public String getClientCertificateHeader() throws GuacamoleException {
        return environment.getProperty(SSL_AUTH_CLIENT_CERTIFICATE_HEADER, DEFAULT_CLIENT_CERTIFICATE_HEADER);
    }
Returns the name of the header to use to retrieve the URL-encoded client
certificate from an HTTP request received from an SSL termination
service providing SSL/TLS client authentication.

@return
    The name of the header to use to retrieve the URL-encoded client
    certificate from an HTTP request received from an SSL termination
    service providing SSL/TLS client authentication.

@throws GuacamoleException
    If the property for configuring the client certificate header cannot
    be parsed.
extensions/guacamole-auth-sso/modules/guacamole-auth-sso-ssl/src/main/java/org/apache/guacamole/auth/ssl/conf/ConfigurationService.java