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/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/Format.h>
#include <AK/Optional.h>
#include <stdio.h>
#include <string.h>
#include <sys/stat.h>
#include <unistd.h>
/* the new mode will be computed using the boolean function(for each bit):
|current mode|removal mask|applying mask|result |
| 0 | 0 | 0 | 0 |
| 0 | 0 | 1 | 1 |
| 0 | 1 | 0 | 0 |
| 0 | 1 | 1 | 1 | ---> find the CNF --> find the minimal CNF
| 1 | 0 | 0 | 1 |
| 1 | 0 | 1 | 1 |
| 1 | 1 | 0 | 0 |
| 1 | 1 | 1 | 1 |
*/
class Mask {
private:
mode_t removal_mask; // the bits that will be removed
mode_t applying_mask; // the bits that will be set
public:
Mask()
: removal_mask(0)
, applying_mask(0)
{
}
Mask& operator|=(const Mask& other)
{
removal_mask |= other.removal_mask;
applying_mask |= other.applying_mask;
return *this;
}
mode_t& get_removal_mask() { return removal_mask; }
mode_t& get_applying_mask() { return applying_mask; }
};
Optional<Mask> string_to_mode(char access_scope, const char*& access_string);
Optional<Mask> apply_permission(char access_scope, char permission, char operation);
int main(int argc, char** argv)
{
if (pledge("stdio rpath fattr", nullptr) < 0) {
perror("pledge");
return 1;
}
if (argc < 3) {
warnln("usage: chmod <octal-mode> <path...>");
warnln(" chmod [[ugoa][+-=][rwx...],...] <path...>");
return 1;
}
Mask mask;
/* compute a mask */
if (argv[1][0] >= '0' && argv[1][0] <= '7') {
if (sscanf(argv[1], "%ho", &mask.get_applying_mask()) != 1) {
perror("sscanf");
return 1;
}
mask.get_removal_mask() = ~mask.get_applying_mask();
} else {
const char* access_string = argv[1];
while (*access_string != '\0') {
Optional<Mask> tmp_mask;
switch (*access_string) {
case 'u':
tmp_mask = string_to_mode('u', ++access_string);
break;
case 'g':
tmp_mask = string_to_mode('g', ++access_string);
break;
case 'o':
tmp_mask = string_to_mode('o', ++access_string);
break;
case 'a':
tmp_mask = string_to_mode('a', ++access_string);
break;
case '=':
case '+':
case '-':
tmp_mask = string_to_mode('a', access_string);
break;
case ',':
++access_string;
continue;
}
if (!tmp_mask.has_value()) {
warnln("chmod: invalid mode: {}", argv[1]);
return 1;
}
mask |= tmp_mask.value();
}
}
/* set the mask for each file's permissions */
struct stat current_access;
int i = 2;
while (i < argc) {
if (stat(argv[i], ¤t_access) != 0) {
perror("stat");
return 1;
}
/* found the minimal CNF by The Quine–McCluskey algorithm and use it */
mode_t mode = mask.get_applying_mask()
| (current_access.st_mode & ~mask.get_removal_mask());
if (chmod(argv[i++], mode) != 0) {
perror("chmod");
}
}
return 0;
}
Optional<Mask> string_to_mode(char access_scope, const char*& access_string)
{
char operation = *access_string;
if (operation != '+' && operation != '-' && operation != '=') {
return {};
}
Mask mask;
if (operation == '=') {
switch (access_scope) {
case 'u':
mask.get_removal_mask() = (S_IRUSR | S_IWUSR | S_IXUSR);
break;
case 'g':
mask.get_removal_mask() = (S_IRGRP | S_IWGRP | S_IXGRP);
break;
case 'o':
mask.get_removal_mask() = (S_IROTH | S_IWOTH | S_IXOTH);
break;
case 'a':
mask.get_removal_mask() = (S_IRUSR | S_IWUSR | S_IXUSR
| S_IRGRP | S_IWGRP | S_IXGRP
| S_IROTH | S_IWOTH | S_IXOTH);
break;
}
operation = '+';
}
access_string++;
while (*access_string != '\0' && *access_string != ',') {
Optional<Mask> tmp_mask;
tmp_mask = apply_permission(access_scope, *access_string, operation);
if (!tmp_mask.has_value()) {
return {};
}
mask |= tmp_mask.value();
access_string++;
}
return mask;
}
Optional<Mask> apply_permission(char access_scope, char permission, char operation)
{
if (permission != 'r' && permission != 'w' && permission != 'x') {
return {};
}
Mask mask;
mode_t tmp_mask = 0;
switch (access_scope) {
case 'u':
switch (permission) {
case 'r':
tmp_mask = S_IRUSR;
break;
case 'w':
tmp_mask = S_IWUSR;
break;
case 'x':
tmp_mask = S_IXUSR;
break;
}
break;
case 'g':
switch (permission) {
case 'r':
tmp_mask = S_IRGRP;
break;
case 'w':
tmp_mask = S_IWGRP;
break;
case 'x':
tmp_mask = S_IXGRP;
break;
}
break;
case 'o':
switch (permission) {
case 'r':
tmp_mask = S_IROTH;
break;
case 'w':
tmp_mask = S_IWOTH;
break;
case 'x':
tmp_mask = S_IXOTH;
break;
}
break;
case 'a':
mask |= apply_permission('u', permission, operation).value();
mask |= apply_permission('g', permission, operation).value();
mask |= apply_permission('o', permission, operation).value();
break;
}
if (operation == '+') {
mask.get_applying_mask() |= tmp_mask;
} else {
mask.get_removal_mask() |= tmp_mask;
}
return mask;
}
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