LXR busybox/libbb/parse

   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
  18int 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 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 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}
 151