ponepaste/includes/Parsedown/SecureParsedown.php

<?php

namespace Aidantwoods\SecureParsedown;

class SecureParsedown extends \Parsedown
{
    const version = '1.0.1';

    function setSafeMode($safeMode)
    {
        $this->safeMode = (bool) $safeMode;

        return $this;
    }

    protected $safeMode;

    protected $safeLinksWhitelist = array(
        'http://',
        'https://',
        'ftp://',
        'ftps://',
        'mailto:',
        'data:image/png;base64,',
        'data:image/gif;base64,',
        'data:image/jpeg;base64,',
        'irc:',
        'ircs:',
        'git:',
        'ssh:',
        'news:',
        'steam:',
    );

    protected function blockCodeComplete($Block)
    {
         $text = $Block['element']['text']['text'];

         $Block['element']['text']['text'] = $text;

         return $Block;
    }

    protected function blockComment($Line)
    {
        if ($this->markupEscaped or $this->safeMode)
        {
            return;
        }

        if (isset($Line['text'][3]) and $Line['text'][3] === '-' and $Line['text'][2] === '-' and $Line['text'][1] === '!')
        {
            $Block = array(
                'markup' => $Line['body'],
            );

            if (preg_match('/-->$/', $Line['text']))
            {
                $Block['closed'] = true;
            }

            return $Block;
        }
    }

    protected function blockFencedCodeComplete($Block)
    {
        $text = $Block['element']['text']['text'];

        $Block['element']['text']['text'] = $text;

        return $Block;
    }

    protected function blockMarkup($Line)
    {
        if ($this->markupEscaped or $this->safeMode)
        {
            return;
        }

        if (preg_match('/^<(\w*)(?:[ ]*'.$this->regexHtmlAttribute.')*[ ]*(\/)?>/', $Line['text'], $matches))
        {
            $element = strtolower($matches[1]);

            if (in_array($element, $this->textLevelElements))
            {
                return;
            }

            $Block = array(
                'name' => $matches[1],
                'depth' => 0,
                'markup' => $Line['text'],
            );

            $length = strlen($matches[0]);

            $remainder = substr($Line['text'], $length);

            if (trim($remainder) === '')
            {
                if (isset($matches[2]) or in_array($matches[1], $this->voidElements))
                {
                    $Block['closed'] = true;

                    $Block['void'] = true;
                }
            }
            else
            {
                if (isset($matches[2]) or in_array($matches[1], $this->voidElements))
                {
                    return;
                }

                if (preg_match('/<\/'.$matches[1].'>[ ]*$/i', $remainder))
                {
                    $Block['closed'] = true;
                }
            }

            return $Block;
        }
    }

    protected function inlineCode($Excerpt)
    {
        $marker = $Excerpt['text'][0];

        if (preg_match('/^('.$marker.'+)[ ]*(.+?)[ ]*(?<!'.$marker.')\1(?!'.$marker.')/s', $Excerpt['text'], $matches))
        {
            $text = $matches[2];
            $text = preg_replace("/[ ]*\n/", ' ', $text);

            return array(
                'extent' => strlen($matches[0]),
                'element' => array(
                    'name' => 'code',
                    'text' => $text,
                ),
            );
        }
    }

    protected function inlineLink($Excerpt)
    {
        $Element = array(
            'name' => 'a',
            'handler' => 'line',
            'text' => null,
            'attributes' => array(
                'href' => null,
                'title' => null,
            ),
        );

        $extent = 0;

        $remainder = $Excerpt['text'];

        if (preg_match('/\[((?:[^][]++|(?R))*+)\]/', $remainder, $matches))
        {
            $Element['text'] = $matches[1];

            $extent += strlen($matches[0]);

            $remainder = substr($remainder, $extent);
        }
        else
        {
            return;
        }

        if (preg_match('/^[(]\s*+((?:[^ ()]++|[(][^ )]+[)])++)(?:[ ]+("[^"]*"|\'[^\']*\'))?\s*[)]/', $remainder, $matches))
        {
            $Element['attributes']['href'] = $matches[1];

            if (isset($matches[2]))
            {
                $Element['attributes']['title'] = substr($matches[2], 1, - 1);
            }

            $extent += strlen($matches[0]);
        }
        else
        {
            if (preg_match('/^\s*\[(.*?)\]/', $remainder, $matches))
            {
                $definition = strlen($matches[1]) ? $matches[1] : $Element['text'];
                $definition = strtolower($definition);

                $extent += strlen($matches[0]);
            }
            else
            {
                $definition = strtolower($Element['text']);
            }

            if ( ! isset($this->DefinitionData['Reference'][$definition]))
            {
                return;
            }

            $Definition = $this->DefinitionData['Reference'][$definition];

            $Element['attributes']['href'] = $Definition['url'];
            $Element['attributes']['title'] = $Definition['title'];
        }

        return array(
            'extent' => $extent,
            'element' => $Element,
        );
    }

    protected function inlineMarkup($Excerpt)
    {
        if ($this->markupEscaped or $this->safeMode or strpos($Excerpt['text'], '>') === false)
        {
            return;
        }

        if ($Excerpt['text'][1] === '/' and preg_match('/^<\/\w*[ ]*>/s', $Excerpt['text'], $matches))
        {
            return array(
                'markup' => $matches[0],
                'extent' => strlen($matches[0]),
            );
        }

        if ($Excerpt['text'][1] === '!' and preg_match('/^<!---?[^>-](?:-?[^-])*-->/s', $Excerpt['text'], $matches))
        {
            return array(
                'markup' => $matches[0],
                'extent' => strlen($matches[0]),
            );
        }

        if ($Excerpt['text'][1] !== ' ' and preg_match('/^<\w*(?:[ ]*'.$this->regexHtmlAttribute.')*[ ]*\/?>/s', $Excerpt['text'], $matches))
        {
            return array(
                'markup' => $matches[0],
                'extent' => strlen($matches[0]),
            );
        }
    }

    protected function inlineUrl($Excerpt)
    {
        if ($this->urlsLinked !== true or ! isset($Excerpt['text'][2]) or $Excerpt['text'][2] !== '/')
        {
            return;
        }

        if (preg_match('/\bhttps?:[\/]{2}[^\s<]+\b\/*/ui', $Excerpt['context'], $matches, PREG_OFFSET_CAPTURE))
        {
            $url = $matches[0][0];

            $Inline = array(
                'extent' => strlen($matches[0][0]),
                'position' => $matches[0][1],
                'element' => array(
                    'name' => 'a',
                    'text' => $url,
                    'attributes' => array(
                        'href' => $url,
                    ),
                ),
            );

            return $Inline;
        }
    }

    protected function inlineUrlTag($Excerpt)
    {
        if (strpos($Excerpt['text'], '>') !== false and preg_match('/^<(\w+:\/{2}[^ >]+)>/i', $Excerpt['text'], $matches))
        {
            $url = $matches[1];

            return array(
                'extent' => strlen($matches[0]),
                'element' => array(
                    'name' => 'a',
                    'text' => $url,
                    'attributes' => array(
                        'href' => $url,
                    ),
                ),
            );
        }
    }

    protected function element(array $Element)
    {
        if ($this->safeMode)
        {
            $Element = $this->sanitiseElement($Element);
        }

        $markup = '<'.$Element['name'];

        if (isset($Element['attributes']))
        {
            foreach ($Element['attributes'] as $name => $value)
            {
                if ($value === null)
                {
                    continue;
                }

                $markup .= ' '.$name.'="'.self::escape($value).'"';
            }
        }

        if (isset($Element['text']))
        {
            $markup .= '>';

            if (isset($Element['handler']))
            {
                $markup .= $this->{$Element['handler']}($Element['text']);
            }
            else
            {
                $markup .= self::escape($Element['text'], true);
            }

            $markup .= '</'.$Element['name'].'>';
        }
        else
        {
            $markup .= ' />';
        }

        return $markup;
    }

    protected function sanitiseElement(array $Element)
    {
        static $goodAttribute = '/^[a-zA-Z0-9][a-zA-Z0-9-_]*+$/';
        static $safeUrlNameToAtt  = array(
            'a'   => 'href',
            'img' => 'src',
        );

        if (isset($safeUrlNameToAtt[$Element['name']]))
        {
            $Element = $this->filterUnsafeUrlInAttribute($Element, $safeUrlNameToAtt[$Element['name']]);
        }

        if ( ! empty($Element['attributes']))
        {
            foreach ($Element['attributes'] as $att => $val)
            {
                # filter out badly parsed attribute
                if ( ! preg_match($goodAttribute, $att))
                {
                    unset($Element['attributes'][$att]);
                }
                # dump onevent attribute
                elseif (self::striAtStart($att, 'on'))
                {
                    unset($Element['attributes'][$att]);
                }
            }
        }

        return $Element;
    }

    protected function filterUnsafeUrlInAttribute(array $Element, $attribute)
    {
        foreach ($this->safeLinksWhitelist as $scheme)
        {
            if (self::striAtStart($Element['attributes'][$attribute], $scheme))
            {
                return $Element;
            }
        }

        $Element['attributes'][$attribute] = str_replace(':', '%3A', $Element['attributes'][$attribute]);

        return $Element;
    }

    protected static function escape($text, $allowQuotes = false)
    {
        return htmlspecialchars($text, $allowQuotes ? ENT_NOQUOTES : ENT_QUOTES, 'UTF-8');
    }

    protected static function striAtStart($string, $needle)
    {
        $len = strlen($needle);

        if ($len > strlen($string))
        {
            return false;
        }
        else
        {
            return strtolower(substr($string, 0, $len)) === strtolower($needle);
        }
    }
}