linux-kernel - Re: [PATCH v3 00/14] KEYS: Add support for PGP keys and signatures

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Message-ID: <1266435.1726219950@warthog.procyon.org.uk>
Date: Fri, 13 Sep 2024 10:32:30 +0100
From: David Howells <dhowells@...hat.com>
To: Herbert Xu <herbert@...dor.apana.org.au>
Cc: dhowells@...hat.com, Roberto Sassu <roberto.sassu@...weicloud.com>,
    dwmw2@...radead.org, 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, torvalds@...ux-foundation.org,
    roberto.sassu@...wei.com
Subject: Re: [PATCH v3 00/14] KEYS: Add support for PGP keys and signatures

Herbert Xu <herbert@...dor.apana.org.au> wrote:

> Personally I don't think the argument above holds water.  With
> IPsec we had a similar issue of authenticating untrusted peers
> using public key cryptography.  In that case we successfully
> delegated the task to user-space and it is still how it works
> to this day.

It transpires that we do actually need at least a PGP parser in the kernel -
and it needs to be used prior to loading any modules: some Lenovo Thinkpads,
at least, may have EFI variables holding a list of keys in PGP form, not X.509
form.

For example, in dmesg, you might see:

May 16 04:01:01 localhost kernel: integrity: Loading X.509 certificate: UEFI:MokListRT (MOKvar table)
May 16 04:01:01 localhost kernel: integrity: Problem loading X.509 certificate -126

On my laptop, if I dump this variable:

	efivar -e /tmp/q --name=605dab50-e046-4300-abb6-3dd810dd8b23-MokListRT

And then looking at the data exported:

	file /tmp/q

I see:

	/tmp/q: PGP Secret Sub-key -

The kernel doesn't currently have a PGP parser.  I've checked and the value
doesn't parse as ASN.1:

	openssl asn1parse -in /tmp/q -inform DER
	    0:d=0  hl=2 l=  21 prim: cont [ 23 ]       
	Error in encoding
	001EBA93B67F0000:error:0680007B:asn1 encoding routines:ASN1_get_object:header too long:crypto/asn1/asn1_lib.c:105:

which would suggest that it isn't X.509.

David