Re: [PATCH v10 5/8] security: keys: trusted: Make sealed key properly interoperable

From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: linux-integrity@vger.kernel.org, Mimi Zohar <zohar@linux.ibm.com>,
	David Woodhouse <dwmw2@infradead.org>,
	keyrings@vger.kernel.org, David Howells <dhowells@redhat.com>
Subject: Re: [PATCH v10 5/8] security: keys: trusted: Make sealed key properly interoperable
Date: Wed, 17 Jun 2020 23:46:41 +0000	[thread overview]
Message-ID: <20200617234641.GL62794@linux.intel.com> (raw)
In-Reply-To: <20200616160229.8018-6-James.Bottomley@HansenPartnership.com>

On Tue, Jun 16, 2020 at 09:02:26AM -0700, James Bottomley wrote:
> The current implementation appends a migratable flag to the end of a
> key, meaning the format isn't exactly interoperable because the using
> party needs to know to strip this extra byte.  However, all other
> consumers of TPM sealed blobs expect the unseal to return exactly the
> key.  Since TPM2 keys have a key property flag that corresponds to
> migratable, use that flag instead and make the actual key the only
> sealed quantity.  This is secure because the key properties are bound
> to a hash in the private part, so if they're altered the key won't
> load.
> 
> Backwards compatibility is implemented by detecting whether we're
> loading a new format key or not and correctly setting migratable from
> the last byte of old format keys.
> 
> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

/Jarkko