Re: [RFC 6/8] KEYS: PGP data parser

From: "H. Peter Anvin" <hpa@zytor.com>
To: Roberto Sassu <roberto.sassu@huaweicloud.com>,
	Matthew Wilcox <willy@infradead.org>,
	Petr Tesarik <petrtesarik@huaweicloud.com>
Cc: "Dave Hansen" <dave.hansen@intel.com>,
	"Petr Tesařík" <petr@tesarici.cz>,
	"Jonathan Corbet" <corbet@lwn.net>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Ingo Molnar" <mingo@redhat.com>,
	"Borislav Petkov" <bp@alien8.de>,
	"Dave Hansen" <dave.hansen@linux.intel.com>,
	"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
	<x86@kernel.org>, "Andy Lutomirski" <luto@kernel.org>,
	"Oleg Nesterov" <oleg@redhat.com>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Xin Li" <xin3.li@intel.com>, "Arnd Bergmann" <arnd@arndb.de>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Rick Edgecombe" <rick.p.edgecombe@intel.com>,
	"Kees Cook" <keescook@chromium.org>,
	"Masami Hiramatsu (Google)" <mhiramat@kernel.org>,
	"Pengfei Xu" <pengfei.xu@intel.com>,
	"Josh Poimboeuf" <jpoimboe@kernel.org>,
	"Ze Gao" <zegao2021@gmail.com>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	"Kai Huang" <kai.huang@intel.com>,
	"David Woodhouse" <dwmw@amazon.co.uk>,
	"Brian Gerst" <brgerst@gmail.com>,
	"Jason Gunthorpe" <jgg@ziepe.ca>,
	"Joerg Roedel" <jroedel@suse.de>,
	"Mike Rapoport (IBM)" <rppt@kernel.org>,
	"Tina Zhang" <tina.zhang@intel.com>,
	"Jacob Pan" <jacob.jun.pan@linux.intel.com>,
	"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
	"open list" <linux-kernel@vger.kernel.org>,
	"David Howells" <dhowells@redhat.com>,
	"Petr Tesarik" <petr.tesarik1@huawei-partners.com>
Subject: Re: [RFC 6/8] KEYS: PGP data parser
Date: Fri, 16 Feb 2024 09:08:09 -0800	[thread overview]
Message-ID: <EC53BCED-0D4C-4561-9041-584378326DD5@zytor.com> (raw)
In-Reply-To: <5916fa3ac3d0ce2ade71e7ed1c9eb6923e374c1f.camel@huaweicloud.com>

On February 16, 2024 8:53:01 AM PST, Roberto Sassu <roberto.sassu@huaweicloud.com> wrote:
>On Fri, 2024-02-16 at 16:44 +0000, Matthew Wilcox wrote:
>> On Fri, Feb 16, 2024 at 04:24:33PM +0100, Petr Tesarik wrote:
>> > From: David Howells <dhowells@redhat.com>
>> > 
>> > Implement a PGP data parser for the crypto key type to use when
>> > instantiating a key.
>> > 
>> > This parser attempts to parse the instantiation data as a PGP packet
>> > sequence (RFC 4880) and if it parses okay, attempts to extract a public-key
>> > algorithm key or subkey from it.
>> 
>> I don't understand why we want to do this in-kernel instead of in
>> userspace and then pass in the actual key.
>
>Sigh, this is a long discussion.
>
>PGP keys would be used as a system-wide trust anchor to verify RPM
>package headers, which already contain file digests that can be used as
>reference values for kernel-enforced integrity appraisal.
>
>With the assumptions that:
>
>- In a locked-down system the kernel has more privileges than root
>- The kernel cannot offload this task to an user space process due to
>  insufficient isolation
>
>the only available option is to do it in the kernel (that is what I got
>as suggestion).
>
>Roberto
>
>

Ok, at least one of those assumptions is false, and *definitely* this approach seems to be a solution in search of a problem.