HAProxy `SSL handshake failure` when proxing request from another server

Question

I'm trying to proxy HTTP requests from one server to another - both are running HAProxy.

I have the backend defined from the originating server as:

    backend site100
        option redispatch
        option forwardfor 
        server server1 123.123.123.123 maxconn 32

However when doing a request the response is a 502 Bad Gateway and in in the debug logs of the destination server I'm just getting a SSL handshake failure:

Feb 24 10:43:11 XenonKiloCranberry haproxy[5749]: 116.203.70.99:36908 [24/Feb/2020:10:43:11.960] https-in/1: SSL handshake failure

Is this possibly due to the SSL certificate being a SAN / SNI? Perhaps haproxy does not support this? How can I resolve this?

Answer 1

Solved it with:

    backend site100
        option redispatch
        option forwardfor 
        option tcplog
        option ssl-hello-chk
        server server1 123.123.123.123 maxconn 32 check ssl verify required ca-file /etc/ssl/certs/ca-certificates.crt

Seems it's due to the ssl verify required ca-file /etc/ssl/certs/ca-certificates.crt options