X-Git-Url: https://git.librecmc.org/?a=blobdiff_plain;f=loginutils%2Fsu.c;h=d04b85fb13767521c655efe4dd4f46ebad70af43;hb=0af5265180877f4e8fbf8f1d9f2999b3fd2205d3;hp=db303af6dfc79620ac91b7d7e778b29f374a4c39;hpb=a9e25ffa678a357c581b9b7f65a7b2ce1ae2a63e;p=oweals%2Fbusybox.git

diff --git a/loginutils/su.c b/loginutils/su.c
index db303af6d..d04b85fb1 100644
--- a/loginutils/su.c
+++ b/loginutils/su.c
@@ -4,20 +4,43 @@
  *
  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
  */
-
-#include "libbb.h"
-#include <syslog.h>
+//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:       "[OPTIONS] [-] [USER]"
+//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:     "\nOptions:"
-//usage:     "\n	-,-l	Clear environment, run shell as login shell"
+//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>
+
 #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.  */
@@ -57,8 +80,12 @@ int su_main(int argc UNUSED_PARAM, char **argv)
 #endif
 	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);
-	//argc -= optind;
 	argv += optind;
 
 	if (argv[0] && LONE_DASH(argv[0])) {
@@ -94,7 +121,7 @@ int su_main(int argc UNUSED_PARAM, char **argv)
 
 	pw = xgetpwnam(opt_username);
 
-	if (cur_uid == 0 || correct_password(pw)) {
+	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);
@@ -102,6 +129,7 @@ int su_main(int argc UNUSED_PARAM, char **argv)
 		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");
 	}
 
@@ -114,20 +142,14 @@ int su_main(int argc UNUSED_PARAM, char **argv)
 		opt_shell = getenv("SHELL");
 	}
 
-	/* Make sure pw->pw_shell is non-NULL.  It may be NULL when NEW_USER
-	 * is a username that is retrieved via NIS (YP), that doesn't have
-	 * a default shell listed.  */
-	if (!pw->pw_shell || !pw->pw_shell[0])
-		pw->pw_shell = (char *)DEFAULT_SHELL;
-
 #if ENABLE_FEATURE_SU_CHECKS_SHELLS
-	if (opt_shell && cur_uid != 0 && restricted_shell(pw->pw_shell)) {
+	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.  */
 		bb_error_msg("using restricted shell");
-		opt_shell = NULL;
+		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. */
@@ -138,12 +160,34 @@ int su_main(int argc UNUSED_PARAM, char **argv)
 	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_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";
+	}
+
+	/* 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, opt_command, (const char**)argv);
+	run_shell(opt_shell, flags & SU_OPT_l, (const char**)argv);
 
 	/* return EXIT_FAILURE; - not reached */
 }