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https://github.com/fergalmoran/DnsServer.git
synced 2026-01-03 23:34:49 +00:00
NxDomainOverride: added new app to allow overriding nxdomain responses.
This commit is contained in:
Shreyas Zare
252
Apps/NxDomainOverrideApp/App.cs
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252
Apps/NxDomainOverrideApp/App.cs
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/*
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Technitium DNS Server
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Copyright (C) 2024 Shreyas Zare (shreyas@technitium.com)
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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using DnsServerCore.ApplicationCommon;
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using System;
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using System.Collections.Generic;
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using System.Net;
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using System.Net.Sockets;
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using System.Text.Json;
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using System.Threading.Tasks;
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using TechnitiumLibrary;
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using TechnitiumLibrary.Net.Dns;
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using TechnitiumLibrary.Net.Dns.ResourceRecords;
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namespace NxDomainOverride
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{
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public sealed class App : IDnsApplication, IDnsPostProcessor
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{
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#region variables
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bool _enableOverride;
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uint _defaultTtl;
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Dictionary<string, string[]> _domainSetMap;
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Dictionary<string, Set> _sets;
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#endregion
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#region IDisposable
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public void Dispose()
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{
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//do nothing
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}
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#endregion
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#region private
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private static string GetParentZone(string domain)
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{
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int i = domain.IndexOf('.');
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if (i > -1)
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return domain.Substring(i + 1);
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//dont return root zone
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return null;
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}
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private bool TryGetMappedSets(string domain, out string[] setNames)
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{
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domain = domain.ToLowerInvariant();
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string parent;
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do
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{
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if (_domainSetMap.TryGetValue(domain, out setNames))
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return true;
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parent = GetParentZone(domain);
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if (parent is null)
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{
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if (_domainSetMap.TryGetValue("*", out setNames))
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return true;
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break;
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}
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domain = "*." + parent;
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if (_domainSetMap.TryGetValue(domain, out setNames))
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return true;
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domain = parent;
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}
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while (true);
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return false;
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}
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#endregion
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#region public
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public Task InitializeAsync(IDnsServer dnsServer, string config)
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{
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using JsonDocument jsonDocument = JsonDocument.Parse(config);
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JsonElement jsonConfig = jsonDocument.RootElement;
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_enableOverride = jsonConfig.GetPropertyValue("enableOverride", true);
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_defaultTtl = jsonConfig.GetPropertyValue("defaultTtl", 300u);
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_domainSetMap = jsonConfig.ReadObjectAsMap("domainSetMap", delegate (string domain, JsonElement jsonSets)
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{
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string[] sets = jsonSets.GetArray();
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return new Tuple<string, string[]>(domain.ToLowerInvariant(), sets);
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});
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_sets = jsonConfig.ReadArrayAsMap("sets", delegate (JsonElement jsonSet)
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{
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Set set = new Set(jsonSet);
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return new Tuple<string, Set>(set.Name, set);
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});
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return Task.CompletedTask;
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}
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public Task<DnsDatagram> PostProcessAsync(DnsDatagram request, IPEndPoint remoteEP, DnsTransportProtocol protocol, DnsDatagram response)
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{
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if (!_enableOverride)
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return Task.FromResult(response);
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if (response.DnssecOk)
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return Task.FromResult(response);
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if (response.OPCODE != DnsOpcode.StandardQuery)
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return Task.FromResult(response);
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if (response.RCODE != DnsResponseCode.NxDomain)
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return Task.FromResult(response);
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DnsQuestionRecord question = request.Question[0];
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switch (question.Type)
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{
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case DnsResourceRecordType.A:
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case DnsResourceRecordType.AAAA:
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break;
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default:
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//NO DATA response
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return Task.FromResult(new DnsDatagram(response.Identifier, true, response.OPCODE, response.AuthoritativeAnswer, response.Truncation, response.RecursionDesired, response.RecursionAvailable, response.AuthenticData, response.CheckingDisabled, DnsResponseCode.NoError, response.Question, response.Answer, response.Authority, response.Additional) { Tag = response.Tag });
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}
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string nxDomain = question.Name;
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foreach (DnsResourceRecord record in response.Answer)
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{
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if (record.Type == DnsResourceRecordType.CNAME)
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nxDomain = (record.RDATA as DnsCNAMERecordData).Domain;
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}
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if (!TryGetMappedSets(nxDomain, out string[] setNames))
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return Task.FromResult(response);
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List<DnsResourceRecord> newAnswer = new List<DnsResourceRecord>();
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newAnswer.AddRange(response.Answer);
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foreach (string setName in setNames)
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{
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if (_sets.TryGetValue(setName, out Set set))
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{
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switch (question.Type)
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{
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case DnsResourceRecordType.A:
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foreach (DnsResourceRecordData rdata in set.RecordDataAddresses)
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{
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if (rdata is DnsARecordData)
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newAnswer.Add(new DnsResourceRecord(nxDomain, DnsResourceRecordType.A, DnsClass.IN, _defaultTtl, rdata));
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}
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break;
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case DnsResourceRecordType.AAAA:
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foreach (DnsResourceRecordData rdata in set.RecordDataAddresses)
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{
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if (rdata is DnsAAAARecordData)
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newAnswer.Add(new DnsResourceRecord(nxDomain, DnsResourceRecordType.AAAA, DnsClass.IN, _defaultTtl, rdata));
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}
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break;
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default:
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throw new InvalidOperationException();
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}
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}
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}
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return Task.FromResult(new DnsDatagram(response.Identifier, true, response.OPCODE, response.AuthoritativeAnswer, response.Truncation, response.RecursionDesired, response.RecursionAvailable, response.AuthenticData, response.CheckingDisabled, DnsResponseCode.NoError, response.Question, newAnswer) { Tag = response.Tag });
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}
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#endregion
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#region properties
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public string Description
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{ get { return "Overrides NX Domain response with custom A/AAAA record response for configured domain names."; } }
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#endregion
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class Set
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{
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#region variables
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readonly string _name;
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readonly DnsResourceRecordData[] _rdataAddresses;
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#endregion
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#region constructor
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public Set(JsonElement jsonSet)
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{
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_name = jsonSet.GetProperty("name").GetString();
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_rdataAddresses = jsonSet.ReadArray<DnsResourceRecordData>("addresses", delegate (string item)
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{
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IPAddress address = IPAddress.Parse(item);
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switch (address.AddressFamily)
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{
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case AddressFamily.InterNetwork:
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return new DnsARecordData(address);
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case AddressFamily.InterNetworkV6:
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return new DnsAAAARecordData(address);
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default:
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throw new NotSupportedException("Address family not supported: " + address.AddressFamily.ToString());
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}
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});
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}
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#endregion
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#region properties
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public string Name
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{ get { return _name; } }
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public DnsResourceRecordData[] RecordDataAddresses
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{ get { return _rdataAddresses; } }
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#endregion
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}
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}
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}
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