multiserver

A single interface that can work with multiple protocols, and multiple transforms of those protocols (eg, security layer)

address format

Addresses describe everything needed to connect to a peer. each address is divided into protocol sections separated by ~. Each protocol section is divided itself by :. A protocol section starts with a name for that protocol, and then whatever arguments that protocol needs.

For example, the address for my ssb pubserver is:

net:wx.larpa.net:8008~shs:DTNmX+4SjsgZ7xyDh5xxmNtFqa6pWi5Qtw7cE8aR9TQ=

That says use the net protocol (TCP) to connect to the domain wx.larpa.net on port 8008, and then encrypt the session using shs (secret-handshake) to the public key DTNmX+4SjsgZ7xyDh5xxmNtFqa6pWi5Qtw7cE8aR9TQ=.

Usually, the first section is a network protocol, and the rest are transforms, such as encryption or compression.

Multiserver makes it easy to use multiple protocols at once. For example, my pub server also supports shs over websockets.

So, this is another way to connect:

wss://wx.larpa.net~shs:DTNmX+4SjsgZ7xyDh5xxmNtFqa6pWi5Qtw7cE8aR9TQ=

net

TCP is net:{host}:{port} port is not optional.

ws

WebSockets is ws://{host}:{port}? port defaults to 80 if not provided.

WebSockets over https is wss://{host}:{port}? where port is 443 if not provided.

onion

Connect over tor using local proxy (9050). Onion is onion:{host}:{port} port is not optional.

shs

Secret-handshake is shs:{public_key}:{seed}?. seed is used to create a one-time shared private key, that may enable a special access. For example, you'll see that ssb invite codes have shs with two sections following. Normally, only a single argument (the remote public key) is necessary.

TODO

A short list of other protocols which could be implemented:

• cjdns
• other encryption protocols...

motivation

Developing a p2p system is hard. especially hard is upgrading protocol layers. The contemporary approach is to update code via a backdoor, but as easily as security can be added, it can be taken away. We need an approach to upgrading that is itself decentralized, and also does not accumulate legacy baggage. after upgrading past a version of the protocol, the system should be able to discard that without a trace.

Traditionally, protocol versions are upgraded by negioating the version used in a handshake. But, how do you upgrade the handshake? You can't. This also tends to accumulate legacy, because you never know if you'll meet an old peer.

Some HTTP APIs provide upgradability a better, simpler way. By putting a version number within the url. A new version of the API can then be used without touching the old one at all.

I propose to adapt this approach to lower level protocols. Do not negioate versions/ciphersuits in the handshake. Instead, run multiple protocols at once, and "lookup" which versions a peer supports currently. Most p2p systems have some sort of lookup system to find peers anyway (might be DHT, a tracker server, or gossip), just put version information in there.

There are two main situations where I expect this to be useful: upgrading ciphers and bridging across enviroments that are otherwise cannot talk to each other (web browser to desktop)

upgrade

If a peer wants to upgrade from weak protocol to a strong one, they simply start serving strong via another port, and advertise that in the lookup system. Now peers that have support for strong can connect via that protocol.

Once most peers have upgraded to strong, support for weak can be discontinued.

bridging

Regular servers can do TCP. Desktop clients can speak TCP, but can't create TCP servers reliably. Browsers can use WebSockets and WebRTC. WebRTC gives you p2p, but needs an introducer. Another option is utp

• probably the most convienent, because it doesn't need an introducer on every connection (but it does require some bootstrapping), but that doesn't work in the browser either.

var MultiServer = require('multiserver')

var ms = MultiServer([
  require('multiserver/plugins/net')({port: 1234}),
  require('multiserver/plugins/ws')({port: 2345})
])

//start a server (for both protocols!)
//returns function to close the server.
var close = ms.server(function (stream) {
  //handle incoming connection
})

//connect to a protocol. uses whichever
//handler understands the address (in this case, websockets)
var abort = ms.client('ws://localhost:1234', function (err, stream) {
  //...
})

//at any time abort() can be called to cancel the connection attempt.
//if it's called after the connection is established, it will
//abort the stream.

example - server with two security protocols

This is just how some services (eg, github) have an API version in their URL scheme. It is now easy to use two different versions in parallel. later, they can close down the old API.

var MultiServer = require('multiserver')
var ms = MultiServer([
  [ //net + secret-handshake
    require('multiserver/plugins/net')({port: 3333}),
    require('secret-handshake-multiserver')({
      keys: //keypair
      appKey: //application key
      auth: //auth function (only needed for server)
    }),
  ],
  [ //net + secret-handshake2
    //(not implemented yet, but incompatible with shs)
    require('multiserver/plugins/net')({port: 4444}),
    require('secret-handshake2-multiserver')({
      keys: //keypair
      appKey: //application key
      auth: //auth function (only needed for server)
    }),
  ]
]

console.log(ms.stringify())

//=> net:<host>:3333~shs:<key>;net:<host>:4444~shs2:<key>

//run two servers on two ports.
//newer peers can connect directly to 4444 and use shs2.
//this means the protocol can be _completely_ upgraded.
ms.server(function (stream) {

})

//connect to legacy protocol
ms.client('net:<host>:3333~shs:<key>', function (err, stream) {
  //...
})

//connect to modern protocol
ms.client('net:<host>:4444~shs2:<key>', function (err, stream) {
  //...
})

License

MIT