X-Git-Url: https://git.librecmc.org/?a=blobdiff_plain;f=loginutils%2Fsu.c;h=d04b85fb13767521c655efe4dd4f46ebad70af43;hb=0af5265180877f4e8fbf8f1d9f2999b3fd2205d3;hp=1273831ff64fca5bb483cebd829e3219dd1bda20;hpb=df798b7f58237e414e738fa0bd453cf13471bf76;p=oweals%2Fbusybox.git diff --git a/loginutils/su.c b/loginutils/su.c index 1273831ff..d04b85fb1 100644 --- a/loginutils/su.c +++ b/loginutils/su.c @@ -1,162 +1,193 @@ /* vi: set sw=4 ts=4: */ /* - Licensed under the GPL v2, see the file LICENSE in this tarball. -*/ - -#include -#include -#include -#include -#include + * 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: 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: "[-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, 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 -#include -#include -#include -#include -#include -#include -#include -#include - -#include "busybox.h" - -/* The shell to run if none is given in the user's passwd entry. */ -#ifndef DEFAULT_SHELL -#define DEFAULT_SHELL "/bin/sh" -#endif - -/* Default user. */ -#define DEFAULT_USER "root" - -/* #define SYSLOG_SUCCESS */ -#define SYSLOG_FAILURE - -#if defined( SYSLOG_SUCCESS ) || defined( SYSLOG_FAILURE ) -/* Log the fact that someone has run su */ - -# if defined( SYSLOG_SUCCESS ) && defined( SYSLOG_FAILURE ) -static void log_su (const char *successful, const char *old_user, - const char *tty) +#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) { - syslog ( LOG_NOTICE, "%s%s on %s", successful, old_user, tty); + 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; } -# define log_su_successful(cu, u, tty) if(!cu) log_su("", u, tty) -# define log_su_failure(cu, u, tty) if(!cu) log_su("FAILED SU ", u, tty) -# else - /* partial logging */ -# if !defined( SYSLOG_SUCESS ) -# define log_su_successful(cu, u, tty) -# define log_su_failure(cu, u, t) if(!cu) \ - syslog(LOG_NOTICE, "FAILED SU %s on %s", u, t) -# else -# define log_su_successful(cu, u, t) if(!cu) \ - syslog(LOG_NOTICE, "%s on %s", u, t) -# define log_su_failure(cu, u, tty) -# endif -# endif -#else - /* logging not used */ -# define log_su_successful(cu, u, tty) -# define log_su_failure(cu, u, tty) #endif +#define SU_OPT_mp (3) +#define SU_OPT_l (4) -int su_main ( int argc, char **argv ) +int su_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; +int su_main(int argc UNUSED_PARAM, char **argv) { - unsigned long flags; - char *opt_shell = 0; - char *opt_command = 0; - char *opt_username = DEFAULT_USER; - char **opt_args = 0; + unsigned flags; + char *opt_shell = NULL; + char *opt_command = NULL; + const char *opt_username = "root"; struct passwd *pw; uid_t cur_uid = getuid(); - -#if defined( SYSLOG_SUCCESS ) || defined( SYSLOG_FAILURE ) const char *tty; - const char *old_user; +#if ENABLE_FEATURE_UTMP + char user_buf[64]; #endif + const char *old_user; - flags = bb_getopt_ulflags(argc, argv, "mplc:s:", - &opt_command, &opt_shell); -#define SU_OPT_m (3) -#define SU_OPT_p (3) -#define SU_OPT_l (4) + /* 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); + argv += optind; - if (optind < argc && argv[optind][0] == '-' && argv[optind][1] == 0) { + if (argv[0] && LONE_DASH(argv[0])) { flags |= SU_OPT_l; - ++optind; - } + argv++; + } /* get user if specified */ - if ( optind < argc ) - opt_username = argv [optind++]; - - if ( optind < argc ) - opt_args = argv + optind; - -#if defined( SYSLOG_SUCCESS ) || defined( SYSLOG_FAILURE ) -#ifdef CONFIG_FEATURE_UTMP - /* The utmp entry (via getlogin) is probably the best way to identify - the user, especially if someone su's from a su-shell. */ - old_user = getlogin ( ); - if ( !old_user ) -#endif - { - /* getlogin can fail -- usually due to lack of utmp entry. - Resort to getpwuid. */ - pw = getpwuid ( cur_uid ); - old_user = ( pw ? pw->pw_name : "" ); + if (argv[0]) { + opt_username = argv[0]; + argv++; } - tty = ttyname ( 2 ); - if(!tty) - tty = "none"; - openlog ( bb_applet_name, 0, LOG_AUTH ); + 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 = getpwnam ( opt_username ); - if ( !pw ) - bb_error_msg_and_die ( "user %s does not exist", 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; + pw = xgetpwnam(opt_username); - if ((( cur_uid == 0 ) || correct_password ( pw ))) { - log_su_successful(pw->pw_uid, old_user, tty ); + 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 { - log_su_failure (pw->pw_uid, old_user, tty ); - bb_error_msg_and_die ( "incorrect password" ); + 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 defined( SYSLOG_SUCCESS ) || defined( SYSLOG_FAILURE ) - closelog(); -#endif + if (ENABLE_FEATURE_CLEAN_UP && ENABLE_FEATURE_SU_SYSLOG) { + closelog(); + } - if ( !opt_shell && (flags & SU_OPT_p)) - opt_shell = getenv ( "SHELL" ); + if (!opt_shell && (flags & SU_OPT_mp)) { + /* -s SHELL is not given, but "preserve env" opt is */ + opt_shell = getenv("SHELL"); + } - if ( opt_shell && cur_uid && restricted_shell ( pw->pw_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. */ - fputs ( "using restricted shell\n", stderr ); - opt_shell = 0; + * 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 */ } - - if ( !opt_shell ) + /* 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, !(flags & SU_OPT_p), pw); -#if ENABLE_SELINUX - set_current_security_context(NULL); -#endif - run_shell(opt_shell, flags & SU_OPT_l, opt_command, (const char**)opt_args); + 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);) + + if (opt_command) { + *--argv = opt_command; + *--argv = (char*)"-c"; + } - return EXIT_FAILURE; + /* A nasty ioctl exists which can stuff data into input queue: + * #include + * 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, (const char**)argv); + + /* return EXIT_FAILURE; - not reached */ }