zookeeper ssl alert “alert bad certificate”

Hi there!

<https://serverfault.com/posts/1074579/timeline>

I am using Kafka (version 2.3.0) and Zookeeper (version 3.5.5-3) - the
stable version is 3.6.3.

When I test the SSL of my Zookeeper using this command:

openssl s_client -showcerts -connect 127.0.0.1:2280 -CAfile
/certs/ca-chain.cert.pem

and I am getting this error:

140371409225024:error:14094412:SSL routines:ssl3_read_bytes:sslv3 alert bad
certificate:../ssl/record/rec_layer_s3.c:1543:SSL alert number 42

But if I will install Zookeeper version 3.5.7 and up and I can add this in
my zoo.cnf or zookeeper.properties:

ssl.clientAuth=want and I no longer see any SSL errors.

Any tips/suggestions on how to fix this SSL error without upgrading (I
don't want to update at the moment to avoid other conflicts like Kafka
Cruise Control and others).

Thanks in advance!

Best regards,

John Mark Causing