From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751767Ab2KFMFn (ORCPT ); Tue, 6 Nov 2012 07:05:43 -0500 Received: from charlotte.tuxdriver.com ([70.61.120.58]:46418 "EHLO smtp.tuxdriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751074Ab2KFMFl (ORCPT ); Tue, 6 Nov 2012 07:05:41 -0500 Date: Tue, 6 Nov 2012 07:05:23 -0500 From: Neil Horman To: Jarod Wilson Cc: linux-kernel@vger.kernel.org, Herbert Xu , "David S. Miller" , Matt Mackall , linux-crypto@vger.kernel.org Subject: Re: [PATCH] random: prime last_data value per fips requirements Message-ID: <20121106120523.GA2805@hmsreliant.think-freely.org> References: <1352149210-4790-1-git-send-email-jarod@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1352149210-4790-1-git-send-email-jarod@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Spam-Score: -2.9 (--) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 05, 2012 at 04:00:10PM -0500, Jarod Wilson wrote: > The value stored in last_data must be primed for FIPS 140-2 purposes. Upon > first use, either on system startup or after an RNDCLEARPOOL ioctl, we > need to take an initial random sample, store it internally in last_data, > then pass along the value after that to the requester, so that consistency > checks aren't being run against stale and possibly known data. > > CC: Herbert Xu > CC: "David S. Miller" > CC: Neil Horman > CC: Matt Mackall > CC: linux-crypto@vger.kernel.org > Signed-off-by: Jarod Wilson > --- > drivers/char/random.c | 11 +++++++++++ > 1 files changed, 11 insertions(+), 0 deletions(-) > > diff --git a/drivers/char/random.c b/drivers/char/random.c > index b86eae9..24d17b8 100644 > --- a/drivers/char/random.c > +++ b/drivers/char/random.c > @@ -437,6 +437,7 @@ struct entropy_store { > int entropy_count; > int entropy_total; > unsigned int initialized:1; > + bool last_data_init; > __u8 last_data[EXTRACT_SIZE]; > }; > > @@ -967,6 +968,15 @@ static ssize_t extract_entropy(struct entropy_store *r, void *buf, > if (fips_enabled) { > unsigned long flags; > > + /* prime last_data value if need be, per fips 140-2 */ > + if (!r->last_data_init) { > + spin_lock_irqsave(&r->lock, flags); > + memcpy(r->last_data, tmp, EXTRACT_SIZE); > + r->last_data_init = true; > + spin_unlock_irqrestore(&r->lock, flags); > + continue; Continue? Is that left over from earlier work? Or did you have some other purpose in mind for it? Also, not that its in a hot path or anything, but it might be nice to consolodate this code such that you only lock and unlock r->flags once instead of twice here. Best Neil > + } > + > spin_lock_irqsave(&r->lock, flags); > if (!memcmp(tmp, r->last_data, EXTRACT_SIZE)) > panic("Hardware RNG duplicated output!\n"); > @@ -1086,6 +1096,7 @@ static void init_std_data(struct entropy_store *r) > > r->entropy_count = 0; > r->entropy_total = 0; > + r->last_data_init = false; > mix_pool_bytes(r, &now, sizeof(now), NULL); > for (i = r->poolinfo->POOLBYTES; i > 0; i -= sizeof(rv)) { > if (!arch_get_random_long(&rv)) > -- > 1.7.1 > >