require 'uri'
require 'digest/sha1'

module Pingpp
  module CertificateBlacklist

    BLACKLIST = {
      "api.pingxx.com" => [
      ]
    }

    # Preflight the SSL certificate presented by the backend. This isn't 100%
    # bulletproof, in that we're not actually validating the transport used to
    # communicate with Pingpp, merely that the first attempt to does not use a
    # revoked certificate.

    # Unfortunately the interface to OpenSSL doesn't make it easy to check the
    # certificate before sending potentially sensitive data on the wire. This
    # approach raises the bar for an attacker significantly.

    def self.check_ssl_cert(uri, ca_file)
      uri = URI.parse(uri)

      sock = TCPSocket.new(uri.host, uri.port)
      ctx = OpenSSL::SSL::SSLContext.new
      ctx.set_params(:verify_mode => OpenSSL::SSL::VERIFY_PEER,
                     :ca_file => ca_file)

      socket = OpenSSL::SSL::SSLSocket.new(sock, ctx)
      socket.connect

      certificate = socket.peer_cert.to_der
      fingerprint = Digest::SHA1.hexdigest(certificate)

      if blacklisted_certs = BLACKLIST[uri.host]
        if blacklisted_certs.include?(fingerprint)
          raise APIConnectionError.new(
            "Invalid server certificate. You tried to connect to a server that" +
            "has a revoked SSL certificate, which means we cannot securely send" +
            "data to that server. Please email support@pingxx.com if you need" +
            "help connecting to the correct API server."
          )
        end
      end

      socket.close

      return true
    end
  end
end