From: Nikos Mavrogiannopoulos Subject: Re: [RFC][PATCH 0/6] /dev/random - a new approach Date: Tue, 3 May 2016 18:20:57 +0200 Message-ID: References: <9192755.iDgo3Omyqe@positron.chronox.de> <1499137.D4Mft7n8bh@tauon.atsec.com> <2009968.Rf1hsrr5t0@tauon.atsec.com> <20160426011137.GC28496@thunk.org> <20160503144824.GB11832@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 To: "Theodore Ts'o" , Nikos Mavrogiannopoulos , Stephan Mueller , Herbert Xu , Linux Crypto Mailing List , Linux Kernel Mailing List , Sandy Harris Return-path: Received: from mail-yw0-f175.google.com ([209.85.161.175]:33290 "EHLO mail-yw0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932543AbcECQVi (ORCPT ); Tue, 3 May 2016 12:21:38 -0400 In-Reply-To: <20160503144824.GB11832@thunk.org> Sender: linux-crypto-owner@vger.kernel.org List-ID: On Tue, May 3, 2016 at 4:48 PM, wrote: > On Tue, May 03, 2016 at 03:57:15PM +0200, Nikos Mavrogiannopoulos wrote: >> I believe their main concern is that they want to protect applications >> which do not check error codes of system calls, when running on a >> kernel which does not provide getrandom(). That way, they have an >> almost impossible task to simulate getrandom() on kernel which do not >> support it. > > The whole *point* of creating the getrandom(2) system call is that it > can't be simulated/emulated in userspace. If it can be, then there's > no reason why the system call should exist. This is one of the > reasons why haven't implemented mysql or TLS inside the kernel. :-) > So if their standard is "we need to simulate getrandom(2) on a kernel > which does not have it", we'll **never** see glibc support for it. By > definition, this is *impossible*. I know, and I share this opinion. To their defense they will have to provide a call which doesn't make applications fail in the following scenario: 1. crypto/ssl libraries are compiled to use getrandom() because it is available in libc and and in kernel 2. everything works fine 3. the administrator downgrades the kernel to a version without getrandom() because his network card works better with that version 4. Mayhem as applications fail However I don't see a way to avoid issues - though limited to corner cases - with any imperfect emulation. It would be much clear for glibc to just require a kernel with getrandom(). regards, Nikos