filter/tex/lib.php

   1 <?php
   2 // This file is part of Moodle - http://moodle.org/
   3 //
   4 // Moodle is free software: you can redistribute it and/or modify
   5 // it under the terms of the GNU General Public License as published by
   6 // the Free Software Foundation, either version 3 of the License, or
   7 // (at your option) any later version.
   8 //
   9 // Moodle is distributed in the hope that it will be useful,
  10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 // GNU General Public License for more details.
  13 //
  14 // You should have received a copy of the GNU General Public License
  15 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
  16
  17 /**
  18  * TeX filter library functions.
  19  *
  20  * @package    filter
  21  * @subpackage tex
  22  * @copyright  2004 Zbigniew Fiedorowicz fiedorow@math.ohio-state.edu
  23  *             Originally based on code provided by Bruno Vernier bruno@vsbeducation.ca
  24  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  25  */
  26
  27 defined('MOODLE_INTERNAL') || die();
  28
  29 function filter_tex_get_executable($debug=false) {
  30     global $CFG;
  31
  32     if ((PHP_OS == "WINNT") || (PHP_OS == "WIN32") || (PHP_OS == "Windows")) {
  33         return "$CFG->dirroot/filter/tex/mimetex.exe";
  34     }
  35
  36     if ($pathmimetex = get_config('filter_tex', 'pathmimetex')) {
  37         if (is_executable($pathmimetex)) {
  38             return $pathmimetex;
  39         } else {
  40             throw new \moodle_exception('mimetexnotexecutable', 'error');
  41         }
  42     }
  43
  44     $custom_commandpath = "$CFG->dirroot/filter/tex/mimetex";
  45     if (file_exists($custom_commandpath)) {
  46         if (is_executable($custom_commandpath)) {
  47             return $custom_commandpath;
  48         } else {
  49             throw new \moodle_exception('mimetexnotexecutable', 'error');
  50         }
  51     }
  52
  53     switch (PHP_OS) {
  54         case "Darwin":  return "$CFG->dirroot/filter/tex/mimetex.darwin";
  55         case "FreeBSD": return "$CFG->dirroot/filter/tex/mimetex.freebsd";
  56         case "Linux":
  57             if (php_uname('m') == 'aarch64') {
  58                 return "$CFG->dirroot/filter/tex/mimetex.linux.aarch64";
  59             }
  60
  61             return "$CFG->dirroot/filter/tex/mimetex.linux";
  62     }
  63
  64     throw new \moodle_exception('mimetexisnotexist', 'error');
  65 }
  66
  67 /**
  68  * Check the formula expression against the list of denied keywords.
  69  *
  70  * List of allowed could be more complete but also harder to maintain.
  71  *
  72  * @param string $texexp Formula expression to check.
  73  * @return string Formula expression with denied keywords replaced with 'forbiddenkeyword'.
  74  */
  75 function filter_tex_sanitize_formula(string $texexp): string {
  76
  77     $denylist = [
  78         'include', 'command', 'loop', 'repeat', 'open', 'toks', 'output',
  79         'input', 'catcode', 'name', '^^',
  80         '\def', '\edef', '\gdef', '\xdef',
  81         '\every', '\errhelp', '\errorstopmode', '\scrollmode', '\nonstopmode',
  82         '\batchmode', '\read', '\write', 'csname', '\newhelp', '\uppercase',
  83         '\lowercase', '\relax', '\aftergroup',
  84         '\afterassignment', '\expandafter', '\noexpand', '\special',
  85         '\let', '\futurelet', '\else', '\fi', '\chardef', '\makeatletter', '\afterground',
  86         '\noexpand', '\line', '\mathcode', '\item', '\section', '\mbox', '\declarerobustcommand',
  87         '\ExplSyntaxOn',
  88     ];
  89
  90     $allowlist = ['inputenc'];
  91
  92     // Prepare the denylist for regular expression.
  93     $denylist = array_map(function($value){
  94         return '/' . preg_quote($value, '/') . '/i';
  95     }, $denylist);
  96
  97     // Prepare the allowlist for regular expression.
  98     $allowlist = array_map(function($value){
  99         return '/\bforbiddenkeyword_(' . preg_quote($value, '/') . ')\b/i';
 100     }, $allowlist);
 101
 102     // First, mangle all denied words.
 103     $texexp = preg_replace_callback($denylist,
 104         function($matches) {
 105             return 'forbiddenkeyword_' . $matches[0];
 106         },
 107         $texexp
 108     );
 109
 110     // Then, change back the allowed words.
 111     $texexp = preg_replace_callback($allowlist,
 112         function($matches) {
 113             return $matches[1];
 114         },
 115         $texexp
 116     );
 117
 118     return $texexp;
 119 }
 120
 121 function filter_tex_get_cmd($pathname, $texexp) {
 122     $texexp = filter_tex_sanitize_formula($texexp);
 123     $texexp = escapeshellarg($texexp);
 124     $executable = filter_tex_get_executable(false);
 125
 126     if ((PHP_OS == "WINNT") || (PHP_OS == "WIN32") || (PHP_OS == "Windows")) {
 127         $executable = str_replace(' ', '^ ', $executable);
 128         return "$executable ++ -e  \"$pathname\" -- $texexp";
 129
 130     } else {
 131         return "\"$executable\" -e \"$pathname\" -- $texexp";
 132     }
 133 }
 134
 135 /**
 136  * Purge all caches when settings changed.
 137  */
 138 function filter_tex_updatedcallback($name) {
 139     global $CFG, $DB;
 140     reset_text_filters_cache();
 141
 142     if (file_exists("$CFG->dataroot/filter/tex")) {
 143         remove_dir("$CFG->dataroot/filter/tex");
 144     }
 145     if (file_exists("$CFG->dataroot/filter/algebra")) {
 146         remove_dir("$CFG->dataroot/filter/algebra");
 147     }
 148     if (file_exists("$CFG->tempdir/latex")) {
 149         remove_dir("$CFG->tempdir/latex");
 150     }
 151
 152     $DB->delete_records('cache_filters', array('filter'=>'tex'));
 153     $DB->delete_records('cache_filters', array('filter'=>'algebra'));
 154
 155     $pathlatex = get_config('filter_tex', 'pathlatex');
 156     if ($pathlatex === false) {
 157         // detailed settings not present yet
 158         return;
 159     }
 160
 161     $pathlatex = trim($pathlatex, " '\"");
 162     $pathdvips = trim(get_config('filter_tex', 'pathdvips'), " '\"");
 163     $pathconvert = trim(get_config('filter_tex', 'pathconvert'), " '\"");
 164     $pathdvisvgm = trim(get_config('filter_tex', 'pathdvisvgm'), " '\"");
 165
 166     $supportedformats = array('gif');
 167     if ((is_file($pathlatex) && is_executable($pathlatex)) &&
 168             (is_file($pathdvips) && is_executable($pathdvips))) {
 169         if (is_file($pathconvert) && is_executable($pathconvert)) {
 170              $supportedformats[] = 'png';
 171         }
 172         if (is_file($pathdvisvgm) && is_executable($pathdvisvgm)) {
 173              $supportedformats[] = 'svg';
 174         }
 175     }
 176     if (!in_array(get_config('filter_tex', 'convertformat'), $supportedformats)) {
 177         set_config('convertformat', array_pop($supportedformats), 'filter_tex');
 178     }
 179
 180 }
 181