reverse proxy client certificate authentication

Hi,

I'm looking for a reverse proxy that is able to forward client certificates to the backend. Is nginx capable of doing this?

My situation:

Client with personalized Certificate -> reverse proxy -> Backend (IIS) with Client Certificate Authentication

I know that I can forward the client certificate in the Header via

proxy_set_header SSL_CLIENT_CERT $ssl_client_cert;

but this is not sufficient for Microsoft IIS. Seems like IIS is expecting the certificate not in the Header or something else is missing.

Any help is appreciated.