diff --git a/Apps/SplitHorizonApp/SimpleCNAME.cs b/Apps/SplitHorizonApp/SimpleCNAME.cs new file mode 100644 index 00000000..0b6e1cd3 --- /dev/null +++ b/Apps/SplitHorizonApp/SimpleCNAME.cs @@ -0,0 +1,98 @@ +/* +Technitium DNS Server +Copyright (C) 2021 Shreyas Zare (shreyas@technitium.com) + +This program is free software: you can redistribute it and/or modify +it under the terms of the GNU General Public License as published by +the Free Software Foundation, either version 3 of the License, or +(at your option) any later version. + +This program is distributed in the hope that it will be useful, +but WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +GNU General Public License for more details. + +You should have received a copy of the GNU General Public License +along with this program. If not, see . + +*/ + +using DnsApplicationCommon; +using Newtonsoft.Json; +using System; +using System.Collections.Generic; +using System.Net; +using System.Threading.Tasks; +using TechnitiumLibrary.Net; +using TechnitiumLibrary.Net.Dns; +using TechnitiumLibrary.Net.Dns.ResourceRecords; + +namespace SplitHorizon +{ + public class SimpleCNAME : IDnsApplicationRequestHandler + { + #region IDisposable + + public void Dispose() + { + //do nothing + } + + #endregion + + #region public + + public Task InitializeAsync(IDnsServer dnsServer, string config) + { + //no config needed + return Task.CompletedTask; + } + + public Task ProcessRequestAsync(DnsDatagram request, IPEndPoint remoteEP, string zoneName, uint appRecordTtl, string appRecordData, bool isRecursionAllowed, IDnsServer dnsServer) + { + dynamic jsonAppRecordData = JsonConvert.DeserializeObject(appRecordData); + dynamic jsonCname; + + if (NetUtilities.IsPrivateIP(remoteEP.Address)) + jsonCname = jsonAppRecordData.@private; + else + jsonCname = jsonAppRecordData.@public; + + if (jsonCname == null) + return Task.FromResult(null); + + string cname = jsonCname.Value; + if (string.IsNullOrEmpty(cname)) + return Task.FromResult(null); + + IReadOnlyList answers; + + if (request.Question[0].Name.Equals(zoneName, StringComparison.OrdinalIgnoreCase)) //check for zone apex + answers = new DnsResourceRecord[] { new DnsResourceRecord(request.Question[0].Name, DnsResourceRecordType.ANAME, DnsClass.IN, appRecordTtl, new DnsANAMERecord(cname)) }; //use ANAME + else + answers = new DnsResourceRecord[] { new DnsResourceRecord(request.Question[0].Name, DnsResourceRecordType.CNAME, DnsClass.IN, appRecordTtl, new DnsCNAMERecord(cname)) }; + + return Task.FromResult(new DnsDatagram(request.Identifier, true, request.OPCODE, true, false, request.RecursionDesired, isRecursionAllowed, false, false, DnsResponseCode.NoError, request.Question, answers)); + } + + #endregion + + #region properties + + public string Description + { get { return "Returns different CNAME record for clients querying over public and private networks. Note that the app will return ANAME record for an APP record at zone apex."; } } + + public string ApplicationRecordDataTemplate + { + get + { + return @"{ + ""public"": ""api.example.com"", + ""private"": ""api.example.corp"" +}"; + } + } + + #endregion + } +}