What is the base exception for an invalid JWT in PyJWT?

Question

According to the documentation for PyJWT, the class jwt.exceptions.InvalidTokenError is the base error when the decode method fails. However, the following code still breaks with different exceptions:

try:
  jwt.decode(jwt_token, os.environ['SECRET'], algorithms="HS256")
except jwt.exceptions.InvalidTokenError:
  pass

My thinking was that since InvalidTokenError is the base error, this except block should catch all the other possible PyJWT errors such as InvalidSignatureError, DecodeError etc. My question is if there is a base error for PyJwt I could use. I know using except Exception is always an option but that's bad form so I'd like to avoid it if possible. Thanks!

Answer 1

I got this micro example working. In general, don't pass an exception, at least print the error message.

#pip install pyjwt
import os, jwt, hashlib
jwt_token = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.VUI28NztICBIB9m6kZolIEzYJojrw0eUr_4bVoQ1Ong"
os.environ['SECRET'] = hashlib.sha256(b"0").hexdigest()
try:
    print(jwt.decode(jwt_token, os.environ['SECRET'], algorithms="HS256"))
except jwt.exceptions.InvalidTokenError as e:
    print(repr(e))
except Exception as e:
    print("WARNING NORMAL EXCEPTION CAUGHT")
    print(repr(e))

Output:

{'sub': '1234567890', 'name': 'John Doe', 'iat': 1516239022}

Which error was raised? My best guess is that you have another problem. KeyError for Secret, is not an error related to jwt:

WARNING NORMAL EXCEPTION CAUGHT
KeyError('SECRET')

If your token is incorrect, you get this:

DecodeError('Not enough segments')

And if your signare is not correct, this:

InvalidSignatureError('Signature verification failed')