server config, <Global>, <VirtualHost>
1.2.7rc1 and later
The TLSCertificateChainFile directive sets the optional all-in-one file where you can assemble the certificates of Certification Authorities (CA) which form the certificate chain of the server certificate. This starts with the issuing CA certificate of the server certificate and can range up to the root CA certificate. Such a file is simply the concatenation of the various PEM-encoded CA Certificate files in certificate chain order. This server certificate chain is sent to the client, in addition to the server's certificate.
If TLSCertificateChainFile is not used, and TLSCACertificatePath is used, the certificate chain is built from the certificates in that path. TLSCertificateChainFile should be used as an alternative to TLSCACertificatePath for explicitly constructing the server certificate chain. It is especially useful to avoid conflicts with CA certificates when using client authentication. For although placing a CA certificate of the server certificate chain into the TLSCACertificatePath has the same effect for the certificate chain construction, it has the side-effect that client certificates issued by this same CA certificate are also accepted on client authentication. This is usually not what one expects.
Be careful: providing the certificate chain works only if you are using a single (either RSA or DSA) based server certificate. If you are using a coupled RSA+DSA certificate pair, this will work only if actually both certificates use the same certificate chain. Otherwise, clients will become confused.