Insecure encryption algorithm - ECB
Need
Secure encryption algorithm implementation
Context
- Usage of PHP 7.0+ for server-side scripting and web development
- Usage of illuminate/support for providing support and utility functions in the Illuminate framework
Description
Non compliant code
<?php
use Illuminate\\Support\\Facades\\Crypt;
$data = "Sensitive information to be encrypted";
$encryptedData = Crypt::encryptString($data);
echo $encryptedData;
In the above code, we are using Laravel's default encryption method to encrypt some sensitive data. Laravel uses the Electronic Code Book (ECB) mode for encryption, which is not secure.
ECB mode is a type of operation for block ciphers. One of its main weaknesses is that it does not provide serious message confidentiality, because it encrypts identical plaintext blocks into identical ciphertext blocks. Thus, it does not hide data patterns well. In some senses, it doesn't provide serious message confidentiality at all.
This means that if the same block of text is encrypted twice with the same key, the output will be the same. This can reveal patterns in the encrypted data, making it less secure. This is especially problematic when dealing with sensitive information that needs to be encrypted.
To fix this vulnerability, we should use a more secure mode of operation, such as Cipher Block Chaining (CBC) or Galois/Counter Mode (GCM). These modes provide more security because they include an initialization vector (IV) in their encryption process, which ensures that the same block of text will not be encrypted the same way twice.
Steps
- Identify the encryption method used in the code. In this case, it's the ECB mode which is insecure.
- Replace the ECB mode with a more secure mode such as CBC or GCM. These modes provide better security because they use an initialization vector (IV) for each encryption, making it more difficult for an attacker to decipher the encrypted data.
- Ensure that the initialization vector (IV) is random and unique for each encryption. This can be achieved by using a secure random number generator.
- Store the initialization vector (IV) securely. It's needed for decryption, but it doesn't need to be secret. It can be stored alongside the ciphertext.
- Test the updated code to ensure that it still functions as expected and that the encryption is now secure.
Compliant code
<?php
use Illuminate\\Support\\Facades\\Crypt;
use Illuminate\\Support\\Str;
$data = "Sensitive information to be encrypted";
// Generate a random initialization vector
$iv = random_bytes(openssl_cipher_iv_length('AES-256-CBC'));
// Encrypt the data using AES-256-CBC
$encryptedData = openssl_encrypt($data, 'AES-256-CBC', Crypt::getKey(), 0, $iv);
// The IV is needed for decryption, so it can be stored with the ciphertext
$encryptedData = base64_encode($iv.$encryptedData);
echo $encryptedData;
The original code was using Laravel's Crypt::encryptString method, which uses the insecure ECB mode for encryption. The ECB mode is insecure because it does not use an initialization vector (IV), making the encrypted data easier to decipher.
The updated code uses the more secure AES-256-CBC mode for encryption. This mode uses an IV for each encryption, making it more difficult for an attacker to decipher the encrypted data.
The IV is generated using PHP's random_bytes function, which generates a string of random bytes. The length of the IV is determined by the openssl_cipher_iv_length function, which returns the length of the IV for the specified cipher method.
The data is then encrypted using the openssl_encrypt function, with the AES-256-CBC cipher method, the application's encryption key, and the generated IV.
The IV is needed for decryption, so it is stored with the ciphertext. The IV and the ciphertext are concatenated and then base64 encoded to ensure that they can be safely stored and transmitted.
This updated code provides a more secure method of encryption, reducing the risk of the encrypted data being deciphered by an attacker.