Re: [RFC 0/8] PGP key parser using SandBox Mode

From: "Petr Tesařík" <petr@tesarici.cz>
To: Dave Hansen <dave.hansen@intel.com>
Cc: Petr Tesarik <petrtesarik@huaweicloud.com>,
	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>, "H. Peter Anvin" <hpa@zytor.com>,
	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>,
	Roberto Sassu <roberto.sassu@huaweicloud.com>,
	David Howells <dhowells@redhat.com>,
	Petr Tesarik <petr.tesarik1@huawei-partners.com>
Subject: Re: [RFC 0/8] PGP key parser using SandBox Mode
Date: Fri, 16 Feb 2024 17:08:05 +0100	[thread overview]
Message-ID: <20240216170805.0d0decd5@meshulam.tesarici.cz> (raw)
In-Reply-To: <c65eb8f1-2903-4043-a3ab-945d880043b5@intel.com>

On Fri, 16 Feb 2024 07:38:30 -0800
Dave Hansen <dave.hansen@intel.com> wrote:

> On 2/16/24 07:24, Petr Tesarik wrote:
> > While I started working on my development branch to illustrate how
> > SandBox Mode could be enhanced to allow dynamic memory allocation and
> > other features necessary to convert some existing code, my colleague
> > Roberto Sassu set out and adapted a PGP key parser to run in a sandbox.
> > 
> > Disclaimer:
> > 
> > The code had to be rearranged in order to avoid memory allocations
> > and crypto operations in the sandbox. The code might contain errors.  
> 
> I'm confused by this.  The kernel doesn't (appear to) have a PGP parser
> today.  So are you saying that it *should* have one and it's only
> feasible if its confined in a sandbox?

I'm sorry if this is confusing. Yes, your understanding is correct.
This patch series demonstrates that SBM (even in the initial version
that was submitted) allows to write a PGP parser which can survive
memory safety bugs withoug compromising the rest of the kernel.

> A much more powerful example would be to take something that the kernel
> has already and put it in a sandbox.  That would show us how difficult
> it is to sandbox something versus just doing it _normally_ in the kernel.

That's what I have also tested as a PoC with an earlier version of my
patch series and a few quick hacks on top. As it happens, that code
on top needs to be adapted for the current patch series, so I cannot
post it just yet. Please, stay tuned.

> As it stands, I fear this was just the largest chunk of sandbox code
> that was laying around and it seemed like a good idea to just chuck
> ~1400 lines of code over the wall at a huge cc list.

You asked for some real-world scenarios, and this should be one.
Another is on the way, but see above why it takes a bit of time.

I am not trying to claim I'm the smartest person on this planet. I can
accept it if there is a fundamental flaw in my approach. Yet, I'd be
glad if somebody can make me a favor and at least hint at what exactly
is the issue with it. I have to admit this thing is still not quite
clear to me. I would be sad if I couldn't learn from this experience.

Petr T