HTTPS request, specifying hostname and specific IP address

Question

I have a Node.js-based deployment script for my application servers. One step in the deployment process is to validate that these application servers are listening on HTTPS correctly before registering them with DNS. To do that, I simply need to make an HTTPS request to that server's IP address.

If this were HTTP, it's a non-issue. I can make a HTTP GET request for http://[2001:0db8::0370:7334]/, and this will work. However, if I make an HTTPS GET request for https://[2001:0db8::0370:7334]/, this will fail since the certificate is for a specific hostname like api.example.com.

If I were testing manually, I would temporarily put the IP address in the hosts file and cURL https://api.example.com. However, in this automated process, I may be deploying several hosts at once so this isn't a solution for my deployment script.

How can I make an HTTPS request where I specify the hostname and IP address?

Perhaps there's some way to do this with a custom Agent?

I'm currently using node-fetch, but I'm happy to use whatever API is needed to make this work.

Answer 1

Set the host header for the request:

const https = require('https');

https.get('https://AA.BB.CC.DD', {
  headers : { host : 'api.example.com' }
}, res => {
  console.log('okay');
}).on('error', e => {
  console.log('E', e.message);
});

EDIT: I dug around a bit to see how this works exactly. To allow HTTPS-based virtual hosting, there's a TLS extension called SNI (Server Name Indication). This extension is used by a client to indicate the hostname to which it is trying to connect, so the server can pick the appropriate certificate that belongs to that hostname.

Node's tls module, which is used by https, has an option servername to set this hostname:

https.get('https://AA.BB.CC.DD', {
  servername : api.example.com'
}, ...)

However, you still need to pass a Host header too (that's part of the regular HTTP protocol):

https.get('https://AA.BB.CC.DD', {
  headers : { host : 'api.example.com' },
  servername : 'api.example.com'
}, ...)

To keep things DRY, Node.js will set servername to the Host header, unless it's already set to something else (here).