linux-kernel - Re: [PATCH v3 04/10] certs: Fix blacklist flag type confusion

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Date:   Thu, 21 Jan 2021 01:45:55 +0200
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Mickaël Salaün <mic@...ikod.net>
Cc:     David Howells <dhowells@...hat.com>,
        David Woodhouse <dwmw2@...radead.org>,
        "David S . Miller" <davem@...emloft.net>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        James Morris <jmorris@...ei.org>,
        Mickaël Salaün <mic@...ux.microsoft.com>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        "Serge E . Hallyn" <serge@...lyn.com>, keyrings@...r.kernel.org,
        linux-crypto@...r.kernel.org, linux-integrity@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        Mimi Zohar <zohar@...ux.vnet.ibm.com>
Subject: Re: [PATCH v3 04/10] certs: Fix blacklist flag type confusion

On Wed, Jan 20, 2021 at 12:15:10PM +0100, Mickaël Salaün wrote:
> 
> On 20/01/2021 04:55, Jarkko Sakkinen wrote:
> > On Thu, Jan 14, 2021 at 04:19:03PM +0100, Mickaël Salaün wrote:
> >> From: David Howells <dhowells@...hat.com>
> >>
> >> KEY_FLAG_KEEP is not meant to be passed to keyring_alloc() or key_alloc(),
> >> as these only take KEY_ALLOC_* flags.  KEY_FLAG_KEEP has the same value as
> >> KEY_ALLOC_BYPASS_RESTRICTION, but fortunately only key_create_or_update()
> >> uses it.  LSMs using the key_alloc hook don't check that flag.
> >>
> >> KEY_FLAG_KEEP is then ignored but fortunately (again) the root user cannot
> >> write to the blacklist keyring, so it is not possible to remove a key/hash
> >> from it.
> >>
> >> Fix this by adding a KEY_ALLOC_SET_KEEP flag that tells key_alloc() to set
> >> KEY_FLAG_KEEP on the new key.  blacklist_init() can then, correctly, pass
> >> this to keyring_alloc().
> > 
> > OK, so thing work by luck now, but given the new patches which allow
> > to append new keys they would break, right?
> 
> Without this fix, patch 9/10 would allow to remove and modify keys from
> the blacklist keyring.
> 
> > 
> >> We can also use this in ima_mok_init() rather than setting the flag
> >> manually.
> > 
> > What does ima_mok_init() do?
> 
> This was initially an addition from David Howells, I only fixed the
> argument bit-ORing. ima_mok_init() allocates a blacklist keyring (with
> different properties) dedicated to IMA.
 
Please add this to the commit message.

/Jarkko