Also, added a comment about bug 9401 (TIOCSTI input injection).
function old new delta
packed_usage 30909 30932 +23
su_main 470 487 +17
sulogin_main 260 258 -2
run_applet_and_exit 681 678 -3
run_shell 166 126 -40
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
#endif
extern void bb_do_delay(int seconds) FAST_FUNC;
extern void change_identity(const struct passwd *pw) FAST_FUNC;
-extern void run_shell(const char *shell, int loginshell, const char *command, const char **additional_args) NORETURN FAST_FUNC;
+extern void run_shell(const char *shell, int loginshell, const char **args) NORETURN FAST_FUNC;
/* Returns $SHELL, getpwuid(getuid())->pw_shell, or DEFAULT_SHELL.
* Note that getpwuid result might need xstrdup'ing
if (argv[0]) {
BB_EXECVP_or_die(argv);
}
- run_shell(getenv("SHELL"), /*login:*/ 1, NULL, NULL);
+ run_shell(getenv("SHELL"), /*login:*/ 1, NULL);
}
#endif
/* Run SHELL, or DEFAULT_SHELL if SHELL is "" or NULL.
- * If COMMAND is nonzero, pass it to the shell with the -c option.
- * If ADDITIONAL_ARGS is nonzero, pass it to the shell as more
- * arguments. */
-void FAST_FUNC run_shell(const char *shell, int loginshell, const char *command, const char **additional_args)
+ * If ADDITIONAL_ARGS is not NULL, pass them to the shell.
+ */
+void FAST_FUNC run_shell(const char *shell, int loginshell, const char **additional_args)
{
const char **args;
- int argno;
- int additional_args_cnt = 0;
- for (args = additional_args; args && *args; args++)
- additional_args_cnt++;
+ args = additional_args;
+ while (args && *args)
+ args++;
- args = xmalloc(sizeof(char*) * (4 + additional_args_cnt));
+ args = xmalloc(sizeof(char*) * (2 + (args - additional_args)));
if (!shell || !shell[0])
shell = DEFAULT_SHELL;
args[0] = bb_get_last_path_component_nostrip(shell);
if (loginshell)
args[0] = xasprintf("-%s", args[0]);
- argno = 1;
- if (command) {
- args[argno++] = "-c";
- args[argno++] = command;
- }
+ args[1] = NULL;
if (additional_args) {
- for (; *additional_args; ++additional_args)
- args[argno++] = *additional_args;
+ int cnt = 1;
+ for (;;)
+ if ((args[cnt++] = *additional_args++) == NULL)
+ break;
}
- args[argno] = NULL;
#if ENABLE_SELINUX
if (current_sid)
signal(SIGINT, SIG_DFL);
/* Exec login shell with no additional parameters */
- run_shell(pw->pw_shell, 1, NULL, NULL);
+ run_shell(pw->pw_shell, 1, NULL);
/* return EXIT_FAILURE; - not reached */
}
//kbuild:lib-$(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"
#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])) {
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 */
}
shell = pwd->pw_shell;
/* Exec login shell with no additional parameters. Never returns. */
- run_shell(shell, 1, NULL, NULL);
+ run_shell(shell, 1, NULL);
}