> Date: Mon, 11 May 2020 12:42:13 -0700 (PDT) > From: Paul Goyette <p...@whooppee.com> > > Why can't we allow the user to configure/enable estimation on a > per-source basis? The default can certainly be "disabled", but > why not override? Just like any other super-user thing, there's > no reason not to enable shoot-my-random-foot mode.
You can shoot yourself in the foot with wild abandon by doing dd if=/dev/urandom of=/dev/random The `estimation' -- as in, feeding samples through an extremely dumb statistical model that bears no relation whatsoever to the physical process that produced them, and deciding based on that how much entropy must be in that physical process -- is no longer in the kernel at all, because it is not merely a foot-gun; it is total nonsense. Having it around at all is -- and always has been -- essentially dishonest. When each driver feeds a sample in, it specifies a number which represents a reasonable lower bound on the number of bits of entropy in the process that generated the sample; usually this number is either zero, or determined by reading the manufacturer's data sheet and/or studying the physical device that the driver handles. There's no way for the operator to override the number that is passed alongside every sample at run-time because that would add substantial complexity to an already complex subsystem -- you would, effectively, be changing the driver logic at run-time -- for essentially zero benefit. It would be comparable to inventing a general mechanism by which to make every DELAY issued by a driver configurable at run-time, even though the delays are documented in the data sheet. (If appropriate for a particular driver, that driver could have a sysctl knob to adjust it, of course.)
