linux-kernel - Re: [GIT PULL] MODSIGN: Use PKCS#7 for module signatures

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Message-ID: <CALCETrVwxZD=f38aK1EpHLjv9fnzMsTiuHbHDRqECpFkaMKdqg@mail.gmail.com>
Date:	Mon, 27 Jul 2015 16:15:45 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	David Howells <dhowells@...hat.com>
Cc:	Andy Lutomirski <luto@...nel.org>,
	James Morris <jmorris@...ei.org>,
	David Woodhouse <dwmw2@...radead.org>,
	Luis Rodriguez <mcgrof@...il.com>, keyrings@...ux-nfs.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	LSM List <linux-security-module@...r.kernel.org>
Subject: Re: [GIT PULL] MODSIGN: Use PKCS#7 for module signatures

On Mon, Jul 27, 2015 at 3:43 PM, David Howells <dhowells@...hat.com> wrote:
> Andy Lutomirski <luto@...nel.org> wrote:
>
>> With all this stuff applied, will the kernel accept PKCS#7 signatures that
>> *don't* have authenticated attributes or that are otherwise cryptographically
>> insecure in that they fail to provide the property that an attacker can't
>> manipulate a valid signature on one message to look like a valid signature on
>> a different message?
>
> Hmmm...  That's easy enough to fix (see below).  However, will that cause
> kexec problems, I wonder?  Does mscode require authattrs?
>

Seems sensible.

How would it cause kexec problems?  I can only see it being a problem
if Authenticode can't handle authattrs, right?  There shouldn't be any
legacy PKCS7 kexec images whatsoever, because no existing kernel will
boot them or generate them.

--Andy
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