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# -*- coding: binary -*-
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module Rex
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  module Proto
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    module Kerberos
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      module Model
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        # This class provides a representation of a Kerberos AP-REP (response) data
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        # definition
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        class ApRep < Element
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          # @!attribute pvno
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          #   @return [Integer] The protocol version number
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          attr_accessor :pvno
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          # @!attribute msg_type
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          #   @return [Integer] The type of a protocol message
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          attr_accessor :msg_type
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          # @!attribute enc_part
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          #   @return [Rex::Proto::Kerberos::Model::EncryptedData] The encrypted part of the response
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          attr_accessor :enc_part
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          # Decodes the Rex::Proto::Kerberos::Model::ApRep from an input
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          #
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          # @param input [String, OpenSSL::ASN1::ASN1Data] the input to decode from
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          # @return [self] if decoding succeeds
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          # @raise [Rex::Proto::Kerberos::Model::Error::KerberosDecodingError] if decoding doesn't succeed
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          def decode(input)
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            case input
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            when String
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              decode_string(input)
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            when OpenSSL::ASN1::ASN1Data
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              decode_asn1(input)
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            else
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              raise ::Rex::Proto::Kerberos::Model::Error::KerberosDecodingError, 'Failed to decode ApRep, invalid input'
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            end
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            self
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          end
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          # Encodes the Rex::Proto::Kerberos::Model::ApReq into an ASN.1 String
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          #
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          # @return [String]
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          def encode
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            to_asn1.to_der
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          end
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          # @return [OpenSSL::ASN1::ASN1Data] The ap_req ASN1Data
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          def to_asn1
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            elems = []
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            elems << OpenSSL::ASN1::ASN1Data.new([encode_pvno], 0, :CONTEXT_SPECIFIC)
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            elems << OpenSSL::ASN1::ASN1Data.new([encode_msg_type], 1, :CONTEXT_SPECIFIC)
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            elems << OpenSSL::ASN1::ASN1Data.new([encode_enc_part], 2, :CONTEXT_SPECIFIC)
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            seq = OpenSSL::ASN1::Sequence.new(elems)
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            seq_asn1 = OpenSSL::ASN1::ASN1Data.new([seq], AP_REP, :APPLICATION)
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            seq_asn1
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          end
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          def decrypt_enc_part(key)
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            data = enc_part.decrypt_asn1(key, Rex::Proto::Kerberos::Crypto::KeyUsage::AP_REP_ENCPART)
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            result = Rex::Proto::Kerberos::Model::EncApRepPart::decode(data)
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          end
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          private
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          # Encodes the pvno field
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          #
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          # @return [OpenSSL::ASN1::Integer]
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          def encode_pvno
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            bn = OpenSSL::BN.new(pvno.to_s)
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            int = OpenSSL::ASN1::Integer.new(bn)
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            int
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          end
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          # Encodes the msg_type field
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          #
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          # @return [OpenSSL::ASN1::Integer]
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          def encode_msg_type
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            bn = OpenSSL::BN.new(msg_type.to_s)
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            int = OpenSSL::ASN1::Integer.new(bn)
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            int
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          end
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          # Encodes the enc_part field
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          #
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          # @return [String]
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          def encode_enc_part
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            enc_part.encode
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          end
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          # Decodes a Rex::Proto::Kerberos::Model::ApRep from an String
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          #
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          # @param input [String] the input to decode from
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          def decode_string(input)
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            asn1 = OpenSSL::ASN1.decode(input)
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            decode_asn1(asn1)
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          end
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          # Decodes a Rex::Proto::Kerberos::Model::ApRep
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          #
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          # @param input [OpenSSL::ASN1::ASN1Data] the input to decode from
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          # @raise [Rex::Proto::Kerberos::Model::Error::KerberosDecodingError] if decoding doesn't succeed
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          def decode_asn1(input)
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            input.value[0].value.each do |val|
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              case val.tag
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              when 0
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                self.pvno = decode_pvno(val)
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              when 1
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                self.msg_type = decode_msg_type(val)
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              when 2
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                self.enc_part = decode_enc_part(val)
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              else
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                raise ::Rex::Proto::Kerberos::Model::Error::KerberosDecodingError, "Failed to decode AP-REP SEQUENCE (#{val.tag})"
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              end
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            end
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          end
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          # Decodes the pvno from an OpenSSL::ASN1::ASN1Data
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          #
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          # @param input [OpenSSL::ASN1::ASN1Data] the input to decode from
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          # @return [Integer]
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          def decode_pvno(input)
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            input.value[0].value.to_i
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          end
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          # Decodes the msg_type from an OpenSSL::ASN1::ASN1Data
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          #
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          # @param input [OpenSSL::ASN1::ASN1Data] the input to decode from
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          # @return [Integer]
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          def decode_msg_type(input)
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            input.value[0].value.to_i
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          end
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          # Decodes the enc_part
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          #
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          # @param input [OpenSSL::ASN1::ASN1Data] the input to decode from
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          # @return [Rex::Proto::Kerberos::Model::EncryptedData]
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          def decode_enc_part(input)
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            Rex::Proto::Kerberos::Model::EncryptedData.decode(input.value[0])
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          end
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        end
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      end
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    end
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  end
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end
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