1 | /* vi: set sw=4 ts=4: */
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2 | /*
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3 | * mesg implementation for busybox
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4 | *
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5 | * Copyright (c) 2002 Manuel Novoa III <mjn3@codepoet.org>
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6 | *
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7 | * Licensed under GPLv2 or later, see file LICENSE in this source tree.
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8 | */
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9 |
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10 | //config:config MESG
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11 | //config: bool "mesg"
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12 | //config: default y
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13 | //config: help
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14 | //config: Mesg controls access to your terminal by others. It is typically
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15 | //config: used to allow or disallow other users to write to your terminal
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16 | //config:
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17 | //config:config FEATURE_MESG_ENABLE_ONLY_GROUP
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18 | //config: bool "Enable writing to tty only by group, not by everybody"
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19 | //config: default y
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20 | //config: depends on MESG
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21 | //config: help
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22 | //config: Usually, ttys are owned by group "tty", and "write" tool is
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23 | //config: setgid to this group. This way, "mesg y" only needs to enable
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24 | //config: "write by owning group" bit in tty mode.
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25 | //config:
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26 | //config: If you set this option to N, "mesg y" will enable writing
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27 | //config: by anybody at all. This is not recommended.
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28 |
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29 | //applet:IF_MESG(APPLET(mesg, BB_DIR_USR_BIN, BB_SUID_DROP))
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30 |
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31 | //kbuild:lib-$(CONFIG_MESG) += mesg.o
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32 |
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33 | //usage:#define mesg_trivial_usage
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34 | //usage: "[y|n]"
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35 | //usage:#define mesg_full_usage "\n\n"
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36 | //usage: "Control write access to your terminal\n"
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37 | //usage: " y Allow write access to your terminal\n"
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38 | //usage: " n Disallow write access to your terminal"
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39 |
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40 | #include "libbb.h"
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41 |
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42 | #if ENABLE_FEATURE_MESG_ENABLE_ONLY_GROUP
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43 | #define S_IWGRP_OR_S_IWOTH S_IWGRP
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44 | #else
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45 | #define S_IWGRP_OR_S_IWOTH (S_IWGRP | S_IWOTH)
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46 | #endif
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47 |
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48 | int mesg_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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49 | int mesg_main(int argc UNUSED_PARAM, char **argv)
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50 | {
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51 | struct stat sb;
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52 | mode_t m;
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53 | char c = 0;
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54 |
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55 | argv++;
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56 |
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57 | if (argv[0]
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58 | && (argv[1] || ((c = argv[0][0]) != 'y' && c != 'n'))
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59 | ) {
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60 | bb_show_usage();
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61 | }
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62 |
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63 | if (!isatty(STDIN_FILENO))
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64 | bb_error_msg_and_die("not a tty");
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65 |
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66 | xfstat(STDIN_FILENO, &sb, "stderr");
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67 | if (c == 0) {
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68 | puts((sb.st_mode & (S_IWGRP|S_IWOTH)) ? "is y" : "is n");
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69 | return EXIT_SUCCESS;
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70 | }
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71 | m = (c == 'y') ? sb.st_mode | S_IWGRP_OR_S_IWOTH
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72 | : sb.st_mode & ~(S_IWGRP|S_IWOTH);
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73 | if (fchmod(STDIN_FILENO, m) != 0)
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74 | bb_perror_nomsg_and_die();
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75 | return EXIT_SUCCESS;
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76 | }
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