CODEWITHSUNDEEP
javascriptstring
user1335906
user1335906

Reputation: 145

Extracting Strings from script tag using javascript

How can i extract all the strings present in script tags. I want to extract each string and find whether any shellcode is present. But javascript uses several methods in declaring a string For example a string can be 

 var y="Some text";
 var x1 = "3+4";
 eval("\144\157\143\165\155\145\156\164"); //string given in eval();

It can be in a concatenated format

var x1 = "te ActiveX Co"; var x2 = "ntrol"; var x3 = x1 + x2; 
var x4 = "Execu" + x3;

How can i identify each and every string even if it is defined in eval() or document.write() by using simple javacript code.

Upvotes: 1

Views: 435

Answers (1)

maerics
maerics

Reputation: 156384

This is a very complex problem for which there is no simple solution.

You could use a parser generator and the BNF definition of the ECMAScript language (surely you can find it on the web somewhere) to extract strings from the target source code.

[Edit] Since the linked parser generator is written in JavaScript and supports web browsers as a platform you can generate a custom ECMAScript parser, embed it in a page, and fetch all the embedded script source (e.g. $('script').map(function(){return $(this).text();})). Note that your custom parser could simply echo the parsed strings, e.g. via console.log(...).

Upvotes: 1

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