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Insecure encryption algorithm - ECB

Need​

Secure encryption algorithm implementation

Context​

  • Usage of TypeScript v4.3.5 for type-checking and compiling TypeScript code
  • 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 plaintext = req.query.text as string;
  const key = req.query.key as string;

  const cipher = crypto.createCipheriv('aes-128-ecb', key, '');
  let encrypted = cipher.update(plaintext, 'utf8', 'hex');
  encrypted += cipher.final('hex');

  res.send(encrypted);
});

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

The vulnerability in the given code lies in the use of the insecure encryption algorithm ECB (Electronic Codebook). ECB mode is considered insecure because it encrypts each block of plaintext separately, without considering the context or relationships between blocks. This makes it vulnerable to certain attacks, such as ciphertext manipulation or pattern recognition.

In the code, the vulnerable encryption algorithm is used in the /encrypt route. The plaintext and key are obtained from the query parameters of the request. The crypto.createCipheriv function is used to create a cipher object with the algorithm set to 'aes-128-ecb'. The key is used as the encryption key, and an empty string is provided as the initialization vector (IV).

The cipher.update method is then used to encrypt the plaintext in UTF-8 encoding and convert it to hexadecimal format. Finally, cipher.final is called to complete the encryption process and append the final block of ciphertext to the encrypted string.

The encrypted ciphertext is then sent as the response to the client.

However, using ECB mode for encryption is insecure because it does not provide adequate protection against attacks. An attacker can potentially reverse engineer the ciphertext to retrieve the original plaintext or discover patterns in the data.

To address this vulnerability, it is recommended to use algorithms that are considered cryptographically secure, such as CBC (Cipher Block Chaining) or GCM (Galois/Counter Mode), which provide better security and protection against attacks.

Steps​

  • Replace the insecure encryption algorithm 'aes-128-ecb' with a cryptographically secure algorithm like 'aes-256-cbc'.
  • Generate a random and unique initialization vector (IV) for each encryption operation.
  • Update the code to use the generated IV when creating the cipher.
  • Update the code to send the IV along with the encrypted data to the client.
  • Update the code to use a secure key generation method, such as using a strong password-based key derivation function (PBKDF2) or a key management system.
  • Ensure that the key used for encryption is kept secure and not exposed in the code or transmitted over insecure channels.

Compliant code​

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

const app = express();

app.get('/encrypt', (req, res) => {
  const plaintext = req.query.text as string;
  const password = req.query.password as string;

  // Generate a random and unique initialization vector (IV)
  const iv = crypto.randomBytes(16);

  // Use a secure key generation method, such as PBKDF2
  const key = crypto.pbkdf2Sync(password, iv, 100000, 32, 'sha512');

  const cipher = crypto.createCipheriv('aes-256-cbc', key, iv);
  let encrypted = cipher.update(plaintext, 'utf8', 'hex');
  encrypted += cipher.final('hex');

  // Send the IV along with the encrypted data to the client
  res.send({
    iv: iv.toString('hex'),
    encrypted: encrypted
  });
});

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

The fixed code addresses the vulnerability by implementing secure encryption practices. Here's an explanation of the changes made:

  1. The code imports the necessary modules, 'express' and 'crypto', to handle the server and encryption operations.

  2. The code creates an instance of the Express application using express().

  3. The code sets up a route for the '/encrypt' endpoint using app.get('/encrypt', ...). This endpoint expects two query parameters: 'text' for the plaintext to be encrypted and 'password' for the encryption key.

  4. Inside the route handler, the code retrieves the 'text' and 'password' values from the query parameters and assigns them to variables plaintext and password respectively. The use of the 'as string' type assertion ensures that the variables are treated as strings.

  5. The code generates a random and unique initialization vector (IV) using crypto.randomBytes(16). The IV is crucial for secure encryption.

  6. The code generates a secure encryption key using crypto.pbkdf2Sync(password, iv, 100000, 32, 'sha512'). This function uses the Password-Based Key Derivation Function 2 (PBKDF2) algorithm to derive a key from the password and IV. It iterates 100,000 times and uses the SHA-512 hashing algorithm.

  7. The code creates a cipher object using crypto.createCipheriv('aes-256-cbc', key, iv). It uses the AES-256-CBC encryption algorithm, which is considered secure.

  8. The code encrypts the plaintext using the cipher object by calling cipher.update(plaintext, 'utf8', 'hex') and cipher.final('hex'). The resulting ciphertext is stored in the encrypted variable.

  9. The code sends the IV and encrypted data as a response to the client using res.send({ iv: iv.toString('hex'), encrypted: encrypted }). The IV is converted to a hexadecimal string before sending.

  10. The code starts the server and listens on port 3000 using app.listen(3000, ...). A message is logged to the console to indicate that the server is running.

By implementing these changes, the code now uses a secure encryption algorithm (AES-256-CBC) and follows best practices for key generation and IV usage, mitigating the vulnerability of using an insecure encryption algorithm.

References​

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