/// <summary>
/// Parses specified count of answers from query.
/// </summary>
/// <param name="reply">Server returned query.</param>
/// <param name="answerCount">Number of answers to parse.</param>
/// <param name="offset">Position from where to start parsing answers.</param>
/// <returns></returns>
private List <DNS_rr> ParseAnswers(byte[] reply, int answerCount, ref int offset)
{
/* RFC 1035 4.1.3. Resource record format
*
* 1 1 1 1 1 1
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| |
| / /
| / NAME /
| |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| TYPE |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| CLASS |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| TTL |
| |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| RDLENGTH |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
| / RDATA /
| / /
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
*/
List <DNS_rr> answers = new List <DNS_rr>();
//---- Start parsing answers ------------------------------------------------------------------//
for (int i = 0; i < answerCount; i++)
{
string name = "";
if (!GetQName(reply, ref offset, ref name))
{
break;
}
int type = reply[offset++] << 8 | reply[offset++];
int rdClass = reply[offset++] << 8 | reply[offset++];
int ttl = reply[offset++] << 24 | reply[offset++] << 16 | reply[offset++] << 8 | reply[offset++];
int rdLength = reply[offset++] << 8 | reply[offset++];
if ((DNS_QType)type == DNS_QType.A)
{
answers.Add(DNS_rr_A.Parse(name, reply, ref offset, rdLength, ttl));
}
else if ((DNS_QType)type == DNS_QType.NS)
{
answers.Add(DNS_rr_NS.Parse(name, reply, ref offset, rdLength, ttl));
}
else if ((DNS_QType)type == DNS_QType.CNAME)
{
answers.Add(DNS_rr_CNAME.Parse(name, reply, ref offset, rdLength, ttl));
}
else if ((DNS_QType)type == DNS_QType.SOA)
{
answers.Add(DNS_rr_SOA.Parse(name, reply, ref offset, rdLength, ttl));
}
else if ((DNS_QType)type == DNS_QType.PTR)
{
answers.Add(DNS_rr_PTR.Parse(name, reply, ref offset, rdLength, ttl));
}
else if ((DNS_QType)type == DNS_QType.HINFO)
{
answers.Add(DNS_rr_HINFO.Parse(name, reply, ref offset, rdLength, ttl));
}
else if ((DNS_QType)type == DNS_QType.MX)
{
answers.Add(DNS_rr_MX.Parse(name, reply, ref offset, rdLength, ttl));
}
else if ((DNS_QType)type == DNS_QType.TXT)
{
answers.Add(DNS_rr_TXT.Parse(name, reply, ref offset, rdLength, ttl));
}
else if ((DNS_QType)type == DNS_QType.AAAA)
{
answers.Add(DNS_rr_AAAA.Parse(name, reply, ref offset, rdLength, ttl));
}
else if ((DNS_QType)type == DNS_QType.SRV)
{
answers.Add(DNS_rr_SRV.Parse(name, reply, ref offset, rdLength, ttl));
}
else if ((DNS_QType)type == DNS_QType.NAPTR)
{
answers.Add(DNS_rr_NAPTR.Parse(name, reply, ref offset, rdLength, ttl));
}
else if ((DNS_QType)type == DNS_QType.SPF)
{
answers.Add(DNS_rr_SPF.Parse(name, reply, ref offset, rdLength, ttl));
}
else
{
// Unknown record, skip it.
offset += rdLength;
}
}
return(answers);
}
public bool Filter(string from, IMailServerManagementApi api, SMTP_Session session, out string errorText)
{
errorText = null;
bool result = true;
if (session.IsAuthenticated || this.IsPrivateIP(session.RemoteEndPoint.Address))
{
return(true);
}
try
{
DataSet dataSet = new DataSet();
dataSet.Tables.Add("General");
dataSet.Tables["General"].Columns.Add("CheckHelo");
dataSet.Tables["General"].Columns.Add("LogRejections");
dataSet.Tables.Add("BlackListSettings");
dataSet.Tables["BlackListSettings"].Columns.Add("ErrorText");
dataSet.Tables.Add("BlackList");
dataSet.Tables["BlackList"].Columns.Add("IP");
dataSet.Tables.Add("Servers");
dataSet.Tables["Servers"].Columns.Add("Cost");
dataSet.Tables["Servers"].Columns.Add("Server");
dataSet.Tables["Servers"].Columns.Add("DefaultRejectionText");
dataSet.ReadXml(Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location) + "\\DnsBlackList.xml");
bool flag = false;
if (dataSet.Tables["General"].Rows.Count == 1)
{
if (Convert.ToBoolean(dataSet.Tables["General"].Rows[0]["CheckHelo"]))
{
DnsServerResponse dnsServerResponse = Dns_Client.Static.Query(session.EhloHost, DNS_QType.A);
if (dnsServerResponse.ConnectionOk && dnsServerResponse.ResponseCode != DNS_RCode.SERVER_FAILURE)
{
bool flag2 = false;
DNS_rr_A[] aRecords = dnsServerResponse.GetARecords();
for (int i = 0; i < aRecords.Length; i++)
{
DNS_rr_A dNS_rr_A = aRecords[i];
if (session.RemoteEndPoint.Address.Equals(dNS_rr_A.IP))
{
flag2 = true;
break;
}
}
if (!flag2)
{
errorText = "Not valid DNS EHLO/HELO name for your IP '" + session.EhloHost + "' !";
bool result2 = false;
return(result2);
}
}
}
flag = ConvertEx.ToBoolean(dataSet.Tables["General"].Rows[0]["LogRejections"]);
}
foreach (DataRow dataRow in dataSet.Tables["BlackList"].Rows)
{
if (this.IsAstericMatch(dataRow["IP"].ToString(), session.RemoteEndPoint.Address.ToString()))
{
errorText = dataSet.Tables["BlackListSettings"].Rows[0]["ErrorText"].ToString();
bool result2 = false;
return(result2);
}
}
foreach (DataRow dataRow2 in dataSet.Tables["Servers"].Rows)
{
DnsServerResponse dnsServerResponse2 = Dns_Client.Static.Query(this.ReverseIP(session.RemoteEndPoint.Address) + "." + dataRow2["Server"].ToString(), DNS_QType.ANY);
DNS_rr_A[] aRecords2 = dnsServerResponse2.GetARecords();
if (aRecords2.Length > 0)
{
if (flag)
{
this.WriteFilterLog(string.Concat(new string[]
{
"Sender:",
from,
" IP:",
session.RemoteEndPoint.Address.ToString(),
" blocked\r\n"
}));
}
errorText = dataRow2["DefaultRejectionText"].ToString();
if (dnsServerResponse2.GetTXTRecords().Length > 0)
{
errorText = dnsServerResponse2.GetTXTRecords()[0].Text;
}
if (errorText == "")
{
errorText = "You are in '" + dataRow2["Server"].ToString() + "' rejection list !";
}
bool result2 = false;
return(result2);
}
}
}
catch
{
}
return(result);
}
