添加 github.com/pion/dtls 代码

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

@@ -0,0 +1,62 @@
+package extension
+
+import (
+	"encoding/binary"
+
+	"github.com/pion/dtls/v2/pkg/crypto/elliptic"
+)
+
+const (
+	supportedGroupsHeaderSize = 6
+)
+
+// SupportedEllipticCurves allows a Client/Server to communicate
+// what curves they both support
+//
+// https://tools.ietf.org/html/rfc8422#section-5.1.1
+type SupportedEllipticCurves struct {
+	EllipticCurves []elliptic.Curve
+}
+
+// TypeValue returns the extension TypeValue
+func (s SupportedEllipticCurves) TypeValue() TypeValue {
+	return SupportedEllipticCurvesTypeValue
+}
+
+// Marshal encodes the extension
+func (s *SupportedEllipticCurves) Marshal() ([]byte, error) {
+	out := make([]byte, supportedGroupsHeaderSize)
+
+	binary.BigEndian.PutUint16(out, uint16(s.TypeValue()))
+	binary.BigEndian.PutUint16(out[2:], uint16(2+(len(s.EllipticCurves)*2)))
+	binary.BigEndian.PutUint16(out[4:], uint16(len(s.EllipticCurves)*2))
+
+	for _, v := range s.EllipticCurves {
+		out = append(out, []byte{0x00, 0x00}...)
+		binary.BigEndian.PutUint16(out[len(out)-2:], uint16(v))
+	}
+
+	return out, nil
+}
+
+// Unmarshal populates the extension from encoded data
+func (s *SupportedEllipticCurves) Unmarshal(data []byte) error {
+	if len(data) <= supportedGroupsHeaderSize {
+		return errBufferTooSmall
+	} else if TypeValue(binary.BigEndian.Uint16(data)) != s.TypeValue() {
+		return errInvalidExtensionType
+	}
+
+	groupCount := int(binary.BigEndian.Uint16(data[4:]) / 2)
+	if supportedGroupsHeaderSize+(groupCount*2) > len(data) {
+		return errLengthMismatch
+	}
+
+	for i := 0; i < groupCount; i++ {
+		supportedGroupID := elliptic.Curve(binary.BigEndian.Uint16(data[(supportedGroupsHeaderSize + (i * 2)):]))
+		if _, ok := elliptic.Curves()[supportedGroupID]; ok {
+			s.EllipticCurves = append(s.EllipticCurves, supportedGroupID)
+		}
+	}
+	return nil
+}