tls: check size on "MAC-only, no crypt" code path too

[oweals/busybox.git] / loginutils / su.c

diff --git a/loginutils/su.c b/loginutils/su.c
index 2ec05e12552e04588cc92be1f45d9ef337fd1fb0..d04b85fb13767521c655efe4dd4f46ebad70af43 100644 (file)
--- a/loginutils/su.c
+++ b/loginutils/su.c
@@ -4,19 +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:     "\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.  */
@@ -56,8 +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])) {
@@ -93,7 +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);
@@ -101,6 +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");
        }
 
@@ -136,8 +165,29 @@ int su_main(int argc UNUSED_PARAM, char **argv)
                        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 */
 }