Getting started with Burp Suite extension_Getting started with Burp Suite extension.png

EducativeDockerBurpV2.tar.gz

BurpSuiteCommunityBuildTheJarV4

This course is for folks who are new to security, are experts already, or are just curious. We will learn how to build Burp Suite extension plugins with a focus on development using IntelliJ & Java.

You will be able to build Burp Suite Extension Plugins from scratch with live development and testing in Java by the end of the course. These projects will be useful learning experiences for both web application security specialists and developers. This course assumes a rudimentary understanding of Burp Suite as well as basic object-oriented programming experience.

Burp Suite Extension Development

## Understand public interface IIntruderPayloadProcessor
Extensions can implement the interface  `IIntruderPayloadProcessor` and then to register a custom Intruder payload processor.



## Implement and register IIntruderPayloadProcessor

To begin with, we need to implement `IIntruderPayloadProcessor`. The process is fairly simple after that, as we have done in our previous chapters. First, create a class which implements `IIntruderPayloadProcessor` , then register the instance of the class to `IBurpExtender.callbacks.registerIntruderPayloadProcessor()`.

The `IIntruderPayloadProcessor` interface contains two method signatures of the following structure. These will be overridden in the implementer class.

* String `getProcessorName()`: This provides the name of the payload processor in the Burp Suite UI.

* `byte[] processPayload(byte[] currentPayload, byte[] originalPayload, byte[] baseValue)`: This is the function responsible for payload processing. The processed payload should return as a byte array. 
    * `currentPayload` - The value of the payload to be processed.
    * `originalPayload` - The value of the original payload prior to processing by any already-applied processing rules.
    * `baseValue` - The base value of the payload position, which will be replaced with the current payload.
* We can use helpers to convert `String to byte[]` by invoking `stringToBytes()`. To achieve the opposite, `bytestoString()` can be used from the `callbacks.getHelpers()`.

```java
/*
IntruderProcessor.java
*/
package burp;

public class IntruderPayloadProcessor implements IIntruderPayloadProcessor{

    IExtensionHelpers helpers;

    public IntruderPayloadProcessor(IBurpExtenderCallbacks callbacks){
        /*
            We can use the helpers string to byte array method as processPayload needs to return byte[]
         */
        helpers = callbacks.getHelpers();
    }

    @Override public String getProcessorName() {
        /*
            This name will be shown in the Burp Suite Intruder UI as the processor name.
         */
        return "Base64 Processor";
    }

    @Override public byte[] processPayload(byte[] currentPayload, byte[] originalPayload, byte[] baseValue) {
        if(currentPayload != null){
            return helpers.stringToBytes(helpers.base64Encode(currentPayload));
        }
        return null;
    }
}
```

Next, we'll tell Burp that we have a payload processor.

```java
/*
BurpExtender.java
*/

package burp;

public class BurpExtender implements IBurpExtender {
    @Override public void registerExtenderCallbacks(IBurpExtenderCallbacks callbacks) {
        callbacks.setExtensionName("Intruder Processing");
        callbacks.issueAlert("Plugin loaded");

        // Notice this.
        callbacks.registerIntruderPayloadProcessor(new IntruderPayloadProcessor(callbacks));
    }
}
```
Finally, we must build the artifact and load it in Burp. Visit the "Extender" tab, click on "Add", and select the JAR file’s location. It will look something like this.


# Understand public interface IIntruderPayloadProcessor
Extensions can implement the interface  `IIntruderPayloadProcessor` and then to register a custom Intruder payload processor.



# Implement and register IIntruderPayloadProcessor

To begin with, we need to implement `IIntruderPayloadProcessor`. The process is fairly simple after that, as we have done in our previous chapters. First, create a class which implements `IIntruderPayloadProcessor` , then register the instance of the class to `IBurpExtender.callbacks.registerIntruderPayloadProcessor()`.

The `IIntruderPayloadProcessor` interface contains two method signatures of the following structure. These will be overridden in the implementer class.

* String `getProcessorName()`: This provides the name of the payload processor in the Burp Suite UI.

* `byte[] processPayload(byte[] currentPayload, byte[] originalPayload, byte[] baseValue)`: This is the function responsible for payload processing. The processed payload should return as a byte array. 
    * `currentPayload` - The value of the payload to be processed.
    * `originalPayload` - The value of the original payload prior to processing by any already-applied processing rules.
    * `baseValue` - The base value of the payload position, which will be replaced with the current payload.
* We can use helpers to convert `String to byte[]` by invoking `stringToBytes()`. To achieve the opposite, `bytestoString()` can be used from the `callbacks.getHelpers()`.

```java
/*
IntruderProcessor.java
*/
package burp;

public class IntruderPayloadProcessor implements IIntruderPayloadProcessor{

    IExtensionHelpers helpers;

    public IntruderPayloadProcessor(IBurpExtenderCallbacks callbacks){
        /*
            We can use the helpers string to byte array method as processPayload needs to return byte[]
         */
        helpers = callbacks.getHelpers();
    }

    @Override public String getProcessorName() {
        /*
            This name will be shown in the Burp Suite Intruder UI as the processor name.
         */
        return "Base64 Processor";
    }

    @Override public byte[] processPayload(byte[] currentPayload, byte[] originalPayload, byte[] baseValue) {
        if(currentPayload != null){
            return helpers.stringToBytes(helpers.base64Encode(currentPayload));
        }
        return null;
    }
}
```

Next, we'll tell Burp that we have a payload processor.

```java
/*
BurpExtender.java
*/

package burp;

public class BurpExtender implements IBurpExtender {
    @Override public void registerExtenderCallbacks(IBurpExtenderCallbacks callbacks) {
        callbacks.setExtensionName("Intruder Processing");
        callbacks.issueAlert("Plugin loaded");

        // Notice this.
        callbacks.registerIntruderPayloadProcessor(new IntruderPayloadProcessor(callbacks));
    }
}
```
Finally, we must build the artifact and load it in Burp. Visit the "Extender" tab, click on "Add", and select the JAR file’s location. It will look something like this.


In this lesson, we will examine a short post to create a plugin for an example use case. This plugin will process the payload from the Intruder and will execute the payload after processing.

__default

Extension Example 1: Intruder Payload Processing

Understand public interface IIntruderPayloadProcessor

Implement and register IIntruderPayloadProcessor