linux-kernel - Re: [PATCH 2/2] sign-file: Remove support for signing with PKCS#7

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Message-ID: <a78b70383de5fbde95bd853f1c52eace114e9c69.camel@HansenPartnership.com>
Date: Wed, 12 Nov 2025 10:05:57 -0500
From: James Bottomley <James.Bottomley@...senPartnership.com>
To: Petr Pavlu <petr.pavlu@...e.com>
Cc: David Howells <dhowells@...hat.com>, David Woodhouse
 <dwmw2@...radead.org>,  Luis Chamberlain <mcgrof@...nel.org>, Daniel Gomez
 <da.gomez@...nel.org>, Sami Tolvanen <samitolvanen@...gle.com>, Aaron
 Tomlin <atomlin@...mlin.com>,  keyrings@...r.kernel.org,
 linux-modules@...r.kernel.org,  linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] sign-file: Remove support for signing with PKCS#7

On Wed, 2025-11-12 at 14:51 +0100, Petr Pavlu wrote:
> On 11/11/25 5:53 PM, James Bottomley wrote:
> > On Tue, 2025-11-11 at 16:48 +0100, Petr Pavlu wrote:
> > > The PKCS#7 code in sign-file allows for signing only with SHA-1.
> > > Since SHA-1 support for module signing has been removed, drop
> > > PKCS#7 support in favor of using only CMS.
> > 
> > The change log is a bit alarmist.  CMS really *is* PKCS7 and most
> > literature will refer to CMS as PKCS7.  What you're really
> > deprecating is the use of the PKCS7_sign() API which can only
> > produce SHA-1 Signatures ... openssl is fully capable of producing
> > any hash PKCS7 signatures using a different PKCS7_... API set but
> > the CMS_... API is newer.
> > 
> > The point being the module signature type is still set to
> > PKEY_ID_PKCS7 so it doesn't square with the commit log saying "drop
> > PKCS#7 support". What you really mean is only use the openssl
> > CMS_... API for producing PKCS7 signatures.
> 
> Ok, I plan to update the description to the following in v2:
> 
> sign-file: Use only the OpenSSL CMS API for signing
> 
> The USE_PKCS7 code in sign-file utilizes PKCS7_sign(), which allows
> signing only with SHA-1. Since SHA-1 support for module signing has
> been removed, drop the use of the OpenSSL PKCS7 API by the tool in
> favor of using only the newer CMS API.

Much better, thanks!

Regards,

James