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Insecurely generated token

Need​

Secure token generation mechanism

Context​

  • Usage of TypeScript for adding static typing to JavaScript
  • 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('/login', (req, res) => {
  const userId = req.query.userId;
  const token = generateToken(userId);
  res.send(token);
});

function generateToken(userId: string): string {
  const timestamp = Date.now().toString();
  const token = userId + timestamp;
  return crypto.createHash('md5').update(token).digest('hex');
}

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

The vulnerability in this code lies in the generateToken function. The function generates a token by concatenating the userId and the current timestamp. It then uses the crypto.createHash function to create an MD5 hash of the token.

The problem is that MD5 is a weak cryptographic algorithm that is susceptible to collision attacks. This means that an attacker could potentially crack the hash and obtain the original token, allowing them to impersonate the user associated with that token.

Additionally, the token is generated using predictable components such as the userId and the timestamp. This makes it easier for an attacker to guess or brute-force the token, especially if they have knowledge of the user IDs or can make educated guesses about the timestamp.

The impact of this vulnerability is that an attacker could reuse session tokens even after 14 days have passed since the token was created. This could lead to unauthorized access to user accounts or other sensitive information.

To fix this vulnerability, the code should generate a token using a secure cryptographic mechanism, such as using a cryptographically secure random number generator or a strong hashing algorithm like SHA-256. The token should not contain any predictable or sensitive information.

Steps​

  • Replace the usage of md5 algorithm with a more secure cryptographic algorithm such as SHA-256 or bcrypt.
  • Generate a random component for the token instead of using the timestamp.
  • Do not include any sensitive information in the token.
  • Consider using a library or framework that provides secure token generation and management.

Compliant code​

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

const app = express();

app.get('/login', (req, res) => {
  const userId = req.query.userId;
  const token = generateToken();
  res.send(token);
});

function generateToken(): string {
  const randomBytes = crypto.randomBytes(32).toString('hex');
  return randomBytes;
}

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

The fixed code addresses the vulnerability by generating a token using a secure cryptographic mechanism.

In the code, the crypto module from Node.js is imported to provide cryptographic functionality.

The generateToken function is modified to use the crypto.randomBytes method to generate a random sequence of bytes. These bytes are then converted to a hexadecimal string using the toString method with the 'hex' encoding. This ensures that the generated token is random and secure.

The generateToken function now returns the generated token, which is then sent as a response to the /login route.

By using the crypto.randomBytes method, the code ensures that the token is generated with random components without any sensitive information. This prevents the possibility of cracking the token's hash and obtaining the masked information.

Overall, the fixed code generates a secure token by using a secure cryptographic mechanism, addressing the vulnerability.

References​

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