添加 github.com/pion/dtls 代码

dtls-2.0.9/pkg/protocol/extension/server_name.go

@@ -0,0 +1,78 @@
+package extension
+
+import (
+	"strings"
+
+	"golang.org/x/crypto/cryptobyte"
+)
+
+const serverNameTypeDNSHostName = 0
+
+// ServerName allows the client to inform the server the specific
+// name it wishs to contact. Useful if multiple DNS names resolve
+// to one IP
+//
+// https://tools.ietf.org/html/rfc6066#section-3
+type ServerName struct {
+	ServerName string
+}
+
+// TypeValue returns the extension TypeValue
+func (s ServerName) TypeValue() TypeValue {
+	return ServerNameTypeValue
+}
+
+// Marshal encodes the extension
+func (s *ServerName) Marshal() ([]byte, error) {
+	var b cryptobyte.Builder
+	b.AddUint16(uint16(s.TypeValue()))
+	b.AddUint16LengthPrefixed(func(b *cryptobyte.Builder) {
+		b.AddUint16LengthPrefixed(func(b *cryptobyte.Builder) {
+			b.AddUint8(serverNameTypeDNSHostName)
+			b.AddUint16LengthPrefixed(func(b *cryptobyte.Builder) {
+				b.AddBytes([]byte(s.ServerName))
+			})
+		})
+	})
+	return b.Bytes()
+}
+
+// Unmarshal populates the extension from encoded data
+func (s *ServerName) Unmarshal(data []byte) error {
+	val := cryptobyte.String(data)
+	var extension uint16
+	val.ReadUint16(&extension)
+	if TypeValue(extension) != s.TypeValue() {
+		return errInvalidExtensionType
+	}
+
+	var extData cryptobyte.String
+	val.ReadUint16LengthPrefixed(&extData)
+
+	var nameList cryptobyte.String
+	if !extData.ReadUint16LengthPrefixed(&nameList) || nameList.Empty() {
+		return errInvalidSNIFormat
+	}
+	for !nameList.Empty() {
+		var nameType uint8
+		var serverName cryptobyte.String
+		if !nameList.ReadUint8(&nameType) ||
+			!nameList.ReadUint16LengthPrefixed(&serverName) ||
+			serverName.Empty() {
+			return errInvalidSNIFormat
+		}
+		if nameType != serverNameTypeDNSHostName {
+			continue
+		}
+		if len(s.ServerName) != 0 {
+			// Multiple names of the same name_type are prohibited.
+			return errInvalidSNIFormat
+		}
+		s.ServerName = string(serverName)
+		// An SNI value may not include a trailing dot.
+		if strings.HasSuffix(s.ServerName, ".") {
+			return errInvalidSNIFormat
+		}
+	}
+	return nil
+}