On Wed, Mar 11, 2026 at 02:19:02PM +0100, Thomas Weißschuh wrote:
> > > diff --git a/include/linux/module_signature.h
> > > b/include/linux/module_signature.h
> > > index a45ce3b24403..3b510651830d 100644
> > > --- a/include/linux/module_signature.h
> > > +++ b/include/linux/module_signature.h
> > > @@ -18,6 +18,7 @@ enum pkey_id_type {
> > > PKEY_ID_PGP, /* OpenPGP generated key ID */
> > > PKEY_ID_X509, /* X.509 arbitrary subjectKeyIdentifier */
> > > PKEY_ID_PKCS7, /* Signature in PKCS#7 message */
> > > + PKEY_ID_MERKLE, /* Merkle proof for modules */
> >
> > I recommend making the hash algorithm explicit:
> >
> > PKEY_ID_MERKLE_SHA256, /* SHA-256 merkle proof for modules */
> >
> > While I wouldn't encourage the addition of another hash algorithm
> > (specifying one good algorithm for now is absolutely the right choice),
> > if someone ever does need to add another one, we'd want them to be
> > guided to simply introduce a new value of this enum rather than hack it
> > in some other way.
>
> The idea here was that this will only ever be used for module built as
> part of the kernel build. So the actual implementation could change freely
> without affecting anything.
>
> But I don't have hard feelings about it.
Ah, okay. That's even better then: if someone adds another algorithm it
would simply be a kconfig option.
It seems 'struct module_signature' itself is intended to be a stable
ABI, though. So I think there's an opportunity for confusion here. It
might be worth leaving a note somewhere that the format of the
PKEY_ID_MERKLE portion of the struct does not need to be kept stable and
can freely change in each kernel build.
- Eric
