On ma, 21 marras 2016, Florian Weimer wrote:
On 11/21/2016 01:31 PM, Stephen Gallagher wrote:
Thanks for your explanation.
>So yes, we have protection against that. FreeIPA (which is backing this
>solution) requires preauthentication for all user accounts.
“That” meaning offline attacks without intercepted packets. With
intercepted packets, offline attacks are still feasible, right?
Right -- if you get
initial exchange in the traditional Kerberos 5.
We have been working for several years already to reduce these
possibilities via different means:
- enablement for HTTPS-based tunnel for Kerberos flows based on
- DNS-based announcement of Kerberos MS-KKDCP proxy using DNS URI;
- SPAKE exchange support in MIT Kerberos (slated for 1.15-1.16)
Fedora infrastructure uses MS-KKDCP proxy with Fedora certificate to
tunnel Kerberos 5 traffic. If you have recent Fedora, you'll get it used
automatically with the help of DNS URI. For older clients which don't
support DNS-based discovery you can configure MS-KKDCP proxy access
manually by stating 'kdc=https://id.fedoraproject.org/KdcProxy' for
realm. For very old clients that don't support
MS-KKDCP (RHEL 6, for example), you are back to use naked Kerberos 5
Our effort is to get to SPAKE sooner than later.
/ Alexander Bokovoy