[JS 100 examples of reverse] anti climbing practice platform for net Luozhe question 5: console anti debugging

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Reverse target

• The goal is ： Question 5 of the web crawler anti crawler practice platform ： Console de debugging
• link ：http://spider.wangluozhe.com/challenge/5
• brief introduction ： Open the browser console , Console Console Position output bbbb0 Visible answer , Fill in the answer and submit it .

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Reverse process

Let's just open the console , Found that the right button cannot be used , direct F12, The page will jump directly to the home page , No big problem , Start a new page , To open the first F12 Then enter the page , At this point, you can see that the console is crazy output div label , As shown in the figure below ：

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What's embarrassing here is , Although the console is constantly brushing div, But it doesn't have much impact on our input , Direct input bbbb[0], Look up , You can see the answer , Or just type in copy(bbbb[0]) Just copy the answer directly to the pasteboard . As shown in the figure below ：

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I don't know why , It's possible that the problem is not standardized, so let's directly exploit the loophole , The author's original intention should be to let us get rid of this infinite brush div The situation of , Then go to get the answer , So let's analyze the source code , You can see the output div All the ways 5.js in , Just click in , It's a setInterval Timer method ：

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There are many ways to deal with ：

1. Hook Timer , Will output div Delete ;
2. Replace JS Code , Direct timer or output div Delete ;
3. Direct console Hook, Set the timer method to null .

This time we are directly on the console Hook, Set the timer to empty , Note here , If the program has entered the timer , Again Hook It is no use , So the right thing to do is in front of the timer , such as let div The next breakpoint , Refresh web page , Input again at the console setInterval = function() {}; Set the timer to empty , Then release the breakpoint input bbbb[0] Get answers ：

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We noticed an error on the console Uncaught SyntaxError: Identifier 'div' has already been declared, This is because in the JS And page HTML Each of them made a statement in div As a result of , On page HTML An error will be reported when you make a statement again in , It has no effect on the acquisition of our results . thus , The analysis of this problem is finished . Answer submitted successfully ：

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