From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wr1-f52.google.com (mail-wr1-f52.google.com [209.85.221.52]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0C74923A8 for ; Fri, 27 Jan 2023 07:02:21 +0000 (UTC) Received: by mail-wr1-f52.google.com with SMTP id b7so4089298wrt.3 for ; Thu, 26 Jan 2023 23:02:21 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rivosinc-com.20210112.gappssmtp.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=5HxGtUHBeTmKLxMYYWaiGw2aHRBHP369koztMrMyiwA=; b=1vOE67AhAR9Wo70Q4blgMafsiy27P9P0INmEpVCMXsPf4nopeuS9PoJw3fHsyuiWqy 3I0HRLM1CO0JRy8oXWqjVU4jCGT3a8JorOWM3j9jZxIbgB11V5V0T/LRMNXiZ+x4zAx0 eBmJQ6k5fep/VBOfrEuTZn0vlRBnMETt9Ut/7Wj/X6OpA0kc44ymfUwY0pBt2yyS1Ttf cJQAfj3ITgSGBFJh7UHio91JkFPL/DlPil95KHb60f+WphUgF3KRYAn5Hq6S3f/KDdoJ b6uKzVW0M2RAJVXz96ahpAzDn4na76CzLjRsFAirKqyOpt7T62+p2VF1f7+5oFauQWXf fAkA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=5HxGtUHBeTmKLxMYYWaiGw2aHRBHP369koztMrMyiwA=; b=zlbEdazS5NpLOp7VN04A6iiKRo5JPM5kpRoZOQvQqR8g9clLtl6/lPBzzE+o/qxLso RXeRUTOeu8wsXFdjY2bBfN877rktJj8htpItAFSOFTKgR9J9prQBkN1zW7J6Va6yym4i iR6s2Ynp2vr4zcqSkkcihgP6pSiACT8MZsxluP73cndUD0JbS6AKVJbwU5GTr9uoz7TF +mP0eKJo8WoI6DToDawBC9u3KWEUjicFCkh1hScnefs+IxsVv3eCeZ214L5Y0Qge32D6 4jN8HG6gy7W1jvY55rvEZWPbGWlXJj7gSBDrg/N2gorJ4ULCCRLRFc81uIQXvYsSFUX0 yZdA== X-Gm-Message-State: AO0yUKUE0BXOE9i6yMsz88Tb94Ioy+dlpyaVpAG51ecvsxdMZ7YDxZJP tbf5uDYmPGr7+yBdigAMAd5Lgw== X-Google-Smtp-Source: AK7set/yG7eIZMrhBqHR2aFSoxHMlaYJfh+r3x8BhUulxgeFR3o8g0ofaas4ktkgxbll+A+ZGmrE/w== X-Received: by 2002:adf:a181:0:b0:2bf:ae42:9879 with SMTP id u1-20020adfa181000000b002bfae429879mr10453541wru.32.1674802940065; Thu, 26 Jan 2023 23:02:20 -0800 (PST) Received: from vermeer ([2a01:cb1d:81a9:dd00:b570:b34c:ffd4:c805]) by smtp.gmail.com with ESMTPSA id k4-20020a5d66c4000000b002bdc19f8e8asm3223843wrw.79.2023.01.26.23.02.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 26 Jan 2023 23:02:19 -0800 (PST) Date: Fri, 27 Jan 2023 08:02:16 +0100 From: Samuel Ortiz To: Jonathan Cameron Cc: Lukas Wunner , "Dr. David Alan Gilbert" , Greg Kroah-Hartman , "Reshetova, Elena" , "Shishkin, Alexander" , "Shutemov, Kirill" , "Kuppuswamy, Sathyanarayanan" , "Kleen, Andi" , "Hansen, Dave" , Thomas Gleixner , Peter Zijlstra , Mika Westerberg , "Michael S. Tsirkin" , Jason Wang , "Poimboe, Josh" , "aarcange@redhat.com" , Cfir Cohen , Marc Orr , "jbachmann@google.com" , "pgonda@google.com" , "keescook@chromium.org" , James Morris , Michael Kelley , "Lange, Jon" , "linux-coco@lists.linux.dev" , Linux Kernel Mailing List , linux-pci@vger.kernel.org Subject: Re: Linux guest kernel threat model for Confidential Computing Message-ID: References: <20230125215333.GA18160@wunner.de> <20230126105847.00001b97@Huawei.com> <20230126160729.00006843@Huawei.com> Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230126160729.00006843@Huawei.com> On Thu, Jan 26, 2023 at 04:07:29PM +0000, Jonathan Cameron wrote: > On Thu, 26 Jan 2023 14:15:05 +0100 > Samuel Ortiz wrote: > > > On Thu, Jan 26, 2023 at 10:58:47AM +0000, Jonathan Cameron wrote: > > > On Thu, 26 Jan 2023 10:24:32 +0100 > > > Samuel Ortiz wrote: > > > > > > > Hi Lukas, > > > > > > > > On Wed, Jan 25, 2023 at 11:03 PM Lukas Wunner wrote: > > > > > > > > > [cc += Jonathan Cameron, linux-pci] > > > > > > > > > > On Wed, Jan 25, 2023 at 02:57:40PM +0000, Dr. David Alan Gilbert wrote: > > > > > > Greg Kroah-Hartman (gregkh@linuxfoundation.org) wrote: > > > > > > > Great, so why not have hardware attestation also for your devices you > > > > > > > wish to talk to? Why not use that as well? Then you don't have to > > > > > > > worry about anything in the guest. > > > > > > > > > > > > There were some talks at Plumbers where PCIe is working on adding that; > > > > > > it's not there yet though. I think that's PCIe 'Integrity and Data > > > > > > Encryption' (IDE - sigh), and PCIe 'Security Prtocol and Data Model' - > > > > > > SPDM. I don't know much of the detail of those, just that they're far > > > > > > enough off that people aren't depending on them yet. > > > > > > > > > > CMA/SPDM (PCIe r6.0 sec 6.31) is in active development on this branch: > > > > > > > > > > https://github.com/l1k/linux/commits/doe > > > > > > > > Nice, thanks a lot for that. > > > > > > > > > > > > > > > > > The device authentication service afforded here is generic. > > > > > It is up to users and vendors to decide how to employ it, > > > > > be it for "confidential computing" or something else. > > > > > > > > > > Trusted root certificates to validate device certificates can be > > > > > installed into a kernel keyring using the familiar keyctl(1) utility, > > > > > but platform-specific roots of trust (such as a HSM) could be > > > > > supported as well. > > > > > > > > > > > > > This may have been discussed at LPC, but are there any plans to also > > > > support confidential computing flows where the host kernel is not part > > > > of the TCB and would not be trusted for validating the device cert chain > > > > nor for running the SPDM challenge? > > > > > > There are lots of possible models for this. One simple option if the assigned > > > VF supports it is a CMA instance per VF. That will let the guest > > > do full attestation including measurement of whether the device is > > > appropriately locked down so the hypervisor can't mess with > > > configuration that affects the guest (without a reset anyway and that > > > is guest visible). > > > > So the VF would be directly assigned to the guest, and the guest kernel > > would create a CMA instance for the VF, and do the SPDM authentication > > (based on a guest provided trusted root certificate). I think one > > security concern with that approach is assigning the VF to the > > (potentially confidential) guest address space without the guest being > > able to attest of the device trustworthiness first. That's what TDISP is > > aiming at fixing (establish a secure SPDM between the confidential guest > > and the device, lock the device from the guest, attest and then enable > > DMA). > > Agreed, TDISP is more comprehensive, but also much more complex with > more moving parts that we don't really have yet. > > Depending on your IOMMU design (+ related stuff) and interaction with > the secure guest, you might be able to block any rogue DMA until > after attestation / lock down checks even if the Hypervisor was letting > it through. Provided that the guest or, in the TDX and AP-TEE cases, the TSM have protected access to the IOMMU, yes. But then the implementation becomes platform specific. Cheers, Samuel.