JWT Decoder Python — Dekódování JWT s PyJWT

import jwt

# Sdílené tajemství mezi vydavatelem a touto službou
SECRET_KEY = "k8s-webhook-signing-secret-2026"

# Zakódování tokenu (simulace toho, co vydá auth server)
token = jwt.encode(
    {"sub": "usr_8f2a", "role": "admin", "team": "platform"},
    SECRET_KEY,
    algorithm="HS256"
)
print(token)
# eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiJ1c3Jf...

# Dekódování a ověření tokenu
payload = jwt.decode(token, SECRET_KEY, algorithms=["HS256"])
print(payload)
# {'sub': 'usr_8f2a', 'role': 'admin', 'team': 'platform'}
print(payload["role"])
# admin

import jwt
from datetime import datetime, timedelta, timezone

SECRET_KEY = "webhook-processor-secret"

# Vytvoření tokenu s platností 1 hodinu
payload = {
    "sub": "svc_payment_processor",
    "iss": "auth.internal.example.com",
    "aud": "https://api.example.com",
    "exp": datetime.now(timezone.utc) + timedelta(hours=1),
    "permissions": ["orders:read", "refunds:create"],
}

token = jwt.encode(payload, SECRET_KEY, algorithm="HS256")

# Když token přijde v hlavičce požadavku:
try:
    decoded = jwt.decode(
        token,
        SECRET_KEY,
        algorithms=["HS256"],
        audience="https://api.example.com",
        issuer="auth.internal.example.com",
    )
    print(f"Service: {decoded['sub']}")
    print(f"Permissions: {decoded['permissions']}")
except jwt.ExpiredSignatureError:
    print("Token expired — request re-authentication")
except jwt.InvalidAudienceError:
    print("Token not intended for this API")
except jwt.InvalidIssuerError:
    print("Token issued by unknown authority")

import jwt

token = (
    "eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCIsImtpZCI6InNpZy0xNzI2In0"
    ".eyJzdWIiOiJ1c3JfM2M3ZiIsInNjb3BlIjoicmVhZDpvcmRlcnMiLCJpc3MiOiJhdXRoLmV4YW1wbGUuY29tIn0"
    ".signature_placeholder"
)

# Krok 1: Čtení claims bez ověření pro získání informací o směrování
unverified = jwt.decode(
    token,
    options={"verify_signature": False},
    algorithms=["RS256"]
)
print(unverified)
# {'sub': 'usr_3c7f', 'scope': 'read:orders', 'iss': 'auth.example.com'}

# Krok 2: Čtení hlavičky pro zjištění, který klíč použít
header = jwt.get_unverified_header(token)
print(header)
# {'alg': 'RS256', 'typ': 'JWT', 'kid': 'sig-1726'}
# Nyní použijte header['kid'] k načtení správného veřejného klíče z JWKS endpointu

import jwt

# Vyžadování přítomnosti konkrétních claims — vyvolá MissingRequiredClaimError při jejich absenci
payload = jwt.decode(
    token,
    SECRET_KEY,
    algorithms=["HS256"],
    options={"require": ["exp", "iss", "sub"]},
    issuer="auth.internal.example.com",
)

# Pouze při vývoji: přeskočení vypršení platnosti pro testování se starými tokeny
dev_payload = jwt.decode(
    token,
    SECRET_KEY,
    algorithms=["HS256"],
    options={"verify_exp": False},  # DO NOT use in production
)

import base64
import json

def decode_jwt_payload(token: str) -> dict:
    """Decode the JWT payload without signature verification.
    Works with any JWT — HS256, RS256, ES256, etc.
    """
    parts = token.split(".")
    if len(parts) != 3:
        raise ValueError(f"Expected 3 JWT segments, got {len(parts)}")

    payload_b64 = parts[1]
    # base64url uses - and _ instead of + and /
    # Python's urlsafe_b64decode handles this, but needs padding
    payload_b64 += "=" * (-len(payload_b64) % 4)
    payload_bytes = base64.urlsafe_b64decode(payload_b64)
    return json.loads(payload_bytes)


def decode_jwt_header(token: str) -> dict:
    """Decode the JWT header (algorithm, key ID, type)."""
    header_b64 = token.split(".")[0]
    header_b64 += "=" * (-len(header_b64) % 4)
    return json.loads(base64.urlsafe_b64decode(header_b64))


# Example usage
token = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiJ1c3JfOGYyYSIsInJvbGUiOiJhZG1pbiIsImV4cCI6MTcxMTgxNTYwMH0.dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk"

header = decode_jwt_header(token)
print(f"Algorithm: {header['alg']}")
# Algorithm: HS256

claims = decode_jwt_payload(token)
print(f"Subject: {claims['sub']}")
print(f"Role: {claims['role']}")
# Subject: usr_8f2a
# Role: admin

import jwt
import httpx  # or requests

TOKEN_ENDPOINT = "https://auth.example.com/oauth/token"
SECRET_KEY = "shared-webhook-signing-key"

def get_and_decode_token() -> dict:
    """Fetch an access token from the auth server and decode it."""
    try:
        response = httpx.post(
            TOKEN_ENDPOINT,
            data={
                "grant_type": "client_credentials",
                "client_id": "svc_order_processor",
                "client_secret": "cs_9f3a7b2e",
            },
            timeout=10.0,
        )
        response.raise_for_status()
    except httpx.HTTPError as exc:
        raise RuntimeError(f"Token request failed: {exc}") from exc

    token_data = response.json()
    access_token = token_data["access_token"]

    try:
        payload = jwt.decode(
            access_token,
            SECRET_KEY,
            algorithms=["HS256"],
            audience="https://api.example.com",
        )
        return payload
    except jwt.InvalidTokenError as exc:
        raise RuntimeError(f"Invalid token from auth server: {exc}") from exc


claims = get_and_decode_token()
print(f"Service: {claims['sub']}, Scopes: {claims.get('scope', 'none')}")

import jwt
from pathlib import Path
from datetime import datetime, timezone

TOKEN_PATH = Path("/var/run/secrets/service-account-token")
PUBLIC_KEY_PATH = Path("/etc/ssl/auth/public_key.pem")

def decode_token_from_file() -> dict:
    """Read a JWT from a file, verify with a PEM public key."""
    try:
        token = TOKEN_PATH.read_text().strip()
        public_key = PUBLIC_KEY_PATH.read_text()
    except FileNotFoundError as exc:
        raise RuntimeError(f"Missing file: {exc.filename}") from exc

    try:
        payload = jwt.decode(
            token,
            public_key,
            algorithms=["RS256"],
            audience="https://internal-api.example.com",
        )
    except jwt.ExpiredSignatureError:
        exp_time = jwt.decode(
            token,
            options={"verify_signature": False},
            algorithms=["RS256"],
        ).get("exp", 0)
        expired_at = datetime.fromtimestamp(exp_time, tz=timezone.utc)
        raise RuntimeError(f"Token expired at {expired_at.isoformat()}")
    except jwt.InvalidTokenError as exc:
        raise RuntimeError(f"Token verification failed: {exc}") from exc

    return payload


claims = decode_token_from_file()
print(f"Subject: {claims['sub']}, Issuer: {claims['iss']}")

# Decode JWT payload from clipboard or variable (no verification)
echo "eyJhbGciOiJIUzI1NiJ9.eyJzdWIiOiJ1c3JfOGYyYSIsInJvbGUiOiJhZG1pbiJ9.sig" \
  | python3 -c "
import sys, base64, json
token = sys.stdin.read().strip()
payload = token.split('.')[1]
payload += '=' * (-len(payload) % 4)
print(json.dumps(json.loads(base64.urlsafe_b64decode(payload)), indent=2))
"
# {
#   "sub": "usr_8f2a",
#   "role": "admin"
# }

# Decode JWT header to check algorithm and key ID
echo "eyJhbGciOiJSUzI1NiIsImtpZCI6InNpZy0xNzI2In0.payload.sig" \
  | python3 -c "
import sys, base64, json
token = sys.stdin.read().strip()
header = token.split('.')[0]
header += '=' * (-len(header) % 4)
print(json.dumps(json.loads(base64.urlsafe_b64decode(header)), indent=2))
"
# {
#   "alg": "RS256",
#   "kid": "sig-1726"
# }

# If PyJWT is installed, verify and decode in one step
python3 -c "
import jwt, sys, json
token = sys.argv[1]
payload = jwt.decode(token, options={'verify_signature': False}, algorithms=['HS256'])
print(json.dumps(payload, indent=2))
" "eyJhbGciOiJIUzI1NiJ9.eyJzdWIiOiJ1c3JfOGYyYSJ9.sig"

# pip install python-jose[cryptography]
from jose import jwt as jose_jwt

token = "eyJhbGciOiJIUzI1NiJ9.eyJzdWIiOiJ1c3JfOGYyYSIsInNjb3BlIjoib3JkZXJzOnJlYWQifQ.signature"

# Verified decode — same pattern as PyJWT
payload = jose_jwt.decode(
    token,
    "signing-secret-key",
    algorithms=["HS256"],
    audience="https://api.example.com",
)
print(payload)
# {'sub': 'usr_8f2a', 'scope': 'orders:read'}

# Unverified decode
claims = jose_jwt.get_unverified_claims(token)
header = jose_jwt.get_unverified_header(token)
print(f"Algorithm: {header['alg']}, Subject: {claims['sub']}")

# pip install rich PyJWT
import jwt
from rich import print_json

token = "eyJhbGciOiJIUzI1NiJ9.eyJzdWIiOiJ1c3JfOGYyYSIsInJvbGUiOiJhZG1pbiIsInBlcm1pc3Npb25zIjpbIm9yZGVyczpyZWFkIiwicmVmdW5kczpjcmVhdGUiXSwiZXhwIjoxNzExODE1NjAwfQ.sig"

payload = jwt.decode(
    token,
    options={"verify_signature": False},
    algorithms=["HS256"]
)

# Colorized, indented JSON output in the terminal
print_json(data=payload)
# {
#   "sub": "usr_8f2a",           ← strings in green
#   "role": "admin",
#   "permissions": [
#     "orders:read",
#     "refunds:create"
#   ],
#   "exp": 1711815600            ← numbers in cyan
# }

import jwt
import json
from pathlib import Path

SECRET_KEY = "audit-log-signing-key"

def validate_token_log(log_path: str) -> dict:
    """Process an NDJSON file where each line has a 'token' field.
    Returns counts of valid, expired, and invalid tokens.
    """
    stats = {"valid": 0, "expired": 0, "invalid": 0}

    with open(log_path) as fh:
        for line_num, line in enumerate(fh, 1):
            line = line.strip()
            if not line:
                continue

            try:
                record = json.loads(line)
                token = record["token"]
            except (json.JSONDecodeError, KeyError):
                stats["invalid"] += 1
                continue

            try:
                jwt.decode(token, SECRET_KEY, algorithms=["HS256"])
                stats["valid"] += 1
            except jwt.ExpiredSignatureError:
                stats["expired"] += 1
            except jwt.InvalidTokenError:
                stats["invalid"] += 1

    return stats


result = validate_token_log("auth-events-2026-03.ndjson")
print(f"Valid: {result['valid']}, Expired: {result['expired']}, Invalid: {result['invalid']}")
# Valid: 14832, Expired: 291, Invalid: 17

import base64
import json
from datetime import datetime, timezone

def extract_claims_stream(input_path: str, output_path: str):
    """Read tokens line by line, decode payloads, write flattened claims."""
    with open(input_path) as infile, open(output_path, "w") as outfile:
        for line in infile:
            line = line.strip()
            if not line:
                continue

            record = json.loads(line)
            token = record.get("access_token", "")
            parts = token.split(".")
            if len(parts) != 3:
                continue

            payload_b64 = parts[1] + "=" * (-len(parts[1]) % 4)
            claims = json.loads(base64.urlsafe_b64decode(payload_b64))

            # Flatten into an audit-friendly record
            flat = {
                "timestamp": record.get("timestamp"),
                "subject": claims.get("sub"),
                "issuer": claims.get("iss"),
                "expired_at": datetime.fromtimestamp(
                    claims.get("exp", 0), tz=timezone.utc
                ).isoformat(),
            }
            outfile.write(json.dumps(flat) + "\n")

extract_claims_stream("token-audit.ndjson", "claims-extract.ndjson")