/**
* 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 <slibc-human.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <sys/stat.h>
/**
* Owner can execute/list or/and set UID.
*/
#define S_ISUSR (S_ISUID | S_IXUSR)
/**
* Group can execute/list or/and set GID.
*/
#define S_ISGRP (S_ISGID | S_IXGRP)
/**
* Others (not in group) can execute/list or/and sticky bit.
*/
#define S_ISOTH (S_ISVTX | S_IXOTH)
/**
* Store permission bits.
*
* @param V:mode_t The variables for the permissions.
* @param U:int type First-level index in `bits` for the user.
* @param T:int type Second-level index in `bits` for bits to verify are unset.
* @param S:int type Second-level index in `bits` for bits to set.
*/
#define BITS_(V, U, T, S) if ((V) & bits[U][T]) goto invalid; else V |= bits[U][S]
/**
* Store permission bits.
*
* @param S:char Character representing the bits to set.
* @param V:mode_t The variables for the permissions.
* @param U:int type First-level index in `bits` for the user.
*/
#define BITS(S, V, U) \
if ((S) == 'r') { BITS_(V, U, 0, 0); } \
else if ((S) == 'w') { BITS_(V, U, 1, 1); } \
else if ((S) == 'x') { BITS_(V, U, 3, 2); } \
else if ((S) == 's') { BITS_(V, U, 3, 3); } \
else if ((S) == 't') { BITS_(V, U, 3, 3); } \
else if ((S) == 'S') { BITS_(V, U, 3, 4); } \
else if ((S) == 'T') { BITS_(V, U, 3, 4); } \
else if ((S) != '-') goto invalid
/**
* User {0=owner. 1=group, 2=others} to permissions {0=can read,
* 1=can write, 2=can execute/list, 3=can execute/list or/and
* special, 4=special} to permissions bits map.
*/
static mode_t bits[][5] = {
{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},
};
/**
* Parse a symbolic file permission string with partial update.
*
* @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.
*/
static inline int partial_symbolic(mode_t* restrict mode, mode_t* restrict mask, const char* restrict str)
{
#define TEST_(S, T, V) (strstarts(str, S) && !((T) & (symbols = (V))))
#define TEST(S, T) (TEST_(S"+", T, 1) || TEST_(S"-", T, 2) || TEST_(S"=", T, 3))
#define TESTV(T) (TEST(#T, T) ? (T |= symbols) : 0)
int u = 0, g = 0, o = 0, symbols, first, user, last;
mode_t or = 0, andn = 0, partial_or;
char symbol;
for (; *str; str++)
{
/* Check a/u/g/o and =/+/-. */
if (TEST("a", u|g|o)) first = 3, u |= symbols, g |= symbols, o |= symbols;
else if (TESTV(u)) first = 0;
else if (TESTV(g)) first = 1;
else if (TESTV(o)) first = 2;
else
goto invalid;
/* Get range of effected users. */
if (first < 3) last = first + 1;
else last = first, first = 0;
/* Get =/+/- and jump to permissions. */
symbol = str[1], str += 2;
/* Get permissions. */
for (partial_or = 0; *str && (*str != ','); str++)
for (user = first; user < last; user++)
BITS(*str, partial_or, user);
/* Apply permissions. */
if (symbol != '-') or |= partial_or;
if (symbol != '=') andn |= partial_or;
else
for (user = first; user < last; user++)
andn |= bits[user][0] | bits[user][1] | bits[user][3];
}
if (mode) *mode = or;
if (mask) *mask = andn;
return 0;
invalid:
return errno = EINVAL, -1;
}
/**
* Parse a full symbolic file permission string.
*
* @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.
*/
static inline int exact_symbolic(mode_t* restrict mode, mode_t* restrict mask, const char* restrict str)
{
mode_t or = 0;
long int user, perm;
for (user = 0; user < 3; user++)
for (perm = 0; perm < 3; perm++, str++)
BITS(*str, or, user);
if (mode) *mode = or;
if (mask) *mask = 07777;
return 0;
invalid:
return errno = EINVAL, -1;
}
/**
* Parse a numeric file permission string.
*
* @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.
*/
static inline int exact_numeric(mode_t* restrict mode, mode_t* restrict mask, const char* restrict str)
{
mode_t or = 0;
char s;
for (; (s = *str); str++)
if (('0' > s) || (s > '7') || (or = (or << 3) | (s & 15), or > 07777))
return errno = EINVAL, -1;
if (mode) *mode = or;
if (mask) *mask = 07777;
return 0;
}
/**
* 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.
*
* @since Always.
*/
int machinemode(mode_t* restrict mode, mode_t* restrict mask, const char* restrict str)
{
switch (*str)
{
case '\0':
return errno = EINVAL, -1;
case 'a': case 'u': case 'g': case 'o':
return partial_symbolic(mode, mask, str);
case 'r': case 'w': case 'x': case '-':
case 's': case 'S': case 't': case 'T':
return exact_symbolic(mode, mask, str);
default:
return exact_numeric(mode, mask, str);
}
}
