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

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Message-ID: <ZsNf1VdfkHqD8R4Q@earth.li>
Date: Mon, 19 Aug 2024 16:08:05 +0100
From: Jonathan McDowell <noodles@...th.li>
To: Roberto Sassu <roberto.sassu@...weicloud.com>
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 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.

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.

> 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.

-- 
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