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POIs this use of Javascript eval() 100% safe?
 

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  1. POIs this use of Javascript eval() 100% safe?
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    <p>I'm writing a PHP library which generates Javascript code.</p> <p>The Javascript code has a number of components named <code>component001</code>, <code>component002</code>, etc.</p> <p>Pages are loaded dynamically via AJAX.</p> <p>I need to pass the name of the component via URL variable which is then evaled() by the script.</p> <p>The only way I am protecting what is being evaled is with the regular expression <code>^component[0-9]{3}$</code>: if it passes it gets evaled, otherwise it does not.</p> <p><strong>To me this is 100% safe since nothing will get executed unless it is simply the name of one of my known components, or is there something about the <code>eval()</code> command that could be exploited in this code sample, e.g. regex injection, some kind of cross site scripting etc.?</strong></p> <pre><code>window.onload = function() { // *** DEFINED IN ANOTHER JAVASCRIPT FILE: var component001 = 'testing111'; var component002 = 'testing222'; var component003 = 'testing333'; var APP = {}; APP.getUrlVars = function() { var vars = [], hash; var hashes = window.location.href.slice(window.location.href.indexOf('?') + 1).split('&amp;'); for(var i = 0; i &lt; hashes.length; i++) { hash = hashes[i].split('='); vars.push(hash[0]); vars[hash[0]] = hash[1]; } return vars; } APP.getUrlVar = function(name, defaultValue) { defaultValue = (typeof defaultValue == 'undefined') ? '' : defaultValue; var vars = APP.getUrlVars(); if(vars[name] === undefined) { return defaultValue; } else { return vars[name]; } } APP.safeEval = function(nameOfComponent) { var REGEX_VALID_NAME = /^component[0-9]{3}$/; if(REGEX_VALID_NAME.test(nameOfComponent)) { return eval(nameOfComponent); } else { return 'ERROR'; } } // *** JAVASCRIPT FILE LOADED VIA AJAX: var nameOfComponentToDisplay = APP.getUrlVar('compname', 'component001'); var component = APP.safeEval(nameOfComponentToDisplay); document.write(component); } </code></pre>
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    1. USEdward Tanguay
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      1. VTUpMod
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    1. CONothing is 100% safe :P
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      1. POIs this use of Javascript eval() 100% safe?
      1. USLloyd
    2. COInstead of using `eval` for this, I'd use the square bracket notation to call your function (e.g. `APP[nameOfComponent]();`)
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      1. POIs this use of Javascript eval() 100% safe?
      1. USMarcel Korpel
    3. COregex and eval() are both open ended tools that introduce risk. The problem you describe need not embrace that risk. Instead - as @Marcel Korpel and @ChaosPandio have writ - use string matching and function invoking to avoid.
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      1. USorangepips
 

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