fix rc4

crypto/rc4.go

@@ -10,34 +10,36 @@ type Ciphers struct {
 	server *rc4.Cipher // For encryption (server->client)
 }
 
-// NewCiphers creates a new pair of RC4 ciphers for the client and server
+// NewCiphers returns a new pair of ciphers based on the given key
 func NewCiphers(key int64) (*Ciphers, error) {
+	// Encryption only when key > 0
+	if key <= 0 {
+		return &Ciphers{}, nil
+	}
+
+	// key (little-endian bytes)
 	keyBytes := make([]byte, 8)
 	binary.LittleEndian.PutUint64(keyBytes, uint64(key))
 
-	// Client cipher uses NOT of key
-	clientKeyBytes := make([]byte, 8)
-	binary.LittleEndian.PutUint64(clientKeyBytes, uint64(^key))
+	// ~key (little-endian bytes)
+	notKeyBytes := make([]byte, 8)
+	binary.LittleEndian.PutUint64(notKeyBytes, uint64(^key))
 
-	clientCipher, err := rc4.NewCipher(keyBytes)
+	clientCipher, err := rc4.NewCipher(notKeyBytes)
+	if err != nil {
+		return nil, err
+	}
+	serverCipher, err := rc4.NewCipher(keyBytes)
 	if err != nil {
 		return nil, err
 	}
 
-	serverCipher, err := rc4.NewCipher(clientKeyBytes)
-	if err != nil {
-		return nil, err
-	}
-
-	// Drop first 20 bytes from both ciphers
+	// Burn first 20 bytes on both streams
 	drop := make([]byte, 20)
 	clientCipher.XORKeyStream(drop, drop)
 	serverCipher.XORKeyStream(drop, drop)
 
-	return &Ciphers{
-		client: clientCipher,
-		server: serverCipher,
-	}, nil
+	return &Ciphers{client: clientCipher, server: serverCipher}, nil
 }
 
 // Decrypt decrypts data received from the client