Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sun, 18 Aug 2002 02:44:49 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sun, 18 Aug 2002 02:44:49 -0400 Received: from waste.org ([209.173.204.2]:30696 "EHLO waste.org") by vger.kernel.org with ESMTP id ; Sun, 18 Aug 2002 02:44:48 -0400 Date: Sun, 18 Aug 2002 01:48:46 -0500 From: Oliver Xymoron To: Robert Love Cc: Linus Torvalds , linux-kernel Subject: Re: [PATCH] (0/4) Entropy accounting fixes Message-ID: <20020818064846.GQ21643@waste.org> References: <1029652262.898.12.camel@phantasy> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1029652262.898.12.camel@phantasy> User-Agent: Mutt/1.3.28i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2864 Lines: 88 On Sun, Aug 18, 2002 at 02:31:02AM -0400, Robert Love wrote: > On Sun, 2002-08-18 at 00:01, Linus Torvalds wrote: > > > So I think that if we just made the code be much less trusting (say, > > consider the TSC information per interrupt to give only a single bit of > > entropy, for example), and coupled that with making network devices always > > be considered sources of entropy, we'd have a reasonable balance. > > I think that sounds good. > > I have a patch which I can send - it needs to be rediffed I suspect - > that has each network device feed the entropy pool. (Actually, it > creates a new flag, SA_NET_RANDOM, that defines to SA_SAMPLE_RANDOM or 0 > depending on a configure setting. If you want it unconditional, that is > just as easy though). I think I have a compromise that'll make everyone happy here. I've added a tunable called trust_pct in /proc/sys/kernel/random. Set it to 100% and untrusted sources will always add a bit of entropy. Defaults to zero, which should be fine for everyone who's got a head. Then we can add SA_SAMPLE_RANDOM for network devices unconditionally. Untested, applies on top of my previous patches: diff -ur a/drivers/char/random.c b/drivers/char/random.c --- a/drivers/char/random.c 2002-08-17 20:54:02.000000000 -0500 +++ b/drivers/char/random.c 2002-08-18 01:38:58.000000000 -0500 @@ -724,6 +724,7 @@ */ static int benford[16]={0,0,0,1,2,3,4,5,5,6,7,7,8,9,9,10}; static int last_ctxt=0; +static int trust_break=50, trust_pct=0, trust_min=0, trust_max=100; void add_timing_entropy(void *src, unsigned datum) { @@ -764,6 +765,18 @@ delta>>=es->shift; bits=benford[int_log2_16bits(delta & 0xffff)]; } + + /* Throw in an untrusted bit as entropy trust_pct% of the time */ + if(trust_pct && !bits) + { + trust_break+=trust_pct; + if(trust_break>100) + { + bits=1; + trust_break-=100; + } + } + batch_entropy_store(datum^time, bits); } @@ -1779,6 +1792,10 @@ {RANDOM_UUID, "uuid", NULL, 16, 0444, NULL, &proc_do_uuid, &uuid_strategy}, + {RANDOM_TRUST_PCT, "trust_pct", + &trust_pct, sizeof(int), 0644, NULL, + &proc_dointvec_minmax, &sysctl_intvec, 0, + &trust_min, &trust_max}, {0} }; diff -ur a/include/linux/sysctl.h b/include/linux/sysctl.h --- a/include/linux/sysctl.h 2002-08-17 00:30:00.000000000 -0500 +++ b/include/linux/sysctl.h 2002-08-18 01:37:54.000000000 -0500 @@ -182,7 +182,8 @@ RANDOM_READ_THRESH=3, RANDOM_WRITE_THRESH=4, RANDOM_BOOT_ID=5, - RANDOM_UUID=6 + RANDOM_UUID=6, + RANDOM_TRUST_PCT=7 }; /* /proc/sys/bus/isa */ -- "Love the dolphins," she advised him. "Write by W.A.S.T.E.." - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/