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. -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
