libbb/parse_mode.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * parse_mode implementation for busybox
   4  *
   5  * Copyright (C) 2003  Manuel Novoa III  <mjn3@codepoet.org>
   6  *
   7  * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
   8  */
   9
  10 /* http://www.opengroup.org/onlinepubs/007904975/utilities/chmod.html */
  11
  12 #include "libbb.h"
  13
  14 /* This function is used from NOFORK applets. It must not allocate anything */
  15
  16 #define FILEMODEBITS (S_ISUID | S_ISGID | S_ISVTX | S_IRWXU | S_IRWXG | S_IRWXO)
  17
  18 int FAST_FUNC bb_parse_mode(const char *s, mode_t *current_mode)
  19 {
  20         static const mode_t who_mask[] = {
  21                 S_ISUID | S_ISGID | S_ISVTX | S_IRWXU | S_IRWXG | S_IRWXO, /* a */
  22                 S_ISUID | S_IRWXU,           /* u */
  23                 S_ISGID | S_IRWXG,           /* g */
  24                 S_IRWXO                      /* o */
  25         };
  26         static const mode_t perm_mask[] = {
  27                 S_IRUSR | S_IRGRP | S_IROTH, /* r */
  28                 S_IWUSR | S_IWGRP | S_IWOTH, /* w */
  29                 S_IXUSR | S_IXGRP | S_IXOTH, /* x */
  30                 S_IXUSR | S_IXGRP | S_IXOTH, /* X -- special -- see below */
  31                 S_ISUID | S_ISGID,           /* s */
  32                 S_ISVTX                      /* t */
  33         };
  34         static const char who_chars[] ALIGN1 = "augo";
  35         static const char perm_chars[] ALIGN1 = "rwxXst";
  36
  37         const char *p;
  38         mode_t wholist;
  39         mode_t permlist;
  40         mode_t new_mode;
  41         char op;
  42
  43         if (((unsigned int)(*s - '0')) < 8) {
  44                 unsigned long tmp;
  45                 char *e;
  46
  47                 tmp = strtoul(s, &e, 8);
  48                 if (*e || (tmp > 07777U)) { /* Check range and trailing chars. */
  49                         return 0;
  50                 }
  51                 *current_mode = tmp;
  52                 return 1;
  53         }
  54
  55         new_mode = *current_mode;
  56
  57         /* Note: we allow empty clauses, and hence empty modes.
  58          * We treat an empty mode as no change to perms. */
  59
  60         while (*s) {    /* Process clauses. */
  61                 if (*s == ',') {        /* We allow empty clauses. */
  62                         ++s;
  63                         continue;
  64                 }
  65
  66                 /* Get a wholist. */
  67                 wholist = 0;
  68  WHO_LIST:
  69                 p = who_chars;
  70                 do {
  71                         if (*p == *s) {
  72                                 wholist |= who_mask[(int)(p-who_chars)];
  73                                 if (!*++s) {
  74                                         return 0;
  75                                 }
  76                                 goto WHO_LIST;
  77                         }
  78                 } while (*++p);
  79
  80                 do {    /* Process action list. */
  81                         if ((*s != '+') && (*s != '-')) {
  82                                 if (*s != '=') {
  83                                         return 0;
  84                                 }
  85                                 /* Since op is '=', clear all bits corresponding to the
  86                                  * wholist, or all file bits if wholist is empty. */
  87                                 permlist = ~FILEMODEBITS;
  88                                 if (wholist) {
  89                                         permlist = ~wholist;
  90                                 }
  91                                 new_mode &= permlist;
  92                         }
  93                         op = *s++;
  94
  95                         /* Check for permcopy. */
  96                         p = who_chars + 1;      /* Skip 'a' entry. */
  97                         do {
  98                                 if (*p == *s) {
  99                                         int i = 0;
 100                                         permlist = who_mask[(int)(p-who_chars)]
 101                                                          & (S_IRWXU | S_IRWXG | S_IRWXO)
 102                                                          & new_mode;
 103                                         do {
 104                                                 if (permlist & perm_mask[i]) {
 105                                                         permlist |= perm_mask[i];
 106                                                 }
 107                                         } while (++i < 3);
 108                                         ++s;
 109                                         goto GOT_ACTION;
 110                                 }
 111                         } while (*++p);
 112
 113                         /* It was not a permcopy, so get a permlist. */
 114                         permlist = 0;
 115  PERM_LIST:
 116                         p = perm_chars;
 117                         do {
 118                                 if (*p == *s) {
 119                                         if ((*p != 'X')
 120                                          || (new_mode & (S_IFDIR | S_IXUSR | S_IXGRP | S_IXOTH))
 121                                         ) {
 122                                                 permlist |= perm_mask[(int)(p-perm_chars)];
 123                                         }
 124                                         if (!*++s) {
 125                                                 break;
 126                                         }
 127                                         goto PERM_LIST;
 128                                 }
 129                         } while (*++p);
 130  GOT_ACTION:
 131                         if (permlist) { /* The permlist was nonempty. */
 132                                 mode_t tmp = wholist;
 133                                 if (!wholist) {
 134                                         mode_t u_mask = umask(0);
 135                                         umask(u_mask);
 136                                         tmp = ~u_mask;
 137                                 }
 138                                 permlist &= tmp;
 139                                 if (op == '-') {
 140                                         new_mode &= ~permlist;
 141                                 } else {
 142                                         new_mode |= permlist;
 143                                 }
 144                         }
 145                 } while (*s && (*s != ','));
 146         }
 147
 148         *current_mode = new_mode;
 149         return 1;
 150 }