/*
All communications inside of the domain protocol are carried in a single
format called a message. The top level format of message is divided
into 5 sections (some of which are empty in certain cases) shown below:
+---------------------+
| Header |
+---------------------+
| Question | the question for the name server
+---------------------+
| Answer | RRs answering the question
+---------------------+
| Authority | RRs pointing toward an authority
+---------------------+
| Additional | RRs holding additional information
+---------------------+
*/
public static byte[] EncodeDnsMessage(DnsMessage message)
{
MemoryStream stream = new MemoryStream(512);
BinaryWriter writer = new BinaryWriter(stream);
byte[] header = EncodeHeader(message);
writer.Write(header);
foreach (DnsQuery query in message.Querys)
{
writer.Write(EncodeDnsQuery(query));
}
foreach (DnsResource answer in message.Answers)
{
writer.Write(EncodeDnsResource(answer));
}
foreach (DnsResource record in message.AuthorityRecords)
{
writer.Write(EncodeDnsResource(record));
}
foreach (DnsResource record in message.AdditionalRecords)
{
writer.Write(EncodeDnsResource(record));
}
return stream.ToArray();
}
/*
* Header Structure, the bit labeled 0 is the most significant bit.
*
* 0 1 2 3 4 5 6 7 8 9 A B C D E F
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ID |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|QR| Opcode |AA|TC|RD|RA| Z | RCODE |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| QDCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ANCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| NSCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ARCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
*/
public static byte[] EncodeHeader(DnsMessage message)
{
MemoryStream stream = new MemoryStream(12);
BinaryWriter writer = new BinaryWriter(stream);
WriteUInt16BE(writer, message.ID);
int fields = (int)message.ResponseCode;
if (message.IsRecursionAvailable)
{
fields |= 0x80;
}
if (message.IsRecursionDesired)
{
fields |= 0x100;
}
if (message.IsTruncated)
{
fields |= 0x200;
}
if (message.IsRecursionAvailable)
{
fields |= 0x400;
}
fields |= (int)message.QueryKind << 11; //Opcode
if (message.Type == MessageType.Response)
{
fields |= 0x8000;
}
WriteUInt16BE(writer, (UInt16)fields);
WriteUInt16BE(writer, (UInt16)message.Querys.Count);
WriteUInt16BE(writer, (UInt16)message.Answers.Count);
WriteUInt16BE(writer, (UInt16)message.AuthorityRecords.Count);
WriteUInt16BE(writer, (UInt16)message.AdditionalRecords.Count);
return(stream.ToArray());
}
/*
* Header Structure, the bit labeled 0 is the most significant bit.
0 1 2 3 4 5 6 7 8 9 A B C D E F
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ID |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|QR| Opcode |AA|TC|RD|RA| Z | RCODE |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| QDCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ANCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| NSCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ARCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
*/
public static byte[] EncodeHeader(DnsMessage message)
{
MemoryStream stream = new MemoryStream(12);
BinaryWriter writer = new BinaryWriter(stream);
WriteUInt16BE(writer, message.ID);
int fields = (int)message.ResponseCode;
if (message.IsRecursionAvailable)
{
fields |= 0x80;
}
if (message.IsRecursionDesired)
{
fields |= 0x100;
}
if (message.IsTruncated)
{
fields |= 0x200;
}
if (message.IsRecursionAvailable)
{
fields |= 0x400;
}
fields |= (int)message.QueryKind << 11; //Opcode
if (message.Type == MessageType.Response)
{
fields |= 0x8000;
}
WriteUInt16BE(writer, (UInt16)fields);
WriteUInt16BE(writer, (UInt16)message.Querys.Count);
WriteUInt16BE(writer, (UInt16)message.Answers.Count);
WriteUInt16BE(writer, (UInt16)message.AuthorityRecords.Count);
WriteUInt16BE(writer, (UInt16)message.AdditionalRecords.Count);
return stream.ToArray();
}
public static DnsMessage DecodeDnsMessage(byte[] msgData)
{
DnsMessage message = new DnsMessage();
message.ID = (UInt16)(msgData[0] << 8 | msgData[1]);
message.Type = (MessageType)(msgData[2] >> 7);
message.QueryKind = (QueryKind)((msgData[2] >> 3) & 15);
message.ResponseCode = (ResponseCode)(msgData[3] & 15);
MemoryStream stream = new MemoryStream(msgData);
stream.Position = 4;
BinaryReader reader = new BinaryReader(stream);
int queryCount = ReadUInt16BE(reader);
int answerCount = ReadUInt16BE(reader);
int nsCount = ReadUInt16BE(reader);
int arCount = ReadUInt16BE(reader);
for (int i = 0; i < queryCount; i++)
{
message.Querys.Add(ReadDnsQuery(reader));
}
for (int i = 0; i < answerCount; i++)
{
message.Answers.Add(ReadResourceRecord(reader));
}
for (int i = 0; i < nsCount; i++)
{
message.AuthorityRecords.Add(ReadResourceRecord(reader));
}
for (int i = 0; i < arCount; i++)
{
message.AdditionalRecords.Add(ReadResourceRecord(reader));
}
return(message);
}
public static DnsMessage DecodeDnsMessage(byte[] msgData)
{
DnsMessage message = new DnsMessage();
message.ID = (UInt16)(msgData[0] << 8 | msgData[1]);
message.Type = (MessageType)(msgData[2] >> 7);
message.QueryKind = (QueryKind)((msgData[2] >> 3) & 15);
message.ResponseCode = (ResponseCode)(msgData[3] & 15);
MemoryStream stream = new MemoryStream(msgData);
stream.Position = 4;
BinaryReader reader = new BinaryReader(stream);
int queryCount = ReadUInt16BE(reader);
int answerCount = ReadUInt16BE(reader);
int nsCount = ReadUInt16BE(reader);
int arCount = ReadUInt16BE(reader);
for (int i = 0; i < queryCount; i++)
{
message.Querys.Add(ReadDnsQuery(reader));
}
for (int i = 0; i < answerCount; i++)
{
message.Answers.Add(ReadResourceRecord(reader));
}
for (int i = 0; i < nsCount; i++)
{
message.AuthorityRecords.Add(ReadResourceRecord(reader));
}
for (int i = 0; i < arCount; i++)
{
message.AdditionalRecords.Add(ReadResourceRecord(reader));
}
return message;
}
private static IPAddress[] GetAddressList(DnsMessage answer, List<string> authorities)
{
List<IPAddress> serverAddresses = new List<IPAddress>();
foreach (DnsResource resource in answer.AdditionalRecords)
{
if (resource.QueryType == QueryType.Address)
{
if (authorities.Contains(resource.Name))
{
IPAddress serverIP = new IPAddress((byte[])resource.Content);
serverAddresses.Add(serverIP);
}
}
}
return serverAddresses.ToArray();
}
private static IPAddress[] GetAuthorityServers(DnsMessage answer)
{
List<string> authorities = new List<string>();
foreach (DnsResource resource in answer.AuthorityRecords)
{
if (resource.QueryType == QueryType.NameServer)
{
string nameServer = (string)resource.Content;
authorities.Add(nameServer);
}
}
if (answer.AdditionalRecords.Count > 0)
{
return GetAddressList(answer, authorities);
}
else
{
List<IPAddress> serverAddresses = new List<IPAddress>();
foreach (string authority in authorities)
{
serverAddresses.AddRange(System.Net.Dns.GetHostAddresses(authority));
}
return serverAddresses.ToArray();
}
}
private static string[] GetMailExchangeAliases(string domainName, DnsMessage answer)
{
List<string> aliases = new List<string>();
foreach (DnsResource resource in answer.Answers)
{
if (resource.QueryType == QueryType.MailExchange && resource.Name == domainName)
{
MailExchange mailExchange = (MailExchange)resource.Content;
aliases.Add(mailExchange.HostName);
}
}
return aliases.ToArray();
}
private static IPAddress[] GetAddressList(string domainName, DnsMessage answer)
{
List<IPAddress> addresseList = new List<IPAddress>();
foreach (DnsResource resource in answer.Answers)
{
if (resource.QueryType == QueryType.Address && resource.Name == domainName)
{
IPAddress ipAddress = new IPAddress((byte[])resource.Content);
addresseList.Add(ipAddress);
}
}
return addresseList.ToArray();
}
public static DnsMessage InverseQuery()
{
DnsMessage message = new DnsMessage();
message.ID = GenerateID();
message.Type = MessageType.Query;
message.QueryKind = QueryKind.InverseQuery;
return message;
}
public static DnsMessage StandardQuery()
{
DnsMessage message = new DnsMessage();
message.ID = GenerateID();
message.Type = MessageType.Query;
message.QueryKind = QueryKind.StandardQuery;
return message;
}