The PHP package bundled with Apple's Server.app uses SecureTransport, not OpenSSL. This causes multiple errors on Mac OS X. Is there planned support for SecureTransport?
Would be great to support this, and a Pull Request is welcome/wanted!
Note that easiest way to solve this is to install openSSL on your PHP by following these instructions http://stackoverflow.com/questions/26461966/osx-10-10-curl-post-to-https-url-gives-sslread-error
While it's not difficult to do this if you're relying on your own LAMP stack (MacPorts, Homebrew, MAMP, that Swiss guy who used to offer a pre-compiled solution, roll your own etc.), for those of us using Apple's Server.app and bundled Apache, this is another story.
Maybe it would be a good idea to offer some user-facing message about SecureTransport? As of the current version, install works but there are a lot of odd errors that pop up during upgrade.
Errors reported in the post https://forum.piwik.org/t/curl-exec-ssl-invalid-ca-certificate-1-offset-0-in-bundle/22561/5
Does the problem also occur when clicking "Check for updates" link in the box in the Admin area? (wondering if api.piwik.org still can be connected via securetransport and onlyp plugins.piwik.org would be affected)
I just upgraded successfully to 3.0.4. Like the upgrade to 3.0, 1, 2, 3, I got several SSL errors during the upgrade but despite saying "Upgrade failed" it worked fine. Here is what I see in my Admin panel: