https://gist.github.com/fnichol/867550

win_fetch_cacerts.rb

require 'net/https'
require 'uri'

# create a path to the file "C:\RailsInstaller\cacert.pem"
cacert_file = File.join(%w{c: RailsInstaller cacert.pem})

uri = URI.parse("https://curl.haxx.se/ca/cacert.pem")
http = Net::HTTP.new(uri.host, uri.port)
http.use_ssl = true
http.verify_mode = OpenSSL::SSL::VERIFY_NONE
request = Net::HTTP::Get.new(uri.request_uri)

response = http.request(request)

if response.code == "200"
  open(cacert_file, "wb") { |file| file.write(response.body) }
  puts "\n\nA bundle of certificate authorities has been installed to"
  puts "C:\\RailsInstaller\\cacert.pem\n"
  puts "* Please set SSL_CERT_FILE in your current command prompt session with:"
  puts "     set SSL_CERT_FILE=C:\\RailsInstaller\\cacert.pem"
  puts "* To make this a permanent setting, add it to Environment Variables"
  puts "  under Control Panel -> Advanced -> Environment Variables"
else
  abort "\n\n>>>> A cacert.pem bundle could not be downloaded."
end