@bogdan-nita/netopia-card/functions/decrypt.js

Improved Netopia card gateway library

const forge = require('node-forge');
const rc4 = require('./arc4');

// Helper function to check if a string is base64 encoded
const isBase64 = (str) => {
  try {
    return Buffer.from(str, 'base64').toString('base64') === str;
  } catch (err) {
    return false;
  }
};

const decrypt = (privateKeyPem, envKey, data) => {
  try {
    // Parse the private key from PEM format
    const privateKey = forge.pki.privateKeyFromPem(privateKeyPem);

    // Decode envKey from base64 or utf-8 as needed
    const envBuffer = isBase64(envKey)
      ? Buffer.from(envKey, 'base64')
      : Buffer.from(envKey, 'utf8');

    // Decrypt the envKey using PKCS#1 v1.5
    const decryptedKey = privateKey.decrypt(envBuffer.toString('binary'), 'RSAES-PKCS1-V1_5');

    // Initialize RC4 with the decrypted key
    const cipher = rc4(decryptedKey);

    // Decode data if it's base64, otherwise treat as utf-8
    const dataBuffer = isBase64(data) ? Buffer.from(data, 'base64') : Buffer.from(data, 'utf8');
    return cipher.decode(dataBuffer, 'utf8');
  } catch (error) {
    console.error('Decryption error:', error);
    throw new Error('Decryption failed. Ensure the private key and data formats are correct.');
  }
};

module.exports = decrypt;