Add first draft for Kerberos responses

lib/rex/proto/kerberos/model/message/kdc_response.rb

@@ -12,10 +12,108 @@ module Rex
             # @!attribute msg_type
             #   @return [Fixnum] The type of a protocol message
             attr_accessor :msg_type
-            # @!attribute pa_data
-            #   @return [Rex::Proto::Kerberos::Model::Field::PreAuthData] Authentication information which may
-            #   be needed before credentials can be issued or decrypted
-            attr_accessor :pa_data
+            # @!attribute crealm
+            #   @return [String] The realm part of the client's principal identifier
+            attr_accessor :crealm
+            # @!attribute cname
+            #   @return [Rex::Proto::Kerberos::Type::PrincipalName] The name part of the client's principal identifier
+            attr_accessor :cname
+            # @!attribute ticket
+            #   @return [Rex::Proto::Kerberos::Type::PrincipalName] The name part of the client's principal identifier
+            attr_accessor :ticket
+            # @!attribute enc_auth_data
+            #   @return [Rex::Proto::Kerberos::Type::EncryptedData] The newly issued ticket
+            attr_accessor :enc_part
+
+            # Decodes the Rex::Proto::Kerberos::Model::Message::KrbError from an input
+            #
+            # @param input [String, OpenSSL::ASN1::ASN1Data] the input to decode from
+            # @return [self] if decoding succeeds
+            # @raise [RuntimeError] if decoding doesn't succeed
+            def decode(input)
+              case input
+              when String
+                decode_string(input)
+              when OpenSSL::ASN1::ASN1Data
+                decode_asn1(input)
+              else
+                raise ::RuntimeError, 'Failed to decode KRB Error, invalid input'
+              end
+
+              self
+            end
+
+            def encode
+              raise ::RuntimeError, 'KrbError encoding not supported'
+            end
+
+            private
+
+            # Decodes a Rex::Proto::Kerberos::Model::Message::KrbError from an String
+            #
+            # @param input [String] the input to decode from
+            def decode_string(input)
+              asn1 = OpenSSL::ASN1.decode(input)
+
+              decode_asn1(asn1)
+            end
+
+            # Decodes a Rex::Proto::Kerberos::Model::Message::KrbError
+            #
+            # @param input [OpenSSL::ASN1::ASN1Data] the input to decode from
+            # @raise [RuntimeError] if decoding doesn't succeed
+            def decode_asn1(input)
+              input.value[0].value.each do |val|
+                case val.tag
+                when 0
+                  self.pvno = decode_pvno(val)
+                when 1
+                  self.msg_type = decode_msg_type(val)
+                when 3
+                  self.crealm = decode_crealm(val)
+                when 4
+                  self.cname = decode_cname(val)
+                when 5
+                  self.ticket = decode_ticket(val)
+                when 6
+                  self.enc_part = decode_enc_part(val)
+                else
+                  raise ::RuntimeError, 'Failed to decode KDC-RESPONSE SEQUENCE'
+                end
+              end
+            end
+
+            # Decodes the pvno from an OpenSSL::ASN1::ASN1Data
+            #
+            # @param input [OpenSSL::ASN1::ASN1Data] the input to decode from
+            # @return [Fixnum]
+            def decode_pvno(input)
+              input.value[0].value.to_i
+            end
+
+            # Decodes the msg_type from an OpenSSL::ASN1::ASN1Data
+            #
+            # @param input [OpenSSL::ASN1::ASN1Data] the input to decode from
+            # @return [Fixnum]
+            def decode_msg_type(input)
+              input.value[0].value.to_i
+            end
+
+            # Decodes the crealm field
+            #
+            # @param input [OpenSSL::ASN1::ASN1Data] the input to decode from
+            # @return [String]
+            def decode_crealm(input)
+              input.value[0].value
+            end
+
+            # Decodes the cname field
+            #
+            # @param input [OpenSSL::ASN1::ASN1Data] the input to decode from
+            # @return [Rex::Proto::Kerberos::Type::PrincipalName]
+            def decode_cname(input)
+              Rex::Proto::Kerberos::Model::Type::PrincipalName.decode(input.value[0])
+            end
           end
         end
       end