Proyectos de Subversion Moodle

<?php

// This file is part of Moodle - http://moodle.org/

//

// Moodle 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.

//

// Moodle 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 Moodle.  If not, see <http://www.gnu.org/licenses/>.

/**

 * TeX filter library functions.

 *

 * @package    filter

 * @subpackage tex

 * @copyright  2004 Zbigniew Fiedorowicz fiedorow@math.ohio-state.edu

 *             Originally based on code provided by Bruno Vernier bruno@vsbeducation.ca

 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

defined('MOODLE_INTERNAL') || die();

function filter_tex_get_executable($debug=false) {

    global $CFG;

    if ((PHP_OS == "WINNT") || (PHP_OS == "WIN32") || (PHP_OS == "Windows")) {

        return "$CFG->dirroot/filter/tex/mimetex.exe";

    }

    if ($pathmimetex = get_config('filter_tex', 'pathmimetex')) {

        if (is_executable($pathmimetex)) {

            return $pathmimetex;

        } else {

            throw new \moodle_exception('mimetexnotexecutable', 'error');

        }

    }

    $custom_commandpath = "$CFG->dirroot/filter/tex/mimetex";

    if (file_exists($custom_commandpath)) {

        if (is_executable($custom_commandpath)) {

            return $custom_commandpath;

        } else {

            throw new \moodle_exception('mimetexnotexecutable', 'error');

        }

    }

    switch (PHP_OS) {

        case "Darwin":  return "$CFG->dirroot/filter/tex/mimetex.darwin";

        case "FreeBSD": return "$CFG->dirroot/filter/tex/mimetex.freebsd";

        case "Linux":

            if (php_uname('m') == 'aarch64') {

                return "$CFG->dirroot/filter/tex/mimetex.linux.aarch64";

            }

            return "$CFG->dirroot/filter/tex/mimetex.linux";

    }

    throw new \moodle_exception('mimetexisnotexist', 'error');

}

/**

 * Check the formula expression against the list of denied keywords.

 *

 * List of allowed could be more complete but also harder to maintain.

 *

 * @param string $texexp Formula expression to check.

 * @return string Formula expression with denied keywords replaced with 'forbiddenkeyword'.

 */

function filter_tex_sanitize_formula(string $texexp): string {

    $denylist = [

        'include', 'command', 'loop', 'repeat', 'open', 'toks', 'output',

        'input', 'catcode', 'name', '^^',

        '\def', '\edef', '\gdef', '\xdef',

        '\every', '\errhelp', '\errorstopmode', '\scrollmode', '\nonstopmode',

        '\batchmode', '\read', '\write', 'csname', '\newhelp', '\uppercase',

        '\lowercase', '\relax', '\aftergroup',

        '\afterassignment', '\expandafter', '\noexpand', '\special',

        '\let', '\futurelet', '\else', '\fi', '\chardef', '\makeatletter', '\afterground',

        '\noexpand', '\line', '\mathcode', '\item', '\section', '\mbox', '\declarerobustcommand',

        '\ExplSyntaxOn', '\pdffiledump', '\mathtex',

    ];

    $allowlist = ['inputenc'];

    // Add encoded backslash (\) versions of backslashed items to deny list.

    $encodedslashdenylist = array_map(function($value) {

        $encoded = str_replace('\\', '\', $value);

        // Return an encoded slash version if a slash is found, otherwise null so we can filter it off.

        return $encoded != $value ? $encoded : null;

    }, $denylist);

    $encodedslashdenylist = array_filter($encodedslashdenylist);

    $denylist = array_merge($denylist, $encodedslashdenylist);

    // Prepare the denylist for regular expression.

    $denylist = array_map(function($value){

        return '/' . preg_quote($value, '/') . '/i';

    }, $denylist);

    // Prepare the allowlist for regular expression.

    $allowlist = array_map(function($value){

        return '/\bforbiddenkeyword_(' . preg_quote($value, '/') . ')\b/i';

    }, $allowlist);

    // First, mangle all denied words.

    $texexp = preg_replace_callback($denylist,

        function($matches) {

            // Remove backslashes to make commands impotent.

            $noslashes = str_replace('\\', '', $matches[0]);

            return 'forbiddenkeyword_' . $noslashes;

        },

        $texexp

    );

    // Then, change back the allowed words.

    $texexp = preg_replace_callback($allowlist,

        function($matches) {

            return $matches[1];

        },

        $texexp

    );

    return $texexp;

}

function filter_tex_get_cmd($pathname, $texexp) {

    $texexp = filter_tex_sanitize_formula($texexp);

    $texexp = escapeshellarg($texexp);

    $executable = filter_tex_get_executable(false);

    if ((PHP_OS == "WINNT") || (PHP_OS == "WIN32") || (PHP_OS == "Windows")) {

        $executable = str_replace(' ', '^ ', $executable);

        return "$executable ++ -e  \"$pathname\" -- $texexp";

    } else {

        return "\"$executable\" -e \"$pathname\" -- $texexp";

    }

}

/**

 * Purge all caches when settings changed.

 */

function filter_tex_updatedcallback($name) {

    global $CFG, $DB;

    reset_text_filters_cache();

    if (file_exists("$CFG->dataroot/filter/tex")) {

        remove_dir("$CFG->dataroot/filter/tex");

    }

    if (file_exists("$CFG->dataroot/filter/algebra")) {

        remove_dir("$CFG->dataroot/filter/algebra");

    }

    if (file_exists("$CFG->tempdir/latex")) {

        remove_dir("$CFG->tempdir/latex");

    }

    $DB->delete_records('cache_filters', array('filter'=>'tex'));

    $DB->delete_records('cache_filters', array('filter'=>'algebra'));

    $pathlatex = get_config('filter_tex', 'pathlatex');

    if ($pathlatex === false) {

        // detailed settings not present yet

        return;

    }

    $pathlatex = trim($pathlatex, " '\"");

    $pathdvips = trim(get_config('filter_tex', 'pathdvips'), " '\"");

    $pathconvert = trim(get_config('filter_tex', 'pathconvert'), " '\"");

    $pathdvisvgm = trim(get_config('filter_tex', 'pathdvisvgm'), " '\"");

    $supportedformats = array('gif');

    if ((is_file($pathlatex) && is_executable($pathlatex)) &&

            (is_file($pathdvips) && is_executable($pathdvips))) {

        if (is_file($pathconvert) && is_executable($pathconvert)) {

             $supportedformats[] = 'png';

        }

        if (is_file($pathdvisvgm) && is_executable($pathdvisvgm)) {

             $supportedformats[] = 'svg';

        }

    }

    if (!in_array(get_config('filter_tex', 'convertformat'), $supportedformats)) {

        set_config('convertformat', array_pop($supportedformats), 'filter_tex');

    }

}