1 | /*
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2 | * add-shell and remove-shell implementation for busybox
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3 | *
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4 | * Copyright (C) 2010 Nokia Corporation. All rights reserved.
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5 | * Written by Alexander Shishkin <virtuoso@slind.org>
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6 | *
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7 | * Licensed under GPLv2 or later, see the LICENSE file in this source tree
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8 | * for details.
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9 | */
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10 |
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11 | //applet:IF_ADD_SHELL( APPLET_ODDNAME(add-shell , add_remove_shell, BB_DIR_USR_SBIN, BB_SUID_DROP, add_shell ))
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12 | //applet:IF_REMOVE_SHELL(APPLET_ODDNAME(remove-shell, add_remove_shell, BB_DIR_USR_SBIN, BB_SUID_DROP, remove_shell))
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13 |
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14 | //kbuild:lib-$(CONFIG_ADD_SHELL) += add-remove-shell.o
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15 | //kbuild:lib-$(CONFIG_REMOVE_SHELL) += add-remove-shell.o
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16 |
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17 | //config:config ADD_SHELL
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18 | //config: bool "add-shell"
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19 | //config: default y if DESKTOP
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20 | //config: help
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21 | //config: Add shells to /etc/shells.
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22 | //config:
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23 | //config:config REMOVE_SHELL
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24 | //config: bool "remove-shell"
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25 | //config: default y if DESKTOP
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26 | //config: help
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27 | //config: Remove shells from /etc/shells.
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28 |
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29 | //usage:#define add_shell_trivial_usage
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30 | //usage: "SHELL..."
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31 | //usage:#define add_shell_full_usage "\n\n"
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32 | //usage: "Add SHELLs to /etc/shells"
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33 |
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34 | //usage:#define remove_shell_trivial_usage
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35 | //usage: "SHELL..."
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36 | //usage:#define remove_shell_full_usage "\n\n"
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37 | //usage: "Remove SHELLs from /etc/shells"
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38 |
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39 | #include "libbb.h"
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40 |
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41 | #define SHELLS_FILE "/etc/shells"
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42 |
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43 | #define REMOVE_SHELL (ENABLE_REMOVE_SHELL && (!ENABLE_ADD_SHELL || applet_name[0] == 'r'))
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44 | #define ADD_SHELL (ENABLE_ADD_SHELL && (!ENABLE_REMOVE_SHELL || applet_name[0] == 'a'))
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45 |
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46 | /* NB: we use the _address_, not the value, of this string
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47 | * as a "special value of pointer" in the code.
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48 | */
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49 | static const char dont_add[] ALIGN1 = "\n";
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50 |
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51 | int add_remove_shell_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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52 | int add_remove_shell_main(int argc UNUSED_PARAM, char **argv)
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53 | {
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54 | FILE *orig_fp;
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55 | char *orig_fn;
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56 | char *new_fn;
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57 |
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58 | argv++;
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59 |
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60 | orig_fn = xmalloc_follow_symlinks(SHELLS_FILE);
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61 | if (!orig_fn)
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62 | return EXIT_FAILURE;
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63 | orig_fp = fopen_for_read(orig_fn);
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64 |
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65 | new_fn = xasprintf("%s.tmp", orig_fn);
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66 | /*
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67 | * O_TRUNC or O_EXCL? At the first glance, O_EXCL looks better,
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68 | * since it prevents races. But: (1) it requires a retry loop,
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69 | * (2) if /etc/shells.tmp is *stale*, then retry loop
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70 | * with O_EXCL will never succeed - it should have a timeout,
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71 | * after which it should revert to O_TRUNC.
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72 | * For now, I settle for O_TRUNC instead.
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73 | */
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74 | xmove_fd(xopen(new_fn, O_WRONLY | O_CREAT | O_TRUNC), STDOUT_FILENO);
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75 |
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76 | /* TODO:
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77 | struct stat sb;
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78 | xfstat(fileno(orig_fp), &sb);
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79 | xfchown(STDOUT_FILENO, sb.st_uid, sb.st_gid);
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80 | xfchmod(STDOUT_FILENO, sb.st_mode);
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81 | */
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82 |
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83 | if (orig_fp) {
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84 | /* Copy old file, possibly skipping removed shell names */
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85 | char *line;
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86 | while ((line = xmalloc_fgetline(orig_fp)) != NULL) {
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87 | char **cpp = argv;
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88 | while (*cpp) {
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89 | if (strcmp(*cpp, line) == 0) {
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90 | /* Old file has this shell name */
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91 | if (REMOVE_SHELL) {
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92 | /* we are remove-shell */
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93 | /* delete this name by not copying it */
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94 | goto next_line;
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95 | }
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96 | /* we are add-shell */
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97 | /* mark this name as "do not add" */
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98 | *cpp = (char*)dont_add;
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99 | }
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100 | cpp++;
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101 | }
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102 | /* copy shell name from old to new file */
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103 | printf("%s\n", line);
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104 | next_line:
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105 | free(line);
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106 | }
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107 | if (ENABLE_FEATURE_CLEAN_UP)
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108 | fclose(orig_fp);
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109 | }
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110 |
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111 | if (ADD_SHELL) {
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112 | char **cpp = argv;
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113 | while (*cpp) {
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114 | if (*cpp != dont_add)
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115 | printf("%s\n", *cpp);
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116 | cpp++;
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117 | }
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118 | }
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119 |
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120 | /* Ensure we wrote out everything */
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121 | if (fclose(stdout) != 0) {
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122 | xunlink(new_fn);
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123 | bb_perror_msg_and_die("%s: write error", new_fn);
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124 | }
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125 |
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126 | /* Small hole: if rename fails, /etc/shells.tmp is not removed */
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127 | xrename(new_fn, orig_fn);
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128 |
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129 | if (ENABLE_FEATURE_CLEAN_UP) {
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130 | free(orig_fn);
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131 | free(new_fn);
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132 | }
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133 |
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134 | return EXIT_SUCCESS;
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135 | }
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