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[209.85.208.181]) by smtp.gmail.com with ESMTPSA id s9sm1087704ljh.46.2020.08.05.09.39.34 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 05 Aug 2020 09:39:35 -0700 (PDT) Received: by mail-lj1-f181.google.com with SMTP id 185so38213403ljj.7 for ; Wed, 05 Aug 2020 09:39:34 -0700 (PDT) X-Received: by 2002:a2e:9a11:: with SMTP id o17mr1798783lji.314.1596645574541; Wed, 05 Aug 2020 09:39:34 -0700 (PDT) MIME-Version: 1.0 References: <9f74230f-ba4d-2e19-5751-79dc2ab59877@gmail.com> <20200805024941.GA17301@1wt.eu> <66f06ea1-3221-5661-e0de-6eef45ac3664@gmail.com> In-Reply-To: <66f06ea1-3221-5661-e0de-6eef45ac3664@gmail.com> From: Linus Torvalds Date: Wed, 5 Aug 2020 09:39:17 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: Flaw in "random32: update the net random state on interrupt and activity" To: Marc Plumb Cc: Willy Tarreau , "Theodore Ts'o" , Netdev , Amit Klein , Eric Dumazet , "Jason A. Donenfeld" , Andrew Lutomirski , Kees Cook , Thomas Gleixner , Peter Zijlstra , stable Content-Type: text/plain; charset="UTF-8" Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, Aug 5, 2020 at 8:44 AM Marc Plumb wrote: > > I thought net_rand_state was assumed to be insecure and that anyone > could determine the internal state. Isn't this Working as Designed? I was working as designed - because it wasn't really designed to be "real crypto" - but sadly it's also the only thing that is fast enough for a lot of networking. So it may be _designed_ to be "not real crypto" and to have a discoverable internal state. But once again, reality interferes, and it turns out that people really want something very very fast that is also not deterministic enough to be discoverable at least remotely. The stuff that is actually designed and intended to be a complete black box is sadly also much too slow. By about an order of magnitude. Linus