HTTPS and DNS poisoning attack

The best explanation of HTTPS I have seen was written by Jeff Moser, highly recommended!

After reading the article, there was only one thing left unclear, so I asked the author, Jeff Moser, and he responded:

Me:


Just one thing is really unclear to me - DNS poisoning: The attacker obtains certificate from amazon.com, I enter "amazon.com" to browser, browser goes to attacker's site, which responds by valid amazon.com certificate signed by Verisign. How does the browser tell this is an attack?


Jeff:

Great question! Note that if an attacker did this, they'd run into trouble in the "Trading Secrets" section that I described. Without knowing Amazon.com's private key, they couldn't decrypt the pre-master secret that the client sends out because the certificate from Verisign has Amazon's public key. Thus, the client would use that public key (and not one an attacker generated).


DNS poisoning is an attack when attacker fools DNS server. You type "amazon.com" in the browser, the browser asks the DNS server to resolve the URL = to translate the URL to IP address. Since the DNS server is poisoned, it returns attacker's IP address and browser connects to attacker's server, while address bar reads "amazon.com" - quite nasty.

Now everything is 100% clear, thanks Jeff!

Posted by Martin Konicek on 2:08 AM

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