linux-kernel - Re: [PATCH v2 00/14] KEYS: Add support for PGP keys and signatures

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Message-ID: <f142b1c4e662d4701a2ab67fa5fc839ab7109e5e.camel@huaweicloud.com>
Date: Mon, 19 Aug 2024 17:15:02 +0200
From: Roberto Sassu <roberto.sassu@...weicloud.com>
To: Jonathan McDowell <noodles@...th.li>
Cc: dhowells@...hat.com, dwmw2@...radead.org, herbert@...dor.apana.org.au, 
 davem@...emloft.net, linux-kernel@...r.kernel.org,
 keyrings@...r.kernel.org,  linux-crypto@...r.kernel.org,
 zohar@...ux.ibm.com,  linux-integrity@...r.kernel.org, Roberto Sassu
 <roberto.sassu@...wei.com>
Subject: Re: [PATCH v2 00/14] KEYS: Add support for PGP keys and signatures

On Mon, 2024-08-19 at 16:08 +0100, Jonathan McDowell wrote:
> On Sun, Aug 18, 2024 at 06:57:42PM +0200, Roberto Sassu wrote:
> > From: Roberto Sassu <roberto.sassu@...wei.com>
> > 
> > Support for PGP keys and signatures was proposed by David long time ago,
> > before the decision of using PKCS#7 for kernel modules signatures
> > verification was made. After that, there has been not enough interest to
> > support PGP too.
> 
> You might want to update the RFC/bis references to RFC9580, which was
> published last month and updates things.

Yes, makes sense (but probably isn't too much hassle to support more
things for our purposes?)

> Also, I see support for v2 + v3 keys, and this doesn't seem like a good
> idea. There are cryptographic issues with fingerprints etc there and I
> can't think of a good reason you'd want the kernel to support them. The
> same could probably be said of DSA key support too.

Uhm, if I remember correctly I encountered some old PGP keys used to
verify RPM packages (need to check). DSA keys are not supported, since
the algorithm is not in the kernel.

Thanks

Roberto

> > Lately, when discussing a proposal of introducing fsverity signatures in
> > Fedora [1], developers expressed their preference on not having a separate
> > key for signing, which would complicate the management of the distribution.
> > They would be more in favor of using the same PGP key, currently used for
> > signing RPM headers, also for file-based signatures (not only fsverity, but
> > also IMA ones).
> > 
> > Another envisioned use case would be to add the ability to appraise RPM
> > headers with their existing PGP signature, so that they can be used as an
> > authenticated source of reference values for appraising remaining
> > files [2].
> > 
> > To make these use cases possible, introduce support for PGP keys and
> > signatures in the kernel, and load provided PGP keys in the built-in
> > keyring, so that PGP signatures of RPM headers, fsverity digests, and IMA
> > digests can be verified from this trust anchor.
> > 
> > In addition to the original version of the patch set, also introduce
> > support for signature verification of PGP keys, so that those keys can be
> > added to keyrings with a signature-based restriction (e.g. .ima). PGP keys
> > are searched with partial IDs, provided with signature subtype 16 (Issuer).
> > Search with full IDs could be supported with
> > draft-ietf-openpgp-rfc4880bis-10, by retrieving the information from
> > signature subtype 33 (Issuer Fingerprint). Due to the possibility of ID
> > collisions, the key_or_keyring restriction is not supported.
> 
> 
> J.
>