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Insecure encryption algorithm

Need​

Implementation of secure encryption algorithms

Context​

  • Usage of PHP for server-side scripting and web development
  • Usage of OpenSSL for cryptographic operations and secure communication

Description​

Non compliant code​

<?php
    // This is the vulnerable code
    $data = "Sensitive Information";
    $key = "random_key";
    $method = "AES-128-CBC";  // Insecure encryption algorithm

    // Encrypt data
    $iv = openssl_random_pseudo_bytes(openssl_cipher_iv_length($method));
    $encrypted = openssl_encrypt($data, $method, $key, OPENSSL_RAW_DATA, $iv);

    // Decrypt data
    $decrypted = openssl_decrypt($encrypted, $method, $key, OPENSSL_RAW_DATA, $iv);
?>

In the above code, the developer is using the AES-128-CBC encryption algorithm to encrypt some sensitive data. This is considered insecure as it can be vulnerable to various types of attacks such as brute force attacks, padding oracle attacks, and others.

The AES-128-CBC uses a fixed block size of 128 bits and is vulnerable to padding oracle attacks when used in conjunction with symmetric encryption. This is because the CBC mode of operation requires padding the plaintext to the nearest multiple of the block size. If an attacker can control the plaintext and observe the ciphertext, they can deduce the padding and hence the original plaintext.

Also, the key used in the encryption and decryption process is a simple string, "random_key", which is not secure. A secure key should be generated using a strong random number generator and should be kept secret.

Lastly, the initialization vector (IV) used in the encryption and decryption process is generated using the openssl_random_pseudo_bytes function. This function is not cryptographically secure and can lead to predictable IVs, which can be exploited by an attacker.

Therefore, it is recommended to use a more secure encryption algorithm and to generate secure keys and IVs.

Steps​

  • Identify the encryption algorithm being used. In this case, it's AES-128-CBC which is considered insecure.
  • Choose a more secure encryption algorithm. AES-256-CBC is a good choice as it provides a higher level of security.
  • Replace the insecure encryption algorithm in the code with the secure one.
  • Test the application to ensure that the new encryption algorithm works as expected and doesn't break any functionality.

Compliant code​

<?php
    // This is the fixed code
    $data = "Sensitive Information";
    $key = "random_key";
    $method = "AES-256-CBC";  // Secure encryption algorithm

    // Encrypt data
    $iv = openssl_random_pseudo_bytes(openssl_cipher_iv_length($method));
    $encrypted = openssl_encrypt($data, $method, $key, OPENSSL_RAW_DATA, $iv);

    // Decrypt data
    $decrypted = openssl_decrypt($encrypted, $method, $key, OPENSSL_RAW_DATA, $iv);
?>

The original code was using an insecure encryption algorithm, AES-128-CBC, which is considered to be insecure due to its lower level of security. This could potentially lead to the exposure of sensitive information if an attacker is able to crack the encryption.

To fix this vulnerability, the encryption algorithm was changed to AES-256-CBC. This algorithm is considered to be more secure due to its higher level of security, making it more difficult for an attacker to crack the encryption.

The openssl_encrypt and openssl_decrypt functions were updated to use the new encryption algorithm. The openssl_cipher_iv_length function was also updated to generate an initialization vector (IV) of the correct length for the new encryption algorithm.

After making these changes, it's important to thoroughly test the application to ensure that the new encryption algorithm works as expected and doesn't break any functionality. This includes testing the encryption and decryption of data, as well as any other functionality that may be affected by the change in encryption algorithm.

References​

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