1 | /* vi: set sw=4 ts=4: */
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2 | /*
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3 | * parse_mode implementation for busybox
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4 | *
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5 | * Copyright (C) 2003 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 | /* http://www.opengroup.org/onlinepubs/007904975/utilities/chmod.html */
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11 |
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12 | #include "libbb.h"
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13 |
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14 | /* This function is used from NOFORK applets. It must not allocate anything */
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15 |
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16 | #define FILEMODEBITS (S_ISUID | S_ISGID | S_ISVTX | S_IRWXU | S_IRWXG | S_IRWXO)
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17 |
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18 | int FAST_FUNC bb_parse_mode(const char *s, mode_t *current_mode)
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19 | {
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20 | static const mode_t who_mask[] = {
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21 | S_ISUID | S_ISGID | S_ISVTX | S_IRWXU | S_IRWXG | S_IRWXO, /* a */
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22 | S_ISUID | S_IRWXU, /* u */
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23 | S_ISGID | S_IRWXG, /* g */
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24 | S_IRWXO /* o */
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25 | };
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26 | static const mode_t perm_mask[] = {
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27 | S_IRUSR | S_IRGRP | S_IROTH, /* r */
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28 | S_IWUSR | S_IWGRP | S_IWOTH, /* w */
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29 | S_IXUSR | S_IXGRP | S_IXOTH, /* x */
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30 | S_IXUSR | S_IXGRP | S_IXOTH, /* X -- special -- see below */
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31 | S_ISUID | S_ISGID, /* s */
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32 | S_ISVTX /* t */
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33 | };
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34 | static const char who_chars[] ALIGN1 = "augo";
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35 | static const char perm_chars[] ALIGN1 = "rwxXst";
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36 |
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37 | const char *p;
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38 | mode_t wholist;
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39 | mode_t permlist;
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40 | mode_t new_mode;
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41 | char op;
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42 |
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43 | if ((unsigned char)(*s - '0') < 8) {
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44 | unsigned long tmp;
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45 | char *e;
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46 |
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47 | tmp = strtoul(s, &e, 8);
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48 | if (*e || (tmp > 07777U)) { /* Check range and trailing chars. */
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49 | return 0;
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50 | }
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51 | *current_mode = tmp;
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52 | return 1;
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53 | }
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54 |
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55 | new_mode = *current_mode;
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56 |
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57 | /* Note: we allow empty clauses, and hence empty modes.
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58 | * We treat an empty mode as no change to perms. */
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59 |
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60 | while (*s) { /* Process clauses. */
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61 | if (*s == ',') { /* We allow empty clauses. */
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62 | ++s;
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63 | continue;
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64 | }
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65 |
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66 | /* Get a wholist. */
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67 | wholist = 0;
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68 | WHO_LIST:
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69 | p = who_chars;
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70 | do {
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71 | if (*p == *s) {
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72 | wholist |= who_mask[(int)(p-who_chars)];
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73 | if (!*++s) {
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74 | return 0;
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75 | }
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76 | goto WHO_LIST;
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77 | }
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78 | } while (*++p);
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79 |
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80 | do { /* Process action list. */
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81 | if ((*s != '+') && (*s != '-')) {
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82 | if (*s != '=') {
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83 | return 0;
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84 | }
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85 | /* Since op is '=', clear all bits corresponding to the
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86 | * wholist, or all file bits if wholist is empty. */
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87 | permlist = ~FILEMODEBITS;
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88 | if (wholist) {
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89 | permlist = ~wholist;
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90 | }
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91 | new_mode &= permlist;
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92 | }
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93 | op = *s++;
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94 |
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95 | /* Check for permcopy. */
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96 | p = who_chars + 1; /* Skip 'a' entry. */
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97 | do {
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98 | if (*p == *s) {
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99 | int i = 0;
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100 | permlist = who_mask[(int)(p-who_chars)]
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101 | & (S_IRWXU | S_IRWXG | S_IRWXO)
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102 | & new_mode;
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103 | do {
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104 | if (permlist & perm_mask[i]) {
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105 | permlist |= perm_mask[i];
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106 | }
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107 | } while (++i < 3);
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108 | ++s;
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109 | goto GOT_ACTION;
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110 | }
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111 | } while (*++p);
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112 |
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113 | /* It was not a permcopy, so get a permlist. */
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114 | permlist = 0;
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115 | PERM_LIST:
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116 | p = perm_chars;
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117 | do {
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118 | if (*p == *s) {
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119 | if ((*p != 'X')
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120 | || (new_mode & (S_IFDIR | S_IXUSR | S_IXGRP | S_IXOTH))
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121 | ) {
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122 | permlist |= perm_mask[(int)(p-perm_chars)];
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123 | }
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124 | if (!*++s) {
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125 | break;
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126 | }
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127 | goto PERM_LIST;
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128 | }
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129 | } while (*++p);
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130 | GOT_ACTION:
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131 | if (permlist) { /* The permlist was nonempty. */
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132 | mode_t tmp = wholist;
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133 | if (!wholist) {
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134 | mode_t u_mask = umask(0);
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135 | umask(u_mask);
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136 | tmp = ~u_mask;
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137 | }
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138 | permlist &= tmp;
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139 | if (op == '-') {
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140 | new_mode &= ~permlist;
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141 | } else {
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142 | new_mode |= permlist;
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143 | }
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144 | }
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145 | } while (*s && (*s != ','));
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146 | }
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147 |
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148 | *current_mode = new_mode;
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149 | return 1;
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150 | }
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