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Subject: Re: [PATCH v3 08/10] evm: Enforce signatures on unsupported
 filesystem for EVM_INIT_X509
From: Mimi Zohar <zohar@linux.ibm.com>
To: Stefan Berger <stefanb@linux.ibm.com>, linux-integrity@vger.kernel.org,
        linux-security-module@vger.kernel.org, linux-unionfs@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, paul@paul-moore.com, jmorris@namei.org,
        serge@hallyn.com, roberto.sassu@huawei.com, amir73il@gmail.com,
        brauner@kernel.org, miklos@szeredi.hu
Date: Tue, 19 Mar 2024 19:26:57 -0400
In-Reply-To: <20240223172513.4049959-9-stefanb@linux.ibm.com>
References: <20240223172513.4049959-1-stefanb@linux.ibm.com>
	 <20240223172513.4049959-9-stefanb@linux.ibm.com>
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On Fri, 2024-02-23 at 12:25 -0500, Stefan Berger wrote:
> Unsupported filesystems currently do not enforce any signatures. Add
> support for signature enforcement of the "original" and "portable &
> immutable" signatures when EVM_INIT_X509 is enabled.
> 
> The "original" signature type contains filesystem specific metadata.
> Thus it cannot be copied up and verified. However with EVM_INIT_X509
> and EVM_ALLOW_METADATA_WRITES enabled, the "original" file signature
> may be written.
> 
> When EVM_ALLOW_METADATA_WRITES is not set or once it is removed from
> /sys/kernel/security/evm by setting EVM_INIT_HMAC for example, it is not
> possible to write or remove xattrs on the overlay filesystem.

This paragraph is currently correct, but at some point EVM_ALLOW_METADATA_WRITES
will be deprecated.  Refer to commit 1434c6a1d32a ("evm: Deprecate
EVM_ALLOW_METADATA_WRITES").

Mimi

> 
> This change still prevents EVM from writing HMAC signatures on
> unsupported filesystem when EVM_INIT_HMAC is enabled.
> 
> Co-developed-by: Mimi Zohar <zohar@linux.ibm.com>
> Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>

Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>