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

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Message-ID: <ZsSkTs4TFfx2pK8r@earth.li>
Date: Tue, 20 Aug 2024 15:12:30 +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 Mon, Aug 19, 2024 at 05:15:02PM +0200, Roberto Sassu wrote:
> 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?)

I'm mostly suggesting that the comments/docs point to the latest
standard rather than the draft version, not changing to support the new
v6 keys.

> > 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.

I would question the benefit gained from using obsolete key/signature
types for verification (I was involved in the process of Debian dropping
them back in *2010* which was later than it should have been). Dropping
the code for that path means a smaller attack surface/maintenance
overhead for something that isn't giving a benefit.

J.

-- 
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