title: Apache httpd: How to trust specific client certificates?
body: <p>How can I configure the Apache httpd to trust specific client certificates?</p>
  
  <p>We need to restrict the access to a webservice to a specific (known) partner's servers.<br>
  We planned to use an CA-based solution for this (a trusted CA which would only sign trustworthy CSRs as we accepted them); however, our company's CA will not create Certificates for external companies.</p>
  
  <p>In order to establish the secured connection anyway, until the necessary PKI is ready, we wanted to configure specific client certificates as trusted on our Apache httpd proxy.</p>
  
  <p>But httpd does not accept connections by the clients, which are trying to connect by using the client certificate, which has been added to the CACertificateFile (concatenated x509 certificates encoded in Base64 and of DER format(PEM)), configured for the virtual host.</p>
  
  <p>The client certificate is in this case not a self-signed certificate.</p>