title: Perl, LWP "certificate verify failed" with paypal.com
body: <p>Not 100% sure this is a Perl issue, but it seems to be. I have an IPN script that connects with PayPal to verify transactions. It was working fine until yesterday, when I installed LWP::Protocol::https. Since then, it's been failing with the error:</p>
  
  <pre><code>Can't connect to www.paypal.com:443 (certificate verify failed)
  
  LWP::Protocol::https::Socket: SSL connect attempt failed error:14090086:SSL routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed at /usr/local/share/perl5/LWP/Protocol/http.pm line 47.
  </code></pre>
  
  <p>Running <code>GET https://www.paypal.com</code> from bash (which uses LWP) yields the same error message. OTOH, running <code>GET https://www.gmail.com</code> is successful. Running <code>openssl s_client -host paypal.com -port 443</code> returns (among other things) <code>Verify return code: 0 (ok)</code>. <code>curl "https://www.paypal.com/cgi-bin/webscr?cmd=_notify-validate"</code> successfully receives a response from PayPal. So it does seem to be Perl-specific.</p>
  
  <p>Module versions:</p>
  
  <pre><code>LWP 6.13
  LWP::Protocol::https 6.06
  IO::Socket::SSL 2.015
  Mozilla::CA 20141217 (note: I've tried the script both using Mozilla::CA and without it... results have been the same)
  </code></pre>
  
  <p>Please let me know if there are other relevant modules. Perl version is 5.10.1. Server OS is RHEL 6.</p>