EscaperExtension.php

<?php

/*
 * This file is part of Twig.
 *
 * (c) Fabien Potencier
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Twig\Extension;

use Twig\Environment;
use Twig\Error\RuntimeError;
use Twig\FileExtensionEscapingStrategy;
use Twig\Markup;
use Twig\Node\Expression\ConstantExpression;
use Twig\Node\Node;
use Twig\NodeVisitor\EscaperNodeVisitor;
use Twig\TokenParser\AutoEscapeTokenParser;
use Twig\TwigFilter;

final class EscaperExtension extends AbstractExtension
{
    private $defaultStrategy;
    private $escapers = [];

    /** @internal */
    public $safeClasses = [];

    /** @internal */
    public $safeLookup = [];

    /**
     * @param string|false|callable $defaultStrategy An escaping strategy
     *
     * @see setDefaultStrategy()
     */
    public function __construct($defaultStrategy = 'html')
    {
        $this->setDefaultStrategy($defaultStrategy);
    }

    public function getTokenParsers(): array
    {
        return [new AutoEscapeTokenParser()];
    }

    public function getNodeVisitors(): array
    {
        return [new EscaperNodeVisitor()];
    }

    public function getFilters(): array
    {
        return [
            new TwigFilter('escape', [self::class, 'escape'], ['needs_environment' => true, 'is_safe_callback' => [self::class, 'escapeFilterIsSafe']]),
            new TwigFilter('e', [self::class, 'escape'], ['needs_environment' => true, 'is_safe_callback' => [self::class, 'escapeFilterIsSafe']]),
            new TwigFilter('raw', [self::class, 'raw'], ['is_safe' => ['all']]),
        ];
    }

    /**
     * Sets the default strategy to use when not defined by the user.
     *
     * The strategy can be a valid PHP callback that takes the template
     * name as an argument and returns the strategy to use.
     *
     * @param string|false|callable $defaultStrategy An escaping strategy
     */
    public function setDefaultStrategy($defaultStrategy): void
    {
        if ('name' === $defaultStrategy) {
            $defaultStrategy = [FileExtensionEscapingStrategy::class, 'guess'];
        }

        $this->defaultStrategy = $defaultStrategy;
    }

    /**
     * Gets the default strategy to use when not defined by the user.
     *
     * @param string $name The template name
     *
     * @return string|false The default strategy to use for the template
     */
    public function getDefaultStrategy(string $name)
    {
        // disable string callables to avoid calling a function named html or js,
        // or any other upcoming escaping strategy
        if (!\is_string($this->defaultStrategy) && false !== $this->defaultStrategy) {
            return \call_user_func($this->defaultStrategy, $name);
        }

        return $this->defaultStrategy;
    }

    /**
     * Defines a new escaper to be used via the escape filter.
     *
     * @param string   $strategy The strategy name that should be used as a strategy in the escape call
     * @param callable $callable A valid PHP callable
     */
    public function setEscaper($strategy, callable $callable)
    {
        $this->escapers[$strategy] = $callable;
    }

    /**
     * Gets all defined escapers.
     *
     * @return callable[] An array of escapers
     */
    public function getEscapers()
    {
        return $this->escapers;
    }

    public function setSafeClasses(array $safeClasses = [])
    {
        $this->safeClasses = [];
        $this->safeLookup = [];
        foreach ($safeClasses as $class => $strategies) {
            $this->addSafeClass($class, $strategies);
        }
    }

    public function addSafeClass(string $class, array $strategies)
    {
        $class = ltrim($class, '\\');
        if (!isset($this->safeClasses[$class])) {
            $this->safeClasses[$class] = [];
        }
        $this->safeClasses[$class] = array_merge($this->safeClasses[$class], $strategies);

        foreach ($strategies as $strategy) {
            $this->safeLookup[$strategy][$class] = true;
        }
    }

    /**
     * Marks a variable as being safe.
     *
     * @param string $string A PHP variable
     *
     * @internal
     */
    public static function raw($string)
    {
        return $string;
    }

    /**
     * @internal
     */
    public static function escapeFilterIsSafe(Node $filterArgs)
    {
        foreach ($filterArgs as $arg) {
            if ($arg instanceof ConstantExpression) {
                return [$arg->getAttribute('value')];
            }

            return [];
        }

        return ['html'];
    }

    /**
     * Escapes a string.
     *
     * @param mixed  $string     The value to be escaped
     * @param string $strategy   The escaping strategy
     * @param string $charset    The charset
     * @param bool   $autoescape Whether the function is called by the auto-escaping feature (true) or by the developer (false)
     *
     * @return string|Markup
     *
     * @internal
     */
    public static function escape(Environment $env, $string, $strategy = 'html', $charset = null, $autoescape = false)
    {
        if ($autoescape && $string instanceof Markup) {
            return $string;
        }

        if (!\is_string($string)) {
            if (\is_object($string) && method_exists($string, '__toString')) {
                if ($autoescape) {
                    $c = \get_class($string);
                    $ext = $env->getExtension(self::class);
                    if (!isset($ext->safeClasses[$c])) {
                        $ext->safeClasses[$c] = [];
                        foreach (class_parents($string) + class_implements($string) as $class) {
                            if (isset($ext->safeClasses[$class])) {
                                $ext->safeClasses[$c] = array_unique(array_merge($ext->safeClasses[$c], $ext->safeClasses[$class]));
                                foreach ($ext->safeClasses[$class] as $s) {
                                    $ext->safeLookup[$s][$c] = true;
                                }
                            }
                        }
                    }
                    if (isset($ext->safeLookup[$strategy][$c]) || isset($ext->safeLookup['all'][$c])) {
                        return (string) $string;
                    }
                }

                $string = (string) $string;
            } elseif (\in_array($strategy, ['html', 'js', 'css', 'html_attr', 'url'])) {
                return $string;
            }
        }

        if ('' === $string) {
            return '';
        }

        if (null === $charset) {
            $charset = $env->getCharset();
        }

        switch ($strategy) {
            case 'html':
                // see https://www.php.net/htmlspecialchars

                // Using a static variable to avoid initializing the array
                // each time the function is called. Moving the declaration on the
                // top of the function slow downs other escaping strategies.
                static $htmlspecialcharsCharsets = [
                    'ISO-8859-1' => true, 'ISO8859-1' => true,
                    'ISO-8859-15' => true, 'ISO8859-15' => true,
                    'utf-8' => true, 'UTF-8' => true,
                    'CP866' => true, 'IBM866' => true, '866' => true,
                    'CP1251' => true, 'WINDOWS-1251' => true, 'WIN-1251' => true,
                    '1251' => true,
                    'CP1252' => true, 'WINDOWS-1252' => true, '1252' => true,
                    'KOI8-R' => true, 'KOI8-RU' => true, 'KOI8R' => true,
                    'BIG5' => true, '950' => true,
                    'GB2312' => true, '936' => true,
                    'BIG5-HKSCS' => true,
                    'SHIFT_JIS' => true, 'SJIS' => true, '932' => true,
                    'EUC-JP' => true, 'EUCJP' => true,
                    'ISO8859-5' => true, 'ISO-8859-5' => true, 'MACROMAN' => true,
                ];

                if (isset($htmlspecialcharsCharsets[$charset])) {
                    return htmlspecialchars($string, \ENT_QUOTES | \ENT_SUBSTITUTE, $charset);
                }

                if (isset($htmlspecialcharsCharsets[strtoupper($charset)])) {
                    // cache the lowercase variant for future iterations
                    $htmlspecialcharsCharsets[$charset] = true;

                    return htmlspecialchars($string, \ENT_QUOTES | \ENT_SUBSTITUTE, $charset);
                }

                $string = CoreExtension::convertEncoding($string, 'UTF-8', $charset);
                $string = htmlspecialchars($string, \ENT_QUOTES | \ENT_SUBSTITUTE, 'UTF-8');

                return iconv('UTF-8', $charset, $string);

            case 'js':
                // escape all non-alphanumeric characters
                // into their \x or \uHHHH representations
                if ('UTF-8' !== $charset) {
                    $string = CoreExtension::convertEncoding($string, 'UTF-8', $charset);
                }

                if (!preg_match('//u', $string)) {
                    throw new RuntimeError('The string to escape is not a valid UTF-8 string.');
                }

                $string = preg_replace_callback('#[^a-zA-Z0-9,\._]#Su', function ($matches) {
                    $char = $matches[0];

                    /*
                    * A few characters have short escape sequences in JSON and JavaScript.
                    * Escape sequences supported only by JavaScript, not JSON, are omitted.
                    * \" is also supported but omitted, because the resulting string is not HTML safe.
                    */
                    static $shortMap = [
                        '\\' => '\\\\',
                        '/' => '\\/',
                        "\x08" => '\b',
                        "\x0C" => '\f',
                        "\x0A" => '\n',
                        "\x0D" => '\r',
                        "\x09" => '\t',
                    ];

                    if (isset($shortMap[$char])) {
                        return $shortMap[$char];
                    }

                    $codepoint = mb_ord($char, 'UTF-8');
                    if (0x10000 > $codepoint) {
                        return sprintf('\u%04X', $codepoint);
                    }

                    // Split characters outside the BMP into surrogate pairs
                    // https://tools.ietf.org/html/rfc2781.html#section-2.1
                    $u = $codepoint - 0x10000;
                    $high = 0xD800 | ($u >> 10);
                    $low = 0xDC00 | ($u & 0x3FF);

                    return sprintf('\u%04X\u%04X', $high, $low);
                }, $string);

                if ('UTF-8' !== $charset) {
                    $string = iconv('UTF-8', $charset, $string);
                }

                return $string;

            case 'css':
                if ('UTF-8' !== $charset) {
                    $string = CoreExtension::convertEncoding($string, 'UTF-8', $charset);
                }

                if (!preg_match('//u', $string)) {
                    throw new RuntimeError('The string to escape is not a valid UTF-8 string.');
                }

                $string = preg_replace_callback('#[^a-zA-Z0-9]#Su', function ($matches) {
                    $char = $matches[0];

                    return sprintf('\\%X ', 1 === \strlen($char) ? \ord($char) : mb_ord($char, 'UTF-8'));
                }, $string);

                if ('UTF-8' !== $charset) {
                    $string = iconv('UTF-8', $charset, $string);
                }

                return $string;

            case 'html_attr':
                if ('UTF-8' !== $charset) {
                    $string = CoreExtension::convertEncoding($string, 'UTF-8', $charset);
                }

                if (!preg_match('//u', $string)) {
                    throw new RuntimeError('The string to escape is not a valid UTF-8 string.');
                }

                $string = preg_replace_callback('#[^a-zA-Z0-9,\.\-_]#Su', function ($matches) {
                    /**
                     * This function is adapted from code coming from Zend Framework.
                     *
                     * @copyright Copyright (c) 2005-2012 Zend Technologies USA Inc. (https://www.zend.com)
                     * @license   https://framework.zend.com/license/new-bsd New BSD License
                     */
                    $chr = $matches[0];
                    $ord = \ord($chr);

                    /*
                    * The following replaces characters undefined in HTML with the
                    * hex entity for the Unicode replacement character.
                    */
                    if (($ord <= 0x1F && "\t" != $chr && "\n" != $chr && "\r" != $chr) || ($ord >= 0x7F && $ord <= 0x9F)) {
                        return '&#xFFFD;';
                    }

                    /*
                    * Check if the current character to escape has a name entity we should
                    * replace it with while grabbing the hex value of the character.
                    */
                    if (1 === \strlen($chr)) {
                        /*
                        * While HTML supports far more named entities, the lowest common denominator
                        * has become HTML5's XML Serialisation which is restricted to the those named
                        * entities that XML supports. Using HTML entities would result in this error:
                        *     XML Parsing Error: undefined entity
                        */
                        static $entityMap = [
                            34 => '&quot;', /* quotation mark */
                            38 => '&amp;',  /* ampersand */
                            60 => '&lt;',   /* less-than sign */
                            62 => '&gt;',   /* greater-than sign */
                        ];

                        if (isset($entityMap[$ord])) {
                            return $entityMap[$ord];
                        }

                        return sprintf('&#x%02X;', $ord);
                    }

                    /*
                    * Per OWASP recommendations, we'll use hex entities for any other
                    * characters where a named entity does not exist.
                    */
                    return sprintf('&#x%04X;', mb_ord($chr, 'UTF-8'));
                }, $string);

                if ('UTF-8' !== $charset) {
                    $string = iconv('UTF-8', $charset, $string);
                }

                return $string;

            case 'url':
                return rawurlencode($string);

            default:
                $escapers = $env->getExtension(self::class)->getEscapers();
                if (\array_key_exists($strategy, $escapers)) {
                    return $escapers[$strategy]($env, $string, $charset);
                }

                $validStrategies = implode('", "', array_merge(['html', 'js', 'url', 'css', 'html_attr'], array_keys($escapers)));

                throw new RuntimeError(sprintf('Invalid escaping strategy "%s" (valid ones: "%s").', $strategy, $validStrategies));
        }
    }
}