I need to sign a message with crypto.sign() function in NodeJS to get a valid JWT. I have a private key (base 64) like this:
Dm2xriMD6riJagld4WCA6zWqtuWh40UzT/ZKO0pZgtHATOt0pGw90jG8BQHCE3EOjiCkFR2/gaW6JWi+3nZp8A==
And I tried to get a signature:
const getJWT = () => {
const privateKey =
"Dm2xriMD6riJagld4WCA6zWqtuWh40UzT/ZKO0pZgtHATOt0pGw90jG8BQHCE3EOjiCkFR2/gaW6JWi+3nZp8A==";
const payload = {
iss: "test",
aud: "test.com",
iat: 1650101178,
exp: 1650101278,
sub: "12345678-1234-1234-1234-123456789123"
};
const token = encode(payload, privateKey);
return token
};
const encode = (payload, key) => {
const header = {
typ: "JWT",
alg: "EdDSA"
};
const headerBase64URL = base64url(JSON.stringify(header));
const payloadBase64URL = base64url(JSON.stringify(payload));
const msg = Buffer.from(`${headerBase64URL}.${payloadBase64URL}`);
const keyDecoded = Buffer.from(key, "base64");
const signature = crypto.sign("Ed25519", msg, keyDecoded); //Here is the problem
const signatureBase64url = base64url(Buffer.from(signature));
return `${msg}.${signatureBase64url}`;
};
I received this error:
internal/crypto/sig.js:142
return _signOneShot(keyData, keyFormat, keyType, keyPassphrase, data,
^
Error: error:0909006C:PEM routines:get_name:no start line
library: 'PEM routines',
function: 'get_name',
reason: 'no start line',
code: 'ERR_OSSL_PEM_NO_START_LINE'
How can I adapt my private key to a valid format?
The crypto.sign() method requires for Ed25519 a private key in PKCS#8 format. Your key is a raw key consisting of the concatenation of the raw private 32 bytes key and the raw public 32 bytes, base64 encoded. A DER encoded PKCS#8 key can be derived and imported as follows:
302e020100300506032b657004220420Accordingly, the key import in getJWT() must be changed as follows:
const privateKey = toPkcs8der('Dm2xriMD6riJagld4WCA6zWqtuWh40UzT/ZKO0pZgtHATOt0pGw90jG8BQHCE3EOjiCkFR2/gaW6JWi+3nZp8A==');
with
const toPkcs8der = (rawB64) => {
var rawPrivate = Buffer.from(rawB64, 'base64').subarray(0, 32);
var prefixPrivateEd25519 = Buffer.from('302e020100300506032b657004220420','hex');
var der = Buffer.concat([prefixPrivateEd25519, rawPrivate]);
return crypto.createPrivateKey({key: der, format: "der", type: "pkcs8"})
}
Furthermore, in the encode() function:
Remove the line const keyDecoded = Buffer.from(key, "base64")
Create the signature with
const signature = crypto.sign(null, msg, key)
Note that for Ed25519, a null must be passed as first parameter in the sign() call. The algorithm comes from the key.
With these changes, the NodeJS code returns the following JWT:
eyJ0eXAiOiJKV1QiLCJhbGciOiJFZERTQSJ9.eyJpc3MiOiJ0ZXN0IiwiYXVkIjoidGVzdC5jb20iLCJpYXQiOjE2NTAxMDExNzgsImV4cCI6MTY1MDEwMTI3OCwic3ViIjoiMTIzNDU2NzgtMTIzNC0xMjM0LTEyMzQtMTIzNDU2Nzg5MTIzIn0.f7WG_02UKljrMeVVOTNNBAGxtLXJUT_8QAnujNhomV18Pn5cU-0lHRgVlmRttOlqI7Iol_fHut3C4AOXxDGnAQ
that matches the expected JWT.