VLESS protocol: Add lightweight Post-Quantum ML-KEM-768-based PFS 1-RTT / anti-replay 0-RTT AEAD encryption

https://github.com/XTLS/Xray-core/pull/4952#issuecomment-3163335040

proxy/vless/encryption/common.go

@@ -0,0 +1,55 @@
+package encryption
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"strconv"
+
+	"github.com/xtls/xray-core/common/errors"
+	"golang.org/x/crypto/chacha20poly1305"
+)
+
+func encodeHeader(b []byte, l int) {
+	b[0] = 23
+	b[1] = 3
+	b[2] = 3
+	b[3] = byte(l >> 8)
+	b[4] = byte(l)
+}
+
+func decodeHeader(b []byte) (int, error) {
+	if b[0] == 23 && b[1] == 3 && b[2] == 3 {
+		l := int(b[3])<<8 | int(b[4])
+		if l < 17 || l > 17000 { // TODO
+			return 0, errors.New("invalid length in record's header: " + strconv.Itoa(l))
+		}
+		return l, nil
+	}
+	return 0, errors.New("invalid record's header")
+}
+
+func newAead(c byte, k []byte) cipher.AEAD {
+	switch c {
+	case 0:
+		if block, err := aes.NewCipher(k); err == nil {
+			aead, _ := cipher.NewGCM(block)
+			return aead
+		}
+	case 1:
+		aead, _ := chacha20poly1305.New(k)
+		return aead
+	}
+	return nil
+}
+
+func increaseNonce(nonce []byte) {
+	for i := range 12 {
+		nonce[11-i]++
+		if nonce[11-i] != 0 {
+			break
+		}
+		if i == 11 {
+			// TODO
+		}
+	}
+}