Burp Suite MessagePack decode extension

A Java extension for BurpSuite, which intercepts any packets encoded in the MessagePack binary serialization format. Decoded messages are then passed to the rest of the stack and displayed within Proxy -> WebSocket history with the decoded content in the Notes field.

Requirements

Java 21 (Not later, as Burp only supports extensions written in Java 21 or lower.)

Building the extension

When you're ready to test and use your extension, follow these steps to build a JAR file and load it into Burp.

Building the JAR file

To build the JAR file, run the following command in the root directory of this project:

• For UNIX-based systems: ./gradlew jar
• For Windows systems: gradlew jar

If successful, the JAR file is saved to <project_root_directory>/build/libs/<project_name>.jar. If the build fails, errors are shown in the console. By default, the project name is extension-template-project. You can change this in the settings.gradle.kts file.

Loading the JAR file into Burp

To load the JAR file into Burp:

1. In Burp, go to Extensions > Installed.
2. Click Add.
3. Under Extension details, click Select file.
4. Select the JAR file you just built, then click Open.
5. [Optional] Under Standard output and Standard error, choose where to save output and error messages.
6. Click Next. The extension is loaded into Burp.
7. Review any messages displayed in the Output and Errors tabs.
8. Click Close.

Your extension is loaded and listed in the Burp extensions table. You can test its behavior and make changes to the code as necessary.

Reloading the JAR file in Burp

If you make changes to the code, you must rebuild the JAR file and reload your extension in Burp for the changes to take effect.

To rebuild the JAR file, follow the steps for building the JAR file.

To quickly reload your extension in Burp:

1. In Burp, go to Extensions > Installed.
2. Hold Ctrl or ⌘, and select the Loaded checkbox next to your extension.