On Sun, May 03, 2015 at 05:33:00PM +0200, Stephan Mueller wrote: > The patch set adds an in-kernel /dev/random equivalent that was discussed with > Ted Ts'o last July -- see [2] and [3]. A test module for testing the > asynchronous operation of the in-kernel /dev/random is given with the code > below. > > Ted: shall we really create and maintain a new entropy pool (the kernel_pool), > or should the in-kernel /dev/random logic draw directly from the input_pool? > In other words, shall we drop the first patch and update the 2nd patch to > use input_pool? Also, I would not recommend using the blocking_pool as this > would mix kernel and user land operation. I'd drop the 3rd pool, and just simply block until the non-blocking pool has been initialized. That's now considered the best practice for userspace programs, which is to use getrandom(2), which by default will block until the nonblocking pool has been initialized with an estimated 128 bits of entropy, and after that point, all of the kernel users should be quite satisfied with cryptographic entropy. Certainly from the perspective of the perspective of a NIST evaluator for a DRBG, using if they're happy using jitterentropy as a noise source, they should be quite happy using the non-blocking pool as a noise source, so long as it has been properly initialized. As far as the concern of user space being able to block a kernel user "indefinitely", in practice I really don't think that's going to be an issue as far as boot-time initialization is concerned. In practice the urandom pool gets 128 bits of entropy *very* quickly, as in, before the boot process is finished. [ 1.368585] random: systemd-udevd urandom read with 21 bits of entropy available [ 2.870497] EXT4-fs (sda3): mounted filesystem with ordered data mode. Opts: (null) [ 3.217209] EXT4-fs (sda3): re-mounted. Opts: errors=remount-ro [ 3.497191] random: nonblocking pool is initialized [ 7.705482] EXT4-fs (dm-9): mounted filesystem with ordered data mode. Opts: (null) [ 8.007435] EXT4-fs (dm-10): mounted filesystem with ordered data mode. Opts: (null) [ 8.165517] EXT4-fs (dm-0): mounted filesystem with ordered data mode. Opts: (null) (And if the attacker is able to inject arbitrary programs running during the init sequence, they are almost certainly running as root, and you've got other problems.) - Ted -- 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
