lorawan: add initial LoRaWAN stack support

Signed-off-by: deadprogram <ron@hybridgroup.com>

lora/lorawan/mic.go

@@ -0,0 +1,38 @@
+package lorawan
+
+import (
+	"encoding/binary"
+)
+
+// genPayloadMIC computes MIC given the payload and the key
+func genPayloadMIC(payload []uint8, key [16]uint8) [4]uint8 {
+	var mic [4]uint8
+	hash, _ := NewCmac(key[:])
+	hash.Write(payload)
+	hb := hash.Sum([]byte{})
+	copy(mic[:], hb[0:4])
+	return mic
+}
+
+func calcMessageMIC(payload []uint8, key [16]uint8, dir uint8, addr []byte, fCnt uint32, lenMessage uint8) [4]uint8 {
+	var b0 []byte
+	b0 = append(b0, 0x49, 0x00, 0x00, 0x00, 0x00)
+	b0 = append(b0, dir)
+	b0 = append(b0, addr[:]...)
+	var b [4]byte
+	binary.LittleEndian.PutUint32(b[:], fCnt)
+	b0 = append(b0, b[:]...)
+	b0 = append(b0, 0x00)
+	b0 = append(b0, lenMessage)
+
+	var full []byte
+	full = append(full, b0...)
+	full = append(full, payload...)
+
+	var mic [4]uint8
+	hash, _ := NewCmac(key[:])
+	hash.Write(full)
+	hb := hash.Sum([]byte{})
+	copy(mic[:], hb[0:4])
+	return mic
+}