[keycloak-dev] JWS signatures using PS256 or ES256 algorithms for signing

乗松隆志 / NORIMATSU,TAKASHI takashi.norimatsu.ws at hitachi.com
Wed May 30 01:49:16 EDT 2018


Thank you for your comments.

I think it might be better to determine which kind of Token Signature Provider be used by not parsing JWS, for example, looking up Client or Realm settings.
This PR might have impacts on keycloak's performance because it has parsed JWS to determine it every time keycloak receives JWS Token.

As for existing Key Provider, I've already implemented ECDSA Key Provider (for only signing) in this PR. Therefore, I could contribute it.

As for Token Signature SPI, I agree with you. I hope I would like to implement this SPI's provider for ES256 at first and PS256 in the future.

I think it is the best way that keycloak's core committers design and implement this Token Signature SPI.
However, if they do not have yet such a plan to do that at this time and in the future, I would like to give some ideas on Token Signature SPI. How do you think about that?

Best regards,
Takashi Norimatsu
Hitachi Ltd.,

From: Stian Thorgersen <sthorger at redhat.com> 
Sent: Tuesday, May 29, 2018 4:40 PM
To: 乗松隆志 / NORIMATSU,TAKASHI <takashi.norimatsu.ws at hitachi.com>
Cc: keycloak-dev at lists.jboss.org
Subject: [!]Re: [keycloak-dev] JWS signatures using PS256 or ES256 algorithms for signing


I haven't had time to look at your PR in detail yet, but the way it should work is:

* We need to add a Token Signature SPI that can sign and validate token signatures
* RSA signing should be refactored into a Token Signature provider
* Realm should have a default signing algorithm. Admin console should allow admins to select from any supported algorithm by listing TokenSignatureSPI providers
* Clients should be able to override the signing algorithm
* When verifying signatures in the Keycloak server we should check what the method is for the client (or realm if client doesn't override) and only allow that specific algorithm and nothing else
* We may want to consider adding an option to client adapters to specify the expected signing algorithm as well
* We also need additional key providers. It looks like you've already added this
* We need to make sure that keys are only used for the correct purpose (correct algorithm and if it's for signing or encrypting). I think this is already covered though

On 25 May 2018 at 05:26, 乗松隆志 / NORIMATSU,TAKASHI <mailto:takashi.norimatsu.ws at hitachi.com> wrote:
I'd like to use more secure JWS signature algorithm in the environment where the high security level is required such as the financial industry.

According to the following RFCs, RSASSA-PSS to which PS256 follows is recommended on behalf of RSASSA-PKCS1-v1_5 to which RS256 follows.

However, according to the following RFC, ES256 is "Recommended+" while PS256 is "Optional".

Moreover, it is said that Elliptic Curve based algorithms have an advantage against RSA base algorithms in volume of its computation.

Therefore, I've tried to make keycloak support ES256 JWS signature along with existing RS256 one.

I've found that it seemed to be relatively easy to implement software components for ES256 JWS signature such as Signature Provider and Key Provider.
However, it seemed to be difficult to implement codes actually calling these providers. The reasons is as follows.

* a lot of places have called these singing and verifying providers.
* such the places have been hard-coded in RSA algorithm specific.

To deal with them, the following ideas have hit on me

1. replace RSA algorithm specific codes with signature algorithm independent codes.
2. re-design JWS signing and verifying scheme on high level.

I'm not familiar with keycloak internals, so I've implemented ES256 JWS signature support on #1 basis experimentally.
I'm not sure whether this way is appropriate or not. I'm very happy if keycloak specialists consider #2 or review my implementation based on #1.

I've issued PR as WIP. Please refer to the following in detail.

Best regards,
Takashi Norimatsu
Hitachi Ltd.,

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