On 2012-09-08 01:28, Russ Allbery wrote:
And I'm not clear on how to authenticate that cookie within the WebAuth
protocol. You would really need public key cryptography to
authenticate a global cookie, with the WebKDC publishing a public
signing key.
Yes... that was my thought too. But to be honerst, I didn't think too
much about it except convincing myself that at least this could be done
with public key cryptography.
Same here. :)
I'm sure that it can be done with a public key signature, but I think
that's the tool that would be needed, which would mean adding some sort of
direct public-key component to the WebAuth protocol. (Right now, it
doesn't use any public-key cryptography apart from TLS to protect various
web connections.)
Couldn't help thinking about this.
I guess there's no way around public key signatures here.
However, maybe one could relax the key strength a bit, making it a less
heavy operation. For two reasons:
* Authenticating the cookie is only meant to close the windows between
pressing the logout button and expiry of the app-token session. Giving
the attacker less time to fake the signature.
* Opposed to ordinary PKI we have an excellent
key-distribution/revocation infrastructure, since each WAS needs to
contact the KDC periodically anyway to get af TGT for it self. That
request could relatively easy incorporate the WebKDC public key du-jour,
cycling SSO signing keys often.
/Peter
