SignSaboteur is a Burp Suite extension for editing, signing, verifying, and attacking signed tokens. It supports different types of tokens: Django TimestampSigner, ItsDangerous Signer, Express cookie-session middleware, OAuth2 Proxy, Tornado's signed cookies, Ruby Rails Signed cookies, Ruby Rails Encrypted cookies, Nimbus JOSE + JWT and Unknown signed string.

It provides automatic detection and in-line editing of token within HTTP requests/responses and WebSocket messages, signing of tokens and automation of brute force attacks against signed tokens implementations.

Features

Wordlist view

The Wordlist View allows to import secrets and salts list files. The extension has own prebuilt dictionary lists. Most secrets are taken from jwt-secrets. As an option, Flask-Unsign-Wordlist can be used. The extension supports JSON strings format for special characters. To use it, quote the secret string with ".

Editor view

The Editor View supports a number of signed tokens: Django, Dangerous, Flask, Express, OAuth2 and Tornado. It allows modification of the signed tokens at Burp Suite's HTTP Request/Response view in the Proxy, History and Repeater tools.
The Dangerous tab can be used for both, Flask and Django tokens, which are selected depending on whether a Dangerous or Django token is detected.
The Unknown tab can be used to brute force unknown signed strings. Guessing mode works only with Balanced and Deep brute force attacks. It supports different message derivation techniques, including:

None: message will be used as is
CONCAT: separator byte will be removed from the message and that new value will be used to calculate signature
Tornado: separator byte will be added to the end of the message string

Editable fields

A JSON text editor is provided to edit each component that contain JSON content:

Dangerous Payload
Django Payload (except pickle serialized payload)
Express Payload
JWT Payload

A timestamp editor is provided to edit each component that contain it:

Dangerous timestamp
Django timestamp
OAuth2 Proxy timestamp
Tornado timestamp

A hex editor is provided to all signed tokens, except Express signatures. NOTE Express Tab doesn't support signature auto update yet. Please copy it manually to corresponding signature cookie.

Sign

Sign presents a signing dialog that can be used to update the Signature by signing the token using a key from the Keys View that has signing capabilities

Brute force

Brute force will attempt to find secret key that was used for signature generation. If a secret key was found, a dialog will be presented.
The Brute force option implements three types of attacks against signed tokens Signatures:

Known keys: Uses previously found secret keys only
Fast: Uses default hashing algorithm and key derivation
Balanced: Uses all known key derivation technics, except PBKDF2WithHmacSHA1, PBKDF2WithHmacSHA256
Deep: Uses all key derivation technics, including different types supported by Ruby Rails framework

Attack

The Attack option implements eight well-known authorization attacks against signed tokens:

User claims
Wrapped user claims
Username and password claims
Flask claims
Express claims
Account user claims
Authenticated claims
User access_token

For more details on attacks, check out the repository or the Portswigger Research blog post -Introducing SignSaboteur: forge signed web tokens with ease.