feat: 实现 shadowTls v2；修订示例,文档,代码; 添加shadowTls的示例文件

shadowTls v2时客户端自动使用utls，且增强了探测防御

proxy.SetCommonReadTimeout -> netLayer.SetCommonReadTimeout

tlsLayer 配置也使用Extra，目前用于 shadowTls

utils/crypto.go

@@ -1,6 +1,73 @@
 package utils
 
-import "runtime"
+import (
+	"crypto/hmac"
+	"crypto/sha1"
+	"hash"
+	"io"
+	"runtime"
+)
 
-//有些系统对aes支持不好，有些支持好。SystemAutoUseAes若为true，则说明支持很好，使用aes作为加密算法速度最佳。
+// 有些系统对aes支持不好，有些支持好。SystemAutoUseAes若为true，则说明支持很好，使用aes作为加密算法速度最佳。
 const SystemAutoUseAes = runtime.GOARCH == "amd64" || runtime.GOARCH == "s390x" || runtime.GOARCH == "arm64"
+
+type HashReader struct {
+	io.Reader
+	hmac hash.Hash
+}
+
+func NewHashReader(conn io.Reader, key []byte) *HashReader {
+	return &HashReader{
+		conn,
+		hmac.New(sha1.New, key),
+	}
+}
+
+func (c *HashReader) Read(b []byte) (n int, err error) {
+	n, err = c.Reader.Read(b)
+	if err != nil {
+		return
+	}
+	_, err = c.hmac.Write(b[:n])
+	return
+}
+
+func (c *HashReader) Sum() []byte {
+	return c.hmac.Sum(nil)[:8]
+}
+
+type HashWriter struct {
+	io.Writer
+	hmac    hash.Hash
+	written bool
+}
+
+func NewHashWriter(conn io.Writer, key []byte) *HashWriter {
+	return &HashWriter{
+		Writer: conn,
+		hmac:   hmac.New(sha1.New, key),
+	}
+}
+
+func (c *HashWriter) Write(p []byte) (n int, err error) {
+	if c.hmac != nil {
+
+		c.hmac.Write(p)
+		c.written = true
+	}
+	return c.Writer.Write(p)
+}
+
+func (c *HashWriter) Sum() []byte {
+	return c.hmac.Sum(nil)[:8]
+}
+
+func (c *HashWriter) StopHashing() {
+	c.hmac = nil
+	c.written = false
+}
+
+// Has the hash been written
+func (c *HashWriter) Written() bool {
+	return c.written
+}