source: MondoRescue/branches/3.3/mindi-busybox/libbb/parse_mode.c@ 3670

/* vi: set sw=4 ts=4: */
/*
 * parse_mode implementation for busybox
 *
 * Copyright (C) 2003  Manuel Novoa III  <mjn3@codepoet.org>
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */

/* http://www.opengroup.org/onlinepubs/007904975/utilities/chmod.html */

#include "libbb.h"

/* This function is used from NOFORK applets. It must not allocate anything */

#define FILEMODEBITS (S_ISUID | S_ISGID | S_ISVTX | S_IRWXU | S_IRWXG | S_IRWXO)

int FAST_FUNC bb_parse_mode(const char *s, unsigned current_mode)
{
    static const mode_t who_mask[] = {
        S_ISUID | S_ISGID | S_ISVTX | S_IRWXU | S_IRWXG | S_IRWXO, /* a */
        S_ISUID | S_IRWXU,           /* u */
        S_ISGID | S_IRWXG,           /* g */
        S_IRWXO                      /* o */
    };
    static const mode_t perm_mask[] = {
        S_IRUSR | S_IRGRP | S_IROTH, /* r */
        S_IWUSR | S_IWGRP | S_IWOTH, /* w */
        S_IXUSR | S_IXGRP | S_IXOTH, /* x */
        S_IXUSR | S_IXGRP | S_IXOTH, /* X -- special -- see below */
        S_ISUID | S_ISGID,           /* s */
        S_ISVTX                      /* t */
    };
    static const char who_chars[] ALIGN1 = "augo";
    static const char perm_chars[] ALIGN1 = "rwxXst";

    const char *p;
    mode_t wholist;
    mode_t permlist;
    mode_t new_mode;
    char op;

    if ((unsigned char)(*s - '0') < 8) {
        unsigned long tmp;
        char *e;

        tmp = strtoul(s, &e, 8);
        if (*e || (tmp > 07777U)) { /* Check range and trailing chars. */
            return -1;
        }
        return tmp;
    }

    new_mode = current_mode;

    /* Note: we allow empty clauses, and hence empty modes.
     * We treat an empty mode as no change to perms. */

    while (*s) {  /* Process clauses. */
        if (*s == ',') {  /* We allow empty clauses. */
            ++s;
            continue;
        }

        /* Get a wholist. */
        wholist = 0;
 WHO_LIST:
        p = who_chars;
        do {
            if (*p == *s) {
                wholist |= who_mask[(int)(p-who_chars)];
                if (!*++s) {
                    return -1;
                }
                goto WHO_LIST;
            }
        } while (*++p);

        do {    /* Process action list. */
            if ((*s != '+') && (*s != '-')) {
                if (*s != '=') {
                    return -1;
                }
                /* Since op is '=', clear all bits corresponding to the
                 * wholist, or all file bits if wholist is empty. */
                permlist = ~FILEMODEBITS;
                if (wholist) {
                    permlist = ~wholist;
                }
                new_mode &= permlist;
            }
            op = *s++;

            /* Check for permcopy. */
            p = who_chars + 1;  /* Skip 'a' entry. */
            do {
                if (*p == *s) {
                    int i = 0;
                    permlist = who_mask[(int)(p-who_chars)]
                             & (S_IRWXU | S_IRWXG | S_IRWXO)
                             & new_mode;
                    do {
                        if (permlist & perm_mask[i]) {
                            permlist |= perm_mask[i];
                        }
                    } while (++i < 3);
                    ++s;
                    goto GOT_ACTION;
                }
            } while (*++p);

            /* It was not a permcopy, so get a permlist. */
            permlist = 0;
 PERM_LIST:
            p = perm_chars;
            do {
                if (*p == *s) {
                    if ((*p != 'X')
                     || (new_mode & (S_IFDIR | S_IXUSR | S_IXGRP | S_IXOTH))
                    ) {
                        permlist |= perm_mask[(int)(p-perm_chars)];
                    }
                    if (!*++s) {
                        break;
                    }
                    goto PERM_LIST;
                }
            } while (*++p);
 GOT_ACTION:
            if (permlist) { /* The permlist was nonempty. */
                mode_t tmp = wholist;
                if (!wholist) {
                    mode_t u_mask = umask(0);
                    umask(u_mask);
                    tmp = ~u_mask;
                }
                permlist &= tmp;
                if (op == '-') {
                    new_mode &= ~permlist;
                } else {
                    new_mode |= permlist;
                }
            }
        } while (*s && (*s != ','));
    }

    return new_mode;
}