blob: c51f26f70f0a65fc1dde85a5ecffb8203ac50272
1 | /* vi: set sw=4 ts=4: */ |
2 | /* |
3 | * Mini su implementation for busybox |
4 | * |
5 | * Licensed under GPLv2 or later, see file LICENSE in this source tree. |
6 | */ |
7 | |
8 | #include "libbb.h" |
9 | #include <syslog.h> |
10 | |
11 | //usage:#define su_trivial_usage |
12 | //usage: "[OPTIONS] [-] [USER]" |
13 | //usage:#define su_full_usage "\n\n" |
14 | //usage: "Run shell under USER (by default, root)\n" |
15 | //usage: "\n -,-l Clear environment, run shell as login shell" |
16 | //usage: "\n -p,-m Do not set new $HOME, $SHELL, $USER, $LOGNAME" |
17 | //usage: "\n -c CMD Command to pass to 'sh -c'" |
18 | //usage: "\n -s SH Shell to use instead of user's default" |
19 | |
20 | #if ENABLE_FEATURE_SU_CHECKS_SHELLS |
21 | /* Return 1 if SHELL is a restricted shell (one not returned by |
22 | * getusershell), else 0, meaning it is a standard shell. */ |
23 | static int restricted_shell(const char *shell) |
24 | { |
25 | char *line; |
26 | int result = 1; |
27 | |
28 | /*setusershell(); - getusershell does it itself*/ |
29 | while ((line = getusershell()) != NULL) { |
30 | if (/* *line != '#' && */ strcmp(line, shell) == 0) { |
31 | result = 0; |
32 | break; |
33 | } |
34 | } |
35 | if (ENABLE_FEATURE_CLEAN_UP) |
36 | endusershell(); |
37 | return result; |
38 | } |
39 | #endif |
40 | |
41 | #define SU_OPT_mp (3) |
42 | #define SU_OPT_l (4) |
43 | |
44 | int su_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; |
45 | int su_main(int argc UNUSED_PARAM, char **argv) |
46 | { |
47 | unsigned flags; |
48 | char *opt_shell = NULL; |
49 | char *opt_command = NULL; |
50 | const char *opt_username = "root"; |
51 | struct passwd *pw; |
52 | uid_t cur_uid = getuid(); |
53 | const char *tty; |
54 | #if ENABLE_FEATURE_UTMP |
55 | char user_buf[64]; |
56 | #endif |
57 | const char *old_user; |
58 | |
59 | flags = getopt32(argv, "mplc:s:", &opt_command, &opt_shell); |
60 | //argc -= optind; |
61 | argv += optind; |
62 | |
63 | if (argv[0] && LONE_DASH(argv[0])) { |
64 | flags |= SU_OPT_l; |
65 | argv++; |
66 | } |
67 | |
68 | /* get user if specified */ |
69 | if (argv[0]) { |
70 | opt_username = argv[0]; |
71 | argv++; |
72 | } |
73 | |
74 | if (ENABLE_FEATURE_SU_SYSLOG) { |
75 | /* The utmp entry (via getlogin) is probably the best way to |
76 | * identify the user, especially if someone su's from a su-shell. |
77 | * But getlogin can fail -- usually due to lack of utmp entry. |
78 | * in this case resort to getpwuid. */ |
79 | #if ENABLE_FEATURE_UTMP |
80 | old_user = user_buf; |
81 | if (getlogin_r(user_buf, sizeof(user_buf)) != 0) |
82 | #endif |
83 | { |
84 | pw = getpwuid(cur_uid); |
85 | old_user = pw ? xstrdup(pw->pw_name) : ""; |
86 | } |
87 | tty = xmalloc_ttyname(2); |
88 | if (!tty) { |
89 | tty = "none"; |
90 | } |
91 | openlog(applet_name, 0, LOG_AUTH); |
92 | } |
93 | |
94 | pw = xgetpwnam(opt_username); |
95 | |
96 | if (cur_uid == 0 || ask_and_check_password(pw) > 0) { |
97 | if (ENABLE_FEATURE_SU_SYSLOG) |
98 | syslog(LOG_NOTICE, "%c %s %s:%s", |
99 | '+', tty, old_user, opt_username); |
100 | } else { |
101 | if (ENABLE_FEATURE_SU_SYSLOG) |
102 | syslog(LOG_NOTICE, "%c %s %s:%s", |
103 | '-', tty, old_user, opt_username); |
104 | bb_error_msg_and_die("incorrect password"); |
105 | } |
106 | |
107 | if (ENABLE_FEATURE_CLEAN_UP && ENABLE_FEATURE_SU_SYSLOG) { |
108 | closelog(); |
109 | } |
110 | |
111 | if (!opt_shell && (flags & SU_OPT_mp)) { |
112 | /* -s SHELL is not given, but "preserve env" opt is */ |
113 | opt_shell = getenv("SHELL"); |
114 | } |
115 | |
116 | #if ENABLE_FEATURE_SU_CHECKS_SHELLS |
117 | if (opt_shell && cur_uid != 0 && pw->pw_shell && restricted_shell(pw->pw_shell)) { |
118 | /* The user being su'd to has a nonstandard shell, and so is |
119 | * probably a uucp account or has restricted access. Don't |
120 | * compromise the account by allowing access with a standard |
121 | * shell. */ |
122 | bb_error_msg("using restricted shell"); |
123 | opt_shell = NULL; /* ignore -s PROG */ |
124 | } |
125 | /* else: user can run whatever he wants via "su -s PROG USER". |
126 | * This is safe since PROG is run under user's uid/gid. */ |
127 | #endif |
128 | if (!opt_shell) |
129 | opt_shell = pw->pw_shell; |
130 | |
131 | change_identity(pw); |
132 | setup_environment(opt_shell, |
133 | ((flags & SU_OPT_l) / SU_OPT_l * SETUP_ENV_CLEARENV) |
134 | + (!(flags & SU_OPT_mp) * SETUP_ENV_CHANGEENV) |
135 | + (!(flags & SU_OPT_l) * SETUP_ENV_NO_CHDIR), |
136 | pw); |
137 | IF_SELINUX(set_current_security_context(NULL);) |
138 | |
139 | /* Never returns */ |
140 | run_shell(opt_shell, flags & SU_OPT_l, opt_command, (const char**)argv); |
141 | |
142 | /* return EXIT_FAILURE; - not reached */ |
143 | } |
144 |