RMUnify logout

controller.rb

class SometController
  
  def logout
    authenticator = Service::RmUnify::Logout.new(params: params)
    @user = authenticator.user
    @user.reset_remember_token!
    redirect_to authenticator.redirect_url
  end
end

servic_object.rb

require 'uuid'
require 'zlib'
require 'base64'

module Service
  module RmUnify
    class Logout
      include Virtus.model
      attribute :params

      def user
        @user ||= ::User.where(rm_unify_uid: uid).first
      end

      def redirect_url
        "#{::Settings.rm_unify.saml.base_url}#{logout_params}"
      end

      protected

      def doc
        @doc ||= Nokogiri::XML(
          decode_raw_saml_response(params['SAMLRequest'])
        ).remove_namespaces!
      end

      def uid
        doc.xpath('//NameID').first.text
      end

      def rid
        doc.root.attr('ID')
      end

      def logout_params
        "#{params[:RelayState]}#{logout_response}"
      end

      def xml_builder
        Nokogiri::XML::Builder.new do |xml|
          xml.send(:'samlp:LogoutResponse',
            'xmlns:samlp' => 'urn:oasis:names:tc:SAML:2.0:protocol',
            'xmlns:saml' => 'urn:oasis:names:tc:SAML:2.0:assertion',
            'ID' => "_#{UUID.new.generate}",
            'Version' => '2.0',
            'IssueInstant' => Time.new.strftime("%Y-%m-%dT%H:%M:%S"),
            'InResponseTo' => rid,
          ) do
            xml.send(:'saml:Issuer', Settings.rm_unify.saml.issuer)
            xml.send(:'samlp:Status') do
              xml.send(:'samlp:StatusCode',
                'Value' => 'urn:oasis:names:tc:SAML:2.0:status:Success')
              xml.send(
                :'samlp:StatusMessage',
                'Successfully logged out from ShowMyHomework'
              )
            end
          end
        end.to_xml
      end

      def xml
        Nokogiri::XML(xml_builder).root.to_xml
      end

      def logout_response
        deflated = Zlib::Deflate.deflate(xml, 9)[2..-5]
        base64 = Base64.encode64(deflated)
        encoded = CGI.escape(base64)
        "&SAMLResponse=#{encoded}"
      end

      def inflate(deflated)
        zlib = Zlib::Inflate.new(-Zlib::MAX_WBITS)
        zlib.inflate(deflated)
      end

      def decode_raw_saml_response(response)
        if response =~ /^</
          response
        elsif (decoded  = Base64.decode64(response)) =~ /^</
          decoded
        elsif (inflated = inflate(decoded)) =~ /^</
          inflated
        else
          raise "Couldn't decode SAMLResponse"
        end
      end
    end
  end
end