HTTP Public Key Pinning (HPKP) middleware

This header has been deprecated citing risks of misuse, and therefore is not recommeded. This module (hpkp) will not receive any new feature development but will still be maintained.

Adds Public Key Pinning headers to Express/Connect applications. To learn more about HPKP, check out the spec, the article on MDN, and this tutorial.

Be very careful when deploying this—you can easily misuse this header and cause problems. Chrome has dropped support for HPKP citing risks of misuse.

Usage:

``js
const express = require("express");
const hpkp = require("hpkp");

const app = express();

const ninetyDaysInSeconds = 7776000;
app.use(
hpkp({
maxAge: ninetyDaysInSeconds,
sha256s: ["AbCdEf123=", "ZyXwVu456="],
includeSubDomains: true, // optional
reportUri: "https://example.com", // optional
reportOnly: false, // optional

// Set the header based on a condition.
// This is optional.
setIf(req, res) {
return req.secure;
},
}),
);
`

Setting reportOnly to true will change the header from Public-Key-Pins to Public-Key-Pins-Report-Only.

Don't let these get out of sync with your certs! It's also recommended to test your HPKP deployment in reportOnly mode, or alternatively, to use a very short maxAge` until you're confident your deployment is correct.