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 source tree.
   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, unsigned 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 char)(*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 -1;
  50                 }
  51                 return tmp;
  52         }
  53
  54         new_mode = current_mode;
  55
  56         /* Note: we allow empty clauses, and hence empty modes.
  57          * We treat an empty mode as no change to perms. */
  58
  59         while (*s) {  /* Process clauses. */
  60                 if (*s == ',') {  /* We allow empty clauses. */
  61                         ++s;
  62                         continue;
  63                 }
  64
  65                 /* Get a wholist. */
  66                 wholist = 0;
  67  WHO_LIST:
  68                 p = who_chars;
  69                 do {
  70                         if (*p == *s) {
  71                                 wholist |= who_mask[(int)(p-who_chars)];
  72                                 if (!*++s) {
  73                                         return -1;
  74                                 }
  75                                 goto WHO_LIST;
  76                         }
  77                 } while (*++p);
  78
  79                 do {    /* Process action list. */
  80                         if ((*s != '+') && (*s != '-')) {
  81                                 if (*s != '=') {
  82                                         return -1;
  83                                 }
  84                                 /* Since op is '=', clear all bits corresponding to the
  85                                  * wholist, or all file bits if wholist is empty. */
  86                                 permlist = ~FILEMODEBITS;
  87                                 if (wholist) {
  88                                         permlist = ~wholist;
  89                                 }
  90                                 new_mode &= permlist;
  91                         }
  92                         op = *s++;
  93
  94                         /* Check for permcopy. */
  95                         p = who_chars + 1;  /* Skip 'a' entry. */
  96                         do {
  97                                 if (*p == *s) {
  98                                         int i = 0;
  99                                         permlist = who_mask[(int)(p-who_chars)]
 100                                                          & (S_IRWXU | S_IRWXG | S_IRWXO)
 101                                                          & new_mode;
 102                                         do {
 103                                                 if (permlist & perm_mask[i]) {
 104                                                         permlist |= perm_mask[i];
 105                                                 }
 106                                         } while (++i < 3);
 107                                         ++s;
 108                                         goto GOT_ACTION;
 109                                 }
 110                         } while (*++p);
 111
 112                         /* It was not a permcopy, so get a permlist. */
 113                         permlist = 0;
 114  PERM_LIST:
 115                         p = perm_chars;
 116                         do {
 117                                 if (*p == *s) {
 118                                         if ((*p != 'X')
 119                                          || (new_mode & (S_IFDIR | S_IXUSR | S_IXGRP | S_IXOTH))
 120                                         ) {
 121                                                 permlist |= perm_mask[(int)(p-perm_chars)];
 122                                         }
 123                                         if (!*++s) {
 124                                                 break;
 125                                         }
 126                                         goto PERM_LIST;
 127                                 }
 128                         } while (*++p);
 129  GOT_ACTION:
 130                         if (permlist) { /* The permlist was nonempty. */
 131                                 mode_t tmp = wholist;
 132                                 if (!wholist) {
 133                                         mode_t u_mask = umask(0);
 134                                         umask(u_mask);
 135                                         tmp = ~u_mask;
 136                                 }
 137                                 permlist &= tmp;
 138                                 if (op == '-') {
 139                                         new_mode &= ~permlist;
 140                                 } else {
 141                                         new_mode |= permlist;
 142                                 }
 143                         }
 144                 } while (*s && (*s != ','));
 145         }
 146
 147         return new_mode;
 148 }