[systemd-devel] Why we need to read/save random seed?

[Cristian Rodríguez]

On Sun, Jun 14, 2015 at 1:43 PM, Greg KH <gregkh at linuxfoundation.org> wrote:
> On Sun, Jun 14, 2015 at 12:49:55PM -0300, Cristian Rodríguez wrote:
>>
>> El jun. 14, 2015 10:21, "cee1" <fykcee1 at gmail.com> escribió:
>> >
>> > Hi all,
>> >
>> > Why we need to read/save random seed? Can it be read from /dev/random each
>> time?
>>
>> Because the kernel is borked and still is needs to be fed of entropy at system
>> startup by user space. Please read the random man page.
>>
>> I agree we shouldn't have to do this at all..
>
> Really?  And how do you suggest we "fix" the kernel when the hardware
> itself doesn't provide us with a proper random number "seed" in the
> first place?  What do you suggest we do instead?

Las time I checked , it required this userspace help even when the
machine has rdrand/rdseed or when a virtual machine is fed from the
host using the virtio-rng driver.. (may take up to 60 seconds to
report
random: nonblocking pool is initialized) Any other possible solution
that I imagined involves either blocking and/or changes in the
behaviour visible to userspace and that is probably unacceptable
.
The random-seed tool also does not increment the entropy count (It
writes to /dev/random instead of using the ioctls) so the ultimate
result is still a system with very little entropy to go on, only
starting rngd or haveged *very* early in the boot sequence seem to
help.