From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751476AbeEBBLU (ORCPT ); Tue, 1 May 2018 21:11:20 -0400 Received: from mail-oi0-f65.google.com ([209.85.218.65]:40081 "EHLO mail-oi0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751283AbeEBBLP (ORCPT ); Tue, 1 May 2018 21:11:15 -0400 X-Google-Smtp-Source: AB8JxZqm6DbpBxSMrc1GfRGsL3MLjr518izuET0IiiAoRoAHA31cDJcLjeBBYLkbVB/8UFI4b2U06g== Date: Tue, 1 May 2018 18:11:11 -0700 From: Sultan Alsawaf To: "Theodore Y. Ts'o" , Justin Forbes , Jeremy Cline , Pavel Machek , LKML , Jann Horn Subject: Re: Linux messages full of `random: get_random_u32 called from` Message-ID: <20180502011111.m2jtl7tvdq3h3nhc@sultan-box> References: <20180429170541.lrzwyihrd6d75rql@sultan-box> <20180429184101.GA31156@amd> <20180429202033.ysmc42mj2rrk3h7p@sultan-box> <20180429220519.GQ5965@thunk.org> <01000163186628e6-3fe4abfc-eaaf-470c-90c8-2d8ad91db8f1-000000@email.amazonses.com> <20180501125518.GI20585@thunk.org> <20180502004317.kxwiu2oephgbi6ok@sultan-box> <20180502005604.GJ10479@thunk.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180502005604.GJ10479@thunk.org> User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 01, 2018 at 08:56:04PM -0400, Theodore Y. Ts'o wrote: > On Tue, May 01, 2018 at 05:43:17PM -0700, Sultan Alsawaf wrote: > > > > I've attached what I think is a reasonable stopgap solution until this is > > actually fixed. If you're willing to revert the CVE-2018-1108 patches > > completely, then I don't think you'll mind using this patch in the meantime. > > I would put it slightly differently; reverting the CVE-2018-1108 > patches is less dangerous than what you are proposing in your attached > patch. > > Again, I think the right answer is to fix userspace to not require > cryptographic grade entropy during early system startup, and for > people to *think* about what they are doing. I've looked at the > systemd's use of hmac in journal-authenticate, and as near as I can > tell, there isn't any kind of explanation about why it was necessary, > or what threat it was trying to protect against. > > - Ted Why is /dev/urandom so much more dangerous than /dev/random? The more I search, the more I see that many sources consider /dev/urandom to be cryptographically secure... and since I hold down a single key on the keyboard to make my computer boot without any kernel workarounds, I'm sure the NSA would eventually notice my predictable behavior and get their hands on my Richard Stallman photos. Fixing all the "broken" userspace instances of entropy usage during early system startup is a tall order. What about barebone machines used as remote servers? I feel like just "fixing userspace" isn't going to cover all of the usecases that the CVE-2018-1108 patches broke. Sultan