Using Yubikey/PKCS11 for Upstream Client Certificates

[erik]

Specifically, I'd like to know if the proxy_ssl_certificate and
proxy_ssl_certificate_key directives can support RFC-7512 PKCS#11 URIs, or
whether they're hardwired to be just local file paths.

With my private key in hardware, I'm looking for the ability to point nginx
to something like:

location /upstream {
    proxy_pass                https://backend.example.com;
    proxy_ssl_certificate     /etc/nginx/client.pem;
    proxy_ssl_certificate_key
'pkcs11:type=private;token=some_token;object=username%40example.org';
}

Cheers,
Erik van Zijst

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,286922,286930#msg-286930