From: dhowells@redhat.com (David Howells)
To: linux-security-module@vger.kernel.org
Subject: [PATCH v12 06/10] KEYS: Consistent ordering for __key_link_begin and restrict check
Date: Fri, 17 Mar 2017 07:43:23 +0000 [thread overview]
Message-ID: <19834.1489736603@warthog.procyon.org.uk> (raw)
In-Reply-To: <alpine.OSX.2.20.1703161654010.36452@suhwanki-mobl.amr.corp.intel.com>
Mat Martineau <mathew.j.martineau@linux.intel.com> wrote:
> > Btw, do you check for cycles anywhere? For example, if I create two keyrings,
> > A and B, and can I then set restrictions such that A is restricted by B and B
> > is restricted by A?
>
> I don't check for cycles yet, but the references held by the restrictions
> could be a problem. I'm not sure how to address it yet, I could clear the
> restriction info when a keyring is revoked/dead/etc or I could check when
> restrictions are created.
Yep.
The way to do it is to store the pointer to the restriction keyring in the
restriction record and then when you set a restriction on keyring A that
refers to keyring B as a source of authority, you go to B's restriction record
and if it points to A, say no, if it points to C, go to C's record and if it
points to A, say no, if it points to D, go to D's record and so on and so on -
all whilst under a master lock.
As the above algorithm only has one pointer to follow each time, it can be
done iteratively, so no particular stack overhead. And as a lock is held
whilst you do the check and the add, you can't get one process adding an A->B
dependency whilst another adds B->A.
David
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next prev parent reply other threads:[~2017-03-17 7:43 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-09 20:23 [PATCH v12 00/10] Make keyring link restrictions accessible from userspace Mat Martineau
2017-03-09 20:23 ` [PATCH v12 01/10] KEYS: Use a typedef for restrict_link function pointers Mat Martineau
2017-03-09 20:23 ` [PATCH v12 02/10] KEYS: Split role of the keyring pointer for keyring restrict functions Mat Martineau
2017-03-09 20:23 ` [PATCH v12 03/10] KEYS: Add a key restriction struct Mat Martineau
2017-03-09 20:23 ` [PATCH v12 04/10] KEYS: Use structure to capture key restriction function and data Mat Martineau
2017-03-09 20:23 ` [PATCH v12 05/10] KEYS: Add an optional lookup_restriction hook to key_type Mat Martineau
2017-03-09 20:23 ` [PATCH v12 06/10] KEYS: Consistent ordering for __key_link_begin and restrict check Mat Martineau
2017-03-09 20:23 ` [PATCH v12 07/10] KEYS: Add KEYCTL_RESTRICT_KEYRING Mat Martineau
2017-03-09 20:23 ` [PATCH v12 08/10] KEYS: Add a lookup_restriction function for the asymmetric key type Mat Martineau
2017-03-09 20:23 ` [PATCH v12 09/10] KEYS: Restrict asymmetric key linkage using a specific keychain Mat Martineau
2017-03-09 20:23 ` [PATCH v12 10/10] KEYS: Keyring asymmetric key restrict method with chaining Mat Martineau
2017-03-16 10:00 ` [PATCH v12 02/10] KEYS: Split role of the keyring pointer for keyring restrict functions David Howells
2017-03-16 10:09 ` [PATCH v12 05/10] KEYS: Add an optional lookup_restriction hook to key_type David Howells
2017-03-16 23:02 ` Mat Martineau
2017-03-16 10:17 ` [PATCH v12 06/10] KEYS: Consistent ordering for __key_link_begin and restrict check David Howells
2017-03-17 0:47 ` Mat Martineau
2017-03-17 7:43 ` David Howells [this message]
2017-03-17 22:35 ` Mat Martineau
2017-03-18 8:10 ` David Howells
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