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Insecure encryption algorithm

Need​

Implementation of secure encryption algorithms

Context​

  • Usage of Java 8 for developing applications with enhanced features and performance
  • Usage of javax.crypto.Cipher for encryption and decryption operations
  • Usage of javax.crypto.spec.SecretKeySpec for generating a secret key specification in cryptography
  • Usage of javax.servlet.http.HttpServlet for creating HTTP servlets in Java
  • Usage of javax.servlet.http.HttpServletRequest for handling HTTP requests in Java Servlets
  • Usage of HttpServletResponse for handling HTTP responses in Java Servlets
  • Usage of java.security.Key for cryptographic key management

Description​

Non compliant code​

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.security.Key;

public class InsecureEncryptionServlet extends HttpServlet {

    private static final String ALGORITHM = "DES";

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) {
        try {
            String data = req.getParameter("data");
            String key = "12345678"; // 8-byte key for DES

            Key secretKey = new SecretKeySpec(key.getBytes(), ALGORITHM);
            Cipher cipher = Cipher.getInstance(ALGORITHM);
            cipher.init(Cipher.ENCRYPT_MODE, secretKey);

            byte[] encryptedData = cipher.doFinal(data.getBytes());

            // ... use the encrypted data ...

        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

The code above represents a servlet in a Java web application that uses an insecure encryption algorithm, specifically the Data Encryption Standard (DES), to encrypt sensitive data.

This servlet takes a parameter "data" from the HTTP request, and uses a hard-coded key to encrypt this data using DES. The encrypted data is then used in the application (the actual use is not shown in this code snippet).

The vulnerability lies in the use of DES, which is considered insecure because it uses a small key size (56 bits), making it susceptible to brute-force attacks. Furthermore, the hard-coded encryption key is also a security risk, as anyone who has access to the code can decrypt the data.

Moreover, the encryption mode used here is ECB (Electronic Codebook) which is the default mode when no mode is specified in the Cipher.getInstance() method. ECB mode doesn't provide serious message confidentiality, because it doesn't hide data patterns well. Even small changes in the plaintext can cause great changes in the ciphertext when using a secure encryption mode, but in ECB, identical plaintext blocks are encrypted into identical ciphertext blocks; thus, patterns are not well hidden.

Finally, the error handling in this code is insecure. The catch block prints the stack trace of any exception that is thrown during the encryption process. This can expose sensitive information about the system, such as file paths, libraries used, and specific information about the failure, which could be useful for an attacker.

Steps​

  • Replace the insecure encryption algorithm with a secure one.
  • Use a strong and secure key for encryption.
  • Ensure that the encryption algorithm and key length meet current security standards.
  • Consider using a library or framework that provides secure encryption functions.

Compliant code​

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.security.Key;
import java.security.SecureRandom;
import javax.crypto.KeyGenerator;

public class SecureEncryptionServlet extends HttpServlet {

    private static final String ALGORITHM = "AES";

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) {
        try {
            String data = req.getParameter("data");

            KeyGenerator keyGenerator = KeyGenerator.getInstance(ALGORITHM);
            keyGenerator.init(256, new SecureRandom()); // Use 256-bit key for AES
            Key secretKey = keyGenerator.generateKey();

            Cipher cipher = Cipher.getInstance(ALGORITHM);
            cipher.init(Cipher.ENCRYPT_MODE, secretKey);

            byte[] encryptedData = cipher.doFinal(data.getBytes());

            // ... use the encrypted data ...

        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

The original code was using the DES encryption algorithm, which is considered insecure due to its small key size. The new code uses the AES encryption algorithm, which is currently considered secure and is widely used.

The key for the encryption is generated using a KeyGenerator instance. The KeyGenerator is initialized with a key size of 256 bits, which is a secure key size for AES. The SecureRandom instance is used to ensure that the key is randomly generated and thus hard to guess.

The Cipher instance is then initialized with the generated key and the AES algorithm. The data is encrypted using the doFinal method of the Cipher instance.

This code ensures that the encryption of the data is done using a secure algorithm and a strong, randomly generated key. This significantly reduces the risk of the encrypted data being decrypted by an attacker.

References​

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