invalid IV lengths

[panva]

A user of this library was having an issue decrypting JWE tokens produced by it in my javascript library. See panva/jose#314

Despite a few hurdles overcome they are not able to interoperate the libraries due to a non-conform JWE implementation in python-jose.

Namely, the Initialization Vectors used for encryption are not conform, their bit lengths are not according to specification.

• A128GCM, A192GCM, A256GCM are REQUIRED to use a 96 bit IV
• A128CBC-HS256, A192CBC-HS384, A256CBC-HS512 are REQUIRED to use a 128 bit IV

[securedimensions]

How about this?

if self._algorithm in ['A128GCM', 'A192GCM', 'A256GCM', 'A128GCMKW', 'A192GCMKW', 'A256GCMKW']:
    #print("generating IV of length 96bit")
    iv = get_random_bytes(12)
else:
    #print("generating IV of length 128bit")
    iv = get_random_bytes(16)

[twwildey]

Folks - is there a concern for resolving this issue, or is the problem that no one has executed on this?

I've opened the following issue for jose here: panva/jose#678

However, the primary maintainer of that package (who also opened this issue) has identified that python-jose is not following the RFC spec for JWE. It seems like this package should follow the specification. If there is no concern for following the JWE spec to adhere to the IV length requirements for AES GCM modes, I will open a PR to do so.

[panva]

I will open a PR to do so.

#300