svn commit: r239598 - head/etc/rc.d

[Doug Barton]

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.
> 
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