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Insecure encryption algorithm - DSA

Need​

Implementation of a secure encryption algorithm

Context​

  • Requirement of PHP 7.0 or higher for running the application
  • Usage of Illuminate\Http\Request for handling HTTP requests in Laravel
  • Usage of phpseclib\Crypt\RSA for RSA encryption and decryption

Description​

Non compliant code​

<?php

namespace App\\Http\\Controllers;

use Illuminate\\Http\\Request;
use phpseclib\\Crypt\\RSA;

class EncryptionController extends Controller
{
    public function encryptData(Request $request)
    {
        $rsa = new RSA();
        $rsa->setPrivateKeyFormat(RSA::PRIVATE_FORMAT_PKCS1);
        $rsa->setPublicKeyFormat(RSA::PUBLIC_FORMAT_PKCS1);
        $rsa->setHash('sha1'); // Vulnerable part
        $rsa->setMGFHash('sha1'); // Vulnerable part
        $rsa->setEncryptionMode(RSA::ENCRYPTION_OAEP); // Vulnerable part

        $plaintext = $request->input('plain_text');
        $ciphertext = $rsa->encrypt($plaintext);

        return response()->json(['encrypted_text' => base64_encode($ciphertext)]);
    }
}

This code is a Laravel controller that handles encryption of data. The controller has a method encryptData() which accepts a Request object. This method is intended to encrypt the 'plain_text' data from the request using the RSA encryption algorithm.

The vulnerability lies in the configuration of the RSA object:

  • The hash function is set to 'sha1' which is considered insecure due to its susceptibility to collision attacks.
  • The mask generation function hash is also set to 'sha1' which shares the same vulnerabilities as the main hash function.
  • The encryption mode is set to RSA::ENCRYPTION_OAEP which is considered insecure as it uses the insecure 'sha1' hash function.

This configuration makes the encryption process weak and susceptible to attacks. An attacker could potentially exploit these weaknesses to decrypt the encrypted data.

Steps​

  • Replace the insecure encryption algorithm DSA with a more secure one such as RSA.
  • Update the hash function from 'sha1' to a more secure one like 'sha256' or 'sha512'.
  • Update the Mask Generation Function hash from 'sha1' to a more secure one like 'sha256' or 'sha512'.
  • Change the encryption mode from RSA::ENCRYPTION_OAEP to a more secure mode.

Compliant code​

<?php

namespace App\\Http\\Controllers;

use Illuminate\\Http\\Request;
use phpseclib\\Crypt\\RSA;

class EncryptionController extends Controller
{
    public function encryptData(Request $request)
    {
        $rsa = new RSA();
        $rsa->setPrivateKeyFormat(RSA::PRIVATE_FORMAT_PKCS1);
        $rsa->setPublicKeyFormat(RSA::PUBLIC_FORMAT_PKCS1);
        $rsa->setHash('sha256'); // Updated part
        $rsa->setMGFHash('sha256'); // Updated part
        $rsa->setEncryptionMode(RSA::ENCRYPTION_PKCS1); // Updated part

        $plaintext = $request->input('plain_text');
        $ciphertext = $rsa->encrypt($plaintext);

        return response()->json(['encrypted_text' => base64_encode($ciphertext)]);
    }
}

The updated code now uses a more secure encryption algorithm. The RSA encryption algorithm is used instead of the insecure DSA. The RSA algorithm is currently one of the most secure encryption algorithms and is widely used in the industry.

The hash function has been updated from 'sha1' to 'sha256'. The 'sha256' hash function is more secure than 'sha1' and is less likely to be broken by an attacker. The same update has been made to the Mask Generation Function hash.

The encryption mode has been changed from RSA::ENCRYPTION_OAEP to RSA::ENCRYPTION_PKCS1. The PKCS1 mode is more secure and is recommended for use in new applications.

The plaintext is encrypted using the RSA algorithm and the ciphertext is returned as a response. The ciphertext is also encoded in base64 format to ensure that it can be safely transmitted over the network.

This update significantly improves the security of the encryption process and reduces the risk of the data being decrypted by an attacker.

References​

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