Runtime Decryption in WebLogic

Here are the detailed steps for encrypting and decrypting Java class files at runtime in a WebLogic server environment:

Step 1: Encrypt the Class Files

Generate an AES Encryption Key:

Use a secure method to generate an AES key.

import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import java.util.Base64;

public class KeyGeneratorExample {
    public static void main(String[] args) throws Exception {
        KeyGenerator keyGen = KeyGenerator.getInstance("AES");
        keyGen.init(256); // 256-bit key
        SecretKey secretKey = keyGen.generateKey();
        String encodedKey = Base64.getEncoder().encodeToString(secretKey.getEncoded());
        System.out.println("AES Key: " + encodedKey);
    }
}

Save the generated key securely. Example output: AES Key: abcdefghijklmnopqrstuvwxyz1234567890ABCDEF

Encrypt the Class File:

Use the AES key to encrypt the class file.

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.Base64;

public class EncryptClassFile {
    public static void main(String[] args) throws Exception {
        String key = "your_base64_encoded_key"; // Replace with your key
        byte[] keyBytes = Base64.getDecoder().decode(key);
        SecretKeySpec secretKey = new SecretKeySpec(keyBytes, "AES");

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

        byte[] classFileBytes = Files.readAllBytes(Paths.get("YourClassFile.class"));
        byte[] encryptedClassFile = cipher.doFinal(classFileBytes);

        Files.write(Paths.get("YourClassFile.class.enc"), encryptedClassFile);
        System.out.println("Class file encrypted successfully.");
    }
}

Replace "YourClassFile.class" with the path to your class file.

Step 2: Deploy the Encrypted WAR File

Replace Original Class Files with Encrypted Ones:
- Rename the encrypted class file with the .class.enc extension and place it in the same directory within the WAR file.
```
mv YourClassFile.class.enc /path/to/war/WEB-INF/classes/YourClassFile.class.enc
```
Repackage the WAR File:
- Use the jar command to repackage the WAR file.
```
cd /path/to/war
jar -cvf ../encrypted.war *
```
Deploy the WAR File:
- Deploy the encrypted WAR file to your WebLogic server using the WebLogic Administration Console or the command line.

Step 3: Configure Runtime Decryption

Modify the Application to Decrypt at Runtime:
- Add decryption logic to your application to decrypt the class files at runtime before loading them.
Load the Decryption Key Securely:
- Store the decryption key securely, such as in a secure key management service or environment variable.

Implement Custom ClassLoader:

Implement a custom ClassLoader that loads and decrypts the class files at runtime.

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.Base64;

public class EncryptedClassLoader extends ClassLoader {
    private SecretKeySpec secretKey;

    public EncryptedClassLoader(ClassLoader parent, String key) {
        super(parent);
        byte[] keyBytes = Base64.getDecoder().decode(key);
        this.secretKey = new SecretKeySpec(keyBytes, "AES");
    }

    @Override
    protected Class<?> findClass(String name) throws ClassNotFoundException {
        try {
            String path = name.replace('.', '/') + ".class.enc";
            byte[] encryptedClassFile = Files.readAllBytes(Paths.get(getClass().getResource("/" + path).toURI()));

            Cipher cipher = Cipher.getInstance("AES");
            cipher.init(Cipher.DECRYPT_MODE, secretKey);
            byte[] classFileBytes = cipher.doFinal(encryptedClassFile);

            return defineClass(name, classFileBytes, 0, classFileBytes.length);
        } catch (Exception e) {
            throw new ClassNotFoundException(name, e);
        }
    }

    public static void main(String[] args) throws Exception {
        String decryptionKey = "your_base64_encoded_key"; // Replace with your key
        EncryptedClassLoader classLoader = new EncryptedClassLoader(ClassLoader.getSystemClassLoader(), decryptionKey);
        Class<?> clazz = classLoader.loadClass("YourClassName");
        Object instance = clazz.newInstance();
        // Invoke methods on the instance
    }
}

Package Your Custom ClassLoader:
Compile your custom ClassLoader and package it into a JAR file. This JAR file will be included in your WebLogic server's classpath or within your application.

Modify weblogic.xml:

The weblogic.xml deployment descriptor is used to configure various settings specific to WebLogic Server. To ensure WebLogic uses your custom ClassLoader, follow these steps:

Open the weblogic.xml file located in the WEB-INF directory of your application.
Add the necessary configurations to use your custom ClassLoader.

Here’s an example of what your weblogic.xml might look like:

xml

<?xml version="1.0" encoding="UTF-8"?>
<weblogic-web-app xmlns="http://xmlns.oracle.com/weblogic/weblogic-web-app"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://xmlns.oracle.com/weblogic/weblogic-web-app
    http://xmlns.oracle.com/weblogic/weblogic-web-app/1.4/weblogic-web-app.xsd">

    <context-root>/yourapp</context-root>

    <container-descriptor>
        <prefer-application-packages>
            <package-name>com.yourpackage.*</package-name>
        </prefer-application-packages>
    </container-descriptor>

    <library-ref>
        <library-name>custom-classloader-lib</library-name>
        <specification-version>1.0</specification-version>
        <implementation-version>1.0</implementation-version>
    </library-ref>

    <class-loader-structure>
        <class-loader-structure>
            <class-loader>
                <name>customClassLoader</name>
                <system-properties>
                    <property>
                        <name>encryptedClassLoader</name>
                        <value>com.yourpackage.EncryptedClassLoader</value>
                    </property>
                    <property>
                        <name>decryptionKey</name>
                        <value>your_base64_encoded_key</value>
                    </property>
                </system-properties>
            </class-loader>
        </class-loader-structure>
    </class-loader-structure>
</weblogic-web-app>

Deploy the Application:
- Ensure the custom ClassLoader JAR file is included in your WAR file or placed in the WebLogic server's classpath.
- Deploy the WAR file to your WebLogic server.

Important Considerations

Security: Ensure that the decryption key is stored securely and not hard-coded in the application.
Performance: Runtime decryption may introduce performance overhead.
Testing: Thoroughly test the application to ensure that the decryption process works correctly and does not introduce any issues.

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Last updated 2 months ago

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