Burp Extensions

• Creating Burp extension (PortSwigger)
• burp-extensions-montoya-api-examples (GitHub, PortSwigger)
• Interface MontoyaApi (GitHub.io, PortSwigger)
• KotlinBurpExtensionBase (GitHub) – template

Build Burp Extensions with Kotlin

Installation & Setup

Install Java SDK

Download Java JDK 21 (Oracle, latest Long-Term Support (LTS) release of the Java SE Platform).

Add or set the environment variables (on Windows):

• JAVA_HOME (SYSTEM): “C:\Program Files\Java\jdk-21”
• PATH (USER): “%PATH%;%JAVA_HOME\bin”

Install extension Gradle for Java in Visual Studio Code

Use Gradle to install dependencies and build the project.

Restart Visual Studio Code if needed (for the Java environment variables).

In Visual Studio Code, click on Extensions and search for Gradle for Java. Click on Install. By default, if you have installed the Gradle for Java extension, the Gradle Build Server is used to import Gradle projects.

Project Setup

Download the Kotlin extension template

Download the ZIP file from KotlinBurpExtensionBase (GitHub).

settings.gradle.kts

Change your project name.

rootProject.name = "KotlinBurpExtensionBase"

rootProject.name = "myProject"

build.gradle.kts

Configurations about Kotlin and the build system. Important to build JAR files (needed to build Burp Suite extensions):

id("com.github.johnrengelman.shadow") version "8.1.1"

Change this to your package name.

group = "com.yournamehere.montoya"

Edit code

Edit code in Project Name folder->src\main\kotlin. Rename this file (in Gradle, right-click, Refactor->Rename. Not sure how in Visual Studio Code).

Rename the file YourBurpKotlinExtensionName.kt AND the class name in the code. Like myExtension.kt and in the code:

class myExtension : BurpExtension {

Replace this code with your extension name that will be displayed in the Burp Suite Extension tab.

api.extension().setName("Your Plugin Name Here")

api.extension().setName("My Extension")

Build

In Visual Studio Code, click on the elephant icon (Gradle).

When you change configurations files (like settings.gradle.kts, build.gradle.kts), you need to click on “…”->Refresh Gradle Project View button (beside Gradle Projects).

To build the extension, double-click on Tasks->shadow->shadowJar. It will build the shadowJar and all the dependencies. It will generate a JAR file under:
Project Name folder->build->libs->myProject-0.1.0-all.jar

The generated JAR file name MUST contain “-all” to contain all the dependencies.

Add the extension in Burp Suite

• Click on the Extensions tab in Burp Suite
• Click on Add
  • Extension type: Java
  • Extension file (.jar): click on Select file, and select Project Name-0.1.0-all.jar
  • Click Next
• Click Close