Re: [dns-privacy] Fw: Fw: New Version Notification for draft-zuo-dprive-encryption-over-udp-00.txt

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From: Ted Hardie
Date: 2015-07-10 02:04
To: yaojk
CC: dns-privacy
Subject: Re: [dns-privacy] Fw: Fw: New Version Notification for draft-zuo-dprive-encryption-over-udp-00.txt
On Wed, Jul 8, 2015 at 12:21 AM, Jiankang Yao <[e-mail]> wrote:


It's also not clear to me, given that the stub public key is sent in the query to the recursive resolver how you avoid an attacker standing up a back-to-back user agent which strips that option, substitutes its own public key, gets the data and then passes it on.  (It may be, of course, that this attack is out of scope).
[Jiankang Yao] 
 Yes, the attacker standing up a back-to-back user agent can strip that option, substitute its own public key, get the data and then pass it on. 
 but I think that it should be no use because the attacker can not know the contents of the DNS packet send by the stub.
​I think I wasn't clear enough about the attack.  If the attacker strips the option and sends it with its own public key​, it can decrypt the response.  It can send its version in advance of sending the original packet along, so it can see the response and potentially drop packets that match some policy.  (If they are acceptable, it just sends the queued packet along).  It can also be done along side the original packet, to enable tracking without applying policy.  That's mildly detectable, since the recursive resolver would see multiple queries, but it would be pretty easy to obfuscate by generating new client public keys and varying the query interval.

Does that make sense?

[Peng Zuo]
since the whole DNS query packet(except the DNS header) is encrypted by the stub using the public key of the recursive resolver, the dns packet structure becomes invisable to attackers, attackers could not locate the additional section of the DNS query, so i think it would be difficult for the attacker to substitute it with its own key.

regards,




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