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- /* vi: set sw=4 ts=4: */
- /*
- * Mini su implementation for busybox
- *
- * Licensed under GPLv2 or later, see file LICENSE in this source tree.
- */
- //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:
- //config: Note that Busybox binary must be setuid root for this applet to
- //config: work properly.
- //config:
- //config:config FEATURE_SU_SYSLOG
- //config: bool "Enable su to write to syslog"
- //config: default y
- //config: depends on SU
- //config:
- //config:config FEATURE_SU_CHECKS_SHELLS
- //config: bool "Enable su to check user's shell to be listed in /etc/shells"
- //config: depends on SU
- //config: default y
- //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:#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 -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. */
- static int restricted_shell(const char *shell)
- {
- char *line;
- int result = 1;
- /*setusershell(); - getusershell does it itself*/
- while ((line = getusershell()) != NULL) {
- if (/* *line != '#' && */ strcmp(line, shell) == 0) {
- result = 0;
- break;
- }
- }
- if (ENABLE_FEATURE_CLEAN_UP)
- endusershell();
- return result;
- }
- #endif
- #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;
- #if ENABLE_FEATURE_UTMP
- char user_buf[64];
- #endif
- const 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. */
- #if ENABLE_FEATURE_UTMP
- old_user = user_buf;
- if (getlogin_r(user_buf, sizeof(user_buf)) != 0)
- #endif
- {
- pw = getpwuid(cur_uid);
- old_user = pw ? xstrdup(pw->pw_name) : "";
- }
- tty = xmalloc_ttyname(2);
- if (!tty) {
- tty = "none";
- }
- openlog(applet_name, 0, LOG_AUTH);
- }
- pw = xgetpwnam(opt_username);
- 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);
- } else {
- 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");
- }
- if (ENABLE_FEATURE_CLEAN_UP && ENABLE_FEATURE_SU_SYSLOG) {
- closelog();
- }
- if (!opt_shell && (flags & SU_OPT_mp)) {
- /* -s SHELL is not given, but "preserve env" opt is */
- opt_shell = getenv("SHELL");
- }
- #if ENABLE_FEATURE_SU_CHECKS_SHELLS
- 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; /* 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. */
- #endif
- if (!opt_shell)
- opt_shell = pw->pw_shell;
- 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_l) * SETUP_ENV_NO_CHDIR),
- pw);
- IF_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 */
- }
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