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