node_modules/validator/lib/xss.js

//This module is adapted from the CodeIgniter framework
//The license is available at http://codeigniter.com/

var html_entity_decode = require('./entities').decode;

var never_allowed_str = {
    'document.cookie':              '[removed]',
    'document.write':               '[removed]',
    '.parentNode':                  '[removed]',
    '.innerHTML':                   '[removed]',
    'window.location':              '[removed]',
    '-moz-binding':                 '[removed]',
    '<!--':                         '&lt;!--',
    '-->':                          '--&gt;',
    '<![CDATA[':                    '&lt;![CDATA['
};

var never_allowed_regex = {
    'javascript\\s*:':              '[removed]',
    'expression\\s*(\\(|&\\#40;)':  '[removed]',
    'vbscript\\s*:':                '[removed]',
    'Redirect\\s+302':              '[removed]'
};

var non_displayables = [
    /%0[0-8bcef]/g,           // url encoded 00-08, 11, 12, 14, 15
    /%1[0-9a-f]/g,            // url encoded 16-31
    /[\x00-\x08]/g,           // 00-08
    /\x0b/g, /\x0c/g,         // 11,12
    /[\x0e-\x1f]/g            // 14-31
];

var compact_words = [
    'javascript', 'expression', 'vbscript',
    'script', 'applet', 'alert', 'document',
    'write', 'cookie', 'window'
];

exports.clean = function(str, is_image) {

    //Recursively clean objects and arrays
    if (typeof str === 'object') {
        for (var i in str) {
            str[i] = exports.clean(str[i]);
        }
        return str;
    }

    //Remove invisible characters
    str = remove_invisible_characters(str);

    //Protect query string variables in URLs => 901119URL5918AMP18930PROTECT8198
    str = str.replace(/\&([a-z\_0-9]+)\=([a-z\_0-9]+)/i, xss_hash() + '$1=$2');

    //Validate standard character entities - add a semicolon if missing.  We do this to enable
    //the conversion of entities to ASCII later.
    str = str.replace(/(&\#?[0-9a-z]{2,})([\x00-\x20])*;?/i, '$1;$2');

    //Validate UTF16 two byte encoding (x00) - just as above, adds a semicolon if missing.
    str = str.replace(/(&\#x?)([0-9A-F]+);?/i, '$1;$2');

    //Un-protect query string variables
    str = str.replace(xss_hash(), '&');

    //Decode just in case stuff like this is submitted:
    //<a href="http://%77%77%77%2E%67%6F%6F%67%6C%65%2E%63%6F%6D">Google</a>
    try{  
      str = decodeURIComponent(str);
    }
    catch(error){
      // str was not actually URI-encoded
    }

    //Convert character entities to ASCII - this permits our tests below to work reliably.
    //We only convert entities that are within tags since these are the ones that will pose security problems.
    str = str.replace(/[a-z]+=([\'\"]).*?\1/gi, function(m, match) {
        return m.replace(match, convert_attribute(match));
    });

    //Remove invisible characters again
    str = remove_invisible_characters(str);

    //Convert tabs to spaces
    str = str.replace('\t', ' ');

    //Captured the converted string for later comparison
    var converted_string = str;

    //Remove strings that are never allowed
    for (var i in never_allowed_str) {
        str = str.replace(i, never_allowed_str[i]);
    }

    //Remove regex patterns that are never allowed
    for (var i in never_allowed_regex) {
        str = str.replace(new RegExp(i, 'i'), never_allowed_regex[i]);
    }

    //Compact any exploded words like:  j a v a s c r i p t
    // We only want to do this when it is followed by a non-word character
    for (var i in compact_words) {
        var spacified = compact_words[i].split('').join('\\s*')+'\\s*';

        str = str.replace(new RegExp('('+spacified+')(\\W)', 'ig'), function(m, compat, after) {
            return compat.replace(/\s+/g, '') + after;
        });
    }

    //Remove disallowed Javascript in links or img tags
    do {
        var original = str;

        if (str.match(/<a/i)) {
            str = str.replace(/<a\s+([^>]*?)(>|$)/gi, function(m, attributes, end_tag) {
                attributes = filter_attributes(attributes.replace('<','').replace('>',''));
                return m.replace(attributes, attributes.replace(/href=.*?(alert\(|alert&\#40;|javascript\:|charset\=|window\.|document\.|\.cookie|<script|<xss|base64\s*,)/gi, ''));
            });
        }

        if (str.match(/<img/i)) {
            str = str.replace(/<img\s+([^>]*?)(\s?\/?>|$)/gi, function(m, attributes, end_tag) {
                attributes = filter_attributes(attributes.replace('<','').replace('>',''));
                return m.replace(attributes, attributes.replace(/src=.*?(alert\(|alert&\#40;|javascript\:|charset\=|window\.|document\.|\.cookie|<script|<xss|base64\s*,)/gi, ''));
            });
        }

        if (str.match(/script/i) || str.match(/xss/i)) {
            str = str.replace(/<(\/*)(script|xss)(.*?)\>/gi, '[removed]');
        }

    } while(original != str);

    //Remove JavaScript Event Handlers - Note: This code is a little blunt.  It removes the event
    //handler and anything up to the closing >, but it's unlikely to be a problem.
    event_handlers = ['[^a-z_\-]on\\w*'];

    //Adobe Photoshop puts XML metadata into JFIF images, including namespacing,
    //so we have to allow this for images
    if (!is_image) {
        event_handlers.push('xmlns');
    }

    str = str.replace(new RegExp("<([^><]+?)("+event_handlers.join('|')+")(\\s*=\\s*[^><]*)([><]*)", 'i'), '<$1$4');

    //Sanitize naughty HTML elements
    //If a tag containing any of the words in the list
    //below is found, the tag gets converted to entities.
    //So this: <blink>
    //Becomes: &lt;blink&gt;
    naughty = 'alert|applet|audio|basefont|base|behavior|bgsound|blink|body|embed|expression|form|frameset|frame|head|html|ilayer|iframe|input|isindex|layer|link|meta|object|plaintext|style|script|textarea|title|video|xml|xss';
    str = str.replace(new RegExp('<(/*\\s*)('+naughty+')([^><]*)([><]*)', 'gi'), function(m, a, b, c, d) {
        return '&lt;' + a + b + c + d.replace('>','&gt;').replace('<','&lt;');
    });

    //Sanitize naughty scripting elements Similar to above, only instead of looking for
    //tags it looks for PHP and JavaScript commands that are disallowed.  Rather than removing the
    //code, it simply converts the parenthesis to entities rendering the code un-executable.
    //For example:    eval('some code')
    //Becomes:        eval&#40;'some code'&#41;
    str = str.replace(/(alert|cmd|passthru|eval|exec|expression|system|fopen|fsockopen|file|file_get_contents|readfile|unlink)(\s*)\((.*?)\)/gi, '$1$2&#40;$3&#41;');

    //This adds a bit of extra precaution in case something got through the above filters
    for (var i in never_allowed_str) {
        str = str.replace(i, never_allowed_str[i]);
    }
    for (var i in never_allowed_regex) {
        str = str.replace(new RegExp(i, 'i'), never_allowed_regex[i]);
    }

    //Images are handled in a special way
    if (is_image && str !== converted_string) {
        throw new Error('Image may contain XSS');
    }

    return str;
}

function remove_invisible_characters(str) {
    for (var i in non_displayables) {
        str = str.replace(non_displayables[i], '');
    }
    return str;
}

function xss_hash() {
    //TODO: Create a random hash
    return '!*$^#(@*#&';
}

function convert_attribute(str) {
    return str.replace('>','&gt;').replace('<','&lt;').replace('\\','\\\\');
}

//Filter Attributes - filters tag attributes for consistency and safety
function filter_attributes(str) {
    out = '';

    str.replace(/\s*[a-z\-]+\s*=\s*(?:\042|\047)(?:[^\1]*?)\1/gi, function(m) {
        $out += m.replace(/\/\*.*?\*\//g, '');
    });

    return out;
}