添加 github.com/pion/dtls 代码

dtls-2.0.9/pkg/protocol/handshake/message_client_key_exchange.go

@@ -0,0 +1,56 @@
+package handshake
+
+import (
+	"encoding/binary"
+)
+
+// MessageClientKeyExchange is a DTLS Handshake Message
+// With this message, the premaster secret is set, either by direct
+// transmission of the RSA-encrypted secret or by the transmission of
+// Diffie-Hellman parameters that will allow each side to agree upon
+// the same premaster secret.
+//
+// https://tools.ietf.org/html/rfc5246#section-7.4.7
+type MessageClientKeyExchange struct {
+	IdentityHint []byte
+	PublicKey    []byte
+}
+
+// Type returns the Handshake Type
+func (m MessageClientKeyExchange) Type() Type {
+	return TypeClientKeyExchange
+}
+
+// Marshal encodes the Handshake
+func (m *MessageClientKeyExchange) Marshal() ([]byte, error) {
+	switch {
+	case (m.IdentityHint != nil && m.PublicKey != nil) || (m.IdentityHint == nil && m.PublicKey == nil):
+		return nil, errInvalidClientKeyExchange
+	case m.PublicKey != nil:
+		return append([]byte{byte(len(m.PublicKey))}, m.PublicKey...), nil
+	default:
+		out := append([]byte{0x00, 0x00}, m.IdentityHint...)
+		binary.BigEndian.PutUint16(out, uint16(len(out)-2))
+		return out, nil
+	}
+}
+
+// Unmarshal populates the message from encoded data
+func (m *MessageClientKeyExchange) Unmarshal(data []byte) error {
+	if len(data) < 2 {
+		return errBufferTooSmall
+	}
+
+	// If parsed as PSK return early and only populate PSK Identity Hint
+	if pskLength := binary.BigEndian.Uint16(data); len(data) == int(pskLength+2) {
+		m.IdentityHint = append([]byte{}, data[2:]...)
+		return nil
+	}
+
+	if publicKeyLength := int(data[0]); len(data) != publicKeyLength+1 {
+		return errBufferTooSmall
+	}
+
+	m.PublicKey = append([]byte{}, data[1:]...)
+	return nil
+}