Jak uzyskać rekordy mx dla nazwy dns z System.Net.DNS?

Question

Czy istnieje jakakolwiek wbudowana metoda w bibliotece .NET, która zwróci wszystkie rekordy MX dla danej domeny? Widzę, jak zdobywasz CNAMES, ale nie rekordy MX.

Answer 1

ARSoft.Tools.Net biblioteka Alexander Reinert wydaje się wykonać zadanie całkiem dobrze.

Jest ona dostępna od Nuget:

PM> Install-Package ARSoft.Tools.Net 

Importowanie nazw:

using ARSoft.Tools.Net.Dns; 

Następnie dokonanie synchronicznego wyszukiwania jest tak proste, jak:

var resolver = new DnsStubResolver(); 
var records = resolver.Resolve<MxRecord>("gmail.com", RecordType.Mx); 
foreach (var record in records) { 
    Console.WriteLine(record.ExchangeDomainName?.ToString()); 
} 

co daje nam wynik:

gmail-smtp-in.l.google.com. 
alt1.gmail-smtp-in.l.google.com. 
alt2.gmail-smtp-in.l.google.com. 
alt3.gmail-smtp-in.l.google.com. 
alt4.gmail-smtp-in.l.google.com. 

Pod maską wygląda na to, że biblioteka tworzy pakiety UDP (lub TCP) niezbędne do wysłania do programu tłumaczącego, jak można się spodziewać. Biblioteka ma nawet logikę (wywoływaną przez DnsClient.Default), aby wykryć serwer DNS, który ma zapytać.

Pełna dokumentacja znajduje się pod adresem here.

Answer 2

Spędziłem cały dzień zastanawiając się, jak wysyłać/odbierać żądania dns i wpadłem na to. Jest to kompletny ogólny program obsługi. Musisz tylko ustawić serwer dns i przekazać np. "D". my.website.com?d=itmanx.com

<%@ WebHandler Language="C#" Class="Handler" %> 

using System; 
using System.Web; 
using System.Text; 
using System.Net; 
using System.Net.Sockets; 
using System.Collections.Generic; 

public class Handler : IHttpHandler 
{ 
    string dns = "dc1"; //change to your dns 
    string qtype = "15"; //A=1 MX=15 
    string domain = ""; 
    int[] resp; 

    public void ProcessRequest(HttpContext context) 
    { 
     context.Response.ContentType = "text/plain"; 

     try 
     { 
      if (context.Request["t"] != null) qtype = context.Request["t"]; 
      if (context.Request["d"] != null) domain = context.Request["d"]; 

      if (string.IsNullOrEmpty(domain)) throw new Exception("Add ?d=<domain name> to url or post data"); 

      Do(context); 
     } 
     catch (Exception ex) 
     { 
      string msg = ex.Message; 
      if (msg == "1") msg = "Malformed packet"; 
      else if (msg == "5") msg = "Refused"; 
      else if (msg == "131") msg = "No such name"; 

      context.Response.Write("Error: " + msg); 
     } 
    } 

    public void Do(HttpContext context) 
    { 
     UdpClient udpc = new UdpClient(dns, 53); 

     // SEND REQUEST-------------------- 
     List<byte> list = new List<byte>(); 
     list.AddRange(new byte[] { 88, 89, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0 }); 

     string[] tmp = domain.Split('.'); 
     foreach (string s in tmp) 
     { 
      list.Add(Convert.ToByte(s.Length)); 
      char[] chars = s.ToCharArray(); 
      foreach (char c in chars) 
       list.Add(Convert.ToByte(Convert.ToInt32(c))); 
     } 
     list.AddRange(new byte[] { 0, 0, Convert.ToByte(qtype), 0, 1 }); 

     byte[] req = new byte[list.Count]; 
     for (int i = 0; i < list.Count; i++) { req[i] = list[i]; } 

     udpc.Send(req, req.Length); 


     // RECEIVE RESPONSE-------------- 
     IPEndPoint ep = null; 
     byte[] recv = udpc.Receive(ref ep); 
     udpc.Close(); 

     resp = new int[recv.Length]; 
     for (int i = 0; i < resp.Length; i++) 
      resp[i] = Convert.ToInt32(recv[i]); 

     int status = resp[3]; 
     if (status != 128) throw new Exception(string.Format("{0}", status)); 
     int answers = resp[7]; 
     if (answers == 0) throw new Exception("No results"); 

     int pos = domain.Length + 18; 
     if (qtype == "15") // MX record 
     { 
      while (answers > 0) 
      { 
       int preference = resp[pos + 13]; 
       pos += 14; //offset 
       string str = GetMXRecord(pos, out pos); 
       context.Response.Write(string.Format("{0}: {1}\n", preference, str)); 
       answers--; 
      } 
     } 
     else if (qtype == "1") // A record 
     { 
      while (answers > 0) 
      { 
       pos += 11; //offset 
       string str = GetARecord(ref pos); 
       context.Response.Write(string.Format("{0}\n", str)); 
       answers--; 
      } 
     } 
    } 

    //------------------------------------------------------ 
    private string GetARecord(ref int start) 
    { 
     StringBuilder sb = new StringBuilder(); 

     int len = resp[start]; 
     for (int i = start; i < start + len; i++) 
     { 
      if (sb.Length > 0) sb.Append("."); 
      sb.Append(resp[i + 1]); 
     } 
     start += len + 1; 
     return sb.ToString(); 
    } 
    private string GetMXRecord(int start, out int pos) 
    { 
     StringBuilder sb = new StringBuilder(); 
     int len = resp[start]; 
     while (len > 0) 
     { 
      if (len != 192) 
      { 
       if (sb.Length > 0) sb.Append("."); 
       for (int i = start; i < start + len; i++) 
        sb.Append(Convert.ToChar(resp[i + 1])); 
       start += len + 1; 
       len = resp[start]; 
      } 
      if (len == 192) 
      { 
       int newpos = resp[start + 1]; 
       if (sb.Length > 0) sb.Append("."); 
       sb.Append(GetMXRecord(newpos, out newpos)); 
       start++; 
       break; 
      } 
     } 
     pos = start + 1; 
     return sb.ToString(); 
    } 

    //------------------------------------------------------ 
    public bool IsReusable { get { return false; } } 
} 

Answer 3

Oto klasa, której używam do wyszukiwania tylko rekordów MX.

using System; 
    using System.Text; 
    using System.Net; 
    using System.Net.Sockets; 
    using System.Collections.Specialized; 

    namespace Mx.Dns 
    { 
     public class Query 
     { 
      //Build a DNS query buffer according to RFC 1035 4.1.1 e 4.1.2 
      private readonly int id; 
     private readonly int flags; 
     private readonly int QDcount; 
     private readonly int ANcount; 
     private readonly int NScount; 
     private readonly int ARcount; 
     private readonly string Qname; 
     private readonly int Qtype; 
     private readonly int Qclass; 
     public byte[] buf; 

     public Query(int ID, string query, int qtype) 
     { 
      //init vectors with given + default values 
      id = ID; 
      flags = 256; 
      QDcount = 1; 
      ANcount = 0; 
      NScount = 0; 
      ARcount = 0; 
      Qname = query; 
      Qtype = qtype; 
      Qclass = 1; //Internet = IN = 1 

      //build a buffer with formatted query data 

      //header information (16 bit padding 
      buf = new byte[12 + Qname.Length + 2 + 4]; 
      buf[0] = (byte)(id/256); 
      buf[1] = (byte)(id - (buf[0] * 256)); 
      buf[2] = (byte)(flags/256); 
      buf[3] = (byte)(flags - (buf[2] * 256)); 
      buf[4] = (byte)(QDcount/256); 
      buf[5] = (byte)(QDcount - (buf[4] * 256)); 
      buf[6] = (byte)(ANcount/256); 
      buf[7] = (byte)(ANcount - (buf[6] * 256)); 
      buf[8] = (byte)(NScount/256); 
      buf[9] = (byte)(NScount - (buf[8] * 256)); 
      buf[10] = (byte)(ARcount/256); 
      buf[11] = (byte)(ARcount - (buf[10] * 256)); 
      //QNAME (RFC 1035 4.1.2) 
      //no padding 
      string[] s = Qname.Split('.'); 
      int index = 12; 
      foreach (string str in s) { 
       buf[index] = (byte)str.Length; 
       index++; 
       byte[] buf1 = Encoding.ASCII.GetBytes(str); 
       buf1.CopyTo(buf, index); 
       index += buf1.Length; 
      } 
      //add root domain label (chr(0)) 
      buf[index] = 0; 

      //add Qtype and Qclass (16 bit values) 
      index = buf.Length - 4; 
      buf[index] = (byte)(Qtype/256); 
      buf[index + 1] = (byte)(Qtype - (buf[index] * 256)); 
      buf[index + 2] = (byte)(Qclass/256); 
      buf[index + 3] = (byte)(Qclass - (buf[index + 2] * 256)); 
     } 
    } 
    public class C_DNSquery 
    { 
     public StringCollection result = new StringCollection(); 
     public int Error = 0; 
     public string ErrorTxt = "undefined text"; 
     public bool Done = false; 
     public UdpClient udpClient; 
     private string DNS; 
     private string Query; 
     private int Qtype; 
     public bool IS_BLACKLIST_QUERY = false; 
     public C_DNSquery(string IPorDNSname, string query, int type) 
     { 
      DNS = IPorDNSname; 
      Query = query; 
      Qtype = type; 
     } 
     public void doTheJob() 
     { 
      //check if provided DNS contains an IP address or a name 
      IPAddress ipDNS; 
      IPHostEntry he; 
      try { 
       //try to parse an IPaddress 
       ipDNS = IPAddress.Parse(DNS); 
      } catch (FormatException) { 
//    Console.WriteLine(e); 
       //format error, probably is a FQname, try to resolve it 
       try { 
        //try to resolve the hostname 
        he = Dns.GetHostEntry(DNS); 
       } catch { 
        //Error, invalid server name or address 
        Error = 98; 
        ErrorTxt = "Invalid server name:" + DNS; 
        Done = true; 
        return; 
       } 
       //OK, get the first server address 
       ipDNS = he.AddressList[0]; 
      } 

      //Query the DNS server 
      //our current thread ID is used to match the reply with this process 

      Query myQuery = new Query(System.Threading.Thread.CurrentThread.ManagedThreadId, Query, Qtype); 
      //data buffer for query return value 
      Byte[] recBuf; 

      //use UDP protocol to connect 
      udpClient = new UdpClient(); 
      do { 
       try { 
        //connect to given nameserver, port 53 (DNS) 
        udpClient.Connect(DNS, 53); 
        //send query 
        udpClient.Send(myQuery.buf, myQuery.buf.Length); 
        //IPEndPoint object allow us to read datagrams.. 
        //..selecting only packet coming from our nameserver and port 
        IPEndPoint RemoteIpEndPoint = new IPEndPoint(ipDNS, 53); 
        //Blocks until a message returns on this socket from a remote host. 
        recBuf = udpClient.Receive(ref RemoteIpEndPoint); 
        udpClient.Close(); 
       } catch (Exception e) { 
        //connection error, probably a wrong server address 
        udpClient.Close(); 
        Error = 99; 
        ErrorTxt = e.Message + "(server:" + DNS + ")"; 
        Done = true; 
        return; 
       } 
       //repeat until we get the reply with our threadID 
      } while (System.Threading.Thread.CurrentThread.ManagedThreadId != ((recBuf[0] * 256) + recBuf[1])); 

      //Check the DNS reply 
      //check if bit QR (Query response) is set 
      if (recBuf[2] < 128) { 
       //response byte not set (probably a malformed packet) 
       Error = 2; 
       ErrorTxt = "Query response bit not set"; 
       Done = true; 
       return; 
      } 
      //check if RCODE field is 0 
      if ((recBuf[3] & 15) > 0) { 
       //DNS server error, invalid reply 
       switch (recBuf[3] & 15) { 
        case 1: 
         Error = 31; 
         ErrorTxt = "Format error. The nameserver was unable to interpret the query"; 
         break; 
        case 2: 
         Error = 32; 
         ErrorTxt = "Server failure. The nameserver was unable to process the query."; 
         break; 
        case 3: 
         Error = 33; 
         ErrorTxt = "Name error. Check provided domain name!!"; 
         break; 
        case 4: 
         Error = 34; 
         ErrorTxt = "Not implemented. The name server does not support the requested query"; 
         break; 
        case 5: 
         Error = 35; 
         ErrorTxt = "Refused. The name server refuses to reply for policy reasons"; 
         break; 
        default: 
         Error = 36; 
         ErrorTxt = "Unknown. The name server error code was: " + Convert.ToString((recBuf[3] & 15)); 
         break; 
       } 
       Done = true; 
       return; 
      } 
      //OK, now we should have valid header fields 
      int QDcnt, ANcnt, NScnt, ARcnt; 
      int index; 
      QDcnt = (recBuf[4] * 256) + recBuf[5]; 
      ANcnt = (recBuf[6] * 256) + recBuf[7]; 
      NScnt = (recBuf[8] * 256) + recBuf[9]; 
      ARcnt = (recBuf[10] * 256) + recBuf[11]; 
      index = 12; 
      //sometimes there are no erros but blank reply... ANcnt == 0... 
      if (ANcnt == 0) { // if blackhole list query, means no spammer !!//if ((ANcnt == 0) & (IS_BLACKLIST_QUERY == false)) 
       //error blank reply, return an empty array 
       Error = 4; 
       ErrorTxt = "Empty string array"; 
       Done = true; 
       return; 
      } 

      //Decode received information 
      string s1; 
      // START TEST 
      s1 = Encoding.ASCII.GetString(recBuf, 0, recBuf.Length); 
      // END TEST 

      if (QDcnt > 0) { 
       //we are not really interested to this string, just parse and skip 
       s1 = ""; 
       index = parseString(recBuf, index, out s1); 
       index += 4; //skip root domain, Qtype and QClass values... unuseful in this contest 
      } 
      if (IS_BLACKLIST_QUERY) { 
       // get the answers, normally one ! 
       // int the four last bytes there is the ip address 
       Error = 0; 
       int Last_Position = recBuf.Length - 1; 
       result.Add(recBuf[Last_Position - 3].ToString() + "." + recBuf[Last_Position - 2].ToString() + "." + recBuf[Last_Position - 1].ToString() + "." + recBuf[Last_Position].ToString()); 
       Done = true; 
       return; 
      } 
      int count = 0; 
      //get all answers 
      while (count < ANcnt) { 
       s1 = ""; 
       index = parseString(recBuf, index, out s1); 
       //Qtype 
       int QType = (recBuf[index] * 256) + recBuf[index + 1]; 
       index += 2; 
       s1 += "," + QType.ToString(); 
       //QClass 
       int QClass = (recBuf[index] * 256) + recBuf[index + 1]; 
       index += 2; 
       s1 += "," + QClass.ToString(); 
       //TTL (Time to live) 
       int TTL = (recBuf[index] * 16777216) + (recBuf[index + 1] * 65536) + (recBuf[index + 2] * 256) + recBuf[index + 3]; 
       index += 4; 
       s1 += "," + TTL.ToString(); 
       int blocklen = (recBuf[index] * 256) + recBuf[index + 1]; 
       index += 2; 
       if (QType == 15) { 
        int MXprio = (recBuf[index] * 256) + recBuf[index + 1]; 
        index += 2; 
        s1 += "," + MXprio.ToString(); 
       } 
       string s2; 
       index = parseString(recBuf, index, out s2); 
       s1 += "," + s2; 
       result.Add(s1); 
       count++; 
      } 
      Error = 0; 
      Done = true; 
     } 
     private int parseString(byte[] buf, int i, out string s) 
     { 
      int len; 
      s = ""; 
      bool end = false; 
      while (!end) { 
       if (buf[i] == 192) { 
        //next byte is a pointer to the string, get it.. 
        i++; 
        s += getString(buf, buf[i]); 
        i++; 
        end = true; 
       } else { 
        //next byte is the string length 
        len = buf[i]; 
        i++; 
        //get the string 
        s += Encoding.ASCII.GetString(buf, i, len); 
        i += len; 
        //check for the null terminator 
        if (buf[i] != 0) { 
         //not null, add a point to the name 
         s += "."; 
        } else { 
         //null char..the string is complete, exit 
         end = true; 
         i++; 
        } 
       } 
      } 
      return i; 
     } 
     private string getString(byte[] buf, int i) 
     { 
      string s = ""; 
      int len; 
      bool end = false; 
      while (!end) { 
       len = buf[i]; 
       i++; 
       s += Encoding.ASCII.GetString(buf, i, len); 
       i += len; 
       if (buf[i] == 192) { 
        i++; 
        s += "." + getString(buf, buf[i]); 
        return s; 
       } 
       if (buf[i] != 0) { 
        s += "."; 
       } else { 
        end = true; 
       } 
      } 
      return s; 
     } 
    } 
} 

Oto jak z niego korzystać.

/// <summary> 
     /// Get the MX from the domain address. 
     /// </summary> 
     public static string getMXrecord(string domain) 
     { 
      domain = domain.Substring(domain.IndexOf('@') + 1); 
      string LocalDNS = GetDnsAdress().ToString(); 
      Console.WriteLine("domain: " + domain); 

      // resolv the authoritative domain (type=2) 
      C_DNSquery DnsQry = new C_DNSquery(LocalDNS, domain, 2); 
      Thread t1 = new Thread(new ThreadStart(DnsQry.doTheJob)); 
      t1.Start(); 
      int timeout = 20; 
      while ((timeout > 0) & (!DnsQry.Done)) { 
       Thread.Sleep(100); 
       timeout--; 
      } 
      if (timeout == 0) { 
       if (DnsQry.udpClient != null) { 
        DnsQry.udpClient.Close(); 
       } 
       t1.Abort(); 
       DnsQry.Error = 100; 
      } 

      string[] ns1; 
      string MyNs = ""; 
      if (DnsQry.Error == 0) { 
       ns1 = DnsQry.result[0].Split(','); 
       MyNs = ns1[4]; 
       t1.Abort(); 
      } else { 
       t1.Abort(); 
       MyNs = LocalDNS; 
      } 

      // Resolve MX (type = 15) 
      DnsQry = new C_DNSquery(MyNs, domain, 15); 
      Thread t2 = new Thread(new ThreadStart(DnsQry.doTheJob)); 
      t2.Start(); 
      timeout = 20; 
      string TTL = ""; 
      string MXName = ""; 
      Int32 preference = 9910000; 
      while ((timeout > 0) & (!DnsQry.Done)) { 
       Thread.Sleep(100); 
       timeout--; 
      } 
      if (timeout == 0) { 
       if (DnsQry.udpClient != null) { 
        DnsQry.udpClient.Close(); 
       } 
       t2.Abort(); 
       DnsQry.Error = 100; 
      } 
      if (DnsQry.Error == 0) { 

       if (DnsQry.result.Count == 1) { 
        string[] ns2 = DnsQry.result[0].Split(','); 
        MXName = ns2[5]; 
        TTL = ns2[3]; 
        preference = Int32.Parse(ns2[4]); 
        Console.WriteLine("domaine: {0} MX: {1} time: {2} pref: {3} ttl: {4}", domain.Substring(domain.IndexOf('@') + 1), MXName, 
         DateTime.Now, preference, TTL); 


       } else { 
        for (int indns = 0; indns <= DnsQry.result.Count - 1; indns++) { 
         string[] ns2 = DnsQry.result[indns].Split(','); 
         if (Int32.Parse(ns2[4]) < preference) { 
          MXName = ns2[5]; 
          TTL = ns2[3]; 
          preference = Int32.Parse(ns2[4]); 
Console.WriteLine("domain: {0} MX: {1} time: {2} pref: {3} ttl: {4}", domain.Substring(domain.IndexOf('@') + 1), MXName, 
           DateTime.Now, preference, TTL); 

          } 
        } 
       } 
      } 
      return MXName; 
     } 

Answer 4

Wystarczy roled własną bibliotekę, bo nie było nic dla rdzenia .net/xplat wsparcia ... https://github.com/MichaCo/DnsClient.NET

działa całkiem świetnie i daje jak wiadomości dziennika, jeśli chcesz.

Prosty w użyciu

var lookup = new LookupClient(); 
var result = await lookup.QueryAsync("google.com", QueryType.ANY); 

i współpracuje z serwerami niestandardowych działa na dowolnych portów, wiele serwerów, itp ...

zobaczyć również DnsClient Website więcej szczegółów

Answer 5

Zaakceptowanych odpowiedź nie robi” t działa na platformie .NET w architekturze < 4.5, więc sugerują, że ci z was, którzy nie mogą używać ARSOFT.Tools mogą używać nazw DNDN od https://dndns.codeplex.com

Poniżej podano aplikację konsolową, która zwraca rekord MX dla danej domeny, modyfikując ich przykłady.

using System; 
using System.Net.Sockets; 
using DnDns.Enums; 
using DnDns.Query; 
using DnDns.Records; 

namespace DnDnsExamples 
{ 
class Program 
{ 
    static void Main(string[] args) 
    { 
     DnsQueryRequest request3 = new DnsQueryRequest(); 
     DnsQueryResponse response3 = request3.Resolve("gmail.com", NsType.MX, NsClass.INET, ProtocolType.Tcp); 
     OutputResults(response3); 
     Console.ReadLine(); 
    } 

    private static void OutputResults(DnsQueryResponse response) 
    { 
     foreach (IDnsRecord record in response.Answers) 
     { 
      Console.WriteLine(record.Answer); 
      Console.WriteLine(" |--- RDATA Field Length: " + record.DnsHeader.DataLength); 
      Console.WriteLine(" |--- Name: " + record.DnsHeader.Name); 
      Console.WriteLine(" |--- NS Class: " + record.DnsHeader.NsClass); 
      Console.WriteLine(" |--- NS Type: " + record.DnsHeader.NsType); 
      Console.WriteLine(" |--- TTL: " + record.DnsHeader.TimeToLive); 
      Console.WriteLine(); 
     }    
    } 
} 
} 

Answer 6

Moje podejście polegało na użyciu nslookup.exe do odzyskania rekordu MX.

Rozwiązanie nie jest tak fantazyjne jak przepisywanie całego DNS lub używanie Systemowej biblioteki DLL -> ale działa, z niewielką ilością linii.

dostać rzeczy rację, to code> po prostu działa < to nie ressource skuteczny ani szybki i ma dużo miejsca dla improvment (wiele hostów, asynchronicznie, bardziej przydatne wartości zwracanej, dodając priorytet):

static List<string> GetMxRecords(string host){ 
    ProcessStartInfo nslookup_config = new ProcessStartInfo("nslookup.exe"); 
    nslookup_config.RedirectStandardInput = true; 
    nslookup_config.RedirectStandardOutput = true; 
    nslookup_config.RedirectStandardError = true; 
    nslookup_config.UseShellExecute = false; 
    var nslookup = Process.Start(nslookup_config); 
    nslookup.StandardInput.WriteLine("set q=mx"); 
    nslookup.StandardInput.WriteLine(host); 
    nslookup.StandardInput.WriteLine("exit"); 
    List<string> lines = new List<string>(); 
    while (!nslookup.StandardOutput.EndOfStream) 
    { 
     string l = nslookup.StandardOutput.ReadLine(); 
     if (l.Contains("internet address =")) 
     { 
      while (l.Contains("\t\t")) 
      { 
       l = l.Replace("\t\t", "\t"); 
      } 
      lines.Add(l.Replace("\tinternet address = ","=")); 
     } 
    } 
    nslookup.Close(); 
} 

Powinien działać międzynarodowo, ponieważ nslookup nie obsługuje żadnego tłumaczenia (pracuję na maszynie w języku niemieckim i uzyskuję angielskie wyniki).

Rezultatem są ciągi tak:

alt4.gmail-smtp-in.l.google.com=74.125.28.27 
alt2.gmail-smtp-in.l.google.com=74.125.200.27 
alt1.gmail-smtp-in.l.google.com=209.85.233.26 
gmail-smtp-in.l.google.com=66.102.1.27 
alt3.gmail-smtp-in.l.google.com=108.177.97.27 

Answer 7

Można użyć this open source bibliotekę zrobić prawie każdy rodzaj zapytania byś zwykle potrzebują.

Zastosowanie:

DnsClient dnsClient = new DnsClient(); 
string mxDomain = dnsClient.ResolveMX("example.com"); 
string mxDomainIP = dnsClient.ResolveMX("example.com", true); 
string mxDomainIPv6 = dnsClient.ResolveMX("example.com", true, true);