#
# Author:: Daniel DeLeo (<dan@chef.io>)
# Copyright:: Copyright (c) Chef Software Inc.
# License:: Apache License, Version 2.0
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

require_relative "../knife"

class Chef
  class Knife
    class SslFetch < Chef::Knife

      deps do
        require_relative "../config"
        require "pp" unless defined?(PP)
        require "socket" unless defined?(Socket)
        require "uri" unless defined?(URI)
        require "openssl" unless defined?(OpenSSL)
        require_relative "../mixin/proxified_socket"
        include Chef::Mixin::ProxifiedSocket
      end

      banner "knife ssl fetch [URL] (options)"

      def initialize(*args)
        super
        @uri = nil
      end

      def uri
        @uri ||= begin
          Chef::Log.trace("Checking SSL cert on #{given_uri}")
          URI.parse(given_uri)
        end
      end

      def given_uri
        (name_args[0] || Chef::Config.chef_server_url)
      end

      def host
        uri.host
      end

      def port
        uri.port
      end

      def validate_uri
        unless host && port
          invalid_uri!
        end
      rescue URI::Error
        invalid_uri!
      end

      def invalid_uri!
        ui.error("Given URI: `#{given_uri}' is invalid")
        show_usage
        exit 1
      end

      def remote_cert_chain
        tcp_connection = proxified_socket(host, port)
        shady_ssl_connection = OpenSSL::SSL::SSLSocket.new(tcp_connection, noverify_peer_ssl_context)
        shady_ssl_connection.connect
        shady_ssl_connection.peer_cert_chain
      end

      def noverify_peer_ssl_context
        @noverify_peer_ssl_context ||= begin
          noverify_peer_context = OpenSSL::SSL::SSLContext.new
          noverify_peer_context.verify_mode = OpenSSL::SSL::VERIFY_NONE
          noverify_peer_context
        end
      end

      def cn_of(certificate)
        subject = certificate.subject
        if cn_field_tuple = subject.to_a.find { |field| field[0] == "CN" }
          cn_field_tuple[1]
        else
          nil
        end
      end

      # Convert the CN of a certificate into something that will work well as a
      # filename. To do so, all `*` characters are converted to the string
      # "wildcard" and then all characters other than alphanumeric and hyphen
      # characters are converted to underscores.
      # NOTE: There is some confusion about what the CN will contain when
      # using internationalized domain names. RFC 6125 mandates that the ascii
      # representation be used, but it is not clear whether this is followed in
      # practice.
      # https://tools.ietf.org/html/rfc6125#section-6.4.2
      def normalize_cn(cn)
        cn.gsub("*", "wildcard").gsub(/[^[:alnum:]\-]/, "_")
      end

      def configuration
        Chef::Config
      end

      def trusted_certs_dir
        configuration.trusted_certs_dir
      end

      def write_cert(cert)
        FileUtils.mkdir_p(trusted_certs_dir)
        cn = cn_of(cert)
        filename = cn.nil? ? "#{host}_#{Time.new.to_i}" : normalize_cn(cn)
        full_path = File.join(trusted_certs_dir, "#{filename}.crt")
        ui.msg("Adding certificate for #{filename} in #{full_path}")
        File.open(full_path, File::CREAT | File::TRUNC | File::RDWR, 0644) do |f|
          f.print(cert.to_s)
        end
      end

      def run
        validate_uri
        ui.warn(<<~TRUST_TRUST)
          Certificates from #{host} will be fetched and placed in your trusted_cert
          directory (#{trusted_certs_dir}).

          Knife has no means to verify these are the correct certificates. You should
          verify the authenticity of these certificates after downloading.

        TRUST_TRUST
        remote_cert_chain.each do |cert|
          write_cert(cert)
        end
      rescue OpenSSL::SSL::SSLError => e
        # 'unknown protocol' usually means you tried to connect to a non-ssl
        # service. We handle that specially here, any other error we let bubble
        # up (probably a bug of some sort).
        raise unless e.message.include?("unknown protocol")

        ui.error("The service at the given URI (#{uri}) does not accept SSL connections")

        if uri.scheme == "http"
          https_uri = uri.to_s.sub(/^http/, "https")
          ui.error("Perhaps you meant to connect to '#{https_uri}'?")
        end
        exit 1
      end

    end
  end
end