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From: Paul Moore <paul@paul-moore.com>
To: Stephen Smalley <stephen.smalley.work@gmail.com>
Cc: David Howells <dhowells@redhat.com>,
	keyrings@vger.kernel.org, SElinux list <selinux@vger.kernel.org>,
	LSM List <linux-security-module@vger.kernel.org>
Subject: Re: [PATCH] selinux: Fix use of KEY_NEED_* instead of KEY__* perms [v2]
Date: Fri, 1 May 2020 12:37:32 -0400	[thread overview]
Message-ID: <CAHC9VhTO0Ag-CODexD8hjZdTzUBEd4nJdR191o__=+iOLUHmFw@mail.gmail.com> (raw)
In-Reply-To: <CAEjxPJ6pFdDfm55pv9bT3CV5DTFF9VqzRmG_Xi5bKNxPaGuOLg@mail.gmail.com>

On Tue, Apr 28, 2020 at 12:19 PM Stephen Smalley
<stephen.smalley.work@gmail.com> wrote:
> On Tue, Apr 28, 2020 at 11:58 AM David Howells <dhowells@redhat.com> wrote:
> > Stephen Smalley <stephen.smalley.work@gmail.com> wrote:
> >
> > > 1) Are we guaranteed that the caller only ever passes a single
> > > KEY_NEED_* perm at a time (i.e. hook is never called with a bitmask
> > > of multiple permissions)?  Where is that guarantee enforced?
> >
> > Currently it's the case that only one perm is ever used at once.  I'm tempted
> > to enforce this by switching the KEY_NEED_* to an enum rather than a bitmask.
> >
> > I'm not sure how I would actually define the meaning of two perms being OR'd
> > together.  Either okay?  Both required?
>
> Both required is the usual convention in functions like
> inode_permission() or avc_has_perm().
> But if you know that you'll never use combinations, we should just
> prohibit it up front, e.g.
> key_task_permission() or whatever can reject them before they reach
> the hook call.  Then the
> hook code doesn't have to revisit the issue.
>
> >
> > > 2) We had talked about adding a BUILD_BUG_ON() or other build-time
> > > guard
> >
> > That doesn't help you trap unallowed perm combinations, though.
>
> I think we want both.

Yep, we want both. #moarsafety

-- 
paul moore
www.paul-moore.com

  reply	other threads:[~2020-05-01 16:37 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-17 15:48 Problem with 9ba09998baa9 ("selinux: Implement the watch_key security hook") in linux-next Paul Moore
2020-04-17 16:32 ` Richard Haines
2020-04-17 16:59   ` Paul Moore
2020-04-21 12:29 ` David Howells
2020-04-22 19:20   ` Paul Moore
2020-04-22 21:09     ` Paul Moore
2020-04-24 23:43   ` David Howells
2020-04-26 20:53     ` Paul Moore
2020-04-27 14:12     ` [PATCH] selinux: Fix use of KEY_NEED_* instead of KEY__* perms David Howells
2020-04-27 14:36       ` Stephen Smalley
2020-04-27 15:24         ` Paul Moore
2020-04-27 17:02       ` Stephen Smalley
2020-04-27 22:17         ` Paul Moore
2020-04-28 12:54 ` [PATCH] selinux: Fix use of KEY_NEED_* instead of KEY__* perms [v2] David Howells
2020-04-28 14:32   ` Stephen Smalley
2020-04-28 15:57   ` David Howells
2020-04-28 16:19     ` Stephen Smalley
2020-05-01 16:37       ` Paul Moore [this message]
2020-05-12 22:33       ` [PATCH] keys: Make the KEY_NEED_* perms an enum rather than a mask David Howells
2020-05-13  1:04         ` Paul Moore
2020-05-13 12:58         ` Stephen Smalley
2020-05-13 15:25         ` Casey Schaufler
2020-05-13 23:13         ` David Howells
2020-05-14 12:08           ` Stephen Smalley
2020-05-14 14:45             ` Stephen Smalley
2020-05-13 23:16         ` David Howells
2020-05-13 23:25         ` David Howells
2020-05-14 11:00         ` Jarkko Sakkinen
2020-05-14 16:58         ` [PATCH] keys: Move permissions checking decisions into the checking code David Howells
2020-05-14 17:06           ` Casey Schaufler
2020-05-15 15:06           ` Stephen Smalley
2020-05-15 16:45           ` David Howells
2020-05-15 18:55             ` Stephen Smalley
2020-05-15 19:10               ` Casey Schaufler
2020-05-15 22:27             ` David Howells

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