First working encryption

still unsafe because key is unencrypted

client.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"crypto/rand"
 	"encoding/hex"
 	"fmt"
 	"net"
@@ -9,9 +10,25 @@ import (
 	"time"
 )
 
+func SendPacket(pck *Packet, key [32]byte, conn *net.UDPConn) {
+	secPck := NewSymetricSecurePacket(key, pck)
+	fmt.Println(secPck)
+	if _, err := conn.Write(secPck.ToBytes()); err != nil {
+		panic(err)
+	}
+}
+
 func GetFile(path string) {
 	request := NewRequest(path)
 
+	k := make([]byte, 32)
+	_, err := rand.Read(k)
+	if err != nil {
+		panic(err)
+	}
+	key := [32]byte(k)
+	keyExchangePck := NewRsaPacket(request.sid, key)
+
 	udpAddr, err := net.ResolveUDPAddr("udp", "0.0.0.0:13374")
 	// udpAddr, err := net.ResolveUDPAddr("udp", "192.168.2.145:13374")
 
@@ -28,11 +45,13 @@ func GetFile(path string) {
 		os.Exit(1)
 	}
 
-	_, err = conn.Write(request.ToBytes())
+	_, err = conn.Write(keyExchangePck.ToBytes())
 	if err != nil {
 		panic(err)
 	}
 
+	SendPacket(request, key, conn)
+
 	bytes := make([]byte, PacketSize)
 	file, err := os.Create("out/" + hex.EncodeToString(request.sid[:]) + ".recv")
 	if err != nil {
@@ -57,7 +76,7 @@ func GetFile(path string) {
 	file.Truncate(int64(size))
 
 	ackPck := NewAck(&pck)
-	conn.Write(ackPck.ToBytes())
+	SendPacket(ackPck, key, conn)
 
 	recvPackets := make([]uint32, 0)
 	var endPacket Packet
@@ -113,7 +132,7 @@ func GetFile(path string) {
 
 			fmt.Printf("Request resend for %v\n", sync)
 			resend := NewResend(uint32(sync), lastPacket)
-			conn.Write(resend.ToBytes())
+			SendPacket(resend, key, conn)
 			lastPacket = resend
 
 			conn.SetReadDeadline(time.Now().Add(10 * time.Second))
@@ -144,7 +163,7 @@ func GetFile(path string) {
 	}
 
 	ack := NewAck(&endPacket)
-	conn.Write(ack.ToBytes())
+	SendPacket(ack, key, conn)
 }
 
 func remove(s []uint32, i int) []uint32 {

go.mod

@@ -1,3 +1,7 @@
 module pablu/uftp
 
-go 1.21.1
+go 1.21.1
+
+require golang.org/x/crypto v0.15.0
+
+require golang.org/x/sys v0.14.0 // indirect

go.sum

@@ -0,0 +1,4 @@
+golang.org/x/crypto v0.15.0 h1:frVn1TEaCEaZcn3Tmd7Y2b5KKPaZ+I32Q2OA3kYp5TA=
+golang.org/x/crypto v0.15.0/go.mod h1:4ChreQoLWfG3xLDer1WdlH5NdlQ3+mwnQq1YTKY+72g=
+golang.org/x/sys v0.14.0 h1:Vz7Qs629MkJkGyHxUlRHizWJRG2j8fbQKjELVSNhy7Q=
+golang.org/x/sys v0.14.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=

packets.go

@@ -5,12 +5,23 @@ import (
 	"encoding/binary"
 	"errors"
 	"fmt"
+
+	"golang.org/x/crypto/chacha20poly1305"
 )
 
 const HeaderSize int = 32 + 1 + 4 + 4
+const SecureHeaderSize int = 1 + 42 + 32 + 4
 
 type SessionID [32]byte
 
+type SecurePacket struct {
+	isRsa         byte // 0 = false everything else is true
+	nonce         [24]byte
+	sid           SessionID
+	dataLength    uint32
+	encryptedData []byte
+}
+
 type Packet struct {
 	// headerLength uint32
 	sid        SessionID
@@ -20,6 +31,84 @@ type Packet struct {
 	data       []byte
 }
 
+func NewSymetricSecurePacket(key [32]byte, pck *Packet) *SecurePacket {
+	sid := pck.sid
+	data := pck.ToBytes()
+	aead, err := chacha20poly1305.NewX(key[:])
+	if err != nil {
+		panic(err)
+	}
+
+	nonce := make([]byte, 24)
+	if _, err = rand.Read(nonce); err != nil {
+		panic(err)
+	}
+
+	encrypted := make([]byte, len(data)+aead.Overhead())
+	encrypted = aead.Seal(nil, nonce, data, nil)
+
+	return &SecurePacket{
+		isRsa:         0,
+		nonce:         [24]byte(nonce),
+		sid:           sid,
+		dataLength:    uint32(len(encrypted)),
+		encryptedData: encrypted,
+	}
+}
+
+func SecurePacketFromBytes(bytes []byte) SecurePacket {
+	isRsa := bytes[0]
+	nonce := bytes[1:25]
+	sid := SessionID(bytes[25:57])
+	length := binary.LittleEndian.Uint32(bytes[57:61])
+	enc := bytes[61 : 61+length]
+
+	return SecurePacket{
+		isRsa:         isRsa,
+		nonce:         [24]byte(nonce),
+		sid:           sid,
+		encryptedData: enc,
+		dataLength:    length,
+	}
+}
+
+func (secPck *SecurePacket) ToBytes() []byte {
+	arr := make([]byte, SecureHeaderSize+len(secPck.encryptedData))
+	arr[0] = secPck.isRsa
+	copy(arr[1:25], secPck.nonce[:])
+	copy(arr[25:57], secPck.sid[:])
+	binary.LittleEndian.PutUint32(arr[57:61], secPck.dataLength)
+	copy(arr[61:], secPck.encryptedData)
+
+	return arr
+}
+
+func (secPck *SecurePacket) ExtractPacket(key [32]byte) (*Packet, error) {
+	aead, err := chacha20poly1305.NewX(key[:])
+	if err != nil {
+		panic(err)
+	}
+	data, err := aead.Open(nil, secPck.nonce[:], secPck.encryptedData, nil)
+	if err != nil {
+		return nil, err
+	}
+	packet := PacketFromBytes(data)
+	return &packet, nil
+}
+
+func NewRsaPacket(sid SessionID, key [32]byte) *SecurePacket {
+	return &SecurePacket{
+		isRsa:         1,
+		nonce:         [24]byte(make([]byte, 24)),
+		sid:           sid,
+		encryptedData: key[:],
+	}
+}
+
+func (secPck *SecurePacket) ExtractKey( /*RSA HERE LATER*/ ) []byte {
+	return secPck.encryptedData[:32]
+}
+
 func PacketFromBytes(bytes []byte) Packet {
 	flag := HeaderFlag(bytes[0])
 	sid := SessionID(bytes[1:33])

server.go

@@ -119,11 +119,9 @@ func (server *Server) sendPTE(conn *net.UDPConn, addr *net.UDPAddr, pck *Packet)
 	ptePck := NewPte(uint32(fileSize), pck)
 	conn.WriteToUDP(ptePck.ToBytes(), addr)
 
-	server.sessions[pck.sid] = &info{
-		path:        path,
-		lastSync:    ptePck.sync,
-		lastPckSend: ptePck.flag,
-	}
+	server.sessions[pck.sid].path = path
+	server.sessions[pck.sid].lastSync = ptePck.sync
+	server.sessions[pck.sid].lastPckSend = ptePck.flag
 }
 
 func (server *Server) sendData(conn *net.UDPConn, addr *net.UDPAddr, pck *Packet) {
@@ -180,7 +178,27 @@ func (server *Server) Serve() {
 			fmt.Println(err)
 			return
 		}
-		pck := PacketFromBytes(buf[:])
-		go server.handlePacket(conn, addr, &pck)
+
+		secPck := SecurePacketFromBytes(buf[:])
+
+		fmt.Println(secPck)
+
+		if secPck.isRsa == 0 {
+			key := server.sessions[secPck.sid].key
+			pck, err := secPck.ExtractPacket(key)
+			if err != nil {
+				fmt.Println(err)
+				//fmt.Println("Could not establish secure connection")
+			}
+			go server.handlePacket(conn, addr, pck)
+		} else {
+			key := secPck.ExtractKey()
+			fmt.Println(key)
+			fmt.Println(secPck.sid)
+			server.sessions[secPck.sid] = &info{
+				key: [32]byte(key),
+			}
+
+		}
 	}
 }