Handover

A plugin for hsd to enable DNS resolution on external networks like Ethererum.

Installation & Usage

Before installing, you need an Infura API key. Go to infura.io, create a new project and get a free API key. The plugin requires master branch of hsd (currently unreleased).

cd /path/to/hsd

# install the plugin
npm install imperviousinc/handover

Your Infura credentials can be passed to the plugin in the same way(s) as all other hsd configuraiton parameters:

Command line:

hsd \
 --plugins=handover \
 --handover-infura-projectid=<...> \
 --handover-infura-projectsecret=<...>

Environment variables:

export HSD_HANDOVER_INFURA_PROJECTID=<...>
export HSD_HANDOVER_INFURA_PROJECTSECRET=<...>
hsd --plugins handover

Configuration file:

~/.hsd/hsd.conf:

handover-infura-projectid: <...>
handover-infura-projectsecret: <...>
plugins: handover

You should see this in the log:

[info] (handover) handover external network resolver plugin is active.

Try it out!

Resolve an ENS name directly without Handshake:

$ dig @127.0.0.1 -p 5350 fuckingfucker.eth +short
184.73.82.1

Resolve a decentralized subdomain of a Handshake TLD:

$ dig @127.0.0.1 -p 5350 certified.badass +short
184.73.82.1

Resolving HNS names on Ethereum

See HIP-0005 for more details.

Notice how the NS record was set for this Handshake domain:

$ hsd-rpc getnameresource badass

{
  "records": [
    {
      "type": "NS",
      "ns": "0x36fc69f0983E536D1787cC83f481581f22CCA2A1._eth."
    }
  ]
}

The _eth TLD indicates an abstract (forked) ENS contract on Ethereum, appended to the contract's address. On Ethereum, the domain certified.badass was registered with this contract, and its DNS records were set using EIP-1185:

$ node

> const {wire} = require('bns')
> wire.Record.fromJSON({name:'certified.badass.', ttl: 60000, class: 'IN', type: 'A', data: {address: '184.73.82.1'}}).encode().toString('hex')
'096365727469666965640662616461737300000100010000ea600004b8495201'

Explanation

When hsd is run with this plugin, a middleware function is added to the HNS root resolver that intercepts queries as they come in. If the query is rooted in either .eth or ._eth TLD, the name is resolved directly using ENS, bypassing Handshake.

Otherwise, HNS resolution proceeds normally. However, the results are inspected by the plugin before being returned. If a domain has an NS record rooted in either .eth or ._eth, the plugin uses the NS address and the original query string to resolve the user's request on Ethereum. If an answer is found there, it is sent back to the recursive resolver.

There is one more complication which is that recursive resolvers (like unbound) may have qname-minimisation set, which means the resolver begins its recursion by ONLY querying the TLD (as opposed to sending the full query string). To deal with this, if the plugin detects a NS pointing to .eth or ._eth but does not have a full query string (i.e. only one label, .badass) the plugin returns an empty response with SOA. This tricks the recursive resolver into making a new request with the full query string (i.e. certified.badass).

Future Work

There's still a lot "TODO":

Local Ethereum provider: Currently the plugin relies on the Infura API. However, it is trivial to add an option to use a local Ethereum full node instead.

Additional ENS types: This plugin currently only supports resolving of EIP-1185 data (aka "actual DNS records on ENS") but ENS itself has support for many abstract data types like content hashes and a special type of text record that requires a key to resolve. An example of a set of these text records with their keys:

brantly.eth          avatar               https://i.imgur.com/JcZESMp.png
brantly.eth          description          "If anyone would come after me, let him deny himself and take up his cross daily and follow me. For whoever would save his life will lose it, but whoever loses his life for my sake will save it. For what does it profit a man if he gains the whole world and loses or forfeits himself?" - Jesus, Luke 9.23-25
brantly.eth          email                me@brantly.xyz
brantly.eth          keywords             catholic, ens, oregon, seinfeld, books
brantly.eth          notice               Not for sale
brantly.eth          url                  http://brantly.xyz/

Subdomains: The plugin has not been tested on sub domains of names registered at the ENS contract root (e.g. whynot.fuckingfucker.eth or yesiam.certified.badass).

Development

To contribute or modify this plugin you can install it in a different working directory with git, but it must be linked into hsd correctly to work:

git clone https://github.com/imperviousinc/handover
cd handover
npm install

cd /path/to/hsd/repo
ln -s /path/to/handover /node_modules

export NODE_PRESERVE_SYMLINKS=1

hsd --plugins handover

If you need sudo to listen on port 53:

export NODE_PRESERVE_SYMLINKS=1
sudo -E hsd --plugins handover --rs-port 53

Testing

Run unit tests: npm run test

Run integration test:

cd /path/to/hsd

node_modules/handover/test/handover-plugin-test.sh

Credit

This plugin relies on the ethers.js library.

Inspiration comes from hsd-ens-resolution by the very handsome and super-friendly @tynes.

Thanks to @rithvikvibhu for the name "handover".