Skill UI

This skill provides comprehensive implementation for secure JWT (RFC 7519) signing and verification using multiple algorithms (HMAC-SHA256, RSA-PSS, ES256, EdDSA). It covers token expiration, claims validation, and crucial defenses against common attacks like algorithm confusion and 'none' algorithm bypass, essential for hardening web application authentication systems.

A specialized tool for authorized penetration testing and security assessments. It exploits the vulnerability of JWT libraries that accept tokens with the "alg": "none" header, bypassing cryptographic signature verification. Users can craft tokens with arbitrary claims (e.g., elevated privileges, impersonation) to validate that a target server correctly rejects unsigned JSON Web Tokens.

A comprehensive checklist detailing advanced attack methodologies for JSON Web Tokens (JWT). Covers critical misconfigurations such as algorithm confusion (alg:none, RS256→HS256), weak secret brute forcing, header injection (kid, jku, jwk), cache poisoning, and improper validation. Also provides specific vectors for extracting JWTs from mobile environments (Android/iOS). Ideal for penetration testers conducting deep security assessments on authentication systems.