On 11/08/2011 06:35 PM, Simo Sorce wrote:
> On Tue, 2011-11-08 at 17:57 -0500, Dmitri Pal wrote:
>> On 11/08/2011 02:56 PM, Dan Scott wrote:
>>> This is a great feature. It feels like I'm always re-installing VMs
>>> and having to remove old SSH keys and re-accept new ones.
>>> One feature I'd like is to have this working cross-realm. We have 2
>>> IPA realms here and it would be great if I could configure SSSD to
>>> check the local realm if I'm SSHing to a local PC and to check the
>>> other IPA server(s) if my SSH target is part of the other realm. Even
>>> better if it could do this without explicit configuration.
>>> Do you think it would be possible to do this securely?
>> When we start to support Cross Realm Kerberos Trusts for IPA to IPA I
>> think this would be doable but then I do not think the ssh host keys
>> will be used (needed). Simo, am I correct?
> We do not have the GSSAPI key exchange patches in OpenSSH. With those
> the ssh host key is not necessary when using GSSAPI auth, even in the
> same realm.
> But when you want to use ssh host keys, across realm kerberos trust is
> not going to help.
> In order to validate keys from different realms I guess we could use
> DNSSEC where the signatures of one realm are trusted by the other.
> Then by storing ssh host keys as DNS fields a different domain could
> still trust those keys. This works only for enrolled hosts though, I
> guess. Or at least only for hosts in DNS domains that are controlled by
> IPA. For hosts in other DNS domains we cannot distribute keys through
> If that is necessary then we would have to define some sort of protocol
> to allow fetching of keys from one domain to the other.
> We could use a mechanism similar to what we will need to implement for
> sid2name resolution for windows domain trusts. Where the IPA server
> becomes a proxy to request host keys from other domains.
> Bottom line, we can come up with something but it is not scoped yet. And
> needs some more thinking so that we put in place something that scales
Sr. Engineering Manager IPA project,
Red Hat Inc.
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