2023-05-02 23:33:14 +00:00
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package dhcp
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import (
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"bytes"
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"encoding/binary"
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"fmt"
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2023-05-05 07:13:46 +00:00
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"io"
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2023-05-02 23:33:14 +00:00
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"net"
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"strings"
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2023-05-05 07:13:46 +00:00
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log "git.wntrmute.dev/kyle/goutils/syslog"
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2023-05-02 23:33:14 +00:00
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)
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const (
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maxHardwareAddrLen = 16
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maxServerName = 64
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maxFileName = 128
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)
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var anyAddr = net.IP([]byte{0, 0, 0, 0})
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func formatMAC(mac []byte) string {
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s := []string{}
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for i := 0; i < len(mac); i++ {
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s = append(s, fmt.Sprintf("%0x", mac[i:i+1]))
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}
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return strings.Join(s, ":")
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}
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type BootRequest struct {
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MessageType uint8
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HardwareType uint8
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HardwareAddress []byte
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Hops uint8
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TransactionID uint32
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SecondsElapsed uint16
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Flags uint16
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ServerName string
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FileName string
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ClientIP net.IP
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YourIP net.IP
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NextIP net.IP
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RelayIP net.IP
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2023-05-06 05:21:27 +00:00
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DHCPType DHCPMessageType // option 53
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HostName string // option 12
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ParameterRequests []OptionTag
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endOptions bool
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}
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func newPacketReaderFunc(r io.Reader) func(v any) error {
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return func(v any) error {
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return binary.Read(r, binary.BigEndian, v)
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}
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2023-05-02 23:33:14 +00:00
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}
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func (req *BootRequest) Read(packet []byte) error {
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buf := bytes.NewBuffer(packet)
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2023-05-06 05:21:27 +00:00
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read := newPacketReaderFunc(buf)
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2023-05-02 23:33:14 +00:00
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if err := read(&req.MessageType); err != nil {
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return err
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}
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if err := read(&req.HardwareType); err != nil {
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return err
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}
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var hwaLength uint8
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if err := read(&hwaLength); err != nil {
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return err
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}
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if err := read(&req.Hops); err != nil {
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return err
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}
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if err := read(&req.TransactionID); err != nil {
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return err
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}
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if err := read(&req.SecondsElapsed); err != nil {
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return err
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}
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if err := read(&req.Flags); err != nil {
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return err
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}
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req.ClientIP = anyAddr[:]
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if _, err := buf.Read(req.ClientIP); err != nil {
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return err
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}
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req.YourIP = anyAddr[:]
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if _, err := buf.Read(req.YourIP); err != nil {
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return err
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}
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req.NextIP = anyAddr[:]
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if _, err := buf.Read(req.NextIP); err != nil {
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return err
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}
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req.RelayIP = anyAddr[:]
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if _, err := buf.Read(req.RelayIP); err != nil {
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return err
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}
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req.HardwareAddress = make([]byte, int(hwaLength))
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if _, err := buf.Read(req.HardwareAddress); err != nil {
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return err
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}
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hwaPad := make([]byte, maxHardwareAddrLen-hwaLength)
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if _, err := buf.Read(hwaPad); err != nil {
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return err
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}
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tempBuf := make([]byte, maxServerName)
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if _, err := buf.Read(tempBuf); err != nil {
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return err
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}
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req.ServerName = string(bytes.Trim(tempBuf, "\x00"))
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tempBuf = make([]byte, maxFileName)
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if _, err := buf.Read(tempBuf); err != nil {
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return err
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}
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req.FileName = string(bytes.Trim(tempBuf, "\x00"))
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2023-05-06 05:21:27 +00:00
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if err := ReadMagicCookie(buf); err != nil {
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return err
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}
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2023-05-05 07:13:46 +00:00
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for {
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2023-05-06 05:21:27 +00:00
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if req.endOptions {
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break
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}
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2023-05-05 07:13:46 +00:00
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tag, err := buf.ReadByte()
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if err != nil {
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if err == io.EOF {
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break
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}
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return err
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}
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err = ReadOption(req, tag, buf)
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if err != nil {
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2023-05-06 05:21:27 +00:00
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log.Spew(*req)
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log.Spew(packet)
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2023-05-05 07:13:46 +00:00
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return err
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}
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}
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2023-05-02 23:33:14 +00:00
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return nil
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}
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func ReadRequest(pkt []byte) (*BootRequest, error) {
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req := &BootRequest{}
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err := req.Read(pkt)
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if err != nil {
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return nil, err
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}
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log.Debugf("dhcp: BOOTP request with txid %d for %s", req.TransactionID, formatMAC(req.HardwareAddress))
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return req, nil
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}
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