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FreeBSD Developer Summit – BSDCan 2014 – DNS WG

The DNS Working Group at the FreeBSD Developer Summit at BSDCan this year was off to a good start by noticing that DNSSEC validation could not work on the University of Ottawa’s wireless network. The university’s resolvers added additional records to the root zone, thus failing validation at the root. This led to some discussion on how to provide a user-friendly way to explain this in an understandable way to the user and giver the user a choice of turning off validation or find another network. This certainly is going to be a major problem when turning on validation by default as broken resolvers are very common at hotels, coffee shops, etc. etc.

On a more positive note, all the FreeBSD projects zones are DNSSEC signed and all project-owned servers have SSHFP records in the zone. Dog food was eaten.

Dag-Erling Smørgrav started off by giving an overview of the current state of affairs. ldns and unbound are imported into base in HEAD and 10.x. unbound is meant to act as a local resolver only and as it is not linked to libevent, it will not scale to anything else. For a network-wide resolver or any other configuration, it is recommended to install unbound from ports. DES further went into some of the implementation details on how the base unbound is installed to make sure it does not conflict with an unbound installed from ports.

DES explained some issues he encountered with local and RFC1918 zones which are filtered by default by unbound. Others reported no issues with the right configuration options, so more investigation is needed.

Some people reported having difficulty getting patches accepted upstream by NLNetLabs, which gave some cause for concern as we clearly want a good and active working relationship with our DNS vendor. Others reported no problem working with NLNetLabs, quite the opposite, they are very interested to see the work going on in operation systems, so we’ll just need to build upon that relationship and make sure to invite them to the next WG meeting. Patches that are currently being worked on, DES has some code cleanups, Björn a DNS64 feature, should be submitted through the “normal” submission process and review with NLNetLabs and we’ll see how that goes.

Erwin Lansing started the brainstorm session on future work. Some command line tools would be nice to have; drill does most things one wants, but people are too used to writing dig and dig has many more options; Peter Wemm would like to see contrib scripts line ldns-dane, which are just really easy to use; the control socket should be a unix socket, there’s a patch floating around and should be submitted upstream.

The “Starbucks” problem came up again, with a proposal to turn on val-permissive-mode by default. Another solution may be by looking at how unbound-trigger does its magic.

After a coffee break, Peter Losher, ISC, went over some of the recent changes at ISC. BIND10 development has been handed over to a new project and ISC will concentrate on BIND9 and a stand-alone project for the DHCP component. BIND 9.10 was recently released and plans are in place for 9.11. ISC is open to suggestions and feature requests.

Peter brought up the topic of clientID for which a IETF draft (draft-edns0-client-subnet) is available. This would help client find the nearest CDN node, etc. ISC wants this to be an opt-out in operating systems as it will peel off a layer of anonymisation, and should be controllable by the user.

Next up was Michael Bentkofsky, Verisign, who, while not involved in the project himself, gave an introduction into the getDNS API, which is a replacement for getaddrinfo and allows the stub resolver to get validation information down at the client level. It’s available in ports. The discussion went into more of a brainstorm on how applications should get DNS and DNSSEC information and who gets to make decisions about its security. There should be a clear separation between policy and mechanism, where application programmers should not have to worry about this; it should be a system policy. There should be a higher level API where an application basically can ask the operating system for a “connection” and the operation system takes care of everything behind the scenes, DNS, DNSSEC, SSL, DANE, etc. and just return a socket, with some information on how the connection was established and which security mechanisms were used. In FreeBSD, it would make sense to let the Casper daemon hand out the different sub-tasks to ensure all lookups, cryptography, etc. are properly compartmentalised. One potential problem with passing on additional information is that all DNS lookups currently go through nsswitch, which would need to grow knowledge about that data as well. Are people still using other mechanisms for hostname lookups besides the hosts file and DNS? We can probably just remove nsswitch for the hostname lookups.

The session ended with some aims for the 11.0 release. We’ll need to have a wider discussion about the aforementioned removal of nsswitch out of the hostname lookups. We’ll also need a better understanding of what API capabilities applications may need. Can Casper provide all these? Can it run unbound behind the scenes to do all the DNS “stuff” for it? Can we capsicumize unbound and will that be accepted upstream? Enough food for thought and even more for writing code.

Thanks again to DK Hostmaster for sponsoring my trip to BSDCan this year, and see you at the DNS WG meet up at EuroBSDCon in Sofia in September.

One Comment

  1. Dag-Erling Smørgrav
    Dag-Erling Smørgrav July 19, 2014

    I fixed the reverse lookup issue earlier today. The problem was twofold. First, unbound filters out reverse lookups for private address ranges. The development version has a knob to turn that off (unblock-lan-zones), which Wouter backported for me. Secondly, the reverse zones are signed, so with validation enabled, unbound will reject any answer other than NXDOMAIN. The solution to that is to turn validation off for these zones (domain-insecure).

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