From a63ca441a93c33d60c3f8b1763bee735dbd84a2f Mon Sep 17 00:00:00 2001
From: Jonathan Barrow <jonbarrow1998@gmail.com>
Date: Mon, 15 Jan 2024 15:07:57 -0500
Subject: [PATCH] encryption: added QuazalRC4

---
 encryption/quazal_rc4.go | 95 ++++++++++++++++++++++++++++++++++++++++
 prudp_packet.go          |  8 ----
 prudp_server.go          |  8 ----
 3 files changed, 95 insertions(+), 16 deletions(-)
 create mode 100644 encryption/quazal_rc4.go

diff --git a/encryption/quazal_rc4.go b/encryption/quazal_rc4.go
new file mode 100644
index 0000000..63c423d
--- /dev/null
+++ b/encryption/quazal_rc4.go
@@ -0,0 +1,95 @@
+package encryption
+
+import (
+	"crypto/rc4"
+)
+
+// QuazalRC4 encrypts data with RC4. Each iteration uses a new cipher instance. The key is always CD&ML
+type QuazalRC4 struct {
+	key             []byte
+	cipher          *rc4.Cipher
+	decipher        *rc4.Cipher
+	cipheredCount   uint64
+	decipheredCount uint64
+}
+
+// Key returns the crypto key
+func (r *QuazalRC4) Key() []byte {
+	return r.key
+}
+
+// SetKey sets the crypto key and updates the ciphers
+func (r *QuazalRC4) SetKey(key []byte) error {
+	r.key = key
+
+	cipher, err := rc4.NewCipher(key)
+	if err != nil {
+		return err
+	}
+
+	decipher, err := rc4.NewCipher(key)
+	if err != nil {
+		return err
+	}
+
+	r.cipher = cipher
+	r.decipher = decipher
+
+	return nil
+}
+
+// Encrypt encrypts the payload with the outgoing QuazalRC4 stream
+func (r *QuazalRC4) Encrypt(payload []byte) ([]byte, error) {
+	r.SetKey([]byte("CD&ML"))
+
+	ciphered := make([]byte, len(payload))
+
+	r.cipher.XORKeyStream(ciphered, payload)
+
+	r.cipheredCount += uint64(len(payload))
+
+	return ciphered, nil
+}
+
+// Decrypt decrypts the payload with the incoming QuazalRC4 stream
+func (r *QuazalRC4) Decrypt(payload []byte) ([]byte, error) {
+	r.SetKey([]byte("CD&ML"))
+
+	deciphered := make([]byte, len(payload))
+
+	r.decipher.XORKeyStream(deciphered, payload)
+
+	r.decipheredCount += uint64(len(payload))
+
+	return deciphered, nil
+}
+
+// Copy returns a copy of the algorithm while retaining it's state
+func (r *QuazalRC4) Copy() Algorithm {
+	copied := NewQuazalRC4Encryption()
+
+	copied.SetKey(r.key)
+
+	// * crypto/rc4 does not expose a way to directly copy streams and retain their state.
+	// * This just discards the number of iterations done in the original ciphers to sync
+	// * the copied ciphers states to the original
+	for i := 0; i < int(r.cipheredCount); i++ {
+		copied.cipher.XORKeyStream([]byte{0}, []byte{0})
+	}
+
+	for i := 0; i < int(r.decipheredCount); i++ {
+		copied.decipher.XORKeyStream([]byte{0}, []byte{0})
+	}
+
+	copied.cipheredCount = r.cipheredCount
+	copied.decipheredCount = r.decipheredCount
+
+	return copied
+}
+
+// NewQuazalRC4Encryption returns a new instance of the QuazalRC4 encryption
+func NewQuazalRC4Encryption() *QuazalRC4 {
+	return &QuazalRC4{
+		key: make([]byte, 0),
+	}
+}
diff --git a/prudp_packet.go b/prudp_packet.go
index a29fa41..535628a 100644
--- a/prudp_packet.go
+++ b/prudp_packet.go
@@ -148,14 +148,6 @@ func (p *PRUDPPacket) decryptPayload() []byte {
 	if p.packetType == DataPacket {
 		slidingWindow := p.sender.SlidingWindow(p.SubstreamID())
 
-		// * According to other Quazal server implementations,
-		// * the RC4 stream is always reset to the default key
-		// * regardless if the client is connecting to a secure
-		// * server (prudps) or not
-		if p.version == 0 && p.sender.Endpoint.Server.PRUDPV0Settings.IsQuazalMode {
-			slidingWindow.SetCipherKey([]byte("CD&ML"))
-		}
-
 		payload, _ = slidingWindow.streamSettings.EncryptionAlgorithm.Decrypt(payload)
 	}
 
diff --git a/prudp_server.go b/prudp_server.go
index 7cfa971..9efdc01 100644
--- a/prudp_server.go
+++ b/prudp_server.go
@@ -268,14 +268,6 @@ func (s *PRUDPServer) sendPacket(packet PRUDPPacketInterface) {
 				logger.Error(err.Error())
 			}
 
-			// * According to other Quazal server implementations,
-			// * the RC4 stream is always reset to the default key
-			// * regardless if the client is connecting to a secure
-			// * server (prudps) or not
-			if packet.Version() == 0 && s.PRUDPV0Settings.IsQuazalMode {
-				slidingWindow.SetCipherKey([]byte("CD&ML"))
-			}
-
 			encryptedPayload, err := slidingWindow.streamSettings.EncryptionAlgorithm.Encrypt(compressedPayload)
 			if err != nil {
 				logger.Error(err.Error())