SSLVerifyClient
SSLVerifyClient level
Default: 0
Server config, virtual host, directory, .htaccess
Available in Apache v 1.3, v2
This directive can be used in either a per-server or per-directory context. In the first case it controls the client authentication process when the connection is set up. In the second it forces a renegotiation after the HTTPS request is read but before the response is sent. The directive defines what you require of clients. Apache v1.3 used numbers; v2 uses keywords:
0 or 'none'
No certificate is required.
1 or 'optional'
The client may present a valid certificate.
2 or 'require'
The client must present a valid certificate.
3 or 'optional_no_ca'
The client may present a valid certificate, but not necessarily from a certification authority for which the server holds a certificate.
In practice, only levels 0 and
2 are useful.