X-Git-Url: https://git.librecmc.org/?a=blobdiff_plain;f=loginutils%2Fsu.c;h=d04b85fb13767521c655efe4dd4f46ebad70af43;hb=0af5265180877f4e8fbf8f1d9f2999b3fd2205d3;hp=33e62e837875c3171a58a0eba2c91357c0b86d68;hpb=1fca558799350fb6caff97f55aa6d1237b08fccb;p=oweals%2Fbusybox.git diff --git a/loginutils/su.c b/loginutils/su.c index 33e62e837..d04b85fb1 100644 --- a/loginutils/su.c +++ b/loginutils/su.c @@ -1,167 +1,193 @@ /* vi: set sw=4 ts=4: */ - -#include "busybox.h" - -#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 - -#include "pwd.h" -#include "grp.h" - -#include "tinylogin.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; -/* The shell to run if none is given in the user's passwd entry. */ -#define DEFAULT_SHELL "/bin/sh" -#define DEFAULT_USER "root" - -//#define SYSLOG_SUCCESS -#define SYSLOG_FAILURE - + /*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 -#if defined( SYSLOG_SUCCESS ) || defined( SYSLOG_FAILURE ) -/* Log the fact that someone has run su to the user given by PW; - if SUCCESSFUL is nonzero, they gave the correct password, etc. */ +#define SU_OPT_mp (3) +#define SU_OPT_l (4) -static void log_su ( const struct passwd *pw, int successful ) +int su_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; +int su_main(int argc UNUSED_PARAM, char **argv) { - const char *old_user, *tty; - -#if !defined( SYSLOG_SUCESS ) - if ( successful ) - return; + 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 -#if !defined( SYSLOG_FAILURE ) - if ( !successful ) - return; -#endif - - if ( pw-> pw_uid ) // not to root -> ignored - return; + 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); + argv += optind; + + if (argv[0] && LONE_DASH(argv[0])) { + flags |= SU_OPT_l; + argv++; + } - /* 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 ) { - /* getlogin can fail -- usually due to lack of utmp entry. Resort to getpwuid. */ - struct passwd *pwd = getpwuid ( getuid ( )); - old_user = ( pwd ? pwd-> pw_name : "" ); + /* get user if specified */ + if (argv[0]) { + opt_username = argv[0]; + argv++; } - - tty = ttyname ( 2 ); - openlog ( "su", 0, LOG_AUTH ); - syslog ( LOG_NOTICE, "%s%s on %s", successful ? "" : "FAILED SU ", old_user, tty ? tty : "none" ); -} + 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 - - - -int su_main ( int argc, char **argv ) -{ - int flag; - int opt_preserve = 0; - int opt_loginshell = 0; - char *opt_shell = 0; - char *opt_command = 0; - char *opt_username = DEFAULT_USER; - char **opt_args = 0; - struct passwd *pw, pw_copy; - - - while (( flag = getopt ( argc, argv, "c:lmps:" )) != -1 ) { - switch ( flag ) { - case 'c': - opt_command = optarg; - break; - case 'm': - case 'p': - opt_preserve = 1; - break; - case 's': - opt_shell = optarg; - break; - case 'l': - opt_loginshell = 1; - break; - default: - show_usage ( ); - break; + { + 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); } - if (( optind < argc ) && ( argv [optind][0] == '-' ) && ( argv [optind][1] == 0 )) { - opt_loginshell = 1; - ++optind; - } + 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"); + } - /* get user if specified */ - if ( optind < argc ) - opt_username = argv [optind++]; - - if ( optind < argc ) - opt_args = argv + optind; - - - pw = getpwnam ( opt_username ); - if ( !pw ) - 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; - - /* Make a copy of the password information and point pw at the local - copy instead. Otherwise, some systems (e.g. Linux) would clobber - the static data through the getlogin call from log_su. */ - pw_copy = *pw; - pw = &pw_copy; - pw-> pw_name = xstrdup ( pw-> pw_name ); - pw-> pw_dir = xstrdup ( pw-> pw_dir ); - pw-> pw_shell = xstrdup ( pw-> pw_shell ); - - if (( getuid ( ) == 0 ) || correct_password ( pw )) - log_su ( pw, 1 ); - else { - log_su ( pw, 0 ); - error_msg_and_die ( "incorrect password" ); + if (ENABLE_FEATURE_CLEAN_UP && ENABLE_FEATURE_SU_SYSLOG) { + closelog(); } - if ( !opt_shell && opt_preserve ) - 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 && getuid ( ) && 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 */ + } + /* 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);) + + if (opt_command) { + *--argv = opt_command; + *--argv = (char*)"-c"; } - if ( !opt_shell ) - opt_shell = xstrdup ( pw-> pw_shell ); - - change_identity ( pw ); - setup_environment ( opt_shell, opt_loginshell, !opt_preserve, pw ); - run_shell ( opt_shell, opt_loginshell, opt_command, opt_args ); - - 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 */ }