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deadprogram
106 lines
2.2 KiB
Go
106 lines
2.2 KiB
Go
package lorawan
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import (
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"crypto/aes"
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"encoding/binary"
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"encoding/hex"
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"errors"
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"math"
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)
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// Session is used to store session data of a LoRaWAN session
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type Session struct {
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NwkSKey [16]uint8
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AppSKey [16]uint8
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DevAddr [4]uint8
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FCntDown uint32
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FCntUp uint32
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CFList [16]uint8
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RXDelay uint8
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DLSettings uint8
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}
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// SetDevAddr configures the Session DevAddr
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func (s *Session) SetDevAddr(devAddr []uint8) error {
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if len(devAddr) != 4 {
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return errors.New("invalid length")
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}
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copy(s.DevAddr[:], devAddr)
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return nil
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}
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func (s *Session) GetDevAddr() string {
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return hex.EncodeToString(s.DevAddr[:])
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}
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// GenMessage Forge an uplink message
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func (s *Session) GenMessage(dir uint8, payload []uint8) ([]uint8, error) {
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var buf []uint8
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buf = append(buf, 0b01000000) // FHDR Unconfirmed up
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buf = append(buf, s.DevAddr[:]...)
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// FCtl : No ADR, No RFU, No ACK, No FPending, No FOpt
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buf = append(buf, 0x00)
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// FCnt Up
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buf = append(buf, uint8(s.FCntUp&0xFF), uint8((s.FCntUp>>8)&0xFF))
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// FPort=1
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buf = append(buf, 0x01)
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fCnt := uint32(0)
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if dir == 0 {
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fCnt = s.FCntUp
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s.FCntUp++
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} else {
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fCnt = s.FCntDown
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}
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data, err := s.genFRMPayload(dir, fCnt, payload, false)
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if err != nil {
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return nil, err
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}
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buf = append(buf, data[:]...)
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mic := calcMessageMIC(buf, s.NwkSKey, dir, s.DevAddr[:], fCnt, uint8(len(buf)))
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buf = append(buf, mic[:]...)
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return buf, nil
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}
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func (s *Session) genFRMPayload(dir uint8, fCnt uint32, payload []byte, isFOpts bool) ([]byte, error) {
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k := len(payload) / aes.BlockSize
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if len(payload)%aes.BlockSize != 0 {
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k++
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}
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if k > math.MaxUint8 {
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return nil, errors.New("Payload too big !")
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}
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encrypted := make([]byte, 0, k*16)
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cipher, err := aes.NewCipher(s.AppSKey[:])
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if err != nil {
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panic(err)
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}
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var a [aes.BlockSize]byte
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a[0] = 0x01
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a[5] = dir
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copy(a[6:10], s.DevAddr[:])
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binary.LittleEndian.PutUint32(a[10:14], fCnt)
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var ss [aes.BlockSize]byte
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var b [aes.BlockSize]byte
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for i := uint8(0); i < uint8(k); i++ {
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copy(b[:], payload[i*aes.BlockSize:])
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if !isFOpts {
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a[15] = i + 1
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}
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cipher.Encrypt(ss[:], a[:])
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for j := 0; j < aes.BlockSize; j++ {
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b[j] = b[j] ^ ss[j]
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}
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encrypted = append(encrypted, b[:]...)
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}
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return encrypted[:len(payload)], nil
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}
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