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

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Date: Fri, 16 Feb 2024 17:53:01 +0100
From: Roberto Sassu <roberto.sassu@...weicloud.com>
To: Matthew Wilcox <willy@...radead.org>, Petr Tesarik
	 <petrtesarik@...weicloud.com>
Cc: Dave Hansen <dave.hansen@...el.com>, Petr Tesařík
 <petr@...arici.cz>, Jonathan Corbet <corbet@....net>, Thomas Gleixner
 <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov
 <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, "maintainer:X86
 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>, "H. Peter Anvin"
 <hpa@...or.com>, Andy Lutomirski <luto@...nel.org>, Oleg Nesterov
 <oleg@...hat.com>, Peter Zijlstra <peterz@...radead.org>, Xin Li
 <xin3.li@...el.com>, Arnd Bergmann <arnd@...db.de>,  Andrew Morton
 <akpm@...ux-foundation.org>, Rick Edgecombe <rick.p.edgecombe@...el.com>,
 Kees Cook <keescook@...omium.org>, "Masami Hiramatsu (Google)"
 <mhiramat@...nel.org>,  Pengfei Xu <pengfei.xu@...el.com>, Josh Poimboeuf
 <jpoimboe@...nel.org>, Ze Gao <zegao2021@...il.com>,  "Kirill A. Shutemov"
 <kirill.shutemov@...ux.intel.com>, Kai Huang <kai.huang@...el.com>, David
 Woodhouse <dwmw@...zon.co.uk>,  Brian Gerst <brgerst@...il.com>, Jason
 Gunthorpe <jgg@...pe.ca>, Joerg Roedel <jroedel@...e.de>, "Mike Rapoport
 (IBM)" <rppt@...nel.org>, Tina Zhang <tina.zhang@...el.com>, Jacob Pan
 <jacob.jun.pan@...ux.intel.com>, "open list:DOCUMENTATION"
 <linux-doc@...r.kernel.org>, open list <linux-kernel@...r.kernel.org>,
 David Howells <dhowells@...hat.com>, Petr Tesarik
 <petr.tesarik1@...wei-partners.com>
Subject: Re: [RFC 6/8] KEYS: PGP data parser

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@...hat.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