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256 lines
7.5 KiB
C++
256 lines
7.5 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <AK/Optional.h>
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#include <AK/StdLibExtras.h>
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#include <AK/kmalloc.h>
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#include <stdio.h>
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#include <string.h>
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#include <sys/stat.h>
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#include <unistd.h>
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/* the new mode will be computed using the boolean function(for each bit):
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|current mode|removal mask|applying mask|result |
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| 0 | 0 | 0 | 0 |
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| 0 | 0 | 1 | 1 |
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| 0 | 1 | 0 | 0 |
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| 0 | 1 | 1 | 1 | ---> find the CNF --> find the minimal CNF
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| 1 | 0 | 0 | 1 |
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| 1 | 0 | 1 | 1 |
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| 1 | 1 | 0 | 0 |
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| 1 | 1 | 1 | 1 |
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*/
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class Mask {
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private:
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mode_t removal_mask; //the bits that will be removed
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mode_t applying_mask; //the bits that will be setted
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public:
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Mask()
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: removal_mask(0)
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, applying_mask(0)
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{
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}
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Mask& operator|=(const Mask& other)
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{
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removal_mask |= other.removal_mask;
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applying_mask |= other.applying_mask;
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return *this;
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}
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mode_t& get_removal_mask() { return removal_mask; }
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mode_t& get_applying_mask() { return applying_mask; }
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};
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Optional<Mask> string_to_mode(char access_scope, const char*& access_string);
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Optional<Mask> apply_permission(char access_scope, char permission, char operation);
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int main(int argc, char** argv)
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{
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if (pledge("stdio rpath fattr", nullptr) < 0) {
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perror("pledge");
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return 1;
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}
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if (argc < 3) {
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printf("usage: chmod <octal-mode> <path...>\n"
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" chmod [[ugoa][+-=][rwx...],...] <path...>\n");
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return 1;
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}
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Mask mask;
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/* compute a mask */
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if (argv[1][0] >= '0' && argv[1][0] <= '7') {
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if (sscanf(argv[1], "%ho", &mask.get_applying_mask()) != 1) {
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perror("sscanf");
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return 1;
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}
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mask.get_removal_mask() = ~mask.get_applying_mask();
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} else {
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const char* access_string = argv[1];
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while (*access_string != '\0') {
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Optional<Mask> tmp_mask;
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switch (*access_string) {
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case 'u':
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tmp_mask = string_to_mode('u', ++access_string);
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break;
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case 'g':
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tmp_mask = string_to_mode('g', ++access_string);
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break;
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case 'o':
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tmp_mask = string_to_mode('o', ++access_string);
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break;
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case 'a':
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tmp_mask = string_to_mode('a', ++access_string);
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break;
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case '=':
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case '+':
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case '-':
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tmp_mask = string_to_mode('a', access_string);
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break;
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case ',':
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++access_string;
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continue;
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}
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if (!tmp_mask.has_value()) {
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fprintf(stderr, "chmod: invalid mode: %s\n", argv[1]);
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return 1;
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}
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mask |= tmp_mask.value();
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}
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}
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/* set the mask for each files' permissions */
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struct stat current_access;
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int i = 2;
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while (i < argc) {
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if (stat(argv[i], ¤t_access) != 0) {
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perror("stat");
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return 1;
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}
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/* found the minimal CNF by The Quine–McCluskey algorithm and use it */
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mode_t mode = mask.get_applying_mask()
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| (current_access.st_mode & ~mask.get_removal_mask());
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if (chmod(argv[i++], mode) != 0) {
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perror("chmod");
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}
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}
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return 0;
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}
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Optional<Mask> string_to_mode(char access_scope, const char*& access_string)
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{
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char operation = *access_string;
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if (operation != '+' && operation != '-' && operation != '=') {
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return {};
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}
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Mask mask;
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if (operation == '=') {
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switch (access_scope) {
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case 'u':
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mask.get_removal_mask() = (S_IRUSR | S_IWUSR | S_IXUSR);
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break;
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case 'g':
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mask.get_removal_mask() = (S_IRGRP | S_IWGRP | S_IXGRP);
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break;
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case 'o':
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mask.get_removal_mask() = (S_IROTH | S_IWOTH | S_IXOTH);
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break;
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case 'a':
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mask.get_removal_mask() = (S_IRUSR | S_IWUSR | S_IXUSR
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| S_IRGRP | S_IWGRP | S_IXGRP
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| S_IROTH | S_IWOTH | S_IXOTH);
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break;
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}
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operation = '+';
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}
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access_string++;
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while (*access_string != '\0' && *access_string != ',') {
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Optional<Mask> tmp_mask;
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tmp_mask = apply_permission(access_scope, *access_string, operation);
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if (!tmp_mask.has_value()) {
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return {};
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}
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mask |= tmp_mask.value();
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access_string++;
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}
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return mask;
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}
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Optional<Mask> apply_permission(char access_scope, char permission, char operation)
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{
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if (permission != 'r' && permission != 'w' && permission != 'x') {
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return {};
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}
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Mask mask;
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mode_t tmp_mask = 0;
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switch (access_scope) {
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case 'u':
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switch (permission) {
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case 'r':
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tmp_mask = S_IRUSR;
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break;
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case 'w':
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tmp_mask = S_IWUSR;
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break;
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case 'x':
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tmp_mask = S_IXUSR;
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break;
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}
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break;
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case 'g':
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switch (permission) {
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case 'r':
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tmp_mask = S_IRGRP;
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break;
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case 'w':
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tmp_mask = S_IWGRP;
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break;
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case 'x':
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tmp_mask = S_IXGRP;
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break;
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}
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break;
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case 'o':
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switch (permission) {
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case 'r':
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tmp_mask = S_IROTH;
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break;
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case 'w':
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tmp_mask = S_IWOTH;
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break;
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case 'x':
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tmp_mask = S_IXOTH;
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break;
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}
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break;
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case 'a':
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mask |= apply_permission('u', permission, operation).value();
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mask |= apply_permission('g', permission, operation).value();
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mask |= apply_permission('o', permission, operation).value();
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break;
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}
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if (operation == '+') {
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mask.get_applying_mask() |= tmp_mask;
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} else {
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mask.get_removal_mask() |= tmp_mask;
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}
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return mask;
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}
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