public DhcpCapture(Parameters parameters)
{
_parameters = parameters;
_packets = new Queue<Packet>();
_pcapFileWriter = new CaptureFileWriterDevice(
LinkLayers.Ethernet, null, _parameters.PcapFilename, FileMode.OpenOrCreate);
}
public static DhcpPacket GenerateDhcpDiscoverPacket(Parameters parameters)
{
var packet = new DhcpPacket(new byte[244]);
// Generate a Transaction ID for this request
var xid = new byte[4];
xid[0] = 0xE7;
xid[1] = 0x03;
xid[2] = 0x00;
xid[3] = 0x00;
//XidRandom.NextBytes(xid);
byte[] macAddress = parameters.MacAddress;
// Actual DHCPDISCOVER packet
byte[] data = packet._data;
Array.Copy(xid, 0, data, 4, 4);
Array.Copy(macAddress, 0, data, 28, 6);
// Set the OP Code to BOOTREQUEST
data[0] = 1;
// Set the Hardware Address Type to Ethernet
data[1] = 1;
// Set the Hardware Address Length (number of bytes)
data[2] = 6;
// Set the Broadcast Flag
data[10] = 128;
// Set the Magic Cookie values
data[236] = 99; // D
data[237] = 130; // H
data[238] = 83; // C
data[239] = 99; // P
// Set the DHCPDiscover Message Type Option
data[240] = 53;
data[241] = 1;
data[242] = 1;
// End Option
data[243] = 255;
return packet;
}
public DhcpClient(Parameters parameters)
{
_parameters = parameters;
CreateSocket();
}
private Program()
{
_parameters = new Parameters();
_captureDriver = new DhcpCapture(_parameters);
}
public void ReadPacket(Parameters parameters, StringBuilder sb)
{
//Field DHCPOFFER
//----- ---------
//'op' BOOTREPLY
//'htype' (From "Assigned Numbers" RFC)
//'hlen' (Hardware address length in octets)
//'hops' 0
//'xid' 'xid' from client DHCPDISCOVER message
//'secs' 0
//'ciaddr' 0
//
//'yiaddr' IP address offered to client
//'siaddr' IP address of next bootstrap server
//'flags' 'flags' from client DHCPDISCOVER message
//'giaddr' 'giaddr' from client DHCPDISCOVER message
//'chaddr' 'chaddr' from client DHCPDISCOVER message
//'sname' Server host name or options
//'file' Client boot file name or options
//'options' options
var binaryReader = new BinaryReader(new MemoryStream(_data));
string serverIp = "?";
string leaseTime = "?";
string renewalTime = "?";
string rebindingTime = "?";
string subnetMask = "?";
string routers = "?";
string dnsServers = "?";
string hostName = "?";
string domainName = "?";
byte otype = 0;
// skip to xid
binaryReader.ReadBytes(4);
// xid chosen by client
uint xid = binaryReader.ReadUInt32();
// skip to ciaddr
binaryReader.ReadBytes(4);
string ciaddr = ReadIpv4(binaryReader);
string yiaddr = ReadIpv4(binaryReader);
// skip 220 bytes to options
binaryReader.ReadBytes(220);
while (binaryReader.BaseStream.Position < binaryReader.BaseStream.Length)
{
byte optionCode = binaryReader.ReadByte();
if (optionCode != 0 && optionCode != 255)
{
byte optionLength = binaryReader.ReadByte();
switch (optionCode)
{
// Subnet Mask
case 1:
subnetMask = ReadIpv4(binaryReader);
break;
case 3:
routers = ReadIpv4List(optionLength, binaryReader);
break;
case 6:
dnsServers = ReadIpv4List(optionLength, binaryReader);
break;
case 12:
if (optionLength > 0)
{
byte[] buffer = binaryReader.ReadBytes(optionLength);
if (buffer.Length != optionLength)
Console.WriteLine("WARNING: Could not read all bytes, option 12");
hostName = Encoding.ASCII.GetString(buffer, 0, buffer.Length);
}
break;
case 15:
if (optionLength > 0)
{
byte[] buffer = binaryReader.ReadBytes(optionLength);
if (buffer.Length != optionLength)
Console.WriteLine("WARNING: Could not read all bytes, option 15");
domainName = Encoding.ASCII.GetString(buffer, 0, buffer.Length - 1);
}
break;
// lease time
case 51:
leaseTime = ReadTimeInterval(binaryReader);
break;
// DHCP message type
case 53:
otype = binaryReader.ReadByte();
//1 DHCPDISCOVER
//2 DHCPOFFER
//3 DHCPREQUEST
//4 DHCPDECLINE
//5 DHCPACK
//6 DHCPNAK
//7 DHCPRELEASE
//8 DHCPINFORM
break;
// DHCP server identifier
case 54:
serverIp = ReadIpv4(binaryReader);
break;
case 58:
renewalTime = ReadTimeInterval(binaryReader);
break;
case 59:
rebindingTime = ReadTimeInterval(binaryReader);
break;
case 24: // MTU aging, ignore
case 46: // Netbios stuff ignore
case 81: // Client FQDN feature ignored
case 254: // extensions, ignore
binaryReader.ReadBytes(optionLength);
break;
default:
{
Console.WriteLine("Option {0} not supported yet (length={1})", optionCode, optionLength);
binaryReader.ReadBytes(optionLength);
break;
}
}
}
}
string loggingText = null;
switch (otype)
{
case 1:
loggingText = string.Format("DISCOVER\t{0:X8}\t{1}", xid, ciaddr);
break;
case 2:
loggingText =
string.Format(
"OFFER\t{0:X8}\t{1}\t{2}\t{3}\t{4}\t{5}\t{6}\tDN={7}\tDNS={8}\tGW={9}",
xid, serverIp, yiaddr,
leaseTime, renewalTime, rebindingTime,
subnetMask,
domainName, dnsServers, routers,
xid);
break;
case 5:
loggingText = string.Format("ACK\t{0:X8}\t{1}\t{2}", xid, ciaddr, yiaddr);
break;
case 8:
loggingText = string.Format("INFORM\t{0:X8}\t{1}\t{2}\t{3}", xid, ciaddr, yiaddr, hostName);
break;
default:
Console.WriteLine("Not handled: DHCP message type {0}", otype);
break;
}
if (loggingText != null)
{
sb.Append(loggingText);
}
}