test hostscan

dhcp/dhcp.go

@@ -0,0 +1,177 @@
+package dhcp
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"net"
+	"strings"
+)
+
+const (
+	MAGIC_COOKIE               uint32 = 0x63825363
+	OPT_CODE_SERVER_IDENTIFIER uint8  = 54
+	OPT_CODE_SUBNET_MASK       uint8  = 1
+	OPT_CODE_ROUTER            uint8  = 3
+	OPT_CODE_DNS               uint8  = 6
+)
+
+type dhcpDiscover struct {
+	MsgType             byte
+	HwType              byte
+	HwAddrLen           byte
+	Hops                byte
+	Xid                 uint32
+	Secs                uint16
+	BootpFlags          uint16
+	ClientIp            uint32
+	YourIp              uint32
+	NextServerIp        uint32
+	RelayAgentIp        uint32
+	ClientMacAddr       [6]byte
+	ClientHwAddrPadding [10]byte
+	ServerHostName      [64]byte
+	BootFileName        [128]byte
+	MagicCookie         uint32
+	Mtype               byte
+	MtypeLen            byte
+	MtypeVal            byte
+	Opts                [200]byte
+	End                 byte
+	Padding             [16]byte
+}
+
+func doDiscover(address string) (map[string]string, error) {
+
+	localAddr, err := net.ResolveUDPAddr("udp", address+":68")
+	if err != nil {
+		return nil, err
+	}
+	conn, err := net.ListenUDP("udp", localAddr)
+	if err != nil {
+		return nil, err
+	}
+	if err != nil {
+		return nil, err
+	}
+	defer conn.Close()
+
+	sendDiscover(conn) // broadcast 255.255.255.255:67
+
+	return readOffer(conn) // unicast
+
+}
+
+func sendDiscover(conn *net.UDPConn) error {
+
+	server := fmt.Sprintf("%s:%d", "255.255.255.255", 67)
+	serverAddr, err := net.ResolveUDPAddr("udp", server)
+	if err != nil {
+		return err
+	}
+
+	dhcp := dhcpDiscover{
+		MsgType:      0x01,
+		HwType:       0x01,
+		HwAddrLen:    0x06,
+		Hops:         0x00,
+		Xid:          0x00000000,
+		Secs:         0x0000,
+		ClientIp:     0x00000000,
+		YourIp:       0x00000000,
+		NextServerIp: 0x00000000,
+		RelayAgentIp: 0x00000000,
+		MagicCookie:  MAGIC_COOKIE,
+		Mtype:        0x35,
+		MtypeLen:     0x01,
+		MtypeVal:     0x01,
+		End:          0xff,
+	}
+
+	var flag uint16 = 0
+	dhcp.BootpFlags = ^flag // flag = unicast , ^flag = broadcast
+
+	writer := new(bytes.Buffer)
+	if err := binary.Write(writer, binary.BigEndian, dhcp); err != nil {
+		return err
+	}
+	_, err = conn.WriteToUDP(writer.Bytes(), serverAddr)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func readOffer(conn *net.UDPConn) (map[string]string, error) {
+	offerOptions := make(map[string]string)
+
+	buf := make([]byte, 1024)
+	_, _, err := conn.ReadFromUDP(buf)
+	if err != nil {
+		return nil, err
+	}
+
+	offer := dhcpDiscover{}
+
+	reader := new(bytes.Buffer)
+	reader.Write(buf)
+	if err := binary.Read(reader, binary.BigEndian, &offer); err != nil {
+		return nil, err
+	}
+	if offer.MagicCookie != MAGIC_COOKIE {
+		return nil, err
+	}
+
+	//option searching
+	r := new(bytes.Buffer)
+	r.Write(offer.Opts[:])
+
+	for i := 0; i < r.Len(); i++ {
+		v := r.Next(1)[0]
+
+		if v == OPT_CODE_SUBNET_MASK && r.Next(1)[0] == 4 {
+			ipStr := byteToIPString(r.Next(4))
+			offerOptions["SUBNETMASK"] = ipStr
+		}
+
+		if v == OPT_CODE_ROUTER && r.Next(1)[0] == 4 {
+			ipStr := byteToIPString(r.Next(4))
+			offerOptions["ROUTER"] = ipStr
+		}
+
+		if v == OPT_CODE_DNS {
+			len := r.Next(1)[0]
+			var dns []string
+			var ipStr string
+			ipStr = byteToIPString(r.Next(4))
+			dns = append(dns, ipStr)
+			if len == 8 {
+				ipStr = byteToIPString(r.Next(4))
+				dns = append(dns, ipStr)
+			}
+			offerOptions["DNS"] = strings.Join(dns, ",")
+		}
+
+		if v == OPT_CODE_SERVER_IDENTIFIER && r.Next(1)[0] == 4 {
+			ipStr := byteToIPString(r.Next(4))
+			offerOptions["DHCP_SERVER"] = ipStr
+		}
+	}
+
+	return offerOptions, nil
+}
+
+func byteToIPString(b []byte) string {
+	var ipStr string
+	len := len(b)
+	for i := 0; i < len; i++ {
+		v := b[i]
+		ipStr += fmt.Sprintf("%d", v)
+		if i < len-1 {
+			ipStr += "."
+		}
+	}
+
+	return ipStr
+}

dhcp/dhcp_test.go

@@ -0,0 +1,13 @@
+package dhcp
+
+import (
+	"testing"
+)
+
+func TestDHCP(t *testing.T) {
+	offer, err := doDiscover("192.168.1.201")
+	if err != nil {
+		t.Errorf("ERROR : %s", err.Error())
+	}
+	t.Log(offer)
+}