Decoder Improved

tl;dr

Within extender load Decoder-Improved.jar latest release

For a walkthrough on how to extend Decoder Improved visit our blog post.

Summary

Burp Suite's built-in decoder component, while useful, is missing important features and cannot be extended. To remedy this, I developed Decoder Improved, a drop-in replacement Burp Suite plugin. It includes all of decoder's functionality while fixing bugs, adding tabs, and includes an improved hex editor. Additionally, the plugin's functionality is straightforward to extend to accommodate any custom data encoding and decoding needs.

Burp Suite Decoder and its Weaknesses

Burp Suite includes an easy-to-use data manipulation toolkit that allows a user to manipulate data by setting a series of transformation filters. These filters allow users to perform simple data manipulation including URL, HTML, Base64, ASCII Hex, Hex, Octal, Binary, and Gzip encoding and decoding; it also includes a few basic hashing functions. Additionally, Burp Suite's decoder has a hex editor and a "smart decode" option that automatically picks a reasonable decoding method. While this set of functionality is useful, it suffers from several issues that limit it heavily:

• A Lack of Tabs

  Unlike many of Burp's other features, the decoder does not support tabs which makes managing multiple chunks of data difficult.

• Difficult to Use Hex Editor

  The included hex editor requires users to right click to insert new bytes or delete existing bytes. Additionally, each byte in the hex editor is a text box making data entry difficult.

• Cannot Handle Non-ASCII Text

  Decoder truncates text characters to one byte, mangling Unicode characters. This makes dealing with non-English character sets brutal.

• Impossible to Extend

  Because Burp Suite is closed-source, it is not feasible to fix bugs and extend the existing decoder via the Burp Extender API to perform custom encoding and decoding.

Decoder Improved

Decoder Improved is a data transformation plugin for Burp Suite that better serves the varying and expanding needs of information security professionals. Decoder Improved includes the following useful features:

All of the Built-in Burp Decoder Modes

Decoder Improved supports all of decoder's encoding, decoding, and hashing modes. Decoder Improved can encode and decode URL, HTML, Base64, ASCII Hex, and GZIP. Additionally, Decoder Improved can hash data using MD2, MD5, SHA, SHA-224, SHA-256, SHA-384, and SHA-512.

Tabs

Like many of Burp Suite's features, Decoder Improved has support for tabs, enabling users to manipulate separate pieces of data simultaneously without having to erase existing work.

Unicode Support

Decoder Improved is backed by arrays of Java Bytes that do not truncate or modify Unicode characters through the modification process. Because Java's Swing elements support displaying Unicode characters, so does Decoder Improved.

An Improved Hex Editor

Decoder Improved comes bundled with the Delta Hexadecimal Editor, a swing Hex Editor, developed by the ExBin project. Delta provides an improved hex editing experience over the built-in decoder's hex editor by allowing easy insertion and removal, highlighting, and Unicode support.

Arbitrary Numeric Base Conversion

Decoder Improved can convert any number represented in base 2 to base 32 (the largest base supported by Java) to its representation in any other base between base 2 and base 32.

Regex Find and Replace

Decoder Improved can perform regular expression find and replace over input to quickly transform text.

HTML/URL Encode Only Special Characters

When HTML and URL encoding strings in decoder, every character in the string is encoded, which limits human readability and occasionally trips broken input filtering rules. Decoder Improved includes encoding modes that only encode special characters while leaving alphanumerics untouched.

Every Hashing Algorithm Available in BouncyCastle

In addition to every hashing algorithm exposed within Burp Suite's built-in decoder, Decoder Improved exposes every hashing algorithm included in the BouncyCastle Java crypto library. In contrast, decoder only contains a smattering of hashing algorithms that do not cover the entire range of hashing needs encountered during testing.

Save Data to Files in Different Formats

Every piece of data can be saved to local files in raw, Hex and UTF-8 encoded formats.

Work State is Saved

Decoder Improved automatically saves and reloads its work state after Burp restarts. Users have the options to export the work state to files.

An Easy Extension Interface

The Decoder Improved can be extended with customized modes with easy-to-use interfaces. See our blog post for a walkthrough on how to extend Decoder Improved.

Build Your Own Jar

1. Prerequisites:

   • Gradle 5.6+
   • JDK 1.8+

2. Build:

   1. $ git clone https://github.com/nccgroup/Decoder-Improved.git
   2. $ cd Decoder-Improved/
   3. $ gradle shadowJar (or simply $ gradle)

3. Find the compiled Jar file ./build/libs/Decoder-Improved-all.jar and load it under Extender -> Extensions.