Convert jwk to pem in nest.js

Question

I have this jwk key that I wanto convert into pem:

const jwkey = {
  kty: 'RSA',
  kid: 'eecb0ced-4d49-4100-9547-841e4100b756',
  n: '...very long string',
  e: 'AQAB',
  alg: 'RS256',
  use: 'sig',
};

I have tried the libraries like jose, node-rsa and jwk-To-Pem but somehow all of them are failing and throws error here and there while configuring.

I literally have no idea how to configure it.

below is the example of node-rsa conversion:

const key = new NodeRSA();
key.importKey(
  {
    n: Buffer.from(jwkey.n, 'base64'),
    e: Buffer.from(jwkey.e, 'base64'),
  },
  'components'
);

 const pem = key.exportKey('pkcs1-private-pem');

*all of them are failing and throws error here and there* - that's not a useful problem description. Show what exactly you did and what errors you got. — jps, Feb 08 '23 at 08:36

score 0 · Accepted Answer · answered Feb 08 '23 at 08:11

You could use 'jwk-to-pem' module.

const jwkToPem = require("jwk-to-pem")

const jwkey = {
  kty: "RSA",
  alg: "RS512",
  kid: "26887d3ee3293c526c0e6dd05f122df53aa3f13d7dad06d25e266fa6f51db79fb52422aaf79f121476237e98dcd6640350fee47fec70e783544ec9a36e4605bc",
  use: "sig",
  n: "14m79mVwIE0JxQdKrgXVf7dVcBS90U0TvG7Yf7dG4NJocz1PNUrKrzGhe_FryOe0JahL_sjA2_rKw7NBCpuVx_zSPFRw6kqjewGicjXGus5Fmlf3zDuqwV4BWIFHyQexMPOly0agFfcM0M0MgBULXjINgBs9MwnRv7JVfRoGqXHsNM45djFDd3o4liu4LPlge_DquZUFLNu-BYAyAlWkz0H2TepZhGrN9VEPmxzQkNzXc1R4MpZvbxrRRgaAA2z094ik3hk86JhfyFq-LDcueZhtshmrYZ95LWgMlQ7PixkeK1HkeEYMt20lmNzR8B8KabimYmibxA4Ay9gpRwfp-Q",
  e: "AQAB",
}

console.log("jwkey : ", jwkey)

const pem = jwkToPem(jwkey)

console.log("create pem : ", pem)

It works with require statement but not with the import statement. Why is that The error: `Argument of type '{ kty: string; kid: string; n: string; e: string; alg: string; use: string; }' is not assignable to parameter of type 'JWK'. Type '{ kty: string; kid: string; n: string; e: string; alg: string; use: string; }' is not assignable to type 'RSA'. Types of property 'kty' are incompatible. Type 'string' is not assignable to type '"RSA"'.` I know this is not the major issue but still... — codeForCoffee, Feb 08 '23 at 08:51

score 0 · Answer 2 · answered Feb 08 '23 at 20:19

I have tried the libraries like jose

The following will always work for an RSA public key, using jose.

const jwk = {
  kty: 'RSA',
  n: 'pksialyL7vdNKFhL9Nu1uVs49L8vKqtRB3O_hSA_bICHKvNLX9_5NtoN1oDV7Mjz_rBOxM3AcnPV97OJPBrHKbQxhX3P5PN0LTqVLh0_Pcn5s7KHRpT1-jhHad5FaeJ2WdBRUhr8cEbVnYvAEmGfB3kduyPGNqSAbJC0PtEEJZlNralFLyJV0wEC1t7a9hRAXXkL52D_UbKnF05Gjn1XioHOKxEjlZirzrj0z8SUHXAD8UPJMAGvzakBRb_K46hcdl8G9_7t3RLjVyGwVwnZOWBZosUU4jOtQx0OZtDEO4rbw4yDMA4cHJs1FCDDsXi_r1tlZ5EKSzU51YDVx3txNQ',
  e: 'AQAB'
}

const key = await jose.importJWK({
  ...jwk,
  ext: true,
}, 'RS256')
const pem = await jose.exportSPKI(key)

console.log(pem)
// -----BEGIN PUBLIC KEY-----
// MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEApksialyL7vdNKFhL9Nu1
// uVs49L8vKqtRB3O/hSA/bICHKvNLX9/5NtoN1oDV7Mjz/rBOxM3AcnPV97OJPBrH
// KbQxhX3P5PN0LTqVLh0/Pcn5s7KHRpT1+jhHad5FaeJ2WdBRUhr8cEbVnYvAEmGf
// B3kduyPGNqSAbJC0PtEEJZlNralFLyJV0wEC1t7a9hRAXXkL52D/UbKnF05Gjn1X
// ioHOKxEjlZirzrj0z8SUHXAD8UPJMAGvzakBRb/K46hcdl8G9/7t3RLjVyGwVwnZ
// OWBZosUU4jOtQx0OZtDEO4rbw4yDMA4cHJs1FCDDsXi/r1tlZ5EKSzU51YDVx3tx
// NQIDAQAB
// -----END PUBLIC KEY-----

Convert jwk to pem in nest.js

2 Answers2