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authorDenys Vlasenko <vda.linux@googlemail.com>2016-11-03 22:13:08 +0100
committerDenys Vlasenko <vda.linux@googlemail.com>2016-11-03 22:13:08 +0100
commit79e2598c48ad7e41d523f62368454c7d74f48268 (patch)
treeb061ea33e433dcd509a99dc9726251f2e0f785e5
parent2b288236e80938d29324072a823f46861bd07cd3 (diff)
downloadbusybox-79e2598c48ad7e41d523f62368454c7d74f48268.tar.gz
su: expand help; simplify passing of -c CMD to run_shell()
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>
-rw-r--r--include/libbb.h2
-rw-r--r--libbb/executable.c2
-rw-r--r--libbb/run_shell.c29
-rw-r--r--loginutils/login.c2
-rw-r--r--loginutils/su.c33
-rw-r--r--loginutils/sulogin.c2
6 files changed, 45 insertions, 25 deletions
diff --git a/include/libbb.h b/include/libbb.h
index 3752df982..20fc7329f 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -1341,7 +1341,7 @@ char *bb_simplify_abs_path_inplace(char *path) FAST_FUNC;
#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
diff --git a/libbb/executable.c b/libbb/executable.c
index 05e70312f..3a1d4ff44 100644
--- a/libbb/executable.c
+++ b/libbb/executable.c
@@ -97,5 +97,5 @@ void FAST_FUNC exec_prog_or_SHELL(char **argv)
if (argv[0]) {
BB_EXECVP_or_die(argv);
}
- run_shell(getenv("SHELL"), /*login:*/ 1, NULL, NULL);
+ run_shell(getenv("SHELL"), /*login:*/ 1, NULL);
}
diff --git a/libbb/run_shell.c b/libbb/run_shell.c
index 4d92c3caa..b6b9360e8 100644
--- a/libbb/run_shell.c
+++ b/libbb/run_shell.c
@@ -50,19 +50,17 @@ void FAST_FUNC set_current_security_context(security_context_t sid)
#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;
@@ -70,16 +68,13 @@ void FAST_FUNC run_shell(const char *shell, int loginshell, const char *command,
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)
diff --git a/loginutils/login.c b/loginutils/login.c
index 94b6c45db..52abc1886 100644
--- a/loginutils/login.c
+++ b/loginutils/login.c
@@ -618,7 +618,7 @@ int login_main(int argc UNUSED_PARAM, char **argv)
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 */
}
diff --git a/loginutils/su.c b/loginutils/su.c
index 3c0e8c100..24ffbde86 100644
--- a/loginutils/su.c
+++ b/loginutils/su.c
@@ -31,10 +31,10 @@
//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"
@@ -81,8 +81,12 @@ 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])) {
@@ -162,8 +166,29 @@ 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 */
}
diff --git a/loginutils/sulogin.c b/loginutils/sulogin.c
index 6befea933..2e32e2bbd 100644
--- a/loginutils/sulogin.c
+++ b/loginutils/sulogin.c
@@ -89,5 +89,5 @@ int sulogin_main(int argc UNUSED_PARAM, char **argv)
shell = pwd->pw_shell;
/* Exec login shell with no additional parameters. Never returns. */
- run_shell(shell, 1, NULL, NULL);
+ run_shell(shell, 1, NULL);
}