jwt_lint.py

#!/usr/bin/env python3
import argparse, base64, json, time

def b64url(data):
    data += '=' * (-len(data)%4)
    return base64.urlsafe_b64decode(data.encode())

def main():
    ap = argparse.ArgumentParser()
    ap.add_argument("--token", required=True)
    args = ap.parse_args()
    try:
        header_b64, payload_b64, _sig = args.token.split(".")
        header = json.loads(b64url(header_b64))
        payload = json.loads(b64url(payload_b64))
        print("== Header ==")
        print(json.dumps(header, indent=2))
        print("== Payload ==")
        print(json.dumps(payload, indent=2))
        now = int(time.time())
        for claim in ["exp","iat","nbf"]:
            if claim in payload:
                print(f"[check] {claim} = {payload[claim]} (now={now})")
        alg = header.get("alg","none")
        print(f"[info] alg={alg}")
    except Exception as e:
        print("Invalid token or parse error:", e)

if __name__ == "__main__":
    main()