Apache not Forwarding Client x509 Certificate to Tomcat via mod_proxy
Solution 1:
Apache is generating a brand new SSL session for the connection to the backend tomcat server, so the client certificate data isn't passed; the system with the cert isn't the client anymore.
If you're ok with an unencrypted connection between Apache and the Tomcat device, then using an AJP proxy connection (ProxyPass / ajp://x.x.x.x:8009/) instead of SSL, and adding an SSLOptions +ExportCertData directive in Apache, should pass the certificate data to Tomcat. There more info on passing certificate information here.