PyJWT get_signing_key_from_jwt throws PyJWKError: Unable to find a algorithm for key

Question

My purpose is to simply get the JWKs key by supplying the access_token to the get_signing_key_from_jwt api

(Using latest PyJWT==2.4.0 with python 3.8.10 on linux)

like that:

import jwt
jwks_uri="https://my_auth_server/keys.json"
jwks_client = jwt.PyJWKClient(jwks_uri)
signing_key = jwks_client.get_signing_key_from_jwt(my_access_token)

Running this I get a nasty exception:

...
File "/home/_work/my_jwks_repo/.venv/lib/python3.8/site-packages/jwt/api_jwk.py", line 61, in __init__
    raise PyJWKError(f"Unable to find a algorithm for key: {self._jwk_data}")
jwt.exceptions.PyJWKError: Unable to find a algorithm for key: {'kty': 'RSA', 'n': '...' ...}

The pub key has an alg property value of RS256, IMO PyJWT should know to deal with this. Instead for some reason it fails.

How to fix this?

Asked By: Mercury

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Source

Answer 1

I noticed that the library file .venv/lib/python3.8/site-packages/jwt/algorithms.py will support additional algorithms only if cryptography lib is installed

so I’ve added cryptography==37.0.4 to my python dependencies and Voila, works (the key is retrieved successfully)

pip install cryptography==37.0.4

Note: installing cryptography also threw some errors – for that I had to update pip to latest using this command: python -m pip install --upgrade pip
(make sure you run this when your virtual env. is activated in case you are working within one)

Answered By: Mercury

PyJWT get_signing_key_from_jwt throws PyJWKError: Unable to find a algorithm for key

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