1 files changed, 102 insertions, 0 deletions
diff --git a/loginutils/su.c b/loginutils/su.c
new file mode 100644
index 0000000..61039d8
--- /dev/null
+++ b/loginutils/su.c
@@ -0,0 +1,102 @@
+/* vi: set sw=4 ts=4: */
+/*
+ *  Mini su implementation for busybox
+ *
+ *  Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
+ */
+
+#include "libbb.h"
+#include <syslog.h>
+
+#define SU_OPT_mp (3)
+#define SU_OPT_l (4)
+
+int su_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+int su_main(int argc UNUSED_PARAM, char **argv)
+{
+	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;
+	char *old_user;
+
+	flags = getopt32(argv, "mplc:s:", &opt_command, &opt_shell);
+	//argc -= optind;
+	argv += optind;
+
+	if (argv[0] && LONE_DASH(argv[0])) {
+		flags |= SU_OPT_l;
+		argv++;
+	}
+
+	/* get user if specified */
+	if (argv[0]) {
+		opt_username = argv[0];
+		argv++;
+	}
+
+	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.  */
+		old_user = xstrdup(USE_FEATURE_UTMP(getlogin() ? : ) (pw = getpwuid(cur_uid)) ? pw->pw_name : "");
+		tty = ttyname(2) ? : "none";
+		openlog(applet_name, 0, LOG_AUTH);
+	}
+
+	pw = getpwnam(opt_username);
+	if (!pw)
+		bb_error_msg_and_die("unknown id: %s", 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;
+
+	if ((cur_uid == 0) || correct_password(pw)) {
+		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_error_msg_and_die("incorrect password");
+	}
+
+	if (ENABLE_FEATURE_CLEAN_UP && ENABLE_FEATURE_SU_SYSLOG) {
+		closelog();
+		free(old_user);
+	}
+
+	if (!opt_shell && (flags & SU_OPT_mp))
+		opt_shell = getenv("SHELL");
+
+#if ENABLE_FEATURE_SU_CHECKS_SHELLS
+	if (opt_shell && cur_uid && 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;
+	}
+#endif
+	if (!opt_shell)
+		opt_shell = pw->pw_shell;
+
+	change_identity(pw);
+	/* setup_environment params: shell, clear_env, change_env, pw */
+	setup_environment(opt_shell, flags & SU_OPT_l, !(flags & SU_OPT_mp), pw);
+	USE_SELINUX(set_current_security_context(NULL);)
+
+	/* Never returns */
+	run_shell(opt_shell, flags & SU_OPT_l, opt_command, (const char**)argv);
+
+	/* return EXIT_FAILURE; - not reached */
+}