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Insecure encryption algorithm - AES

Need​

Implementation of secure encryption algorithms

Context​

  • Usage of Ruby for building dynamic and object-oriented applications
  • Usage of OpenSSL for secure communication and encryption
  • Usage of base64 for encoding and decoding data in base64 format

Description​

Non compliant code​

require 'openssl'
require 'base64'

def encrypt(data)
  cipher = OpenSSL::Cipher::AES.new(256, :CBC)
  cipher.encrypt
  cipher.key = "a" * 32
  cipher.iv = "b" * 16
  encrypted = cipher.update(data) + cipher.final
  Base64.encode64(encrypted)
end

def decrypt(data)
  decipher = OpenSSL::Cipher::AES.new(256, :CBC)
  decipher.decrypt
  decipher.key = "a" * 32
  decipher.iv = "b" * 16
  decrypted = Base64.decode64(data)
  decipher.update(decrypted) + decipher.final
end

The above code shows the usage of AES encryption and decryption in a Ruby on Rails application. Here, the AES encryption algorithm is used with a block mode of CBC and a padding scheme of PKCS5.

In the encrypt method, an OpenSSL::Cipher::AES instance is created with a block size of 256 bits and the block mode set to CBC. The encryption key and initialization vector (IV) are hard-coded and used to encrypt the input data. The encrypted data is then base64 encoded before being returned.

Similarly, in the decrypt method, an OpenSSL::Cipher::AES instance is created with a block size of 256 bits and the block mode set to CBC. The same hard-coded encryption key and IV are used to decrypt the base64 decoded input data.

This code is vulnerable because it uses a hard-coded encryption key and IV, which is a bad practice as it exposes the system to potential attacks. If an attacker can gain access to the source code, they can easily decrypt any data that was encrypted using this code. Furthermore, the usage of CBC mode is considered insecure due to its susceptibility to padding oracle attacks.

Steps​

  • Replace the use of AES/CBC/PKCS5PADDING encryption algorithm with a more secure algorithm, such as AES/GCM or ChaCha20-Poly1305.
  • Generate a random and unique encryption key for each encryption operation.
  • Use a secure method to store and manage the encryption keys, such as a key management service or a secure key vault.
  • Ensure that the encryption key is securely transmitted to the decryption function.
  • Implement proper padding for the encryption algorithm to prevent padding oracle attacks.
  • Consider using authenticated encryption to ensure both confidentiality and integrity of the encrypted data.
  • Regularly update the encryption algorithm and libraries to stay up-to-date with the latest security patches and improvements.

Compliant code​

require 'openssl'
require 'base64'

def encrypt(data)
  cipher = OpenSSL::Cipher.new('aes-256-gcm')
  cipher.encrypt
  cipher.key = cipher.random_key
  cipher.iv = cipher.random_iv
  encrypted = cipher.update(data) + cipher.final
  Base64.encode64(encrypted)
end

def decrypt(data, key, iv)
  decipher = OpenSSL::Cipher.new('aes-256-gcm')
  decipher.decrypt
  decipher.key = key
  decipher.iv = iv
  decrypted = Base64.decode64(data)
  decipher.update(decrypted) + decipher.final
end

The updated code now uses the AES-256-GCM encryption algorithm, which is considered more secure than the previously used AES/CBC/PKCS5PADDING.

In the encrypt function, a new random key and initialization vector (IV) are generated for each encryption operation using the random_key and random_iv methods. This ensures that each encryption operation is unique, increasing the security of the encryption.

The decrypt function now requires the key and IV used during the encryption process. This ensures that the key and IV are securely transmitted to the decryption function.

Please note that the encryption key and IV should be securely stored and managed, such as using a key management service or a secure key vault. This is not shown in the code and should be implemented according to the specific requirements of your application.

The code does not show the use of authenticated encryption or padding, as these are handled by the AES-256-GCM algorithm and the OpenSSL library. However, you should ensure that your application implements these features if required.

Finally, remember to regularly update the encryption algorithm and libraries to stay up-to-date with the latest security patches and improvements.

References​

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