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From: Ahmad Fatoum <a.fatoum@pengutronix.de>
To: Mimi Zohar <zohar@linux.ibm.com>,
	Eric Biggers <ebiggers@kernel.org>,
	Jarkko Sakkinen <jarkko@kernel.org>
Cc: "Theodore Y. Ts'o" <tytso@mit.edu>,
	Jaegeuk Kim <jaegeuk@kernel.org>,
	kernel@pengutronix.de, James Morris <jmorris@namei.org>,
	"Serge E. Hallyn" <serge@hallyn.com>,
	James Bottomley <jejb@linux.ibm.com>,
	Sumit Garg <sumit.garg@linaro.org>,
	David Howells <dhowells@redhat.com>,
	linux-fscrypt@vger.kernel.org, linux-crypto@vger.kernel.org,
	linux-integrity@vger.kernel.org,
	linux-security-module@vger.kernel.org, keyrings@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] fscrypt: support trusted keys
Date: Tue, 17 Aug 2021 15:04:59 +0200	[thread overview]
Message-ID: <a6eb6f38-b9f4-c59c-4181-2049f181e67d@pengutronix.de> (raw)
In-Reply-To: <0e69a0aa394dd20347b06ae4e700aa17d52583ef.camel@linux.ibm.com>

Hi,

On 12.08.21 02:54, Mimi Zohar wrote:
> On Wed, 2021-08-11 at 10:16 -0700, Eric Biggers wrote:
> 
>> Neither of you actually answered my question, which is whether the support for
>> trusted keys in dm-crypt is a mistake.  I think you're saying that it is?  That
>> would imply that fscrypt shouldn't support trusted keys, but rather encrypted
>> keys -- which conflicts with Ahmad's patch which is adding support for trusted
>> keys.  Note that your reasoning for this is not documented at all in the
>> trusted-encrypted keys documentation; it needs to be (email threads don't really
>> matter), otherwise how would anyone know when/how to use this feature?
> 
> True, but all of the trusted-encrypted key examples in the
> documentation are "encrypted" type keys, encrypted/decrypted based on a
> "trusted" type key.  There are no examples of using the "trusted" key
> type directly.  Before claiming that adding "trusted" key support in
> dm-crypt was a mistake, we should ask Ahmad why he felt dm-crypt needed
> to directly support "trusted" type keys.

I wanted to persist the dm-crypt key as a sealed blob. With encrypted keys,
I would have to persist and unseal two blobs (load trusted key blob, load
encrypted key blob rooted to trusted key) with no extra benefit.

I thus added direct support for trusted keys. Jarkko even commented on the
thread, but didn't voice objection to the approach (or agreement for that
matter), so I assumed the approach is fine.

I can see the utility of using a single trusted key for TPMs, but for CAAM,
I see none and having an encrypted key for every trusted key just makes
it more cumbersome.

In v1 here, I added encrypted key support as well, but dropped it for v2,
because I am not in a position to justify its use. Now that you and Eric
discussed it, should I send v3 with support for both encrypted and trusted
keys like with dm-crypt or how should we proceed?

Cheers,
Ahmad

> 
> Mimi
> 
> 


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  reply	other threads:[~2021-08-17 13:05 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-06 15:09 Ahmad Fatoum
2021-08-09  9:44 ` Jarkko Sakkinen
2021-08-09 10:00   ` Ahmad Fatoum
2021-08-09 10:02     ` Ahmad Fatoum
2021-08-10 18:02     ` Jarkko Sakkinen
2021-08-09 20:52   ` Eric Biggers
2021-08-10 18:06     ` Jarkko Sakkinen
2021-08-10 18:46       ` Eric Biggers
2021-08-10 21:21         ` Jarkko Sakkinen
2021-08-10 21:27           ` Eric Biggers
2021-08-11  0:17             ` Jarkko Sakkinen
2021-08-11 11:34               ` Mimi Zohar
2021-08-11 17:16                 ` Eric Biggers
2021-08-12  0:54                   ` Mimi Zohar
2021-08-17 13:04                     ` Ahmad Fatoum [this message]
2021-08-17 13:55                       ` Mimi Zohar
2021-08-17 14:13                         ` Ahmad Fatoum
2021-08-17 14:24                           ` Mimi Zohar
2021-08-18  2:09                             ` Jarkko Sakkinen
2021-08-18  4:53                             ` Sumit Garg
2021-08-09 21:24 ` Eric Biggers
2021-08-10  7:41   ` Ahmad Fatoum
2021-08-10 17:35     ` Eric Biggers

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