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Subject: Re: [PATCH v2] fscrypt: support trusted keys
From:   Mimi Zohar <zohar@linux.ibm.com>
To:     Eric Biggers <ebiggers@kernel.org>
Cc:     Jarkko Sakkinen <jarkko@kernel.org>,
        Ahmad Fatoum <a.fatoum@pengutronix.de>,
        "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
Date:   Wed, 11 Aug 2021 20:54:34 -0400
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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.

Mimi