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Insecure encryption algorithm - Cipher Block Chaining

Need​

Secure encryption algorithm implementation

Context​

  • Usage of Node.js v14.15.1 for server-side JavaScript development
  • Usage of Express for building web applications and APIs
  • Usage of crypto for cryptographic operations and secure data handling

Description​

Non compliant code​

import express from 'express';
import crypto from 'crypto';

const app = express();

app.get('/encrypt', (req, res) => {
  const algorithm = 'aes-128-cbc'; // Insecure encryption algorithm
  const key = 'mysecretkey';
  const iv = crypto.randomBytes(16);

  const cipher = crypto.createCipheriv(algorithm, key, iv);

  let encryptedData = '';
  cipher.on('readable', () => {
    let chunk;
    while (null !== (chunk = cipher.read())) {
      encryptedData += chunk.toString('hex');
    }
  });

  cipher.on('end', () => {
    res.send(encryptedData);
  });

  cipher.write('Sensitive information');
  cipher.end();
});

app.listen(3000, () => {
  console.log('Server is running on port 3000');
});

The vulnerability in this code lies in the use of an insecure encryption algorithm, specifically the 'aes-128-cbc' algorithm. This algorithm uses Cipher Block Chaining (CBC) mode, which is known to have security weaknesses.

In the code, the application creates an instance of the express server and defines a route '/encrypt' to handle encryption requests. Inside the route handler, the algorithm 'aes-128-cbc' is used to create a cipher object using the crypto module. The key used for encryption is hardcoded as 'mysecretkey', and a random initialization vector (IV) is generated using crypto.randomBytes(16).

The sensitive information to be encrypted is passed to the cipher object using the cipher.write() method. The encrypted data is then collected in the encryptedData variable by listening to the 'readable' event of the cipher object. Finally, the encrypted data is sent as a response using res.send().

However, using the 'aes-128-cbc' algorithm for encryption is insecure. CBC mode has vulnerabilities, such as the possibility of padding oracle attacks and the lack of integrity protection. These weaknesses can be exploited to decrypt the encrypted data or modify it.

To address this vulnerability, it is recommended to use algorithms that are considered cryptographically secure, such as AES-GCM or ChaCha20-Poly1305. These algorithms provide both confidentiality and integrity protection, making them more resistant to attacks.

Steps​

  • Replace the insecure encryption algorithm 'aes-128-cbc' with a cryptographically secure algorithm.
  • Generate a secure key for encryption.
  • Ensure the initialization vector (IV) is generated securely.
  • Update the code to use the secure algorithm, key, and IV for encryption.
  • Test the updated code to ensure it is functioning correctly and securely.

Compliant code​

import express from 'express';
import crypto from 'crypto';

const app = express();

app.get('/encrypt', (req, res) => {
  const algorithm = 'aes-256-gcm'; // Cryptographically secure encryption algorithm
  const key = crypto.randomBytes(32); // Generate a secure key for encryption
  const iv = crypto.randomBytes(12); // Generate a secure initialization vector (IV)

  const cipher = crypto.createCipheriv(algorithm, key, iv);

  let encryptedData = '';
  cipher.on('readable', () => {
    let chunk;
    while (null !== (chunk = cipher.read())) {
      encryptedData += chunk.toString('hex');
    }
  });

  cipher.on('end', () => {
    res.send(encryptedData);
  });

  cipher.write('Sensitive information');
  cipher.end();
});

app.listen(3000, () => {
  console.log('Server is running on port 3000');
});

The fixed code addresses the vulnerability by using a cryptographically secure encryption algorithm and generating secure key and initialization vector (IV) for encryption.

The code imports the necessary modules, including the 'express' module for creating the server and the 'crypto' module for cryptographic operations.

The code creates an instance of the express application and sets up a route for the '/encrypt' endpoint.

Inside the route handler, the code specifies the algorithm 'aes-256-gcm', which is considered cryptographically secure. It then generates a secure key using the 'crypto.randomBytes' function with a length of 32 bytes, and a secure IV using the same function with a length of 12 bytes.

The code creates a cipher object using the 'crypto.createCipheriv' function, passing in the algorithm, key, and IV. This cipher object will be used to encrypt the sensitive information.

The code sets up event listeners on the cipher object. The 'readable' event listener reads the encrypted data in chunks and appends them to the 'encryptedData' variable. The 'end' event listener sends the encrypted data as the response.

The code writes the sensitive information to the cipher object using the 'cipher.write' method and then ends the encryption process with 'cipher.end'.

Finally, the code starts the server on port 3000 and logs a message indicating that the server is running.

Overall, the fixed code addresses the vulnerability by using a cryptographically secure encryption algorithm and generating secure key and IV for encryption, ensuring the confidentiality and integrity of the sensitive information.

References​

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