Performance Issue With OpenSSL 1.1.1c

[Steffen Nurpmeso]

Jakob Bohm via openssl-users wrote in <23f8b94d-0078-af3c-b46a-929b9d005\
4ea at wisemo.com>:
 |On 28/05/2019 23:48, Steffen Nurpmeso wrote:
 |> Jay Foster wrote in <84571f12-68b3-f7ee-7896-c891a2e253e7 at roadrunner.com\
 |> >:
 |>|On 5/28/2019 10:39 AM, Jay Foster wrote:
 |>|> I built OpenSSL 1.1.1c from the recent release, but have noticed what
 |>|> seems like a significant performance drop compared with 1.1.1b.  I
 |>|> notice this when starting lighttpd.  With 1.1.1b, lighttpd starts in a
 |>|> few seconds, but with 1.1.1c, it takes several minutes.
 ...
 |>|I think I have tracked down the change in 1.1.1c that is causing this.
 |>|It is the addition of the DEVRANDOM_WAIT functionality for linux in
 |>|e_os.h and crypto/rand/rand_unix.c.  lighttpd (libcrypto) is waiting in
 |>|a select() call on /dev/random.  After this eventually wakes up, it then
 |>|reads from /dev/urandom.  OpenSSL 1.1.1b did not do this, but instead
 |>|just read from /dev/urandom.  Is there more information about this
 |>|change (i.e., a rationale)?  I did not see anything in the CHANGES file
 |>|about it.
 ...
 |> I do not know why lighttpd ends up on /dev/random for you, but in
 |> my opinion the Linux random stuff is both sophisticated and sucks.

P.S.: i have now looked at the OpenSSL code and understand what
you have said.  It indeed selects on /dev/random.

 |> The latter because (it seems that many) people end up using
 |> haveged or similar to pimp up their entropy artificially, whereas
 |> on the other side the initial OS seeding is no longer truly
 |> supported.  Writing some seed to /dev/urandom does not bring any
 |> entropy to the "real" pool.

 |Something equivalent to your program (but not storing a bitcount field)
 |used to be standard in Linux boot scripts before systemd.  But it
 |typically used the old method of just writing the saved random bits
 |into /dev/{u,}random .

Oh, still, for example AlpineLinux did (and still does i think,
using a script originating from Gentoo aka OpenRC) save a kilobyte
of /dev/urandom storage, to restore it upon next boot.  But it
does not feed the pool which feds /dev/random, it does not count
against /proc/sys/kernel/random/entropy_avail.

Even that i can understand a little bit (physical access would
reveal data stored in the entropy file), even though the entropy
is not used but passed through state machines, which could be
furtherly randomized when fed back in, like also dependent on the
host hardware environment interrupts which happen and depend on
actual devices i'd say, and while doing so.

But you loose all the entropy that the machine collected during
its last uptime, so you solely depend on some CPU features and the
noise that system startup produces to create a startup entropy.
After running in the problem and looking around i realized that
many people seem to run the haveged daemon (there is also a kernel
module which does something like this, but using it did not help
me out), which applies some maths, and it is mystic as it can
produce thousands of random bits in less than a second!

Even on my brand new laptop, which (stepped a decade of hardware
development for me and) has a 8th generation i5, i see hangs of
several seconds (iirc) without the little helper i attached in the
last message.  With it i have a (SysV init/BSD rc script aka
CRUX-Linux) boot time of two seconds, which is so horny i have to
write it down.

 |This makes me very surprised that they removed such a widely used
 |interface, can you point out when that was removed from the Linux
 |kernel?

Hm, ok, what they have actually removed was the RNDGETPOOL
ioctl(2) (according to random(4)).  Then my claim regarding
deprecation was misleaded and wrong.

Nonetheless it has to be said that today an administrator does not
have, that is, i have no idea whether systemd provides something
to overcome this, the possibility to simply feed in good entropy
via a shell script, unless i am mistaken.

--steffen
|
|Der Kragenbaer,                The moon bear,
|der holt sich munter           he cheerfully and one by one
|einen nach dem anderen runter  wa.ks himself off
|(By Robert Gernhardt)