Messages in this thread | | | Date | Sun, 14 Aug 2016 18:11:14 +0000 | From | Jason Cooper <> | Subject | Re: [PATCH v2] RANDOM: ATH9K RNG delivers zero bits of entropy |
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Hey Ted,
On Wed, Aug 10, 2016 at 07:44:25PM -0400, Theodore Ts'o wrote: > On Tue, Aug 09, 2016 at 02:04:44PM +0000, Jason Cooper wrote: > > iiuc, Ted, you're saying using the hw_random framework would be > > disasterous because despite most drivers having a default quality of 0, > > rngd assumes 1 bit of entropy for every bit read? > > Sorry, what I was trying to say (but failed) was that bypassing the > hwrng framework and injecting entropy directly the entropy pool was > disatrous.
Ok, whew. :)
> > Thankfully, most hw_random drivers don't set the quality. So unless the > > user sets the default_quality param, it's zero. > > The fact that this is "most" and not "all" does scare me a little.
My recent grep showed that only virtio-rng set it to a non-zero value.
> As far as I'm concerned *all* hw_random drivers should set quality to > zero, since it should be up to the system administrator.
Agreed.
Gathering conversation about this from a few related threads, I have one concern. Apparently there is some confusion in userspace consumers of /dev/hwrng data as to the quality of it. Specifically, rngd (spotted by Stephan Mueller) appears to assume 1bit of entropy per 1 bit read. :-/
So, while moving ath9k-rng to the hwrng framework makes complete sense internally, it's not so good for existing userspace assumptions. I'd think that timeriomem-rng falls in this same category.
In light of this, do you think it's worth the effort (I'm volunteering) to create a subcategory of hwrng drivers that are 'environemntal' rngs? They can contribute to the kernel entropy pools, but not to /dev/hwrng.
thx,
Jason.
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