verifyKey is not taken into consideration

[jakobsa]

Info	Value
Platform Name	ios
Platform Version	10
CocoaLumberjack Version	2.3.0
Integration Method	cocoapods
Xcode Version	Xcode 8.3
Repro rate	all the time (100%)
JWT Version	3-beta4

Issue Description and Steps

I have to verify a JWT token using RS256. The public key material is received from an endpoint as modulus and exponent. I could not use any of the provided key extractors for key material in that format. I had to create the JWTCryptoKeyPublic instance myself and found the verifyKey block useful as it should allow for directly setting the public key the verifier should use.

I was surprised to see that it would not work, and after digging into the sources I found that secretData needed to be set (here is why: JWTCoding+VersionThree:560).

SecretData referred to as key will not be used by RSBaseAlgorithms down the callstack as self.verifyKey is preferred then. (JWTAlgorithmRSBase:127-129).

To summarize.

Holders configured like that do not work:

JWTAlgorithmRSFamilyDataHolder* verifyDataHolder = [JWTAlgorithmRSFamilyDataHolder new];
verifyDataHolder.algorithmName(JWTAlgorithmNameRS256).verifyKey(publicKey);

Holders configured like that will work:

JWTAlgorithmRSFamilyDataHolder* verifyDataHolder = [JWTAlgorithmRSFamilyDataHolder new];
verifyDataHolder.algorithmName(JWTAlgorithmNameRS256).secretData([NSData new]).verifyKey(publicKey);

[lolgear]

@jakobsa Hi!
It is definitely a bug or a big bone! :)
What did you expect and how you would like to solve this?

The core point now is that holders MUST have secretData as a core point of signature purposes. (not good point :/)
Yes, they are too coupled to main HS algorithm. ( which intended to have secretData ).

If you would like, we could make a list of appropriate considerations and desires to further API 3.0.

One of the points: maybe algorithms should hold secret data with which they should work?

[jakobsa]

@lolgear

For me only token verification was relevant, so I didn't consider the implications of signing much.
I am not deep enough into the sources to really make qualified suggestions but I will give it a shot as sometimes a outsiders view can be refreshing (or at least funny ;) ).

My suggestions are only valid if the following assumptions are true:

• SecretData is an arbitrary data format for key material used by dedicated KeyExtractors only.
• SecretData is always converted into an internal key format before it is used for verifying / signing.
• verifyKey is the result of that conversion (for verification only).

Suggestion:

• add signingKey as property to holders
• prefer verifyKey and signingKey over key extraction from secretData (as it already provides the internal key format)
• do the keyExtraction (using secretData, yielding verifyKey + signingKey) as high up in the callstack as possible and only use verifyKey + signingKey down from there.

[lolgear]

@jakobsa Hi, could you check latest master? It has been fixed, I guess