From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lamorak.hansenpartnership.com (lamorak.hansenpartnership.com [198.37.111.173]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2E0E31A239F; Thu, 5 Jun 2025 15:49:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.37.111.173 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749138579; cv=none; b=UR8QfPk83g+E6aDy58sKXNqQCOlLGdgjwI/GO3mDyCt/v4CpWiiYLKB9VQML0WicC24Aeq18Xb5Fr4Uh5ZoO8Tjx62Lr/qK0+9kwrPf3pSA5XklHZhbs3uAtVten7+s1S+mEEAM/fIGHknS8o8E2Hm8wZuoHgjanq7m+KC1iWhc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749138579; c=relaxed/simple; bh=LvFsdaxHPWfAtXNhvilM+GMJO+IHT2LgmSh63Oc2Iiw=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=CqlENt9CNfybiDpwfqwtsXtZpCSmIJF5ThBnLIrRvAfKw6ROegoG8Pe7ZgPWUoRsHnJVu+yYtA0mPqTxRYwjzD3NMAaM9hdE6gJzjM60N3z0dohKN0w1AshKokkVkjTREcODirA5Pnkgz/iQNsoVFm8RFGJPZSaZ/nEUMeQIQ/8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=HansenPartnership.com; spf=pass smtp.mailfrom=HansenPartnership.com; dkim=pass (1024-bit key) header.d=hansenpartnership.com header.i=@hansenpartnership.com header.b=wEKIWEMW; arc=none smtp.client-ip=198.37.111.173 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=HansenPartnership.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=HansenPartnership.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=hansenpartnership.com header.i=@hansenpartnership.com header.b="wEKIWEMW" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=hansenpartnership.com; s=20151216; t=1749138575; bh=LvFsdaxHPWfAtXNhvilM+GMJO+IHT2LgmSh63Oc2Iiw=; h=Message-ID:Subject:From:To:Date:In-Reply-To:References:From; b=wEKIWEMWMLix1gCeR7BCRqWrKZRYWqd4+SuuyYw69QhR4hDPkMuBmWt5ThebYuiLo GDcjvdZ2b6uEYk1lrxLwlpjFLjKLuH+PwZPh4IrF4SCtLWHrzBA2dGdDDZGO2p1yu+ JUNLqPQLVqXmf/dMlerQzKX5Fcx63vsjm2/VsKyw= Received: from [IPv6:2601:5c4:4302:c21::a774] (unknown [IPv6:2601:5c4:4302:c21::a774]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange x25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lamorak.hansenpartnership.com (Postfix) with ESMTPSA id 048AD1C0315; Thu, 05 Jun 2025 11:49:34 -0400 (EDT) Message-ID: Subject: Re: [PATCH RFC 0/1] module: Optionally use .platform keyring for signatures verification From: James Bottomley To: Vitaly Kuznetsov , Eric Snowberg Cc: "linux-security-module@vger.kernel.org" , "linux-integrity@vger.kernel.org" , "linux-modules@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-doc@vger.kernel.org" , "keyrings@vger.kernel.org" , David Howells , David Woodhouse , Jonathan Corbet , Luis Chamberlain , Petr Pavlu , Sami Tolvanen , Daniel Gomez , Mimi Zohar , Roberto Sassu , Dmitry Kasatkin , Paul Moore , James Morris , "Serge E. Hallyn" , Peter Jones , Robert Holmes , Jeremy Cline , Coiby Xu , Gerd Hoffmann Date: Thu, 05 Jun 2025 11:49:33 -0400 In-Reply-To: <87tt4unw1w.fsf@redhat.com> References: <20250602132535.897944-1-vkuznets@redhat.com> <0FD18D05-6114-4A25-BD77-C32C1D706CC3@oracle.com> <87zfemoc76.fsf@redhat.com> <87tt4unw1w.fsf@redhat.com> Autocrypt: addr=James.Bottomley@HansenPartnership.com; prefer-encrypt=mutual; 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 8mT2Eh9SkH+YVOmaKsajgZgrBxA7fWmGoxXswEVxJIFj3vW7yNc0C5HaUdYa5iGOMs4kg2ht4s7yy7NRQuh7BifWjo6BQ6k4S1H+6axZucxhSV1L6zN9d+lr3Xo/vy1unzA== Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.3 Precedence: bulk X-Mailing-List: linux-integrity@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Thu, 2025-06-05 at 15:43 +0200, Vitaly Kuznetsov wrote: > James Bottomley writes: >=20 > > On Thu, 2025-06-05 at 09:54 +0200, Vitaly Kuznetsov wrote: > > > One additional consideration is the fact that we already trust > > > 'db' for dm-verity (since 6fce1f40e951) and kexec (since > > > 278311e417be) and especially the later gives someone who is able > > > to control 'db' access to CPL0; a 'db'-signed module (IMO) > > > wouldn't change much. > >=20 > > Well, the kexec case is because kexec has to verify the new kernel > > as shim would and shim would use the UEFI keys.=C2=A0 The dm-verity one > > was added for a cloud use case by pressuring the maintainers in > > spite of the objection to using the platform keyring (it went to > > dm-devel only so not many integrity people saw it): > >=20 > > https://lore.kernel.org/all/20240617220037.594792-1-luca.boccassi@gmail= .com/ > >=20 > > The point here is I do think the cloud use case is legitimate, but > > it can't be supported simply by ignoring the bare metal security > > domain separation concerns of the integrity community.=C2=A0 The > > argument that distros have done it so it must be safe isn't really > > a winning one (especially as there's no clear explanation of why > > they did it).=C2=A0 So either you need a better argument or we need a > > way to support both sets of communities ... which is why I was > > wondering about a runtime differentiator. >=20 > So far, I got two 'runtime' ideas: > - Observe MokListTrustedRT and distrust .platform when it is > non-empty. This can, of course, be combine with a Kconfig for those, > who do not want it at all. Well, not sure about that specific variable. It seems to be set but not used by shim (however it is used in the kernel to decide whether to import the MoK list), so how would someone with a current distrusted db get it set? But there's also MokIgnoreDB (which is actually a RT import of MokDBState) which is used to prevent importing the db certs into the platform keyring in the first place. I think the reason this is so fragmented is because we didn't really co-ordinate with shim when all the variables and switches were added.=20 Perhaps we should document all the variables and expectations before deciding on a mechanism?=20 The one thing we can guarantee is if the cloud use case is booting without shim (is it?) then none of the RT variables will get created, so checking any (or a set) of them would work. > and/or > - Sysctl toggle. Keep things as they are by default but make > .platform trusted (either for modules or for everything) when > switched 'on'. This can (optionally) by combined with a previous idea > and have e.g. an 'auto' state for the toggle which follows > MokListTrustedRT. I'm less keen on user specifiable runtime because the security policy of the system using a lockdown to make root less privileged than ring 0 can't allow a malicious root to weaken it. However, let's see if we can get a proposal that would mitigate that concern. Ideally, if we can get to something that works for everyone at runtime, we can remove the current Kconfig explosion which is definitely adding to the confusion (as shown in the Debian bug reports). Regards, James