Description

This vulnerability detector identifies hardcoded nonces in AEAD (Authenticated Encryption with Associated Data) encryption operations. Using hardcoded nonces in AEAD encryption severely compromises security as it eliminates the randomness required for secure encryption, potentially allowing attackers to break the encryption scheme.

Detection Strategy

• The code imports cryptographic libraries that provide AEAD encryption functionality

• A function call is made to an AEAD encryption method (like encrypt() on AEAD cipher objects)

• The nonce parameter (typically the second argument) to the encryption function is provided

• The nonce value is traced back to its definition and found to be a hardcoded byte string or constant value rather than randomly generated

• The hardcoded nonce is not properly sanitized or randomized before use

Vulnerable code example

from cryptography.hazmat.primitives.ciphers.aead import AESGCM

def encrypt_data(key, data):
    aesgcm = AESGCM(key)
    # VULNERABLE: hardcoded nonce reused across encryptions
    return aesgcm.encrypt(b"000000000000", data, None)

✅ Secure code example

import os
from cryptography.hazmat.primitives.ciphers.aead import AESGCM

def encrypt_data(key, data):
    aesgcm = AESGCM(key)
    nonce = os.urandom(12)  # Generate random nonce for each encryption
    return aesgcm.encrypt(nonce, data, None)