From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wr1-f65.google.com (mail-wr1-f65.google.com [209.85.221.65]) by mx.groups.io with SMTP id smtpd.web09.4501.1573135774992497027 for ; Thu, 07 Nov 2019 06:09:35 -0800 Authentication-Results: mx.groups.io; dkim=pass header.i=@linaro.org header.s=google header.b=j1Se4Jqt; spf=pass (domain: linaro.org, ip: 209.85.221.65, mailfrom: ard.biesheuvel@linaro.org) Received: by mail-wr1-f65.google.com with SMTP id a15so3152032wrf.9 for ; Thu, 07 Nov 2019 06:09:34 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=sqhgbNz7sLtWLUk1m/b2Lnb5Ms1IygVNHMM0xSDB5/E=; b=j1Se4Jqt4T/pEkrY/KG66Sj3UDGB7XADDsRpFOnL8slEjblwRD3p7d0va5nGHAQdFB LQg45b98DBZw/ek0WeoC48Re+VWazBf+Jo+X/Itl+k/kn1BtZj73c9ryaEkiKsC3PMro cqYRTwjpuOfTL6ZyAVrDAbqqSNz0vAvKe2b0dD5j1veC+Ja2ztwQ/xuON8kBH6HDS0vK j1HbCtg1TmOfAXNQFC4vfNHblKJOJuA64r301BcgxIRQkvcp99z4yk+e2GC3Si1/7+fv yKc3GEBGcoKPq6l6tw3EwPwa9HrLSjqIV+OzFPij27UZpVpZmN32StItTLkzeFSiKmwr 0fqw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=sqhgbNz7sLtWLUk1m/b2Lnb5Ms1IygVNHMM0xSDB5/E=; b=l2F2fohyes1TYs/y/edabvIcolrnFjbUO3x6c5Qct2XnSBroeAEU6C3c/D2bbfwF0X 1ghMQ22XE+2L1Q4LCpqqMhqDM0G8xcC+6ss3zsIQbnvujEJGx+pwYhqK4JcGvgstopEY c/ZKX0dLNJhs3rIIhz1dpBPQgVZ99xBo8S9QciYyhJSwRZOyrgiIwjbrMDlFIeITZCL0 R6x165Ii3FmVm8lK1l8HD8ee59aC4jd5Am8+50ZJSPBzGdB50vKXEDlOG06Br8qdWvTV ao4GQ9aJ84SImWGCt3wrbgaMgCygixwAv6FWyCVcmyzGL9lXpPQ5OPb17VGPUn4dVAdP z+wg== X-Gm-Message-State: APjAAAUtHCD2LZvU2msLZYVytGTJGs/BwCwU/APdXrI2RtakpNXEqBHy Yyn1hmvJUNMzRhltdhxUgeWZ9rGdOGfY1hWUydCRtQ== X-Google-Smtp-Source: APXvYqw48TGy9L5DPThcqmmXqKKYkPtZq+zLbJiKc7XZPAYfaTUmGOPB2+cKMA77dw4HtpRHls57bClzFc3I8SPfeLc= X-Received: by 2002:adf:ec42:: with SMTP id w2mr2931815wrn.32.1573135773478; Thu, 07 Nov 2019 06:09:33 -0800 (PST) MIME-Version: 1.0 References: <03e769cf-a5ad-99ce-cd28-690e0a72a310@redhat.com> <20191107115203.GD120292@redhat.com> <31917972-da28-8e0d-432d-1cb7607ff3e7@redhat.com> In-Reply-To: From: "Ard Biesheuvel" Date: Thu, 7 Nov 2019 15:09:22 +0100 Message-ID: Subject: Re: privileged entropy sources in QEMU/KVM guests To: Laszlo Ersek Cc: Paolo Bonzini , =?UTF-8?Q?Daniel_P=2E_Berrang=C3=A9?= , qemu devel list , Jian J Wang , edk2-devel-groups-io , Bret Barkelew , Erik Bjorge , Sean Brogan , =?UTF-8?Q?Philippe_Mathieu=2DDaud=C3=A9?= Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, 7 Nov 2019 at 14:44, Laszlo Ersek wrote: > > On 11/07/19 13:47, Paolo Bonzini wrote: > > On 07/11/19 12:52, Daniel P. Berrang=C3=A9 wrote: > >> > >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/com= mit/?id=3Dbb5530e4082446aac3a3d69780cd4dbfa4520013 > >> > >> Is it practical to provide a jitter entropy source for EDK2 > >> too ? > > > > The hard part is not collecting jitter (though the firmware might be to= o > > deterministic for that), but rather turning it into a random number see= d > > (mixing data from various sources, crediting entropy, etc.). > > If there is *any* entropy source that (a) we can trust to be random > enough and (b) depends only on the CPU, then we shouldn't struggle with > virtio-rng (or similar devices) at all. RDRAND would be a no-brainer, > but the "community literature" suggests it should not be trusted in itsel= f. > > I've read the commit message linked above, and it appears too good to be > true. > > The CPU Jitter RNG provides a source of good entropy by collecting > CPU executing time jitter. [...] The RNG does not have any > dependencies on any other service in the kernel. The RNG only needs > a high-resolution time stamp. [...] > > http://www.chronox.de/jent.html > > The CPU Jitter Random Number Generator provides a non-physical true > random number generator that works equally in kernel and user land. > The only prerequisite is the availability of a high-resolution timer > that is available in modern CPUs. > > http://www.chronox.de/jent/doc/CPU-Jitter-NPTRNG.html > > Today=E2=80=99s operating systems provide non-physical true random nu= mber > generators which are based on hardware events. With the advent of > virtualization and the ever growing need of more high-quality random > numbers, these random number generators reach their limits. > Additional sources of entropy must be opened up. This document > introduces an entropy source based on CPU execution time jitter. The > design and implementation of a non-physical true random number > generator, the CPU Jitter random number generator, its statistical > properties and the maintenance and behavior of entropy is discussed > in this document. > > If this construct is legit, a core edk2 implementation (available to all > platforms, and on all edk2 arches) would be a huge win. > "that works equally in kernel and user land" Firmware running at boot time on a single core without any serious scheduling or I/O going on is not going to produce any entropy worth mentioning, I'm afraid. And if it does, it is going to delay the boot substantially. > On the other hand, we're having this discussion because the premise of > TianoCore#1871 is that we shouldn't rely on just the CPU and a high > resolution timer... I simply cannot decide if this construct is > trustworthy. (With any solution that was based in the host's /dev/random > or /dev/urandom, the trustworthiness question would be side-stepped in > the firmware.) >