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“DNS Proxy Bypass by Recursive DNS Discovery and LOCAL.ARPA” draft-ietf-dns-recursive-discovery

“DNS Proxy Bypass by Recursive DNS Discovery and LOCAL.ARPA” draft-ietf-dns-recursive-discovery. Ray Bellis IETF76 DNSOP WG Hiroshima, 11 th November 2009. The Fundamental Problem…. Please try again – the DNS proxy on 192.168.1.1 doesn’t work properly (see RFC5625).

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“DNS Proxy Bypass by Recursive DNS Discovery and LOCAL.ARPA” draft-ietf-dns-recursive-discovery

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  1. “DNS Proxy Bypass by Recursive DNSDiscovery and LOCAL.ARPA”draft-ietf-dns-recursive-discovery Ray Bellis IETF76 DNSOP WG Hiroshima, 11th November 2009

  2. The Fundamental Problem… Please try again – the DNS proxy on 192.168.1.1 doesn’t work properly (see RFC5625) DNS Servers (6) = 192.168.1.1 DHCP DISCOVER DHCP OFFER ISP FAIL DNS settings learnt via DHCP or PPP/IPCP DNS

  3. The Chicken and Egg Problem… Still not right – you don’t know the real DNS servers because the LAN came up before the WAN. Didn’t you fix that proxy yet? DNS Servers (6) = 192.168.1.1 DHCP DISCOVER DHCP OFFER ISP FAIL DNS settings learnt via DHCP or PPP/IPCP DNS

  4. The Configuration Problem… Uh-oh - someone forgot to implement TR124 requirement LAN.DNS.2. End-user supplied DNS settings SHOULD be in the DHCP OFFER. BTW – your proxy still doesn’t work properly! DNS Servers (6) = 192.168.1.1 DHCP DISCOVER DHCP OFFER ISP FAIL End-user configures DNS settings DNS

  5. The Proposed Solution… • Let the DHCP stuff happen • Use the DNS proxy initially … • to ask the recursive DNS server for a list of real DNS servers • Then use those instead! IN A? domain.local.arpa. ISP IN A 192.0.2.1 DNS

  6. The Proposed Solution… • Let the DHCP stuff happen • Use the DNS proxy initially … • to ask the recursive DNS server for a list of real DNS servers • Then use those instead! IN A? domain.local.arpa. ISP IN A 192.0.2.1 DNS

  7. A little more detail • Why we’re proposing this: • Because DNS proxies don’t work! • to get DNSSEC through • to get TCP queries through • The draft reserves local.arpa. • for use “within a network’s administrative boundaries” • and domain.local.arpa for this application • Version -02 will have NXDOMAIN redirect detection • probably via nxdomain.local.arpa. • if nxdomain.local.arpa == domain.local.arpa then ignore the results, your ISP is trapping NXDOMAIN

  8. Things we’ve thrown out already • Anycast • If you’re going to use an Anycast address to discover DNS, you might as well use that address for all DNS! • “.local” • Too much baggage

  9. Things we’re still figuring out! • Does the bootstrap query need additional protection, and if so, how? • DNSSEC no good, proxies break it! • A random nonce prefix? • Something else? • Interaction with DNSSEC-signed .arpa • If IANA has an NSEC[3] record that says local.arpa doesn’t exist, then the locally-supplied copy is bogus

  10. Any Questions?

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