A previous question, What is the use of cross signing certificates in X.509? described cross-signed certificates well.
I have a situation where the clients trust CA1 xor CA2, and both need to reach a single service. Logically, this means I need two end-entity certificates for the same hostname. From a single SSL key, I generated a single CSR and submitted to both CAs, and gotten the two separate end-entity certificates.
I configured Apache to serve both certificates together and all relevant intermediates in the chain.
What's gotten me stumped is the ability to get Apache mod_ssl crashes hard with
[Tue Nov 25 15:28:35 2014] [error] Init: Multiple RSA server certificates not allowed'
s_server reads multiple
-dcert arguments, takes the first RSA certificate in the last argument.
Using GnuTLS either via mod_gnutls or directly, either takes just the last certificate or claims
The provided X.509 certificate list is not sorted (in subject to issuer order)
I think, reading RFC4158, what I'm trying to do should be valid. Where have I gone wrong? Why does cross-signing only seem to be valid among intermediate and root certificates?
There is no way ahead of time to differentiate between the clients, so I can't cheat and run different vhosts on different IPs (the clients share DNS). I don't have control over getting both CAs into the clients either. The only working work-around I have so far is to push each group of clients to a unique hostname out-of-band.