
+ endusershell();
+ return result;
+}
+#endif
-#if defined( SYSLOG_SUCCESS ) || defined( SYSLOG_FAILURE )
-/* Log the fact that someone has run su to the user given by PW;
- if SUCCESSFUL is nonzero, they gave the correct password, etc. */
+#define SU_OPT_mp (3)
+#define SU_OPT_l (4)
-static void log_su ( const struct passwd *pw, int successful )
+int su_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+int su_main(int argc UNUSED_PARAM, char **argv)
{
- const char *old_user, *tty;
-
-#if !defined( SYSLOG_SUCESS )
- if ( successful )
- return;
+ unsigned flags;
+ char *opt_shell = NULL;
+ char *opt_command = NULL;
+ const char *opt_username = "root";
+ struct passwd *pw;
+ uid_t cur_uid = getuid();
+ const char *tty;
+#if ENABLE_FEATURE_UTMP
+ char user_buf[64];
#endif
-#if !defined( SYSLOG_FAILURE )
- if ( !successful )
- return;
-#endif
-
- if ( pw-> pw_uid ) // not to root -> ignored
- return;
+ const char *old_user;
+
+ /* Note: we don't use "'+': stop at first non-option" idiom here.
+ * For su, "SCRIPT ARGS" or "-c CMD ARGS" do not stop option parsing:
+ * ARGS starting with dash will be treated as su options,
+ * not passed to shell. (Tested on util-linux 2.28).
+ */
+ flags = getopt32(argv, "mplc:s:", &opt_command, &opt_shell);
+ argv += optind;
+
+ if (argv[0] && LONE_DASH(argv[0])) {
+ flags |= SU_OPT_l;
+ argv++;
+ }
- /* The utmp entry (via getlogin) is probably the best way to identify
- the user, especially if someone su's from a su-shell. */
- old_user = getlogin ( );
- if ( !old_user ) {
- /* getlogin can fail -- usually due to lack of utmp entry. Resort to getpwuid. */
- struct passwd *pwd = getpwuid ( getuid ( ));
- old_user = ( pwd ? pwd-> pw_name : "" );
+ /* get user if specified */
+ if (argv[0]) {
+ opt_username = argv[0];
+ argv++;
}
-
- tty = ttyname ( 2 );
- openlog ( "su", 0, LOG_AUTH );
- syslog ( LOG_NOTICE, "%s%s on %s", successful ? "" : "FAILED SU ", old_user, tty ? tty : "none" );
-}
+ if (ENABLE_FEATURE_SU_SYSLOG) {
+ /* The utmp entry (via getlogin) is probably the best way to
+ * identify the user, especially if someone su's from a su-shell.
+ * But getlogin can fail -- usually due to lack of utmp entry.
+ * in this case resort to getpwuid. */
+#if ENABLE_FEATURE_UTMP
+ old_user = user_buf;
+ if (getlogin_r(user_buf, sizeof(user_buf)) != 0)
#endif
-
-
-
-int su_main ( int argc, char **argv )
-{
- int flag;
- int opt_preserve = 0;
- int opt_loginshell = 0;
- char *opt_shell = 0;
- char *opt_command = 0;
- char *opt_username = DEFAULT_USER;
- char **opt_args = 0;
- struct passwd *pw, pw_copy;
-
-
- while (( flag = getopt ( argc, argv, "c:lmps:" )) != -1 ) {
- switch ( flag ) {
- case 'c':
- opt_command = optarg;
- break;
- case 'm':
- case 'p':
- opt_preserve = 1;
- break;
- case 's':
- opt_shell = optarg;
- break;
- case 'l':
- opt_loginshell = 1;
- break;
- default:
- show_usage ( );
- break;
+ {
+ pw = getpwuid(cur_uid);
+ old_user = pw ? xstrdup(pw->pw_name) : "";
+ }
+ tty = xmalloc_ttyname(2);
+ if (!tty) {
+ tty = "none";
}
+ openlog(applet_name, 0, LOG_AUTH);
}
- if (( optind < argc ) && ( argv [optind][0] == '-' ) && ( argv [optind][1] == 0 )) {
- opt_loginshell = 1;
- ++optind;
- }
+ pw = xgetpwnam(opt_username);
+
+ if (cur_uid == 0 || ask_and_check_password(pw) > 0) {
+ if (ENABLE_FEATURE_SU_SYSLOG)
+ syslog(LOG_NOTICE, "%c %s %s:%s",
+ '+', tty, old_user, opt_username);
+ } else {
+ if (ENABLE_FEATURE_SU_SYSLOG)
+ syslog(LOG_NOTICE, "%c %s %s:%s",
+ '-', tty, old_user, opt_username);
+ bb_do_delay(LOGIN_FAIL_DELAY);
+ bb_error_msg_and_die("incorrect password");
+ }
- /* get user if specified */
- if ( optind < argc )
- opt_username = argv [optind++];
-
- if ( optind < argc )
- opt_args = argv + optind;
-
-
- pw = getpwnam ( opt_username );
- if ( !pw )
- error_msg_and_die ( "user %s does not exist", opt_username );
-
- /* Make sure pw->pw_shell is non-NULL. It may be NULL when NEW_USER
- is a username that is retrieved via NIS (YP), but that doesn't have
- a default shell listed. */
- if ( !pw-> pw_shell || !pw->pw_shell [0] )
- pw-> pw_shell = (char *) DEFAULT_SHELL;
-
- /* Make a copy of the password information and point pw at the local
- copy instead. Otherwise, some systems (e.g. Linux) would clobber
- the static data through the getlogin call from log_su. */
- pw_copy = *pw;
- pw = &pw_copy;
- pw-> pw_name = xstrdup ( pw-> pw_name );
- pw-> pw_dir = xstrdup ( pw-> pw_dir );
- pw-> pw_shell = xstrdup ( pw-> pw_shell );
-
- if (( getuid ( ) == 0 ) || correct_password ( pw ))
- log_su ( pw, 1 );
- else {
- log_su ( pw, 0 );
- error_msg_and_die ( "incorrect password" );
+ if (ENABLE_FEATURE_CLEAN_UP && ENABLE_FEATURE_SU_SYSLOG) {
+ closelog();
}
- if ( !opt_shell && opt_preserve )
- opt_shell = getenv ( "SHELL" );
+ if (!opt_shell && (flags & SU_OPT_mp)) {
+ /* -s SHELL is not given, but "preserve env" opt is */
+ opt_shell = getenv("SHELL");
+ }
- if ( opt_shell && getuid ( ) && restricted_shell ( pw-> pw_shell ))
- {
+#if ENABLE_FEATURE_SU_CHECKS_SHELLS
+ if (opt_shell && cur_uid != 0 && pw->pw_shell && restricted_shell(pw->pw_shell)) {
/* The user being su'd to has a nonstandard shell, and so is
- probably a uucp account or has restricted access. Don't
- compromise the account by allowing access with a standard
- shell. */
- fputs ( "using restricted shell\n", stderr );
- opt_shell = 0;
+ * probably a uucp account or has restricted access. Don't
+ * compromise the account by allowing access with a standard
+ * shell. */
+ bb_error_msg("using restricted shell");
+ opt_shell = NULL; /* ignore -s PROG */
+ }
+ /* else: user can run whatever he wants via "su -s PROG USER".
+ * This is safe since PROG is run under user's uid/gid. */
+#endif
+ if (!opt_shell)
+ opt_shell = pw->pw_shell;
+
+ change_identity(pw);
+ setup_environment(opt_shell,
+ ((flags & SU_OPT_l) / SU_OPT_l * SETUP_ENV_CLEARENV)
+ + (!(flags & SU_OPT_mp) * SETUP_ENV_CHANGEENV)
+ + (!(flags & SU_OPT_l) * SETUP_ENV_NO_CHDIR),
+ pw);
+ IF_SELINUX(set_current_security_context(NULL);)
+
+ if (opt_command) {
+ *--argv = opt_command;
+ *--argv = (char*)"-c";
}
- if ( !opt_shell )
- opt_shell = xstrdup ( pw-> pw_shell );
-
- change_identity ( pw );
- setup_environment ( opt_shell, opt_loginshell, !opt_preserve, pw );
- run_shell ( opt_shell, opt_loginshell, opt_command, opt_args );
-
- return EXIT_FAILURE;
+ /* A nasty ioctl exists which can stuff data into input queue:
+ * #include <sys/ioctl.h>
+ * int main() {
+ * const char *msg = "echo $UID\n";
+ * while (*msg) ioctl(0, TIOCSTI, *msg++);
+ * return 0;
+ * }
+ * With "su USER -c EXPLOIT" run by root, exploit can make root shell
+ * read as input and execute arbitrary command.
+ * It's debatable whether we need to protect against this
+ * (root may hesitate to run unknown scripts interactively).
+ *
+ * Some versions of su run -c CMD in a different session:
+ * ioctl(TIOCSTI) works only on the controlling tty.
+ */
+
+ /* Never returns */
+ run_shell(opt_shell, flags & SU_OPT_l, (const char**)argv);
+
+ /* return EXIT_FAILURE; - not reached */
}
projects / oweals / busybox.git / blobdiff