source: branches/3.0/mindi-busybox/loginutils/su.c @ 2899

Last change on this file since 2899 was 2725, checked in by bruno, 8 years ago
  • Update mindi-busybox to 1.18.3 to avoid problems with the tar command which is now failing on recent versions with busybox 1.7.3
File size: 3.5 KB
Line 
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#if ENABLE_FEATURE_SU_CHECKS_SHELLS
12/* Return 1 if SHELL is a restricted shell (one not returned by
13 * getusershell), else 0, meaning it is a standard shell.  */
14static int restricted_shell(const char *shell)
15{
16    char *line;
17    int result = 1;
18
19    /*setusershell(); - getusershell does it itself*/
20    while ((line = getusershell()) != NULL) {
21        if (/* *line != '#' && */ strcmp(line, shell) == 0) {
22            result = 0;
23            break;
24        }
25    }
26    if (ENABLE_FEATURE_CLEAN_UP)
27        endusershell();
28    return result;
29}
30#endif
31
32#define SU_OPT_mp (3)
33#define SU_OPT_l  (4)
34
35int su_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
36int su_main(int argc UNUSED_PARAM, char **argv)
37{
38    unsigned flags;
39    char *opt_shell = NULL;
40    char *opt_command = NULL;
41    const char *opt_username = "root";
42    struct passwd *pw;
43    uid_t cur_uid = getuid();
44    const char *tty;
45    char user_buf[64];
46    const char *old_user;
47
48    flags = getopt32(argv, "mplc:s:", &opt_command, &opt_shell);
49    //argc -= optind;
50    argv += optind;
51
52    if (argv[0] && LONE_DASH(argv[0])) {
53        flags |= SU_OPT_l;
54        argv++;
55    }
56
57    /* get user if specified */
58    if (argv[0]) {
59        opt_username = argv[0];
60        argv++;
61    }
62
63    if (ENABLE_FEATURE_SU_SYSLOG) {
64        /* The utmp entry (via getlogin) is probably the best way to
65         * identify the user, especially if someone su's from a su-shell.
66         * But getlogin can fail -- usually due to lack of utmp entry.
67         * in this case resort to getpwuid.  */
68#if ENABLE_FEATURE_UTMP
69        old_user = user_buf;
70        if (getlogin_r(user_buf, sizeof(user_buf)) != 0)
71#endif
72        {
73            pw = getpwuid(cur_uid);
74            old_user = pw ? xstrdup(pw->pw_name) : "";
75        }
76        tty = xmalloc_ttyname(2);
77        if (!tty) {
78            tty = "none";
79        }
80        openlog(applet_name, 0, LOG_AUTH);
81    }
82
83    pw = xgetpwnam(opt_username);
84
85    if (cur_uid == 0 || correct_password(pw)) {
86        if (ENABLE_FEATURE_SU_SYSLOG)
87            syslog(LOG_NOTICE, "%c %s %s:%s",
88                '+', tty, old_user, opt_username);
89    } else {
90        if (ENABLE_FEATURE_SU_SYSLOG)
91            syslog(LOG_NOTICE, "%c %s %s:%s",
92                '-', tty, old_user, opt_username);
93        bb_error_msg_and_die("incorrect password");
94    }
95
96    if (ENABLE_FEATURE_CLEAN_UP && ENABLE_FEATURE_SU_SYSLOG) {
97        closelog();
98    }
99
100    if (!opt_shell && (flags & SU_OPT_mp)) {
101        /* -s SHELL is not given, but "preserve env" opt is */
102        opt_shell = getenv("SHELL");
103    }
104
105    /* Make sure pw->pw_shell is non-NULL.  It may be NULL when NEW_USER
106     * is a username that is retrieved via NIS (YP), that doesn't have
107     * a default shell listed.  */
108    if (!pw->pw_shell || !pw->pw_shell[0])
109        pw->pw_shell = (char *)DEFAULT_SHELL;
110
111#if ENABLE_FEATURE_SU_CHECKS_SHELLS
112    if (opt_shell && cur_uid != 0 && restricted_shell(pw->pw_shell)) {
113        /* The user being su'd to has a nonstandard shell, and so is
114         * probably a uucp account or has restricted access.  Don't
115         * compromise the account by allowing access with a standard
116         * shell.  */
117        bb_error_msg("using restricted shell");
118        opt_shell = NULL;
119    }
120    /* else: user can run whatever he wants via "su -s PROG USER".
121     * This is safe since PROG is run under user's uid/gid. */
122#endif
123    if (!opt_shell)
124        opt_shell = pw->pw_shell;
125
126    change_identity(pw);
127    setup_environment(opt_shell,
128            ((flags & SU_OPT_l) / SU_OPT_l * SETUP_ENV_CLEARENV)
129            + (!(flags & SU_OPT_mp) * SETUP_ENV_CHANGEENV),
130            pw);
131    IF_SELINUX(set_current_security_context(NULL);)
132
133    /* Never returns */
134    run_shell(opt_shell, flags & SU_OPT_l, opt_command, (const char**)argv);
135
136    /* return EXIT_FAILURE; - not reached */
137}
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