Hi, i am trying to decypher web push notification in function node, with no luck

General
1

Recieving push notification in http in node. and than using this code to decypher with no luck for now...

const headers = msg.req.headers;
const keys = JSON.parse(msg.payload);

// Extracting headers
const salt = Buffer.from(headers['encryption'].split('=')[1], 'base64');
const clientPublicKey = Buffer.from(headers['crypto-key'].split('=')[1].split(';')[0], 'base64');

// ECDH key agreement
const ecdh = crypto.createECDH('prime256v1');
ecdh.setPrivateKey(Buffer.from(keys.privateKey, 'base64'), 'base64');
const sharedSecret = ecdh.computeSecret(clientPublicKey);

// HKDF
const info = Buffer.concat([Buffer.from('WebPush: info\x00', 'utf8'), clientPublicKey, ecdh.getPublicKey()]);
const rawDerivedKey = crypto.hkdfSync('sha256', sharedSecret, salt, info, 32);
const derivedKey = Buffer.from(rawDerivedKey);

// Decrypting
try {
    const encryptedData = msg.req.body;
    const nonce = encryptedData.slice(0, 12);
    const ciphertext = encryptedData.slice(12, encryptedData.length - 16);
    const authTag = encryptedData.slice(encryptedData.length - 16);

    const decipher = crypto.createDecipheriv('aes-256-gcm', derivedKey, nonce);
    decipher.setAuthTag(authTag);
    const decryptedData = Buffer.concat([decipher.update(ciphertext), decipher.final()]);
    return { payload: decryptedData.toString('utf8') };
} catch (error) {
    console.error(`Error decrypting message: ${error.message}`);
    return { error: error.message };
}
2

It would probably help to provide:

  • Sample input to the function
  • Expected output
  • Some indication of what you think isn't working, e.g. do you think you get the right delivered key?
3

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