Vagrant plugin install complains about SSL ?

There is a long standing issue in Ruby where the net/http library by default does not check the validity of an SSL certificate during a TLS handshake. Rather than deal with the underlying problem (a missing certificate authority, a self-signed certificate, etc.) one tends to see bad hacks everywhere. This can lead to problems down the road. From what I can see the OpenSSL library that Rails Installer delivers has no certificate authorities defined. So, let’s go fetch some from the curl website. And since t

Source : Download a cacert.pem for RailsInstaller · GitHub
You should have a look to that link. Basically it will help you to get a righ certificate to avoid SSL error.