[Request] Get reCAPTCHA image

[Misuki]

Hello guys !

 

I'm searching to get the google reCAPTCHA image (not the NOCAPTCHA RECAPTCHA, care) on a register page since 2 weeks. 

 

I know how it works, but I'm blocking on a thing: on the second step (to generate the challenge) there is a property in the URL named "th" (in fact, the url looks like "http://www.google.co...itekey&reason=i&th=somethingEncrypted").

 

I searched a little and I find that it may be called "thintinel" and it is a JScript client sided obfuscation encrypted system (or something like that, IDK). The thing is, i'm using HttpWebRequest/HttpWebResponse to communicate and get informations to generate at the end of each step the image with the captcha. Without this "th", it generates me a wrong captcha: then i'm here to get informations about how can I generate this "th" property (I know I can't execute the Javascript script 'cause it's only interpreted by the client but with HttpWebRequest we havn't got a client).

 

Can someone help me or put me on the right way ?

Edited by Misuki, 11 July 2015 - 07:29 PM.

[NiceProduct]

I didnt understand at all,you want get the link of a recaptcha image? you can do something like.

w.downloadstring("web");

foreach(string line in w.allLines)

{

if(line.contains(recaptcha)

{

split the line and get the link.

}

}

[Misuki]

Well, i'll try to explain..

 

The URL of the image of the CAPTCHA isn't in the page source code. It means that I can't split the HttpWebResponse of my request to get the URL with regex method for example because it isn't in the source code.

 

Then i'm trying to rebuild the URL with each step: first I recover the challenge with the key of the website, then I follow on the recaptcha.reload to get another challenge link, but in this step I noticed that a new thing appear in the url: a thing called "th". And when I searched how "th" is building, I fall on a Javascript script that is obfuscated and encrypted with double base-64 code.

 

So i'm asking you how can I execute the JS script in my code without using a WebBrowser. But I know that is impossible because the Javascript is executed on the client side: with the objects i'm using,there isn't any client (HttpWebRequest and HttpWebResponse).

 

So... i'm here to get some informations if someone know how can I easily get the URL of the image of the captcha of the death.

 

PS: When you are searching something in a big text, I recommend you to use Regex pattern (because get each lines of the data is longer than regex patterns )

Edited by Misuki, 12 July 2015 - 11:54 PM.

[nexiaz]

extract the Key Value from the <script> tags inside of your HTML

 

http://www.google.co...api/noscript?k=## insert key

[NiceProduct]

Well, i'll try to explain..

 

The URL of the image of the CAPTCHA isn't in the page source code. It means that I can't split the HttpWebResponse of my request to get the URL with regex method for example because it isn't in the source code.

 

Then i'm trying to rebuild the URL with each step: first I recover the challenge with the key of the website, then I follow on the recaptcha.reload to get another challenge link, but in this step I noticed that a new thing appear in the url: a thing called "th". And when I searched how "th" is building, I fall on a Javascript script that is obfuscated and encrypted with double base-64 code.

 

So i'm asking you how can I execute the JS script in my code without using a WebBrowser. But I know that is impossible because the Javascript is executed on the client side: with the objects i'm using,there isn't any client (HttpWebRequest and HttpWebResponse).

 

So... i'm here to get some informations if someone know how can I easily get the URL of the image of the captcha of the death.

 

PS: When you are searching something in a big text, I recommend you to use Regex pattern (because get each lines of the data is longer than regex patterns )

Check this

http://www.codeproje...avaScript-suppo

[Misuki]

extract the Key Value from the <script> tags inside of your HTML

 

http://www.google.co...api/noscript?k=## insert key

 

Wow thank's, I didn't know that a noscript solution has been made by google, that's a good idea ! I'll try with this url.

 

Thank you Nevachana too, i'll check for your thread.