[OpenAFS] "automatic" aklog?

[Jeffrey Altman]

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Adam Megacz wrote:
> One other aspect of my goal is to effectively have aklog become
> "automatic".  That is, if a user's krb5 credentials cache has changed
> in any way since the last time s/he accessed a particular cell, the
> cache manager would ask afsd to run aklog (or perform equivalent
> action) on behalf of that user.

> Is there a reason -- other than "nobody's had time to implement it" --
> that this is not already the case?

Primarily because this would be the wrong behavior.

First, you don't want new afs credentials to be obtained simply because
the user obtained a new service ticket for SSH.

Second, you don't want to obtain new tokens for AFS simply because the
user chose to switch to her administrative principal OR a principal
in another realm.

The desired behavior is that which is implemented in the OpenAFS plug-in
for the Network Identity Manager for Windows.  For each Kerberos
principal there is a configured set of cells for which AFS tokens are
obtained.  In addition, the tokens are refreshed whenever a new TGT is
acquired for the user.

The Network Identity Manager has the benefit of residing on a platform
that supports the Kerberos CCAPI.  As such, it can maintain multiple
caches, one for each Kerberos principal.

The UNIX-like operating systems other than MacOS X lacks the CCAPI at
the current time.   Since a file based ccache can only support a single
principal, it is not possible at the current time to implement this
multiple identification model.  The UNIX-like platforms also have PAGs
which means that the process obtaining the new AFS tokens must be in
the process group for it to be effective.   Russ Allbery has written
a utility that obtains Kerberos tickets and then renews them before
expiration that can be used to maintain current tokens within a PAG
beyond the ticket lifetime.

Jeffrey Altman


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