Re: [dns-privacy] [DNSOP] DNS over DTLS (DNSoD)
Tirumaleswar Reddy (tireddy) tire...@cisco.com wrote: Any specific reason for the firewalls to permit TCP/53 other than for zone transfer ? RFC 5966 Tony. -- f.anthony.n.finch d...@dotat.at http://dotat.at/ South Utsire, Northeast Forties: Easterly 4 or 5, increasing 6 or 7. Slight or moderate. Fair. Good. ___ dns-privacy mailing list dns-privacy@ietf.org https://www.ietf.org/mailman/listinfo/dns-privacy
Re: [dns-privacy] [DNSOP] DNS over DTLS (DNSoD)
On Fri, Apr 25, 2014 at 10:46 AM, Ralf Weber d...@fl1ger.de wrote: Moin! On 25 Apr 2014, at 16:22, Tirumaleswar Reddy (tireddy) tire...@cisco.com wrote: Any specific reason for the firewalls to permit TCP/53 other than for zone transfer ? Wat? Because it is defined in the RFC. RFC1035 may not been totally clear on that. IMHO the language is strong enough, but if not there is RFC5966: All general-purpose DNS implementations MUST support both UDP and TCP transport. Any more questions?! Also all this new DNS stuff like DNSSEC and mitigating DNS amplification attack with RRL or similar techniques require that the TCP transport works. So long Yes and RFC quite definitely says that I get a pony. The existing DNS works as far as the people running their firewalls are concerned. The failure of TCP fallback in practice has been an understood problem for 20+ years. If people want to design a protocol that is going to be usable, they are going to end up having to accept some constraints that are not in the specs. -- Website: http://hallambaker.com/ ___ dns-privacy mailing list dns-privacy@ietf.org https://www.ietf.org/mailman/listinfo/dns-privacy
Re: [dns-privacy] [DNSOP] DNS over DTLS (DNSoD)
On 25 Apr 2014, at 11:14, Phillip Hallam-Baker hal...@gmail.com wrote: The existing DNS works as far as the people running their firewalls are concerned. The failure of TCP fallback in practice has been an understood problem for 20+ years. Understood, perhaps; measured and understood, not so much. What is sorely missing from most/all protocol evolution discussions is a rigorous study of the actual impact of larger response sizes, fragmentation, interception/middebox-mangling, TCP fallback and TCP pipelining in the real world in at least two problem domains, recursive-authority and stub-recursive. If people want to design a protocol that is going to be usable, they are going to end up having to accept some constraints that are not in the specs. And it would be great if we could describe those constraints with confidence. There was concern that signing ORG might cause resolution problems due to larger responses, or might cause TCP fallback on a scale not seen before. The former were not apparent. The latter happened (due to a defect in the signer used for ORG) but did not cause any obvious problems. There was widespread expectation that DNSSEC in the root zone would impact resolvers' ability to prime, hence the DURZ, global netops meeting roadshow, LTQC, etc. No issues were identified. We will get much further, much more quickly if we know more about what problems are likely and which ones are unlikely. Being afraid of every possible negative outcome is just a recipe for doing nothing. No useful risk analysis is possible without data. Joe ___ dns-privacy mailing list dns-privacy@ietf.org https://www.ietf.org/mailman/listinfo/dns-privacy
Re: [dns-privacy] [DNSOP] DNS over DTLS (DNSoD)
-Original Message- From: Paul Vixie [mailto:p...@redbarn.org] Sent: Thursday, April 24, 2014 12:11 AM To: Dan Wing Cc: dn...@ietf.org; dns-privacy@ietf.org; Prashanth Patil (praspati); Tirumaleswar Reddy (tireddy) Subject: Re: [DNSOP] DNS over DTLS (DNSoD) for reasons well-spoken up-thread, if we're going to add a dns transport, i'd like it to be RFC 6013 style TCP (in which session context can be compressed and retained after FIN for full-window-size restart, and which permits the query to be bundled into the SYN packet), or at a minimum, SCTP. SCTP has problems with Firewall and NAT traversal, hence WebRTC is using SCTP over DTLS over DNS (http://tools.ietf.org/html/draft-ietf-rtcweb-data-channel-08). DNSoD does not require server-side DTLS state, this is achieved by the server sending ticket to the DTLS client using the mechanism explained in RFC 5077. -Tiru DTLS does not solve any of the problems described at https://queue.acm.org/detail.cfm?id=2578510. vixie ___ dns-privacy mailing list dns-privacy@ietf.org https://www.ietf.org/mailman/listinfo/dns-privacy
Re: [dns-privacy] [DNSOP] DNS over DTLS (DNSoD)
On 24 Apr 2014, at 10:53, Phillip Hallam-Baker hal...@gmail.com wrote: If you want to use TLS with DNS then use port 443. One of the effects of firewalls is that we now only have three ports for all protocols: Port 80/UDP: Non SSL traffic Port 443/TCP: SSL traffic Port 53/UDP: DNS I think it's important to frame the problem space. I suspect that the firewall challenges you cite most often apply to communications between stub resolvers and recursive resolvers, for hosts that are using an off-net resolver (directly, or via a proxy). I also suspect that any ISP who has ever decided to install firewalls or other packet-mangling middleware in front of their resolver service (and is still in business) has by now collected many reasons not to do that, and that the network path between ISP resolver and authority servers is very likely to be clean. For ISP, read campus, enterprise, etc as appropriate. I have no science to back up my suspicions, here. Given that others apparently have different suspicions, equally plausible, perhaps science is needed. However, I'll note that the conversations surrounding the problem statement in London all seemed to support separating these two uses of the protocol. I don't think it's worth butchering the protocol if it turns out that we have an easy and clean solution that works for a significant part of the problem space (resolvers talking to authority servers), which is what t-dns/draft-hzhwm-start-tls-for-dns looks like to me. This compartmentalisation of the problem space reminds me of RFC 4409, and makes me wonder whether there's a way to replace stub-resolver communications with something new without breaking everything. After all, in a very real sense we really only have two edge platforms to worry about (Android and iOS). Joe ___ dns-privacy mailing list dns-privacy@ietf.org https://www.ietf.org/mailman/listinfo/dns-privacy
Re: [dns-privacy] [DNSOP] DNS over DTLS (DNSoD)
On Thu, Apr 24, 2014 at 11:19 AM, Joe Abley jab...@hopcount.ca wrote: On 24 Apr 2014, at 10:53, Phillip Hallam-Baker hal...@gmail.com wrote: If you want to use TLS with DNS then use port 443. One of the effects of firewalls is that we now only have three ports for all protocols: Port 80/UDP: Non SSL traffic Port 443/TCP: SSL traffic Port 53/UDP: DNS I think it's important to frame the problem space. I suspect that the firewall challenges you cite most often apply to communications between stub resolvers and recursive resolvers, for hosts that are using an off-net resolver (directly, or via a proxy). I also suspect that any ISP who has ever decided to install firewalls or other packet-mangling middleware in front of their resolver service (and is still in business) has by now collected many reasons not to do that, and that the network path between ISP resolver and authority servers is very likely to be clean. For ISP, read campus, enterprise, etc as appropriate. My interest at the start was censorship prevention so my interest is almost exclusively client-resolver. It does look like a totally different protocol to resolver-authoritative though. Since what we are concerned with here is (also) privacy, I agree that the resolver-authoritative loop is also in play. But that is a vastly lower priority than the client-resolver loop. If you don't solve that, you don't have any solution. The two problems are completely separate from a trust point of view. For key management in the Resolver-Authoritative loop you almost certainly want to use DNSSEC. But in the client-resolver loop you might well want to use WebPKI because you would want accountability. I have no science to back up my suspicions, here. Given that others apparently have different suspicions, equally plausible, perhaps science is needed. However, I'll note that the conversations surrounding the problem statement in London all seemed to support separating these two uses of the protocol. I don't think it's worth butchering the protocol if it turns out that we have an easy and clean solution that works for a significant part of the problem space (resolvers talking to authority servers), which is what t-dns/draft-hzhwm-start-tls-for-dns looks like to me. You know when people use loaded terms like 'butchering the protocol' to mean 'do it a different way to me' I start to get a little cross. For me the idea of putting TLS traffic over the same port as non TLS traffic without careful attention to how the upgrade is achieved would be 'butchering the protocol'. Changing the port number to one that is known to work is a cleaner approach. -- Website: http://hallambaker.com/ ___ dns-privacy mailing list dns-privacy@ietf.org https://www.ietf.org/mailman/listinfo/dns-privacy
Re: [dns-privacy] [DNSOP] DNS over DTLS (DNSoD)
On Thu, 24 Apr 2014 11:32:12 -0400, Phillip Hallam-Baker wrote: ... For me the idea of putting TLS traffic over the same port as non TLS traffic without careful attention to how the upgrade is achieved would be 'butchering the protocol'. Changing the port number to one that is known to work is a cleaner approach. ... Agreed that TLS upgrade must be done carefully. Fortunately we have a number of protocools that have survived a TLS retrofit: IMAP, STMP, POP3, FTP, XMPP, LDAP, NNTP (according to http://en.wikipedia.org/wiki/STARTTLS). Several of these protocols are used over WANs, although I would guess DNS has far more frequent help from transparent middleboxes than they do, so YMMV. I think SMTP is a pretty compelling argument that the World May Not End to do STARTTLS, though. It is true that a new port solves the oh noes, something changed and I, the firewall/middlebox, hate you problem. However, it solves that by by turning it into the oh noes, why should I, the firewall, ever open this new port for you. (As as been pointed out.) It seems like a trade-off about which pain one wants to endure. -John ___ dns-privacy mailing list dns-privacy@ietf.org https://www.ietf.org/mailman/listinfo/dns-privacy
