Many server systems are seriously lacking in sources of entropy, as we typically only feed the entropy pool by way of input layer events, a few NIC driver interrupts and disk activity. A non-busy server can easily become entropy-starved. We can mitigate this somewhat by periodically mixing in entropy data based on the delta between multiple high-resolution clocksource reads, per: https://www.osadl.org/Analysis-of-inherent-randomness-of-the-L.rtlws11-developers-okech.0.html Additionally, NIST already approves of similar implementations, so this should be usable in high-securtiy deployments requiring a fair chunk of available entropy data for frequent use of /dev/random. http://csrc.nist.gov/groups/STM/cmvp/documents/140-1/140sp/140sp750.pdf (section 6.1 mentions a clock-based seed source). Yes, thus far, I've only bothered with x86-based clocksources, since that is what I can test most easily. If this patch series isn't deemed totally insane, adding support for other clocksources should be trivial. Also note that unless you explicitly build and load the clock-entropy driver, there should be little or no change whatsoever to the way anything behaves right now, its purely opt-in. There's probably room for some improvement here, and I'm kind of outside my comfort area, but hey, it seems to work pretty well here in my own testing, so here it is... Jarod Wilson (5): random: add new clocksource entropy interface clocksource: add support for entropy-generation function hpet: wire up entropy generation function tsc: wire up entropy generation function misc: add clocksource-based entropy generation driver arch/x86/kernel/hpet.c | 18 ++++++ arch/x86/kernel/tsc.c | 18 ++++++ drivers/char/random.c | 28 ++++++++++ drivers/misc/Kconfig | 14 +++++ drivers/misc/Makefile | 1 + drivers/misc/clock-entropy.c | 122 ++++++++++++++++++++++++++++++++++++++++++ include/linux/clocksource.h | 6 ++ include/linux/random.h | 1 + kernel/time/clocksource.c | 33 +++++++++++ 9 files changed, 241 insertions(+), 0 deletions(-) create mode 100644 drivers/misc/clock-entropy.c CC: Matt Mackall <mpm@xxxxxxxxxxx> CC: "Venkatesh Pallipadi (Venki)" <venki@xxxxxxxxxx> CC: Thomas Gleixner <tglx@xxxxxxxxxxxxx> CC: Ingo Molnar <mingo@xxxxxxx> CC: John Stultz <johnstul@xxxxxxxxxx> CC: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> CC: "David S. Miller" <davem@xxxxxxxxxxxxx> -- 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
