1 /* vi: set sw=4 ts=4: */
3 * Mini su implementation for busybox
5 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
10 //config: select FEATURE_SYSLOG
12 //config: su is used to become another user during a login session.
13 //config: Invoked without a username, su defaults to becoming the super user.
15 //config: Note that Busybox binary must be setuid root for this applet to
16 //config: work properly.
18 //config:config FEATURE_SU_SYSLOG
19 //config: bool "Enable su to write to syslog"
21 //config: depends on SU
23 //config:config FEATURE_SU_CHECKS_SHELLS
24 //config: bool "Enable su to check user's shell to be listed in /etc/shells"
25 //config: depends on SU
28 //applet:/* Needs to be run by root or be suid root - needs to change uid and gid: */
29 //applet:IF_SU(APPLET(su, BB_DIR_BIN, BB_SUID_REQUIRE))
31 //kbuild:lib-$(CONFIG_SU) += su.o
33 //usage:#define su_trivial_usage
34 //usage: "[OPTIONS] [-] [USER]"
35 //usage:#define su_full_usage "\n\n"
36 //usage: "Run shell under USER (by default, root)\n"
37 //usage: "\n -,-l Clear environment, run shell as login shell"
38 //usage: "\n -p,-m Do not set new $HOME, $SHELL, $USER, $LOGNAME"
39 //usage: "\n -c CMD Command to pass to 'sh -c'"
40 //usage: "\n -s SH Shell to use instead of user's default"
45 #if ENABLE_FEATURE_SU_CHECKS_SHELLS
46 /* Return 1 if SHELL is a restricted shell (one not returned by
47 * getusershell), else 0, meaning it is a standard shell. */
48 static int restricted_shell(const char *shell
)
53 /*setusershell(); - getusershell does it itself*/
54 while ((line
= getusershell()) != NULL
) {
55 if (/* *line != '#' && */ strcmp(line
, shell
) == 0) {
60 if (ENABLE_FEATURE_CLEAN_UP
)
69 int su_main(int argc
, char **argv
) MAIN_EXTERNALLY_VISIBLE
;
70 int su_main(int argc UNUSED_PARAM
, char **argv
)
73 char *opt_shell
= NULL
;
74 char *opt_command
= NULL
;
75 const char *opt_username
= "root";
77 uid_t cur_uid
= getuid();
79 #if ENABLE_FEATURE_UTMP
84 flags
= getopt32(argv
, "mplc:s:", &opt_command
, &opt_shell
);
88 if (argv
[0] && LONE_DASH(argv
[0])) {
93 /* get user if specified */
95 opt_username
= argv
[0];
99 if (ENABLE_FEATURE_SU_SYSLOG
) {
100 /* The utmp entry (via getlogin) is probably the best way to
101 * identify the user, especially if someone su's from a su-shell.
102 * But getlogin can fail -- usually due to lack of utmp entry.
103 * in this case resort to getpwuid. */
104 #if ENABLE_FEATURE_UTMP
106 if (getlogin_r(user_buf
, sizeof(user_buf
)) != 0)
109 pw
= getpwuid(cur_uid
);
110 old_user
= pw
? xstrdup(pw
->pw_name
) : "";
112 tty
= xmalloc_ttyname(2);
116 openlog(applet_name
, 0, LOG_AUTH
);
119 pw
= xgetpwnam(opt_username
);
121 if (cur_uid
== 0 || ask_and_check_password(pw
) > 0) {
122 if (ENABLE_FEATURE_SU_SYSLOG
)
123 syslog(LOG_NOTICE
, "%c %s %s:%s",
124 '+', tty
, old_user
, opt_username
);
126 if (ENABLE_FEATURE_SU_SYSLOG
)
127 syslog(LOG_NOTICE
, "%c %s %s:%s",
128 '-', tty
, old_user
, opt_username
);
129 bb_do_delay(LOGIN_FAIL_DELAY
);
130 bb_error_msg_and_die("incorrect password");
133 if (ENABLE_FEATURE_CLEAN_UP
&& ENABLE_FEATURE_SU_SYSLOG
) {
137 if (!opt_shell
&& (flags
& SU_OPT_mp
)) {
138 /* -s SHELL is not given, but "preserve env" opt is */
139 opt_shell
= getenv("SHELL");
142 #if ENABLE_FEATURE_SU_CHECKS_SHELLS
143 if (opt_shell
&& cur_uid
!= 0 && pw
->pw_shell
&& restricted_shell(pw
->pw_shell
)) {
144 /* The user being su'd to has a nonstandard shell, and so is
145 * probably a uucp account or has restricted access. Don't
146 * compromise the account by allowing access with a standard
148 bb_error_msg("using restricted shell");
149 opt_shell
= NULL
; /* ignore -s PROG */
151 /* else: user can run whatever he wants via "su -s PROG USER".
152 * This is safe since PROG is run under user's uid/gid. */
155 opt_shell
= pw
->pw_shell
;
158 setup_environment(opt_shell
,
159 ((flags
& SU_OPT_l
) / SU_OPT_l
* SETUP_ENV_CLEARENV
)
160 + (!(flags
& SU_OPT_mp
) * SETUP_ENV_CHANGEENV
)
161 + (!(flags
& SU_OPT_l
) * SETUP_ENV_NO_CHDIR
),
163 IF_SELINUX(set_current_security_context(NULL
);)
166 run_shell(opt_shell
, flags
& SU_OPT_l
, opt_command
, (const char**)argv
);
168 /* return EXIT_FAILURE; - not reached */