Re: [DNSOP] Working Group Last Call draft-ietf-dnsop-resolver-priming
"Paul Hoffman" <paul.hoffman@vpnc.org> Sun, 14 August 2016 23:27 UTC
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From: Paul Hoffman <paul.hoffman@vpnc.org>
To: Shane Kerr <shane@time-travellers.org>
Date: Sun, 14 Aug 2016 16:27:24 -0700
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Subject: Re: [DNSOP] Working Group Last Call draft-ietf-dnsop-resolver-priming
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On 5 Aug 2016, at 2:45, Shane Kerr wrote: > First, we have: > > "If a priming query does not get a response within 2 seconds, the > recursive resolver SHOULD retry with a different target address from > the configuration." > > The "2 seconds" seems a bit arbitrary. I'm not sure why any > recommendations need to be made at all. The document already says that > these are basically normal DNS queries elsewhere - surely that is > enough? > (And maybe if we do want to recommend a retry then we need to be clear > that if an answer comes from an earlier query that the resolver may > accept it?) It's sounding like people don't like the mention of a time at all. Proposed replacement: If a priming query does not get a response within a short time, the recursive resolver needs to retry the query with a different target address from the configuration. (I am avoiding saying "within a configured time" because I don't think this is easily configured in some common recursors.) > Second, a possible additional security consideration is that a priming > query typically signals a resolver starting with an empty cache > (although not always - the Knot resolver has a persistent cache, for > example). This may be an especially vulnerable time for a resolver for > cache poisoning. I don't know what can be done to mitigate this though > aside from requiring TCP or DNS cookies for a time after startup, so > perhaps this can be left out. Proposed wording: An on-path attacker who sees a priming query coming from a resolver can inject false answers before a root server can give correct answers. If the attacker's answers are accepted, this can set up the ability to give further false answers for future queries to the resolver. False answers for root servers are more dangerous than, say, false answers for TLDs because the root servers are the highest node of the DNS. --Paul Hoffman
- Re: [DNSOP] Working Group Last Call draft-ietf-d… Tim Wicinski
- Re: [DNSOP] Working Group Last Call draft-ietf-dn… 神明達哉
- Re: [DNSOP] Working Group Last Call draft-ietf-dn… Marek Vavruša
- Re: [DNSOP] Working Group Last Call draft-ietf-dn… Warren Kumari
- Re: [DNSOP] Working Group Last Call draft-ietf-dn… Paul Hoffman
- Re: [DNSOP] Working Group Last Call draft-ietf-dn… Andreas Gustafsson
- Re: [DNSOP] Working Group Last Call draft-ietf-dn… Bob Harold
- Re: [DNSOP] Working Group Last Call draft-ietf-dn… Paul Hoffman
- Re: [DNSOP] Working Group Last Call draft-ietf-d… Shane Kerr
- [DNSOP] Working Group Last Call draft-ietf-dnsop… Tim Wicinski
- Re: [DNSOP] Working Group Last Call draft-ietf-d… Edward Lewis
- Re: [DNSOP] Working Group Last Call draft-ietf-d… Stephane Bortzmeyer