SS2022 proxy: Refactor to remove sing* dependencies (#6831)

https://github.com/XTLS/Xray-core/pull/4356#issuecomment-2639571931

proxy/shadowsocks_2022/cipher.go

@@ -0,0 +1,55 @@
+package shadowsocks_2022
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"errors"
+	"strings"
+
+	"golang.org/x/crypto/chacha20poly1305"
+)
+
+type CipherMethod struct {
+	Name          string
+	KeySaltLength int
+	IsChaCha      bool
+}
+
+var methods = map[string]*CipherMethod{
+	MethodAES128GCM:        {Name: MethodAES128GCM, KeySaltLength: 16, IsChaCha: false},
+	MethodAES256GCM:        {Name: MethodAES256GCM, KeySaltLength: 32, IsChaCha: false},
+	MethodChaCha20Poly1305: {Name: MethodChaCha20Poly1305, KeySaltLength: 32, IsChaCha: true},
+}
+
+func GetCipherMethod(name string) (*CipherMethod, error) {
+	name = strings.ToLower(name)
+	if m, ok := methods[name]; ok {
+		return m, nil
+	}
+	return nil, errors.New("unknown shadowsocks 2022 method")
+}
+
+// NewAEAD creates standard stream AEAD cipher instance (AES-GCM or ChaCha20-Poly1305)
+func (m *CipherMethod) NewAEAD(key []byte) (cipher.AEAD, error) {
+	if m.IsChaCha {
+		return chacha20poly1305.New(key)
+	}
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+	return cipher.NewGCM(block)
+}
+
+// NewBlock creates standard 16-byte block cipher for AES header encryption/decryption
+func (m *CipherMethod) NewBlock(key []byte) (cipher.Block, error) {
+	return aes.NewCipher(key)
+}
+
+// NewUDPCipher creates AEAD cipher for UDP packets (XChaCha20-Poly1305 with 24-byte nonce)
+func (m *CipherMethod) NewUDPCipher(key []byte) (cipher.AEAD, error) {
+	if m.IsChaCha {
+		return chacha20poly1305.NewX(key)
+	}
+	return nil, errors.New("shadowsocks-2022: udp separate AEAD cipher only available for chacha20 method")
+}