On Wed, Apr 07, 2021 at 01:53:24PM -0400, Stefan Berger wrote:

On 4/7/21 12:10 PM, Mimi Zohar wrote:

quoted

On Wed, 2021-04-07 at 18:53 +0300, Jarkko Sakkinen wrote:

quoted

On Tue, Apr 06, 2021 at 02:53:38PM -0400, Stefan Berger wrote:

quoted

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...

quoted

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.

In any case, sounds non-trivial issue enough ought to be documented in the
commit message.

/Jarkko