/**
* slibc — Yet another C library
* Copyright © 2015 Mattias Andrée (maandree@member.fsf.org)
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <slib-human.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <sys/stat.h>
/**
* Parses a human representation of file permissions, and updates to file permissions.
*
* Assuming the current file permissions is `value`, and neither
* `mode` nor `mask` is `NULL`, the new permissions should be
* `value & ~*mask | *mode`. The new mode (includes file type) should
* be `value & ~*mask | *mode & 07777`.
*
* @param mode Output parameter for the bits to set, may be `NULL`.
* @param mask Output parameter for the bits to update, may be `NULL`.
* @param str The file permission to parse, must not include file type or be `NULL`.
* @return Zero on success, -1 on error.
*
* @throws EINVAL If `str` is not parseable.
*/
int machinemode(mode_t* restrict mode, mode_t* restrict mask, const char* restrict str)
{
#define S_ISUSR (S_ISUID | S_IXUSR)
#define S_ISGRP (S_ISGID | S_IXGRO)
#define S_ISOTH (S_ISVTX | S_IXOTH)
#define TEST_(S, T, V) (strstarts(str, S) && !(T & (v = V)))
#define TEST(S, T) (TEST_(S"+", T, 1) || TEST_(S"-", T, 2) || TEST_(S"=", T, 3))
#define TESTV(T) (TEST(#T, T) ? (T = v) : 0)
#define BITS_(V, T, S) if (V & bits[i][T]) goto invalid; else var |= bits[i][S]
#define BITS(V) \
if (*str == 'r') { BITS_(V, 0, 0); } \
else if (*str == 'w') { BITS_(V, 1, 1); } \
else if (*str == 'x') { BITS_(V, 3, 2); } \
else if (*str == 's') { BITS_(V, 3, 3); } \
else if (*str == 't') { BITS_(V, 3, 3); } \
else if (*str == 'S') { BITS_(V, 3, 4); } \
else if (*str == 'T') { BITS_(V, 3, 4); } \
else if (*str != '-') goto invalid
int i, j, n, u = 0, g = 0, o = 0, v;
char s;
mode_t or = 0, andn = 0, part;
mode_t bits[][] = {
{S_IRUSR, S_IWUSR, S_IXUSR, S_ISUSR, S_ISUID},
{S_IRGRP, S_IWGRP, S_IXGRP, S_ISGRP, S_ISGID},
{S_IROTH, S_IWOTH, S_IXOTH, S_ISOTH, S_ISVTX},
};
switch (*str)
{
case '\0':
goto invalid;
case 'a': case 'u': case 'g': case 'o':
/* Partial, symbolic. */
for (; *str; str++)
{
if (TEST("a", u|g|o)) i = 3, u |= v, g |= v, o |= v;
else if (TESTV(u)) i = 0;
else if (TESTV(g)) i = 1;
else if (TESTV(o)) i = 2;
else
goto invalid;
if (n < 3) n = i + 1;
else n = i, i = 0;
s = str[1], str += 2;
for (part = 0; *str && (*str != ','); str++)
for (j = i; j < n; j++)
BITS(part);
if (s != '-') or |= part;
if (s != '=') andn |= part;
else
for (j = i; j < n; j++)
andn |= bits[i][0] | bits[i][1] | bits[i][3];
}
break;
case 'r': case 'w': case 'x': case '-':
case 's': case 'S': case 't': case 'T':
/* Exact, symbolic. */
for (andn = 07777, i = 0; i < 3; i++)
for (j = 0; j < 3; j++, str++)
BITS(or);
break;
default:
/* Exact, numeric. */
for (andn = 07777; (s = *str); str++)
if (('0' > s) || (s > '7') || (or = (or << 3) | (s & 15), or > 07777))
goto invalid;
break;
}
if (mode) *mode = or;
if (mask) *mask = andn;
return 0;
invalid:
return errno = EINVAL, -1;
}
