Date: Tue, 04 Sep 2012 21:41:20 -0700 From: Doug Barton <dougb@FreeBSD.org> To: RW <rwmaillists@googlemail.com> Cc: freebsd-security@freebsd.org Subject: Re: svn commit: r239598 - head/etc/rc.d Message-ID: <5046D7F0.1000601@FreeBSD.org> In-Reply-To: <20120905021248.5a17ace9@gumby.homeunix.com> References: <201208222337.q7MNbORo017642@svn.freebsd.org> <5043E449.8050005@FreeBSD.org> <20120904220126.GA85339@dragon.NUXI.org> <50468326.8070009@FreeBSD.org> <20120905021248.5a17ace9@gumby.homeunix.com>
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Can you point out where in the source you're seeing these things? Thanks, Doug On 09/04/2012 06:12 PM, RW wrote: > On Tue, 04 Sep 2012 15:39:34 -0700 > Doug Barton wrote: > >> and given what Yarrow does to >> obfuscate the internal entropy state I'm not confident that hashing >> the input is either necessary or desirable. > > All of the low-grade entropy should go through sha256. > > Anything written into /dev/random is passed by random_yarrow_write() 16 > Bytes at time into random_harvest_internal() which copies it into a > buffer and queues it up. If there are 256 buffers queued > random_harvest_internal() simply returns without doing anything. > > The yarrow kernel thread moves all of the entropy queues into a local > queue, processes that queue and then pauses for 100ms and loops. That > means that each time around the loop only a maximum of 4096 bytes can > be processed. Anything after that is discarded. > > It seems very likely that /entropy is completely discarded most of the > time, which means that the first 4096 bytes of " ps -fauxww ; sysctl -a" > is the only entropy that makes it through to yarrow, and that's > practically nothing. > > On a sufficiently fast system the entropy buffers may still be saturated > when rc.d/random runs, so in theory they could be lost too. And embedded > doesn't necessarily imply slow. > > I'm not overly concerned about this because anything that doesn't > generate enough entropy naturally, increasingly tends to have a hardware > generator, but it's easy to fix it, so it should be fixed. > > _______________________________________________ > freebsd-security@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-security > To unsubscribe, send any mail to "freebsd-security-unsubscribe@freebsd.org" >
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