From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: Re: IRQF_SAMPLE_RANDOM question... Date: Mon, 06 Apr 2009 14:40:05 -0400 Message-ID: <49DA4C85.5090806@garzik.org> References: <200904061430.26276.rgetz@blackfin.uclinux.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Chris Peterson , Matt Mackall , David Miller To: Robin Getz Return-path: Received: from srv5.dvmed.net ([207.36.208.214]:51053 "EHLO mail.dvmed.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751952AbZDFSkN (ORCPT ); Mon, 6 Apr 2009 14:40:13 -0400 In-Reply-To: <200904061430.26276.rgetz@blackfin.uclinux.org> Sender: netdev-owner@vger.kernel.org List-ID: Robin Getz wrote: > Although there was some discussion > http://thread.gmane.org/gmane.linux.kernel/680723 > > about removing IRQF_SAMPLE_RANDOM from the remaining network drivers in May of > 2008, but they still appears to be there in 2.6.29. > > drivers/net/ibmlana.c > drivers/net/macb.c > drivers/net/3c523.c > drivers/net/3c527.c > drivers/net/netxen/netxen_nic_main.c > drivers/net/cris/eth_v10.c > drivers/net/xen-netfront.c > drivers/net/atlx/atl1.c > drivers/net/qla3xxx.c > drivers/net/tg3.c > drivers/net/niu.c > > So what is the plan? If I send a patch to add IRQF_SAMPLE_RANDOM to others > (like the Blackfin) networking drivers - will it get rejected? > > We have lots of embedded headless systems (no keyboard/mouse, no soundcard, no > video) systems with *no* sources of entropy - and people using SSL. > > I didn't really find any docs which describe what should have > IRQF_SAMPLE_RANDOM on it or not. I did find Matt Mackall describing it as: >> We currently assume that IRQF_SAMPLE_RANDOM means 'this is a completely >> trusted unobservable entropy source' which is obviously wrong for >> network devices but is right for some other classes of device. > > Currently - I see most things I see using IRQF_SAMPLE_RANDOM would also fail > the "completely unobservable" test. Other than the TRNG that are inside the > CPU - what does pass? IMO it's not observation but rather that a remote host is essentially your source of entropy -- which means your source of entropy is potentially controllable or influenced by an attacker. Furthermore, with hardware interrupt mitigation, non-trivial traffic levels can imply that interrupts are delivered with timer-based regularity. This, too, may clearly be influenced by a remote attacker. Thus I think IRQF_SAMPLE_RANDOM should be banned from network drivers... but that is not a universal opinion. Jeff