Random weirdness with OpenSSL on Ubuntu 18.04.5

 I hit an interesting problem today, whilst trying to create a public/private key pair: -

openssl req -subj '/C=GB/O=IBM/CN=david_hay.uk.ibm.com' -new -newkey rsa:4096 -x509 -sha256 -days 365 -nodes -out ~/nginx/nginx.crt -keyout ~/nginx/nginx.key

Can't load /root/.rnd into RNG

4396464178976:error:2406F079:random number generator:RAND_load_file:Cannot open file:../crypto/rand/randfile.c:88:Filename=/root/.rnd

Generating a RSA private key

........................++++

........................++++

writing new private key to '/root/nginx/nginx.key'

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on an Ubuntu box: -

lsb_release -a

No LSB modules are available.

Distributor ID: Ubuntu

Description: Ubuntu 18.04.5 LTS

Release: 18.04

Codename: bionic

( actually it's an Ubuntu container running on an IBM Z box, via the Secure Service Container technology,  but that's not the point of the story here ! )

I'd not seen that before ... but I noticed that the missing file was .rnd in my user's home directory - /root.

Taking a punt, I tried creating that file: -

touch ~/.rnd

and re-ran the openssl command: -

openssl req -subj '/C=GB/O=IBM/CN=david_hay.uk.ibm.com' -new -newkey rsa:4096 -x509 -sha256 -days 365 -nodes -out ~/nginx/nginx.crt -keyout ~/nginx/nginx.key

Generating a RSA private key

....................................................................++++

..++++

writing new private key to '/root/nginx/nginx.key'

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I'd previously run the same command on a different Ubuntu container: -

lsb_release -a

No LSB modules are available.

Distributor ID: Ubuntu

Description: Ubuntu 18.04 LTS

Release: 18.04

Codename: bionic

without similar issues.

Both are running the same version of openssl namely: -

openssl version

OpenSSL 1.1.1  11 Sep 2018

Using this as a source: -

Can't load random.rnd into RNG with OpenSSL 1.1.1b 26 Feb 2019 #7

I used openssl to generate the .rnd file: -

openssl rand -out /root/.rnd -hex 256

and validated that I could still generate the key pair: -

openssl req -subj '/C=GB/O=IBM/CN=david_hay.uk.ibm.com' -new -newkey rsa:4096 -x509 -sha256 -days 365 -nodes -out ~/nginx/nginx.crt -keyout ~/nginx/nginx.key

Generating a RSA private key

.....................................................................++++

..................++++

writing new private key to '/root/nginx/nginx.key'

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Weird !