linux-kernel - Re: [PATCH] keys: Make the KEY_NEED_* perms an enum rather than a mask

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Message-ID: <3efc41d3ba70d253e30187485459a724a36bb5a9.camel@linux.intel.com>
Date:   Thu, 14 May 2020 14:00:14 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     David Howells <dhowells@...hat.com>, stephen.smalley.work@...il.com
Cc:     Paul Moore <paul@...l-moore.com>,
        Casey Schaufler <casey@...aufler-ca.com>,
        keyrings@...r.kernel.org, selinux@...r.kernel.org,
        linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] keys: Make the KEY_NEED_* perms an enum rather than a
 mask

On Tue, 2020-05-12 at 23:33 +0100, David Howells wrote:
> Since the meaning of combining the KEY_NEED_* constants is undefined, make
> it so that you can't do that by turning them into an enum.
> 
> The enum is also given some extra values to represent special
> circumstances, such as:
> 
>  (1) The '0' value is reserved and causes a warning to trap the parameter
>      being unset.
> 
>  (2) The key is to be unlinked and we require no permissions on it, only
>      the keyring, (this replaces the KEY_LOOKUP_FOR_UNLINK flag).
> 
>  (3) An override due to CAP_SYS_ADMIN.
> 
>  (4) An override due to an instantiation token being present.
> 
>  (5) The permissions check is being deferred to later key_permission()
>      calls.
> 
> The extra values give the opportunity for LSMs to audit these situations.
> 
> Signed-off-by: David Howells <dhowells@...hat.com>
> cc: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
> cc: Paul Moore <paul@...l-moore.com>
> cc: Stephen Smalley <stephen.smalley.work@...il.com>
> cc: Casey Schaufler <casey@...aufler-ca.com>
> cc: keyrings@...r.kernel.org
> cc: selinux@...r.kernel.org

So extensive comments already from Stephen and Paul that I'll just
wait for the next version (agree with the idea though).

/Jarkko