HTTP Redirection at Handshake

[FlorianBELLAZOUZ]

Hi there !

Like it say in the RFC 6455

   1.  If the status code received from the server is not 101, the
       client handles the response per HTTP [RFC2616] procedures.  In
       particular, the client might perform authentication if it
       receives a 401 status code; the server might redirect the client
       using a 3xx status code (but clients are not required to follow
       them), etc.  Otherwise, proceed as follows.

But when i try a redirect status 302.
The websocket throw an Error 'unexpected server response (302)'

// serv.js
var Net = require('net')
var Wss = require('ws').Server

var server = new Net.Server()

server.on('connection',socket=>{
  socket.write('HTTP/1.1 302 Found\nLocation: ws://localhost:8080\n\n')
  socket.end()
})

server.listen(80)

var wss = new Wss({port:8080})

// ws.js
var Ws = require('ws')

var ws = new Ws('ws://localhost') // throw Error: unexpected server response (302)

I misunderstand something or this is a divergence of the RFC 6455 ?

[dwang2]

+1
Facing the same issue where "follow-redirect" isn't supported.

[lpinca]

Yes, the client does not follow redirects, but if I read the spec correctly "clients are not required to follow them".

[danields761]

Hello!
@lpinca, is there any way to follow them?

[lpinca]

No, at the moment there is no way unless you monkey patch the code.

[blandinw]

Not sure how you'll prioritize this, so here's our use case.
301 redirects are often used when server infra changes, etc.
In our case, we absolutely have to redirect, but users of this library will break when we do so.

Please upvote the original post if you need this feature

[lpinca]

@blandinw a possible workaround is to use a proxy which follows redirects.
A PR to fix the issue is welcome.

[jklepatch]

I started a fix, in lib/WebSocket.js.

During handshake, if server answer by 301 or 302 status code, initAsClient() is called recursively with updated address. It also store the state isRedirecting in the options object to avoid redirect loop if new handshake attempt result in another redirection.

I tried the testing code provided on top of this thread, and it seems the socket is created properly. If this approach receive a good feedback, should we also check that the location header provided by server is well formed before trying another handshake? if yes, is there a spec about what is a well formed url for a websocket?

 function initAsClient (address, protocols, options) {
  options = Object.assign({
    protocolVersion: protocolVersions[1],
    protocol: protocols.join(','),
    perMessageDeflate: true,
    handshakeTimeout: null,
    localAddress: null,
    headers: null,
    family: null,
    origin: null,
    agent: null,
    host: null,
    isRedirection: false,

line 654:

  this._req.on('response', (res) => {
    if(!options.isRedirection && ((res.statusCode == 301) || (res.statusCode == 302))){
      options.isRedirection = true;
      initAsClient.call(this, res.headers.location, protocols, options);
      return;
    }
    if (!this.emit('unexpected-response', this._req, res)) {
      this._req.abort();
      this.emit('error', new Error(`unexpected server response (${res.statusCode})`));
      this.finalize(true);
    }
  });