linux-kernel - Re: [PATCH 2/2] KEYS: Add per-user_namespace registers for persistent per-UID kerberos caches

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Message-ID: <7202.1375462830@warthog.procyon.org.uk>
Date:	Fri, 02 Aug 2013 18:00:30 +0100
From:	David Howells <dhowells@...hat.com>
To:	ebiederm@...ssion.com (Eric W. Biederman)
Cc:	dhowells@...hat.com, keyrings@...ux-nfs.org,
	linux-nfs@...r.kernel.org, krbdev@....edu,
	"Serge E. Hallyn" <serge.hallyn@...ntu.com>,
	linux-kernel@...r.kernel.org, simo@...hat.com
Subject: Re: [PATCH 2/2] KEYS: Add per-user_namespace registers for persistent per-UID kerberos caches

Eric W. Biederman <ebiederm@...ssion.com> wrote:

> > Add support for per-user_namespace registers of persistent per-UID kerberos
> > caches held within the kernel.
> 
> Out of curiosity is this cache per user namspace because the key lookup
> is per user namespace?

Yes.  You can't see keys in another namespace.  I occasionally wonder if I
should make the key serial number tree per namespace so that you don't search
keys outside your namespace and can't try looking them up by ID - but it
complicates the garbage collector which iterates over the entire tree (though
it could maintain a list of per-ns trees).

> Some minor nits below. But I don't see anything particulary scary about
> this patch.  Other than seeming to make it easy for root to get my
> kerbose tickets.

Root can do that anyway with file-based ccaches, I believe.  However, you can
change the key permissions to prevent root even seeing that your keys/keyrings
exist, let alone stealing them.

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