AmneziaWG v1.5 (#84)

device/awg/junk_creator.go

@@ -0,0 +1,70 @@
+package awg
+
+import (
+	"bytes"
+	crand "crypto/rand"
+	"fmt"
+	v2 "math/rand/v2"
+)
+
+type junkCreator struct {
+	aSecCfg  aSecCfgType
+	cha8Rand *v2.ChaCha8
+}
+
+// TODO: refactor param to only pass the junk related params
+func NewJunkCreator(aSecCfg aSecCfgType) (junkCreator, error) {
+	buf := make([]byte, 32)
+	_, err := crand.Read(buf)
+	if err != nil {
+		return junkCreator{}, err
+	}
+	return junkCreator{aSecCfg: aSecCfg, cha8Rand: v2.NewChaCha8([32]byte(buf))}, nil
+}
+
+// Should be called with aSecMux RLocked
+func (jc *junkCreator) CreateJunkPackets(junks *[][]byte) error {
+	if jc.aSecCfg.JunkPacketCount == 0 {
+		return nil
+	}
+
+	for range jc.aSecCfg.JunkPacketCount {
+		packetSize := jc.randomPacketSize()
+		junk, err := jc.randomJunkWithSize(packetSize)
+		if err != nil {
+			return fmt.Errorf("create junk packet: %v", err)
+		}
+		*junks = append(*junks, junk)
+	}
+	return nil
+}
+
+// Should be called with aSecMux RLocked
+func (jc *junkCreator) randomPacketSize() int {
+	return int(
+		jc.cha8Rand.Uint64()%uint64(
+			jc.aSecCfg.JunkPacketMaxSize-jc.aSecCfg.JunkPacketMinSize,
+		),
+	) + jc.aSecCfg.JunkPacketMinSize
+}
+
+// Should be called with aSecMux RLocked
+func (jc *junkCreator) AppendJunk(writer *bytes.Buffer, size int) error {
+	headerJunk, err := jc.randomJunkWithSize(size)
+	if err != nil {
+		return fmt.Errorf("create header junk: %v", err)
+	}
+	_, err = writer.Write(headerJunk)
+	if err != nil {
+		return fmt.Errorf("write header junk: %v", err)
+	}
+	return nil
+}
+
+// Should be called with aSecMux RLocked
+func (jc *junkCreator) randomJunkWithSize(size int) ([]byte, error) {
+	// TODO: use a memory pool to allocate
+	junk := make([]byte, size)
+	_, err := jc.cha8Rand.Read(junk)
+	return junk, err
+}