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Date: Thu, 16 Jun 2022 08:42:43 -0700 From: Evan Green <evgreen@...omium.org> To: "Rafael J. Wysocki" <rafael@...nel.org> Cc: Pavel Machek <pavel@....cz>, LKML <linux-kernel@...r.kernel.org>, Matthew Garrett <mgarrett@...ora.tech>, Daniil Lunev <dlunev@...gle.com>, zohar@...ux.ibm.com, "James E.J. Bottomley" <jejb@...ux.ibm.com>, linux-integrity@...r.kernel.org, Jonathan Corbet <corbet@....net>, "Rafael J. Wysocki" <rjw@...ysocki.net>, Gwendal Grignou <gwendal@...omium.org>, Jarkko Sakkinen <jarkko@...nel.org>, Linux PM <linux-pm@...r.kernel.org>, David Howells <dhowells@...hat.com>, Hao Wu <hao.wu@...rik.com>, James Morris <jmorris@...ei.org>, Jason Gunthorpe <jgg@...pe.ca>, Len Brown <len.brown@...el.com>, Peter Huewe <peterhuewe@....de>, "Serge E. Hallyn" <serge@...lyn.com>, axelj <axelj@...s.com>, keyrings@...r.kernel.org, "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>, linux-security-module@...r.kernel.org Subject: Re: [PATCH 00/10] Encrypted Hibernation On Tue, May 17, 2022 at 10:34 AM Evan Green <evgreen@...omium.org> wrote: > > Hi Rafael, > > On Tue, May 17, 2022 at 9:06 AM Rafael J. Wysocki <rafael@...nel.org> wrote: > > > > On Mon, May 9, 2022 at 6:44 PM Evan Green <evgreen@...omium.org> wrote: > > > > > > On Fri, May 6, 2022 at 9:08 AM Pavel Machek <pavel@....cz> wrote: > > > > > > > > Hi! > > > > > > > > > We are exploring enabling hibernation in some new scenarios. However, > > > > > our security team has a few requirements, listed below: > > > > > 1. The hibernate image must be encrypted with protection derived from > > > > > both the platform (eg TPM) and user authentication data (eg > > > > > password). > > > > > 2. Hibernation must not be a vector by which a malicious userspace can > > > > > escalate to the kernel. > > > > > > > > Can you (or your security team) explain why requirement 2. is needed? > > > > > > > > On normal systems, trusted userspace handles kernel upgrades (for example), > > > > so it can escalate to kernel priviledges. > > > > > > > > > > Our systems are a little more sealed up than a normal distro, we use > > > Verified Boot [1]. To summarize, RO firmware with an embedded public > > > key verifies that the kernel+commandline was signed by Google. The > > > commandline includes the root hash of the rootfs as well (where the > > > modules live). So when an update is applied (A/B style, including the > > > whole rootfs), assuming the RO firmware stayed RO (which requires > > > physical measures to defeat), we can guarantee that the kernel, > > > commandline, and rootfs have not been tampered with. > > > > > > Verified boot gives us confidence that on each boot, we're at least > > > starting from known code. This makes it more challenging for an > > > attacker to persist an exploit across reboot. With the kernel and > > > modules verified, we try to make it non-trivial for someone who does > > > manage to gain root execution once from escalating to kernel > > > execution. Hibernation would be one obvious escalation route, so we're > > > hoping to find a way to enable it without handing out that easy > > > primitive. > > > > > > [1] https://www.chromium.org/chromium-os/chromiumos-design-docs/verified-boot/ > > > > So I guess this really is an RFC. > > Yes, I suppose it is. > > > > > Honestly, I need more time to go through this and there are pieces of > > it that need to be looked at other people (like the TPM-related > > changes). > > No problem, thanks for the reply to let me know. I expect some back > and forth in terms of what should be hidden behind abstractions and > where exactly things should live. But I wanted to get this out to > upstream as early as I could, just to get initial reactions on the > overall concept and design. Looking forward to hearing your thoughts > when you get a chance, and let me know if there are others I should be > adding that I've missed. Gentle bump in case this dropped off of radars, I'd still appreciate any feedback folks had on this series. -Evan > > -Evan > > > > > Thanks!
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