Does Nginx allow to specify multiple root certificates for client certificate verification?

[ffeldhaus]

For a project as part of the European Grid Infrastructure (EGI) we need
SSL client certificate verification for a service running on nginx. As
there are several root CAs allowed within EGI, we need nginx to check
them all during client certificate validation. In the documentation of
nginx I could only find the parameter ssl_client_certificate which
allows to specify just one file containing a root certificate.

Is there a way to specify more than one root CA for client certificate
verification in nginx or do I have to use Apache for this?

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,229129,229129#msg-229129