From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 02D7FC433EF for ; Wed, 6 Jul 2022 15:26:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=yv48NHLWgLWfyXQz85dfkNXecb10YX8nMNFu3N00Qoc=; b=kJnic6IMSi4ZF2 aZCeBr9QkpgYLjsasN2ovgcJuuH03GzRwt2Vfs2C0ARiwsL6OfPYu3Jk2hNesA+oIubPfrFI8NpEc 5AyYTHE7babTCSyxpSTLLnaa9i9NZJdGGiweqjQCs7h+iGzi75X5/EaihXdMcOOqeumWsrGLp8gza 1iTqQc468wx8c5cazcFD4EEgV65MCbjfaHJORLKuwfAsWMIFMiqG7Qv0lbctBnpx5vRv021XUR255 q6M5h03LrnWjwEC9X4/3M+XO6lfkUdAiagIA92tKY12rEhHUlWxM4wn35HgeP71U8RUK2p4mjHXIk VoXEpN2DM9URxioD1FfA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1o96tj-00B115-H0; Wed, 06 Jul 2022 15:25:03 +0000 Received: from dfw.source.kernel.org ([139.178.84.217]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1o96tg-00B0zb-H3 for linux-arm-kernel@lists.infradead.org; Wed, 06 Jul 2022 15:25:02 +0000 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 0B8B061FB1; Wed, 6 Jul 2022 15:25:00 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D3E98C3411C; Wed, 6 Jul 2022 15:24:57 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="MfGZXb8n" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1657121096; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=vjqdS21oaUKcKvXC0EcJ6AHi+otxfA3EET5R3nVpN+M=; b=MfGZXb8npvpYoU43hWe25DYKHe0PBhy4Xe+NehRnPfmEif7iB9fxcAooznnS+za/0ewMYi zAuB8WvEvrHWRsucspGtZ/xyQEiJKL7mObMLaa3ZFdb6jvrPRV4NLOYKbwZbbuDHhY9G4/ PSj7+iJoPiYNS8XRwJYx0lk1+GuwlcE= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id 36d0362c (TLSv1.3:AEAD-AES256-GCM-SHA384:256:NO); Wed, 6 Jul 2022 15:24:55 +0000 (UTC) Date: Wed, 6 Jul 2022 17:24:49 +0200 From: "Jason A. Donenfeld" To: Theodore Ts'o Cc: linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org, Catalin Marinas , Will Deacon , Michael Ellerman , Heiko Carstens , Alexander Gordeev , Thomas Gleixner , "H . Peter Anvin" , Greg Kroah-Hartman , Arnd Bergmann Subject: Re: [PATCH] random: remove CONFIG_ARCH_RANDOM and "nordrand" Message-ID: References: <20220705190121.293703-1-Jason@zx2c4.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220706_082500_787941_DF2BA0B5 X-CRM114-Status: GOOD ( 21.51 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Ted, On Wed, Jul 06, 2022 at 10:55:04AM -0400, Theodore Ts'o wrote: > On Tue, Jul 05, 2022 at 09:01:21PM +0200, Jason A. Donenfeld wrote: > > Later the thinking evolved. With a properly designed RNG, using RDRAND > > values alone won't harm anything, even if the outputs are malicious. > > I personally think it's totally fine to remove nordrand. However, the > reason why it was there was that there were some rather extreme > tin-foil-hatters who believed that if (the completely unavailable to > the public for auditing) RDRAND implementation *were* malicious *and* > the microcode had access to the register file and/or the instruction > pipeline, then in theory, a malicious CPU could subvert how the RDRAND > is mixed into the getrandom output to force a particular output. > > Personally, I've always considered it to be insane, since a much > easier way to compromise a CPU would be to drop a Minix system hidden > into the CPU running a web server that had massive security bugs in it > that were only discovered years later. And if you don't trust the CPU > manufacture to that extent, you should probably simply not use CPU's > from that manufacturer. :-) That specific attack scenario is actually something I've fixed over the last few months, by ensuring that all RDRAND values go through the hash function. So even if the CPU is super malicious, it'd still need a hash preimage, which isn't considered to be computable for blake2s. Minix in the cpu... haha.. surely that would never happen... haha surely... Jason _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel