create RSA SHA256 using crypto for jsonwebtoken on nodejs

Question

I see how to create HMAC 256 encrypted JWTs in NodeJS using Crypto, and the jsonwebtoken library. It's pretty easy

    //encrypt & sign with HS256
    const jwt   = require('jsonwebtoken');
    const pass  = crypto.randomBytes(256).toString('hex');
    const A     = {algorithm:'HS256'};

    const token = jwt.sign({ foo: 'bar' }, pass, A);

   //decrypt & verify
   jwt.verify(token, pass, A, function(err, decoded)
   {
      console.log('decode ',decoded);
      console.log('err    ',err);

      res.send({error:err, text:decoded});
   });

I would like to replace 'pass' with an 'RSA 256 SHA', and A with {algorithm:'RS256'}

In node crypto JS's documentation I see the command

const sign = crypto.createSign('RSA-SHA256');

to create the rsa-sha256

However then the documentation has the function

getPrivateKeySomehow()

Which is not defined or part of crypto.getPrivateKeySomehow()

So I guess I just need help getting the RSA-SHA-256 string returned from crypto, so that I can pass that into jsonwebtoken to sign my JWT.

Note: I do not want to read a private.key from a static file on my server because i see having a single private key for all my users as too big a security risk, hence why i am generating my own 256 bytes passwords and storing them off-site (not included in this post)

also, i'm not sure if i should do something like this (without using something like openssl from command line?)

const begin = '-----BEGIN RSA PRIVATE KEY-----\n';
const enc   = crypto.randomBytes(256).toString('base64') + '\n';
const end   = '-----END RSA PRIVATE KEY-----'
const pass = sign.sign(begin + enc + end);
const A = {algorithm:'RS256'};
const token = jwt.sign({ foo: 'bar' }, pass, A);

arvati · Accepted Answer · 2019-06-01 02:17:25Z

Take a look at this example bellow:

signExample = (str) => {
    crypto.generateKeyPair('rsa', {
        modulusLength: 1024,
        publicKeyEncoding: {
        type: 'spki',
        format: 'pem'
        },
        privateKeyEncoding: {
        type: 'pkcs8',
        format: 'pem'
        }
    }, (err, publicKey, privateKey) => {
        // sign String
        var signerObject = crypto.createSign("RSA-SHA256");
        signerObject.update(str);
        var signature = signerObject.sign({key:privateKey,padding:crypto.constants.RSA_PKCS1_PSS_PADDING}, "base64");
        console.info("signature: %s", signature);
        //verify String
        var verifierObject = crypto.createVerify("RSA-SHA256");
        verifierObject.update(str);
        var verified = verifierObject.verify({key:publicKey, padding:crypto.constants.RSA_PKCS1_PSS_PADDING}, signature, "base64");
        console.info("is signature ok?: %s", verified);
    });
}

Steps:

First you create an key pair with crypto.generateKeyPair('rsa', { ... desired key options
Create a Sign object - crypto.createSign("RSA-SHA256")
The string wanted to be signed - SignerObject.update(str)
Sign the string with your private key - signerObject.sign(
Option to salt - padding:crypto.constants.RSA_PKCS1_PSS_PADDING

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