Burpsuite Plugin to decrypt AES Encrypted traffic on the fly

• Burpsuite

• Burpsuite 2021.4
• Windows 10
• Ubuntu & PopOS

• The IProxyListener decrypt requests and encrypt responses, and an IHttpListener than encrypt requests and decrypt responses.
• Burp sees the decrypted traffic, including Repeater, Intruder and Scanner, but the client/mobile app and server see the encrypted version.

NOTE: Currently support AES/CBC/PKCS5Padding && AES/ECB/PKCS5Padding encryption/decryption.

• Require Secret Key and Initialize Vector which can be obtained by using aes-hook.js and frida-hook.py or by reversing the application (For iOS please use Frida iOS Hook to get AES Secret Key and IV)
• A detailed usage guide can be found at AES Killer - Usage Guide
• This article will help you in Decrypting Mobile App Traffic using AES Killer and Frida

$ git clone https://github.com/Ebryx/AES-Killer/
$ cd AES-Killer
$ ./gradlew clean build

• AES_Killer for JSON request AES_Killer-JSON.java
• AES_Killer for random/alternate Parameters on different endpoints AES_Killer-Parameters.java

AES_Killer-Parameters.java: Let's say if application enforcing encryption on few parameters in request and these parameters will change every time with respect to endpoint/request so all you need to do is as follow

- Add endpoints by adding this.endpoints.add("abc"); in registerExtenderCallbacks function
- Add parameters which will be encrypted in `String[][] parameters`
- Add rest of parameter in grant_type or make blank entry

and let the code do the magic for you.

• AES_Killer_v3.0 a generic variant for alternate parameters on different endpoints with GET, POST (JSON, Form) support AES_Killer_v3.0.java

AES_Killer_v3.0.java: This variant is generic and can deal with any type of request format i-e GET, POST(Form, JSON) with alternate parameters on different endpoints

- Clone the project and replace the BurpExtender.java with AES_Killer_v3.0.java code
- Modify the endpoints and parameters of each request type in order as shown below
- Update SecretKey and IV parameters and other required methods
- Build the project and you are good to go

• AES_Killer_v4.0.java for multi-level encryption on request (Support Form, JSON and XML formats)

AES_Killer_v4.0.java: This variant is for Multi-Level encryption where application is encrypting few request parameters with one key and later on encrypting the whole request body with another key

- Clone the project and replace the BurpExtender.java with AES_Killer_v4.0.java code
- Modify the endpoints and parameters as shown below
- Update Secret Keys and other required methods
- Build the project and add jar file to your extender

NOTE: These variants will not work for you directly due to nature of your request so might need little tweaking.

Download jar file from Release and add in burpsuite

• First setup frida server on IOS and Android device.
• Launch Application on mobile device.
• Run aes-hook.js and frida-hook.py on your host machine to get AES Encryption Key and IV as shown in this post.

• Provide SecretSpecKey under Secret Key field
• Provide IV under Initialize Vector field
• Provide Host/URL to filter request and response for encryption and decryption
• Select appropriate Request and Response options
• Press Start AES Killer

Once we start AES Killer, it takes control of Burp IHttpListener.processHttpMessage which is responsible for handling all outgoing and incoming traffic and AES Killer do the following

• Before sending the final request to a server, ProcessHttpMessage encrypt the request
• Upon receiving a response, ProcessHttpMessage decrypt the response first before showing it to us

So we'll only be getting the Plain Text Response and can play with Plain Text request.

We can also manually encrypt and decrypt strings using AES Killer. Let's take an encrypted string from the request TYROd49FWJjYBfv02oiUzwRQgxWMWiw4W3oCqvNf8h3bnb7X0bobypFzMt797CYU and decrypt it using AES Killer. Similarly, we can perform the encryption too.

Download Demo App from here