How should I store SSL keys on the server?

Question

I have a Node.JS HTTPS webserver instantiated as follows:

var privateKey = fs.readFileSync('./../ssl/localhost.key').toString();
var certificate = fs.readFileSync('./../ssl/localhost.crt').toString();

https.createServer({
    key: privateKey,
    cert: certificate
}, server).listen(80, 'localhost');

My private key is on my server which Node.JS reads to create the HTTPS webserver. If a hacker has read access to server files he can access the private key and impersonate the webserver.

Should the private key be stored on the server? Should it be destroyed once the HTTPS server has been instantiated?

Answer 1

You do not want to destroy your private key: you will need it again if you server restarts. Reboots happen sometimes...

That's a generic observation: you want your server to be able to restart in an unattended fashion. Therefore it must contain the private key, and that private key must be available to the server software.

If an attacker hijacks your complete machine, then he gets a copy of your key. That's a fact of life. Live with it. There are mitigations, though:

• You can use the "DHE" cipher suites for SSL. With these cipher suites, the server key is used for signatures, not for encryption. This means that the attacker who steals your key can thereafter impersonate your server (i.e. run a fake server) but not decrypt SSL sessions which he previously recorded. This is a good property known as Perfect Forward Secrecy.

• If you store the key in a Hardware Security Module then the key will not be stolen. The attacker may play with the key as long as he has effective control of the server, but not extract it. This decreases his power of nuisance (but HSM are expensive).

In practice, you will just make sure that the file containing the private key is readable only to the system account which runs the server (chown and chmod on Unix-like systems, NTFS access rights on Windows).

Answer 2

Probably you are looking for a reverse proxy like nginx. It is considered best practice™.

Applications running in production usually need to run on port 80 (HTTP), port 443 (HTTPS), or both. This can be a challenge if several components of your application interact with the user or you are using a web server on port 80 to deliver other assets. This makes it necessary to proxy to the Socket.IO server, and NGINX is the best way to do that. - Using NGINX and NGINX Plus with Node.js and Socket.IO, the WebSocket API - nginx blog

or HARDENING NODE.JS FOR PRODUCTION PART 3: ZERO DOWNTIME DEPLOYMENTS WITH NGINX

Basically, you are most probably looking for a stable solution also for load balancing, request limiting, etc. while you are trying to store the private key securely.