DoH

Configuring Private DNS via DHCP

At IETF 102 in Montréal, I presented some slides on DHCPv6 Private DNS Discovery at the DRIU BOF.

The talk was based on an Internet Draft that Willem Toorop and I worked on: DHCPv6 Options for private DNS Discovery. It provided a means to include an Authenticated Domain Name (ADN) for a nameserver to be used with DNS over TLS (DoT) or DNS over HTTPS (DoH).

To say that the talk was received poorly is an understatment...

Ted Lemon made a good argument that DHCP should only be used for boostrapping initial network parameters and not for full fledged configuration of all network parameters.

There was enough consensus that we feel that moving forward with this work would go against the wishes of the IETF community.

There still is a need for configuring the ADN in a trusted campus environment but a different proposal will need to be invented for this use case.

Overall, it was a good excercise and I hope that by documenting this here, it will discourage others from going down this path in the future.

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dns-packet

DNS Packet library

Recently, I've been contributing to the node.js library dns-packet. This library takes a JSON description of DNS fields and encodes them into raw DNS packets. On the receiving side, it also decodes raw DNS packets and returns a JSON representation.

It's a handy package that I am using for another future project to be announced soon I hope.

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iPhone/iPad TLS DNS Proxy

As Sarah Dickinson recently mentioned at DNS-OARC 27 in San Jose, CA, https://indico.dns-oarc.net/event/27/session/4/contribution/20, there is a work in progress for a TLS DNS Proxy for the Apple iPhone/iPad running iOS 11 and above. This uses the new DNS Proxy Network Extension and, when enabled, all DNS requests will be sent to a resolver over TLS.

I expect this new DNS Network Extension to be available for macOS in a future release as well.

Check back here in a bit to see the status and sign up for beta testing.

UPDATE:

After receiving the following message on the Console, it appears that the only way to use the new DNS Proxy Network Extension in iOS 11 is through Mobile Device Management (MDM) Tools as a supervised device. This makes it impossible to install for the average user through the App Store.

Therefore, I am suspending this effort until this extension is more useful to a wider audience.

Oct  5 17:29:26 iPhone nehelper(NetworkExtension)[99] <Error>: -[NEHelperConfigurationManager:562  Warning: allowing creation/modification of a DNS proxy configuration on non-supervised device because the requesting app (DNS-TLS) is a development version. This will not be allowed for the production version of DNS-TLS

UPDATE 2:

An Apple representative confirmed this is currently only for supervised devices but he seems to indicate they are considering opening this up to all devices but with no assurances or timeline:

I’ve just confirmed that, as things currently stand, NEDNSProxyProvider is limited to supervised devices.  We have a bug on file (r. 34843801) requesting that this restriction be lifted.  I suspect that this will happen but, as per usual, I can’t make any specific promises about that, or about the timeline for this change.  It certainly wouldn’t hurt for each of you to file your own bug describing your use case, how this restriction is affecting you, and what workarounds you’ve resorted to.
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DNS Delegating Server

Requirements of the delegating server

The hybrid proxy is an authoritative DNS server for one or more subdomains. Each of these subdomains MUST be delegated to the hybrid proxy by the parent zone.

Subdomains

Subdomains are delegated to another server by defining NS records in the delegating server. The following records create three subdomains and delegate those subdomains to the listed servers.

floor1.example.com. IN      NS      server1.example.com.
floor2.exmaple.com. IN      NS      server2.example.com.
floor3.example.com. IN      NS      server3.example.com.

Browse Records

Service Discovery clients will query known search domains to see if they are browseable for services. Initially, they will query for b.dns-sd.udp.example.com. If the domain is browseable, it will have PTR records for one or more browseable domains. This could include a PTR record for the domain and also for subdomains. For a client to search a hybrid proxy for discoverable services, PTR records for the subdomain of each IP subnet represented by the hybrid proxy must be listed in the delegating server.

b._dns-sd._udp IN      PTR     @                   ;apex is browseable
b._dns-sd._udp IN      PTR     floor1.example.com. ;delegated to discovery proxy
b._dns-sd._udp IN      PTR     floor2.example.com.
b._dns-sd._udp IN      PTR     floor3.example.com.

The client will then query each of the subdomains listed to see if they are browseable, for example, b.dns-sd.udp.floor1.example.com. The hybrid proxy should answer this query with its hostname.

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