On 07/17/2014 03:08 PM, Theodore Ts'o wrote: > > There was another complaint more recently, that wasn't related to > nordrand. And I was rather disturbed that in > add_interrupt_randomness() 97% of the entropy was coming from RDSEED. > I'm willing to have some of the entropy come from RDSEED by default, > but 97% seems to really way too much. > OK, the that formula was Linus' suggestion. > And the emergency refill code in random_read() was extremely > problematic. First of all, we're dropping 512 bytes on the stack, > which is kind of bad, but hopefully all of the code paths which call > random_read() won't have a terribly deep stack. 512 bytes is fine here (1K would possibly not have been.) > Secondly, even after the emergency refill, we block anyway. Not unless we don't get any data back. For a nonzero return we loop back to extract_entropy_user(). > Remember, regardless of whether or not you believe (as a former head > of NSA's technology directorate recently claimed) that the DUAL-EC p > and q were generated using NSA's standard high-quality HW RNG system > which they use to generate all of their crypto variables, or (as the > NIST advisory panel has recently concluded) that it was highly likely > that DUAL-EC was backdoored, it's the optics that matter, because > those of us without top-drawer SI security clearances can't prove > things one way or another. Dual-EC was also heavily criticized by the civilian cryptographic community since at least 2006. > And when 99.95% of the entropy when reading large quantities of keying > material from /dev/random is coming from RDSEED, that just has > terrible, terrible optics.... I just want to make sure we don't negatively impact the real security of users because of "optics". We already have a lot of problems with people extracting long-living keys from /dev/urandom because /dev/random is too slow. I have no objection to the khwrngd route -- in fact, as you know, I have been heavily encouraging the development of khwrngd with exactly this in mind -- but it is just an issue of timing. -hpa -- 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
