linux-kernel - Re: [PATCH 0/2] Add support for ECDSA-signed kernel modules

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Date:   Wed, 7 Apr 2021 13:53:24 -0400
From:   Stefan Berger <stefanb@...ux.ibm.com>
To:     Mimi Zohar <zohar@...ux.ibm.com>,
        Jarkko Sakkinen <jarkko@...nel.org>
Cc:     keyrings@...r.kernel.org, dhowells@...hat.com, nayna@...ux.ibm.com,
        linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] Add support for ECDSA-signed kernel modules


On 4/7/21 12:10 PM, Mimi Zohar wrote:
> On Wed, 2021-04-07 at 18:53 +0300, Jarkko Sakkinen wrote:
>> On Tue, Apr 06, 2021 at 02:53:38PM -0400, Stefan Berger wrote:
>>> This series adds support for ECDSA-signed kernel modules.
>>>
>>> The first patch in this series attempts to address the issue where a
>>> developer created an ECDSA key for signing modules and then falls back
>>> to compiling an older version of the kernel that does not support
>>> ECDSA keys. In this case this patch would delete that ECDSA key if it is
>>> in certs/signing_key.pem and trigger the creation of an RSA key. However,
>>> for this to work this patch would have to be applied to previous versions
>>> of the kernel but would also only work for the developer if he/she used a
>>> stable version of the kernel to which this patch was applied. So whether
>>> this patch actually achieves the wanted effect is not always guaranteed.
>> Just wondering why the key needs to be removed in the fallback.
Because if you signed an older kernel's modules with the ECDSA key it 
won't be able to load the modules...
> The main concern is with bisecting the kernel.  Either elliptic curve
> support or the first patch needs to be backported.  This patch will
> cause the kernel module signing key to be regenerated.


This assumes of course that one will bisect via the stable kernels where 
this 1st patch has been applied. Not sure whether that's what people 
will do.

    Stefan


>
> Mimi
>