server config, <Global>, <VirtualHost>
1.2.7rc1 and later
The TLSVerifyClient directive configures how mod_tls handles certificates presented by clients. If off, the module will accept the certificate and establish an SSL/TLS session, but will not verify the certificate. If on, the module will verify a client's certificate and, furthermore, will fail all SSL handshake attempts unless the client presents a certificate when the server requests one. Note that the server can be configured to not request a client certificate via the TLSOptions directive's "NoCertRequest" parameter.