title: ldap_bind to secure LDAP server returns "Unknown CA"
body: <p>Attempting to configure a PHP app to securely authenticate against a remote LDAP server and am running into a wall.   ldap tools are installed and I'm able to connect to the remote LDAP server, but checking the error_log, I'm seeing</p>
  
  <pre><code>Unable to bind to server: Can't contact LDAP server
  </code></pre>
  
  <p>This is triggered by a call to <code>ldap_bind</code> in my application.  <code>ldap_connect</code> doesn't return errors.  I've verified that I can connect to the ldap server using: </p>
  
  <pre><code>openssl s_client -connect ldap.service.company.com:636
  
  SSL-Session:
  Protocol  : TLSv1.2
  Cipher    : AES256-SHA
  Session-ID: (snip)
  Session-ID-ctx: 
  Master-Key: (snip)
  Key-Arg   : None
  Krb5 Principal: None
  PSK identity: None
  PSK identity hint: None
  Start Time: 1389213908
  Timeout   : 300 (sec)
  Verify return code: 0 (ok)
  </code></pre>
  
  <p><code>tcpdump</code> and <code>wireshark</code> were utilized to monitor and analyze network traffic on an attempted LDAP authentication from my application. </p>
  
  <pre><code>tcpdump -s 1514 port 636 -w capture_file
  </code></pre>
  
  <p><code>wireshark</code> revealed a fatal error: </p>
  
  <pre><code>TLSv1   Alert (Level: Fatal, Description: Unknown CA)
  </code></pre>
  
  <p>Apache's ssl.conf config points to files with correct permissions, and no errors are shown when starting/restarting httpd.</p>
  
  <p>Help/pointers appreciated.  Let me know if I can supply more data.</p>