Code required to verify Sign in with app-made Apple JWT tokens server-side in Python

jwt-apple-signin.py

import jwt
from jwt.algorithms import RSAAlgorithm
import requests
from time import time
import json
import os


APPLE_PUBLIC_KEY_URL = "https://appleid.apple.com/auth/keys"
APPLE_PUBLIC_KEY = None
APPLE_KEY_CACHE_EXP = 60 * 60 * 24
APPLE_LAST_KEY_FETCH = 0


class AppleUser(object):
    def __init__(self, apple_id, email=None):
        self.id = apple_id
        self.email = email
        self.full_user = False

        if email is not None:
            self.full_user = True

    def __repr__(self):
        return "<AppleUser {}>".format(self.id)


def _fetch_apple_public_key():
    # Check to see if the public key is unset or is stale before returning
    global APPLE_LAST_KEY_FETCH
    global APPLE_PUBLIC_KEY

    if (APPLE_LAST_KEY_FETCH + APPLE_KEY_CACHE_EXP) < int(time()) or APPLE_PUBLIC_KEY is None:
        key_payload = requests.get(APPLE_PUBLIC_KEY_URL).json()
        APPLE_PUBLIC_KEY = RSAAlgorithm.from_jwk(json.dumps(key_payload["keys"][0]))
        APPLE_LAST_KEY_FETCH = int(time())

    return APPLE_PUBLIC_KEY


def _decode_apple_user_token(apple_user_token):
    public_key = _fetch_apple_public_key()

    try:
        token = jwt.decode(apple_user_token, public_key, audience=os.getenv("APPLE_APP_ID"), algorithm="RS256")
    except jwt.exceptions.ExpiredSignatureError as e:
        raise Exception("That token has expired")
    except jwt.exceptions.InvalidAudienceError as e:
        raise Exception("That token's audience did not match")
    except Exception as e:
        print(e)
        raise Exception("An unexpected error occoured")

    return token


def retrieve_user(user_token):
    token = _decode_apple_user_token(user_token)
    apple_user = AppleUser(token["sub"], token.get("email", None))

    return apple_user

I googling for two days not knowing how to extract the RSA key using the Apple public key
But I solved by looking at your source code
Now, I've completed Apple login authentication in my backend server ( python )

Thank you so much 👍

Glad it helped, @junyoung-noh!

Your implementation of _fetch_apple_public_key() saved me so much time! Thanks for sharing it!

Glad it helped, @erwan-lemonnier!

Thanks for your solution! For other developers: this code may fail importing the algorithms, if that happens you might need to install 'cryptography'.

Thanks for sharing!!, for other developers in testing data maybe got the error InvalidSignatureError('Signature verification failed',) is for the time lapse for the token expired 5min, so short to testing, we have to obtain a new token to tests without troubles.

Hm, does not work for me.

RSAAlgorithm.from_jwk(json.dumps(key_payload["keys"][0]))

returns a cryptography.hazmat.backends.openssl.rsa._RSAPublicKey object as the Apple Public Key, while jwt.decode expects a string as a public key. Is this a different version of jwt?

Hm, does not work for me.

RSAAlgorithm.from_jwk(json.dumps(key_payload["keys"][0]))

returns a cryptography.hazmat.backends.openssl.rsa._RSAPublicKey object as the Apple Public Key, while jwt.decode expects a string as a public key. Is this a different version of jwt?

You might have to install the 'cryptography' package: https://cryptography.io/en/latest/

Hm, does not work for me.

RSAAlgorithm.from_jwk(json.dumps(key_payload["keys"][0]))

returns a cryptography.hazmat.backends.openssl.rsa._RSAPublicKey object as the Apple Public Key, while jwt.decode expects a string as a public key. Is this a different version of jwt?

Yes is expecting a string so you have to convert to a string, im sharing the code:

apple_public_key_as_string = apple_public_key.public_bytes(
                encoding=serialization.Encoding.PEM,
                format=serialization.PublicFormat.SubjectPublicKeyInfo
            )

Thanks very much for your help. Installing 'cryptography' didn't help.

I had tried converting the public key to a string beforehand myself. It returns the error (when used with the Apple key):

jwt.exceptions.InvalidKeyError: The specified key is an asymmetric key or x509 certificate and should not be used as an HMAC secret.

Also, why does the above, unmodified code, work for you, but not for somebody else? Either the API call expects a structured object or a string, but not one thing for the one user and one thing for another.

I'm clueless here.

Thanks very much for your help. Installing 'cryptography' didn't help.

I had tried converting the public key to a string beforehand myself. It returns the error (when used with the Apple key):

jwt.exceptions.InvalidKeyError: The specified key is an asymmetric key or x509 certificate and should not be used as an HMAC secret.

Also, why does the above, unmodified code, work for you, but not for somebody else? Either the API call expects a structured object or a string, but not one thing for the one user and one thing for another.

I'm clueless here.

The original implementation didnt work for me, i had to to change a few things, i will try to modify later this code and push it when i have some time.

That would be very helpful, thank you!

I think I know why the exception above occurred - I wasn't testing with an actual Apple Token, but with a token that needed a symmetric secret for verification. Does anybody know where to get actual Apple signed JWT Tokens for testing?

@emcas88 That is quite a teaser! "The original implementation didn't work for me, i had to to change a few things, i will try to modify later this code and push it when i have some time." Could you send your working version?

I have spent more than a day on this, and need to ask a very basic question. The code/token that I get back from Sign in with Apple ("https://appleid.apple.com/auth/authorize?") via JavaScript is

ce328a54c58114324957c1994932b0856.0.nruqx.9wwNzKYMETQQlZF1UfrGOg

And api_jwt.py base64url_decode pads the header out to

header segment = b'ce328a54c58114324957c1994932b0856==='

And base64.py binascii.a2b_base64 tries to make a 64bit value out of that string of bytes, and throws a binascii.Error 'Invalid header padding'

This issue is so basic, I wonder if I am requesting the correct code/token from Apple?

import json  # pragma: no cover
import jwt   # pragma: no cover
from cryptography.hazmat.primitives import serialization    # pragma: no cover
from jwt.algorithms import RSAAlgorithm     # pragma: no cover

class AppleResolver(object):

    @classmethod
    def __get_right_public_key_info(cls, keys, unverified_header):
        for key in keys:
            if key['kid'] == unverified_header['kid']:
                return key

    @classmethod
    def authenticate(cls, access_token):

        import http.client

        apple_keys_host = 'appleid.apple.com'
        apple_keys_url = '/auth/keys'
        headers = {"Content-type": "application/json"}

        try:

            connection = http.client.HTTPSConnection(apple_keys_host, 443)
            connection.request('GET', apple_keys_url, headers=headers)
            response = connection.getresponse()

            keys_json = json.loads(response.read().decode('utf8'))
            connection.close()

            unverified_header = jwt.get_unverified_header(access_token)

            public_key_info = cls.__get_right_public_key_info(keys_json['keys'], unverified_header)

            apple_public_key = RSAAlgorithm.from_jwk(json.dumps(public_key_info))

            apple_public_key_as_string = apple_public_key.public_bytes(
                encoding=serialization.Encoding.PEM,
                format=serialization.PublicFormat.SubjectPublicKeyInfo
            )

            verified_payload = jwt.decode(access_token, apple_public_key_as_string, audience=config.APPLE_APP_ID, algorithm=public_key_info['alg'])

            return {'email': verified_payload['email']}

        except Exception as ex:
            raise AuthorizationException(AuthorizationSubcode.InvalidProviderToken) from ex

This is my code guys, ignore the exception part. Shoot me any questions if u like.

That's pretty much the solution I ended up with. It's even better than the original one, because it considers the 'kid' parameter for selecting the key, so if Apple one day decides to switch keys and supports an intermediate key, this will still work. The original post's solution won't.

That's pretty much the solution I ended up with. It's even better than the original one, because it considers the 'kid' parameter for selecting the key, so if Apple one day decides to switch keys and supports an intermediate key, this will still work. The original post's solution won't.

exactly !!

Thank you @emcas88, it worked perfectly!

For other newbies:
audience=config.APPLE_APP_ID is a string like "us.wevote.webapp" that you need to configure somewhere

Also part of the verified_payload is the sub element that apple defines as "The subject registered claim identifies the principal that is the subject of the identity token. Since this token is meant for your application, the value is the unique identifier for the user."
The sub solves another issue that I have with repeated signins (from both ios and web) -- it allows us to match prior signins using other OAuth schemes -- which allows the end user to not lose all their data, when they switch to Sign in with Apple..

You are the light in the darkness surrounding everything related to apple sign in.

If you want to know thoroughly. https://sarunw.com/posts/sign-in-with-apple-4/

Thank you @emcas88, it worked perfectly!

For other newbies:
audience=config.APPLE_APP_ID is a string like "us.wevote.webapp" that you need to configure somewhere

Also part of the verified_payload is the sub element that apple defines as "The subject registered claim identifies the principal that is the subject of the identity token. Since this token is meant for your application, the value is the unique identifier for the user."
The sub solves another issue that I have with repeated signins (from both ios and web) -- it allows us to match prior signins using other OAuth schemes -- which allows the end user to not lose all their data, when they switch to Sign in with Apple..

Thanks for this ... it daved me another sleepless night.

Inaddition the

RSAAlgorithm.from_jwk(json.dumps(key_payload["keys"][0]))

I had to use for it to work

RSAAlgorithm.from_jwk(json.dumps(key_payload["keys"][1]))

if index zero doesnot work for you, you can try index one

@ldonjibson

if index zero doesnot work for you, you can try index one

You should use the key that was used for encoding the payload (can be found in token's kid header). @emcas88 has pasted an example above.

Thank you, was very helpful. This is what I used with python-jose[cryptography] instead of old PyJWT

import logging
import requests

from typing import Dict, Union, List
from fastapi import HTTPException
from jose import jwt, jwk, JWTError
from starlette import status

from modules.database.models.member_user import MemberUser
from services.user_service.domain.providers.apple.constants import AppleUtilConstants
from settings.secrets import APPLE_OAUTH2_WEB_CLIENT_ID

def validate_user(provider_id_token_jwt: str) -> Dict[str, str]:
    # Get public key set from Apple
    try:
        keys: Dict[str, List[Dict[str, str]]] = dict(requests.get(AppleUtilConstants.KEYS_URL.value).json())
    except Exception as error:
        logging.exception(repr(error))
        raise Exception("Unable to connect to Apple.")
    # Get headers of our id token
    headers = jwt.get_unverified_headers(token=provider_id_token_jwt)
    # Find matching public key based on the kid header
    public_key: Dict[str, str] = next(filter(lambda key: (key["kid"] == headers["kid"]), keys["keys"]))
    # Construct the actual public_key
    public_rsa_key = jwk.construct(public_key_set)
    try:
        decoded_id_token = dict(
            jwt.decode(
                token=provider_id_token_jwt,
                audience=APPLE_OAUTH2_WEB_CLIENT_ID,
                key=public_key,
                algorithms=["RS256"],
            )
        )
    except jwt.ExpiredSignatureError as error:
        logging.info(repr(error))
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="Token has expired",
        )
    except JWTError as error:
        logging.info(repr(error))
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="Unable to process given id_token",
        )
    except Exception as error:
        logging.exception(repr(error))
        raise Exception("An unexpected error occurred")

    return decoded_id_token

thank you, so match ! I loosed 2 days before found this solution !

This thread is a godsend

pyjwt >= 2.0 diff from pyjwt == 1.7.1 options={"verify_exp": False}, algorithms=["RS256"],

change log

.. code:: python

import jwt
from jwt import PyJWKClient

token = "eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiIsImtpZCI6Ik5FRTFRVVJCT1RNNE16STVSa0ZETlRZeE9UVTFNRGcyT0Rnd1EwVXpNVGsxUWpZeVJrUkZRdyJ9.eyJpc3MiOiJodHRwczovL2Rldi04N2V2eDlydS5hdXRoMC5jb20vIiwic3ViIjoiYVc0Q2NhNzl4UmVMV1V6MGFFMkg2a0QwTzNjWEJWdENAY2xpZW50cyIsImF1ZCI6Imh0dHBzOi8vZXhwZW5zZXMtYXBpIiwiaWF0IjoxNTcyMDA2OTU0LCJleHAiOjE1NzIwMDY5NjQsImF6cCI6ImFXNENjYTc5eFJlTFdVejBhRTJINmtEME8zY1hCVnRDIiwiZ3R5IjoiY2xpZW50LWNyZWRlbnRpYWxzIn0.PUxE7xn52aTCohGiWoSdMBZGiYAHwE5FYie0Y1qUT68IHSTXwXVd6hn02HTah6epvHHVKA2FqcFZ4GGv5VTHEvYpeggiiZMgbxFrmTEY0csL6VNkX1eaJGcuehwQCRBKRLL3zKmA5IKGy5GeUnIbpPHLHDxr-GXvgFzsdsyWlVQvPX2xjeaQ217r2PtxDeqjlf66UYl6oY6AqNS8DH3iryCvIfCcybRZkc_hdy-6ZMoKT6Piijvk_aXdm7-QQqKJFHLuEqrVSOuBqqiNfVrG27QzAPuPOxvfXTVLXL2jek5meH6n-VWgrBdoMFH93QEszEDowDAEhQPHVs0xj7SIzA"
kid = "NEE1QURBOTM4MzI5RkFDNTYxOTU1MDg2ODgwQ0UzMTk1QjYyRkRFQw"
url = "https://dev-87evx9ru.auth0.com/.well-known/jwks.json"

jwks_client = PyJWKClient(url)
signing_key = jwks_client.get_signing_key_from_jwt(token)

data = jwt.decode(
    token,
    signing_key.key,
    algorithms=["RS256"],
    audience="https://expenses-api",
    options={"verify_exp": False},
)
print(data)