Encrypt file stream and pipe to http response

Question

I would like to encrypt a file and serve it as http response on the fly.

My current workflow is this.

const fs = require('fs');
const server = require('http').createServer();

server.on('request', (req, res) => {
  const src = fs.createReadStream('./big.file');
  src.pipe(res);
});

server.listen(8000);

I would like to encrypt the stream before piping it to the response. I know I have to use tranform stream but I am sure the right implementation for this.

Answer 1

This is well supported in Node.js, there's a section in the crypto documentation on this topic which is very useful: https://nodejs.org/dist/latest-v14.x/docs/api/crypto.html (Example: Using Cipher and piped streams):

const cipher = crypto.createCipheriv(algorithm, key, iv);

const input = fs.createReadStream('test.js');
const output = fs.createWriteStream('test.enc');

input.pipe(cipher).pipe(output);

The above example pipes a file read stream to a file write stream, this is just as easy to pipe to a http response as below:

const crypto = require("crypto");
const fs = require("fs");

// Using 256-bit AES here 
const algorithm = "aes-256-cbc";
const key = Buffer.from("22975a65b34aefb6227084727f27bfae234d1be463d1e2f2cc611820e5aa5772", "hex");
const iv = Buffer.from("979843777c873b5a2060c2ad968a20d9", "hex");

const server = require('http').createServer();

server.on('request', (req, res) => {
    const cipher = crypto.createCipheriv(algorithm, key, iv);
    const src = fs.createReadStream('./big.file');
    src.pipe(cipher).pipe(res);
});

server.listen(8000);