Legitimate access with certificate auth or basic auth

Server NGINX
1

Hi

Is there a way to legitimate access to a location (in my case an entire
vhost) with certificate auth and - if no certificate is sent - a
fallback to basic auth?

On Apache (from where I’m currently migrating) this is done with
“FakeBasicAuth” as follows:

SSLVerifyClient require
SSLVerifyDepth 3
SSLCADNRequestFile /path/to/certs.pem
SSLOptions +FakeBasicAuth

Allow from all AuthName 'MySite' AuthType Basic AuthUserFile /path/to/htpasswd Require valid-user

Thanks for your hints!