jwk-rsa-compute-primes/index.js

Compute p, q, dp, dq, and qi from e, d, and n for private JWKs without these parameters

import * as base64url from 'base64url';
import * as BN from 'bn.js';
import { factor } from './factor';
const one = new BN(1);
export function computePrimes(jwk) {
    const required = ['e', 'd', 'n'].filter(r => jwk[r] == null);
    if (required.length > 0) {
        throw Error('The following parameters are required: ' + required.join(', '));
    }
    if (jwk.kty.toUpperCase() !== 'RSA') {
        throw Error('kty MUST be RSA!');
    }
    const d = string2bn(jwk.d);
    const e = string2bn(jwk.e);
    const n = string2bn(jwk.n);
    const { p, q } = factor(e, d, n);
    const dp = d.mod(p.sub(one));
    const dq = d.mod(q.sub(one));
    const qi = q.invm(p);
    return Object.assign({}, jwk, { p: binaryToBase64Url(p), q: binaryToBase64Url(q), dp: binaryToBase64Url(dp), dq: binaryToBase64Url(dq), qi: binaryToBase64Url(qi) });
}
function pad(hex) {
    return hex.length % 2 === 1 ? '0' + hex : hex;
}
function binaryToBase64Url(bn) {
    return base64url(pad(bn.toString('hex')), 'hex');
}
function base64UrlToBinary(str) {
    return new BN(base64url.toBuffer(str));
}
function string2bn(str) {
    if (/^[0-9]+$/.test(str)) {
        return new BN(str, 10);
    }
    return base64UrlToBinary(str);
}
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