implement LuxPacket and AES CBC encryption

net/lux_packet.go

@@ -0,0 +1,87 @@
+package net
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"errors"
+	"lux/crypto"
+	"lux/proto"
+	"net"
+)
+
+const LUX_PROTO_PACKET_HDRLEN = proto.LUX_PROTO_ID_SIZE + 2
+
+type LuxPacket struct {
+	Target proto.LuxID
+	Type   uint
+	Buffer proto.LuxBuffer
+}
+
+func DecryptLuxPacket(dgram LuxDatagram, key crypto.LuxKey) (LuxPacket, error) {
+	packet := LuxPacket{}
+
+	cipherBlock, err := aes.NewCipher(key.Key)
+	if err != nil {
+		return packet, err
+	}
+	decrypter := cipher.NewCBCDecrypter(cipherBlock, key.IV)
+
+	payloadLen := len(dgram.Payload)
+	if payloadLen == 0 || payloadLen%cipherBlock.BlockSize() != 0 {
+		return packet, errors.New("payload is not block aligned")
+	}
+
+	payload := make([]byte, payloadLen)
+	decrypter.CryptBlocks(payload, dgram.Payload)
+
+	packet.Buffer = proto.FromSlice(payload)
+	if err := packet.Target.Read(&packet.Buffer); err != nil {
+		return packet, err
+
+	}
+
+	if pType, err := packet.Buffer.ReadUint16(); err == nil {
+		packet.Type = uint(pType)
+	} else {
+		return packet, err
+	}
+
+	return packet, nil
+}
+
+func EncryptLuxPacket(packet LuxPacket, key crypto.LuxKey, target *net.UDPAddr) (LuxDatagram, error) {
+	dgram := LuxDatagram{}
+
+	cipherBlock, err := aes.NewCipher(key.Key)
+	if err != nil {
+		return dgram, err
+	}
+	encrypter := cipher.NewCBCEncrypter(cipherBlock, key.IV)
+
+	var paddingLen int
+	packetLen := packet.Buffer.Length()
+	if packetLen%encrypter.BlockSize() != 0 {
+		paddingLen = ((packetLen / encrypter.BlockSize()) + 1) * encrypter.BlockSize()
+	} else {
+		paddingLen = 0
+	}
+
+	padding := make([]byte, paddingLen)
+	_, err = rand.Read(padding)
+	if err != nil {
+		return dgram, err
+	}
+
+	wd := proto.AllocLuxBuffer(LUX_PROTO_PACKET_HDRLEN + packetLen + paddingLen)
+	key.Id.Write(&wd)
+	wd.WriteUint16(uint16(packet.Type))
+	wd.WriteBytes(packet.Buffer.AllBytes())
+	wd.WriteBytes(padding)
+
+	dgram.Target = target
+	dgram.Payload = make([]byte, wd.Length())
+
+	encrypter.CryptBlocks(dgram.Payload, wd.AllBytes())
+	return dgram, nil
+}

tests/lux_packet_test.go

@@ -0,0 +1,46 @@
+package tests
+
+import (
+	"bytes"
+	"lux/crypto"
+	"lux/net"
+	"lux/proto"
+	"testing"
+)
+
+func TestEncryptDecrypt(t *testing.T) {
+	key, _ := crypto.NewLuxKey(proto.LuxTypeHost)
+	packet := net.LuxPacket{
+		Target: key.Id,
+		Type:   0x1234,
+		Buffer: proto.NewLuxBuffer(),
+	}
+	packet.Buffer.WriteString("hello world! very unaligned")
+
+	dgram, err := net.EncryptLuxPacket(packet, key, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	new, err := net.DecryptLuxPacket(dgram, key)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if !bytes.Equal(key.Id.UUID[:], new.Target.UUID[:]) {
+		t.Fatal(key.Id)
+		t.Fatal(new.Target.UUID)
+		t.Fatal("LuxIDs are not equal")
+	}
+	if new.Type != 0x1234 {
+		t.Fatalf("%x new lux packet type instead of 0x1234", new.Type)
+	}
+
+	str, err := new.Buffer.ReadString()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if str != "hello world! very unaligned" {
+		t.Fatalf("wrong string: %s", str)
+	}
+}