[keycloak-dev] Requirements to Elytron for Client 2-way SSL authentication

Bill Burke bburke at redhat.com
Tue Jul 14 16:48:28 EDT 2015

On 7/14/2015 2:17 PM, Marek Posolda wrote:
> I want to doublecheck if we are on the same page regarding how client
> certificate authentication should work, so we know what are the
> requirements for Elytron
> to support it. This will allow us to improve things before the Elytron
> code freeze (end of August AFAIK) if needed.
> Right now, I am covering just Service accounts and authenticating of
> clients with the certificate. But I believe that for authenticate of
> users, the requirements will be similar.
> My view is:
> - Admin will upload certificate of some client via Keycloak admin
> console. (I guess many companies want to use their own certificate
> issued by their trusted CA. IMO later Keycloak should provide the
> ability to easily generate trusted certificates and act as CA - not sure
> if it's something Giriraj is looking at. But for now, I assume that
> trusted certificate is always provided by admin and uploaded to Keycloak
> admin console)

Bouncycastle has all the utilities to create our own certificates.  I 
was thinking that admin could upload one, or we could generate one for 
the user.

> - There is REST endpoint, which allows to authenticate with client
> certificate. For example
> "https://localhost:8443/auth/realms/demo/clients/certificate" . Client
> will be able to start SSL handshake with it's certificate when sending
> request to this endpoint. Server will then verify the underlying
> SSLSession from the SSL socket and check that valid client certificate
> was provided during handshake. It will authenticate client based on that.

I'm not sure why you think a specifc URL is needed to do the SSL 
handshake.  The 2-way SSL handshake happens *before* HTTP request is 
even processed

Client app would redirect to the same SAML or OIDC endpoint it does now. 
  The keycloak authentication flow would grab the certificate chain from 
HttpServletRequest, and validate the client certificate.

> To cover this usecase, the Wildfly/Elytron should be able to:
> 1) Support "variable" 2-way SSL .  In other words, there is possibility
> to set flag "setWantClientAuth(true)" in underlying SSLServerSocket.

IIRC, you can't do this at runtime with NIO or BIO.  You must set up the 
SSLContext at boot time.  What can be a little more dynamic is the 
TrustManager, but I'm not sure we need this...read more below...

> This means that I will be able to access admin console
> "https://localhost:8443/auth/admin" with my browser without client
> certificate, but I will be able to provide client certificate on the
> endpoint "https://localhost:8443/auth/realms/demo/clients/certificate" ,
> which is deployed under same context
> 2) Dynamically upload it's truststore at runtime or provide SPI to
> add/remove/update certificates in truststore. This is needed, so that
> when admin uploads the certificate of client in KC admin console, I want
> my client to be able to authenticate with the certificate immediatelly
> without need to restart server and edit any JKS files .

I'm not sure we really need to have any special integration with 
Elytron.  We just need to make sure that it can support certificate 
chains the way we want to support it.  I'm pretty sure EAP 6.x can 
support what we want, read on...

The certficate chain is available from the HttpServletRequest as per the 
spec.  I'm not exactly sure on the specifics, but all you need is one 
"root" certificate in the web server's trust store.  Then you could 
conceivably create a trusted certificate chain as follows:

1) Organization root certificate.

2) Root cert signs Realm cert.

3) Realm cert signs client cert.

Following me?  My guess is that it would be really easy to issue our own 
client certs and that we could have a Required Action that helped set 
this up.

Bill Burke
JBoss, a division of Red Hat

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