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Insecure encryption algorithm - Cipher Block Chaining

Need​

Secure encryption algorithm for data protection

Context​

  • Usage of Ruby for web development and scripting
  • Usage of OpenSSL for secure communication and encryption

Description​

Non compliant code​

require 'openssl'

def encrypt_data(data, key, iv)
  cipher = OpenSSL::Cipher::Cipher.new('aes-256-cbc')
  cipher.encrypt
  cipher.key = key
  cipher.iv = iv
  encrypted = cipher.update(data) + cipher.final
  return encrypted
end

The above code shows a method encrypt_data in a Ruby on Rails backend application that is used to encrypt sensitive data. The method takes three parameters: data, key, and iv (Initialization Vector).

The vulnerability lies in the OpenSSL::Cipher::Cipher.new('aes-256-cbc') line, where the 'aes-256-cbc' is the encryption algorithm being used. CBC stands for Cipher Block Chaining, which is known to be insecure.

In CBC mode, each block of plaintext is XORed with the previous ciphertext block before being encrypted. This means that an attacker can make predictable changes to the plaintext message without knowing the key, leading to a potential breach of data confidentiality.

The 'aes-256-cbc' algorithm is also not authenticated, which means it does not protect the integrity and authenticity of the data. An attacker can change the encrypted data and the receiver has no way of detecting the tampering.

The key and initialization vector are also passed as parameters to the function. If these are not generated securely, it can lead to weak encryption strength, making it easier for an attacker to decrypt the data.

In conclusion, the usage of the insecure 'aes-256-cbc' encryption algorithm and potentially insecure key and initialization vector generation can lead to a compromise in the confidentiality, integrity, and authenticity of the encrypted data.

Steps​

  • Replace the insecure encryption algorithm with a secure one.
  • Use a strong encryption algorithm like AES-256-GCM or ChaCha20-Poly1305.
  • Ensure that the encryption algorithm supports authenticated encryption to provide data integrity.
  • Update the code to use the new encryption algorithm.
  • Make sure to generate a secure and random encryption key.
  • Use a secure method to generate a random initialization vector (IV) for each encryption operation.
  • Store the encryption key and IV securely, such as in a secure key management system or encrypted configuration file.
  • Implement proper key rotation and update the encryption key periodically.
  • Consider using a secure encryption library or framework that handles encryption securely and provides built-in protection against common encryption vulnerabilities.

Compliant code​

require 'openssl'

def encrypt_data(data, key, iv)
  cipher = OpenSSL::Cipher.new('aes-256-gcm')
  cipher.encrypt
  cipher.key = key
  cipher.iv = iv
  encrypted = cipher.update(data) + cipher.final
  return encrypted
end

The previous code was using an insecure encryption algorithm, AES-256-CBC, which is vulnerable to various attacks. The updated code now uses a more secure encryption algorithm, AES-256-GCM.

AES-256-GCM is an authenticated encryption algorithm that provides both data confidentiality and integrity. It uses a technique called Galois/Counter Mode (GCM) which is a mode of operation for symmetric key cryptographic block ciphers that has been widely adopted because of its efficiency and performance.

The cipher.key and cipher.iv are the encryption key and initialization vector respectively. They are used in the encryption process. The key should be generated securely and stored securely, such as in a secure key management system or encrypted configuration file. The initialization vector should be generated randomly for each encryption operation.

The cipher.update(data) + cipher.final part of the code performs the actual encryption of the data.

Please note that it's important to implement proper key rotation and update the encryption key periodically. Also, consider using a secure encryption library or framework that handles encryption securely and provides built-in protection against common encryption vulnerabilities.

References​

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