404 lines
13 KiB
C#
404 lines
13 KiB
C#
using System;
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using System.Collections.Generic;
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using System.IO;
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using System.Net;
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using System.Net.Sockets;
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using System.Text;
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using System.Threading;
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namespace SoFii {
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public class DNSClient : IDisposable {
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public static readonly string[] Servers;
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static DNSClient() {
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string[] servers = Settings.CustomDNSServers;
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if(servers.Length < 1 || string.IsNullOrEmpty(servers[0]))
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servers = EmbeddedResources.GetDNSServers();
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RNG.Shuffle(servers);
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Servers = servers;
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}
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private static int CurrentServerIndex = -1;
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public static string GetNextCommonServer() {
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Interlocked.Increment(ref CurrentServerIndex);
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return Servers[CurrentServerIndex % Servers.Length];
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}
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private readonly Socket Sock;
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public DNSClient() : this(GetNextCommonServer()) { }
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public DNSClient(string ipAddr) : this(
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IPAddress.Parse(ipAddr ?? throw new ArgumentNullException(nameof(ipAddr)))
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) { }
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public DNSClient(IPAddress ipAddr) {
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if(ipAddr == null)
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throw new ArgumentNullException(nameof(ipAddr));
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Sock = new Socket(ipAddr.AddressFamily, SocketType.Dgram, ProtocolType.Udp);
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Sock.Connect(ipAddr, 53);
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}
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public Response QueryRecords(RecordType qType, string qName) {
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if(qName == null)
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throw new ArgumentNullException(nameof(qName));
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if(string.IsNullOrEmpty(qName))
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throw new ArgumentException("domain may not be empty", nameof(qName));
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byte[] transId = new byte[2];
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RNG.NextBytes(transId);
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using(MemoryStream ms = new MemoryStream()) {
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// Transaction ID
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ms.Write(transId, 0, 2);
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// QR, Opcode, AC, TC, RD
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ms.WriteByte(0x01); // RD = Recursion Desired, we want this
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// RA, Z, RCODE
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ms.WriteByte(0);
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// QDCOUNT (1 query)
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ms.WriteByte(0);
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ms.WriteByte(0x01);
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// ANCOUNT
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ms.WriteByte(0);
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ms.WriteByte(0);
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// NSCOUNT
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ms.WriteByte(0);
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ms.WriteByte(0);
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// ARCOUNT
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ms.WriteByte(0);
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ms.WriteByte(0);
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// QNAME
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string[] qNameParts = qName.Split('.');
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for(int i = 0; i < qNameParts.Length; ++i) {
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string qNamePart = qNameParts[i];
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int qNamePartLength = Encoding.ASCII.GetByteCount(qNamePart);
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if(i != (qNameParts.Length - 1) && qNamePartLength < 1)
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throw new ArgumentException("Malformed domain (label too short)", nameof(qName));
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if(qNamePartLength > 0x3F)
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throw new ArgumentException("Malformed domain (label too long)", nameof(qName));
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ms.WriteByte((byte)qNamePartLength);
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if(qNamePartLength > 0)
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ms.Write(Encoding.ASCII.GetBytes(qNamePart), 0, qNamePartLength);
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}
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// QTYPE
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int qTypeNum = (int)qType;
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ms.WriteByte((byte)(qTypeNum >> 8));
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ms.WriteByte((byte)qTypeNum);
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// QCLASS - Interneet Protocol
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ms.WriteByte(0);
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ms.WriteByte(0x01);
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// Sende
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int sent = Sock.Send(ms.ToArray());
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if(sent != ms.Length)
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throw new DNSClientException("Was unable send whole packet");
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}
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int read;
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byte[] buffer = new byte[1024];
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int error;
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List<Query> queries = new List<Query>();
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List<Answer> answers = new List<Answer>();
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using(MemoryStream ms = new MemoryStream()) {
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read = Sock.Receive(buffer);
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if(read < 12)
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throw new DNSClientException("Did not receive a full DNS response header");
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ms.Write(buffer, 0, read);
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while(read >= buffer.Length) {
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read = Sock.Receive(buffer);
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ms.Write(buffer, 0, read);
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}
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ms.Seek(0, SeekOrigin.Begin);
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if(ms.ReadByte() != transId[0] || ms.ReadByte() != transId[1])
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throw new DNSClientException("Response received did not contain the same transaction ID");
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int flags = (ms.ReadByte() << 8) | ms.ReadByte();
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if((flags & 0x8000) == 0)
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throw new DNSClientException("Response did not have the response bit set");
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if((flags & 0x0200) > 0)
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throw new DNSClientException("Truncated responses are not supported");
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if((flags & 0x0080) == 0)
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throw new DNSClientException("This server does not allow recursion");
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error = flags & 0x000F;
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if(error == 1)
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throw new DNSClientException("Request was incorrectly formatted");
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if(error == 2)
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throw new DNSClientException("Name server was unable to process the query");
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if(error == 4)
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throw new DNSClientException("Name server does not support this type of query");
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if(error == 5)
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throw new DNSClientException("Name server refused to respond to this query");
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if(error != 0 && error != 3)
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throw new DNSClientException($"An error occurred while processing this query: {error}");
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int qdCount = (ms.ReadByte() << 8) | ms.ReadByte();
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int anCount = (ms.ReadByte() << 8) | ms.ReadByte();
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int nsCount = (ms.ReadByte() << 8) | ms.ReadByte();
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int arCount = (ms.ReadByte() << 8) | ms.ReadByte();
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for(int i = 0; i < qdCount; ++i) {
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string qdName = string.Join(".", ReadLabels(ms));
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RecordType qdType = (RecordType)((ms.ReadByte() << 8) | ms.ReadByte());
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int qdClass = (ms.ReadByte() << 8) | ms.ReadByte();
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queries.Add(new Query(qdName, qdType, qdClass));
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}
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for(int i = 0; i < anCount; ++i) {
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string anName = string.Join(".", ReadLabels(ms));
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RecordType anType = (RecordType)((ms.ReadByte() << 8) | ms.ReadByte());
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int anClass = (ms.ReadByte() << 8) | ms.ReadByte();
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int anTTL = (ms.ReadByte() << 24) | (ms.ReadByte() << 16) | (ms.ReadByte() << 8) | ms.ReadByte();
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int anDataLength = (ms.ReadByte() << 8) | ms.ReadByte();
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byte[] anData;
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if(anDataLength < 1) {
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#if NETFX4_6_OR_GREATER || NETCOREAPP1_0_OR_GREATER
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anData = Array.Empty<byte>();
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#else
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anData = new byte[0];
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#endif
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} else {
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anData = new byte[anDataLength];
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read = ms.Read(anData, 0, anDataLength);
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if(read != anDataLength)
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throw new DNSClientException("Could not read data field of record");
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}
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answers.Add(new Answer(anName, anType, anClass, anTTL, anDataLength, anData));
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}
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}
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return new Response(
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error,
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queries.ToArray(),
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answers.ToArray()
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);
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}
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private static string[] ReadLabels(Stream stream) {
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int length = stream.ReadByte();
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bool isRef = (length & 0xC0) == 0xC0;
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long jumpTo = 0;
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length &= 0x3F;
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if(isRef) {
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length <<= 8;
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length |= stream.ReadByte();
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jumpTo = stream.Position;
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stream.Seek(length, SeekOrigin.Begin);
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length = stream.ReadByte();
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}
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byte[] buffer = new byte[0x3F];
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List<string> labels = new List<string>();
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int read;
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for(; ; )
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{
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if(length < 1) {
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labels.Add(string.Empty);
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break;
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}
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if(length > 0x3F)
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throw new DNSClientException("Received label field that claims to be longer than 63 bytes");
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read = stream.Read(buffer, 0, length);
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if(read != length)
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throw new DNSClientException("Wasn't able to read the entire label (end of stream?)");
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labels.Add(Encoding.ASCII.GetString(buffer, 0, read));
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length = stream.ReadByte();
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}
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if(isRef)
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stream.Seek(jumpTo, SeekOrigin.Begin);
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return labels.ToArray();
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}
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public struct Response {
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public int Status;
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public Query[] Queries;
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public Answer[] Answers;
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public bool IsSuccess => Status == 0;
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public Response(
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int status,
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Query[] queries,
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Answer[] answers
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) {
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Status = status;
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Queries = queries;
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Answers = answers;
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}
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}
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public struct Query {
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public string Name;
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public RecordType Type;
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public int Class;
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public Query(
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string name,
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RecordType type,
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int @class
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) {
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Name = name;
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Type = type;
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Class = @class;
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}
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public override string ToString() {
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return $"{Name} {Type} {Class}";
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}
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}
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public struct Answer {
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public string Name;
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public RecordType Type;
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public int Class;
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public int TTL;
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public int DataLength;
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public byte[] Data;
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public Answer(
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string name,
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RecordType type,
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int @class,
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int ttl,
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int dataLength,
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byte[] data
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) {
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Name = name;
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Type = type;
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Class = @class;
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TTL = ttl;
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DataLength = dataLength;
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Data = data;
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}
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// TODO: support other record types someday maybe
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public AnswerTXT GetTXTData() {
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return new AnswerTXT(Data);
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}
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public override string ToString() {
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return $"{Name} {Type} {Class} {TTL} {DataLength} {Encoding.ASCII.GetString(Data)}";
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}
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public struct AnswerTXT {
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public int Length;
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public string Text;
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public AnswerTXT(byte[] data) {
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Length = data[0];
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Text = Encoding.ASCII.GetString(data, 1, Length);
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}
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}
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}
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public enum RecordType : ushort {
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A = 0x0001,
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NS = 0x0002,
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CNAME = 0x0005,
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SOA = 0x0006,
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PTR = 0x000C,
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HINFO = 0x000D,
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MX = 0x000F,
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TXT = 0x0010,
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RP = 0x0011,
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AFSDB = 0x0012,
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SIG = 0x0018,
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KEY = 0x0019,
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AAAA = 0x001C,
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LOC = 0x001D,
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SRV = 0x0021,
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NAPTR = 0x0023,
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KX = 0x0024,
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CERT = 0x0025,
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DNAME = 0x0027,
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OPT = 0x0029,
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APL = 0x002A,
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DS = 0x002B,
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SSHFP = 0x002C,
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IPSECKEY = 0x002D,
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RRSIG = 0x002E,
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NSEC = 0x002F,
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DNSKEY = 0x0030,
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DHCID = 0x0031,
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NSEC3 = 0x0032,
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NSEC3PARAM = 0x0033,
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TLSA = 0x0034,
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SMIMEA = 0x0035,
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HIP = 0x0037,
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CDS = 0x003B,
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CDNSKEY = 0x003C,
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OPENPGPKEY = 0x003D,
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CSYNC = 0x003E,
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ZONEMD = 0x003F,
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SVCB = 0x0040,
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HTTPS = 0x0041,
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EUI48 = 0x006C,
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EUI64 = 0x006D,
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TKEY = 0x00F9,
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TSIG = 0x00FA,
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IXFR = 0x00FB,
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AXFR = 0x00FC,
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ANY = 0x00FF,
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URI = 0x0100,
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CAA = 0x0101,
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TA = 0x8000,
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DLV = 0x8001,
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}
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private bool IsDisposed;
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~DNSClient() {
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DoDispose();
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}
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public void Dispose() {
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DoDispose();
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GC.SuppressFinalize(this);
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}
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private void DoDispose() {
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if(IsDisposed)
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return;
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IsDisposed = true;
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Sock?.Close();
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}
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}
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public class DNSClientException : Exception {
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public DNSClientException() : base() { }
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public DNSClientException(string message) : base(message) { }
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public DNSClientException(string message, Exception innerException) : base(message, innerException) { }
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}
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}
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