[TLS] ServerCertificate and intermediate CA certs

[Martin Rex <Martin.Rex@xxxxxxx>]

I just received a request for help with an SSL interopability problem
that a colleague encountered.  He observed that the server certificate
validation failed, reporting an incomplete certificate chain when
he tried to connect to an (apparently Apache) Web-Server.

He had configured the "Verisign Class 3 Public Primary CA" as
trusted, and the Server only sends the Server cert, but fails to
include the intermediate CA cert (VeriSign Class 3 Secure Server CA).

In my reading of SSLv3->TLSv1.1 that is an obvious and serious
violation of the protocol spec.  Omitting the self-signed root certificate
and the end of the servers certificate chain from the ServerCertificate
message is OK/allowed, but omitting intermediate CAs is definitely
NOT allowed by the spec.

IMHO, the SSL/TLS stack ought to enforce that the certificate chain
in the ServerCertificate message is correct, i.e. omits at most
a self-signed root certificate, but NEVER any intermediate CAs
and not even start an SSL handshake if that prerequisite can
not be determined.

Does anyone, by chance, know how/whether that problem can be
fixed by configuration in Apache and how (i.e. how to configure
Apache so that OpenSSL sends out a correct certification path 
in the ServerCertificate message, including all necessary intermediate
CA certificates)?


-Martin


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