support custom peer certificates on mock socket

Context

My node app checks peer-certificates on the socket level like this:

req.on("socket", (socket: TLSSocket) => {
  socket.on("secureConnect", () => {
    // socket.getPeerCertificate()
  })
})

I tried to use nock like this:

nock(hostname)[method](path).reply(statusCode, body).on("socket", socket => {
  console.log("inside secureSocket")
  socket.getPeerCertificate = function() {
    return {}
  }

But it does not override the getPeerCertificate function. It still returns the random string from the mock socket.

If the feature request is accepted, would you be willing to submit a PR?

Yes, I think it could be similary implemented like the socket delay.

nock(...).peerCertificate(...).reply() or when creating the scope: nock(base, { peerCertificate })

[mastermatt]

Thanks for the request @pke

Some things to come to mind right off the bat:

• The current implementation of getPeerCertificate on Nock’s mock Socket class is just flat out wrong. It returns a random base64 string, but per the docs this method has always returned a plain object with the cert info.
• The mock Socket instance is created, attached to the router, and emitted on the request (req.emit('socket', socket)) before a single Scope or Interceptor is selected. This is going to be a big challenge with the feature request, unless we add some global cert registry.

@pke if the Nock Socket class simply added a setPeerCertificate method that you could call in a ‘socket’ event handler (like your example) would that work for you? It wouldn’t have the same API as some of the other Nock settings, but all those settings affect the reply which happen later in the flow. Your implementation would then look like the following:

nock(hostname)[method](path).reply(statusCode, body).on("socket", socket => {
  console.log("inside secureSocket")
  socket.setPeerCertificate({
    raw: <Buffer ... >
    subject: { ... }
   ....
})

Or if you’re using Node v15.6.0+, you could use the new, fancy X509Certificate class.

nock(hostname)[method](path).reply(statusCode, body).on("socket", socket => {
  console.log("inside secureSocket")
  const x509 = new X509Certificate('{... pem encoded cert ...}');
  socket.setPeerCertificate(x509.toLegacyObject())
})

[pke]

The back-compatible way would be fine with me, as I stated before 😉