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module Rex
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  module Parser
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    module NetSarang
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      # @author Kali-Team
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      class NetSarangCrypto
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        attr_accessor :version
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        attr_accessor :username
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        attr_accessor :sid
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        attr_accessor :master_password
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        attr_accessor :key
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        # This class implements encryption and decryption of NetSarang
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        #
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        # @param type [String] only Xshell or Xftp.
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        # @param version [String] Specify version of session file. e.g.:5.3
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        # @param username [String] Specify username. This parameter will be used if version > 5.2.
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        # @param sid [String] Specify SID. This parameter will be used if version >= 5.1.
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        # @option master_password [String] Specify user's master password.
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        #
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        # @return [Rex::Parser::NetSarang::NetSarangCrypto] The NetSarangCrypto object
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        def initialize(type, version, username, sid, master_password = nil)
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          self.version = version.to_f
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          self.username = username
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          self.sid = sid
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          self.master_password = master_password
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          md5 = OpenSSL::Digest.new('MD5')
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          sha256 = OpenSSL::Digest.new('SHA256')
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          if (self.version > 0) && (self.version < 5.1)
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            self.key = (type == 'Xshell') ? md5.digest('!X@s#h$e%l^l&') : md5.digest('!X@s#c$e%l^l&')
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          elsif (self.version >= 5.1) && (self.version <= 5.2)
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            self.key = sha256.digest(self.sid)
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          elsif (self.version > 5.2)
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            if self.master_password.nil?
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              self.key = sha256.digest(self.username + self.sid)
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            else
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              self.key = sha256.digest(self.master_password)
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            end
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          else
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            raise 'Invalid argument: version'
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          end
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        end
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        # Encrypt
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        #
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        # @param string [String]
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        # @return [String] ciphertext
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        def encrypt_string(string)
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          cipher = Rex::Crypto.rc4(key, string)
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          if (version < 5.1)
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            return Rex::Text.encode_base64(cipher)
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          else
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            sha256 = OpenSSL::Digest.new('SHA256')
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            checksum = sha256.digest(string)
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            ciphertext = cipher
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            return Rex::Text.encode_base64(ciphertext + checksum)
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          end
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        end
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        # Decrypt
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        #
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        # @param string [String]
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        # @return [String] plaintext failed return nil
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        def decrypt_string(string)
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          if (version < 5.1)
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            return Rex::Crypto.rc4(key, Rex::Text.decode_base64(string))
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          else
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            data = Rex::Text.decode_base64(string)
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            ciphertext = data[0, data.length - 0x20]
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            plaintext = Rex::Crypto.rc4(key, ciphertext)
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            if plaintext.is_utf8?
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              return plaintext
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            else
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              return nil
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            end
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          end
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        end
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      end
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      # Parse xsh session file provided as a string.
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      #
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      # @param input [String] XSH Session file as a string
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      # @return [Array] An array containing the version, host,
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      #   port, username, and password obtained from the XSH session file.
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      def parser_xsh(input)
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        ini = Rex::Parser::Ini.from_s(input)
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        version = ini['SessionInfo']['Version']
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        port = ini['CONNECTION']['Port']
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        host = ini['CONNECTION']['Host']
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        username = ini['CONNECTION:AUTHENTICATION']['UserName']
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        password = ini['CONNECTION:AUTHENTICATION']['Password'] || nil
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        [version, host, port, username, password]
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      end
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      # parser xfp session file
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      #
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      # @param ini [String]
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      # @return [version, host, port, username, password]
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      def parser_xfp(file)
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        ini = Rex::Parser::Ini.from_s(file)
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        version = ini['SessionInfo']['Version']
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        port = ini['Connection']['Port']
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        host = ini['Connection']['Host']
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        username = ini['Connection']['UserName']
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        password = ini['Connection']['Password']
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        [version, host, port, username, password]
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      end
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    end
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  end
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end
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