support encrypted streams with SRTP and MIKEY (#520) (#809)

pkg/mikey/payload_rand.go

@@ -0,0 +1,46 @@
+package mikey
+
+import "fmt"
+
+// PayloadRAND is a payload with random data.
+type PayloadRAND struct {
+	Data []byte
+}
+
+func (p *PayloadRAND) unmarshal(buf []byte) (int, error) {
+	if len(buf) < 2 {
+		return 0, fmt.Errorf("buffer too short")
+	}
+
+	n := 1
+	dataLen := int(buf[n])
+	n++
+
+	if dataLen < 16 {
+		return 0, fmt.Errorf("invalid data len: %v", dataLen)
+	}
+
+	if len(buf[n:]) < dataLen {
+		return 0, fmt.Errorf("buffer too short")
+	}
+
+	p.Data = buf[n : n+dataLen]
+	n += dataLen
+
+	return n, nil
+}
+
+func (*PayloadRAND) typ() payloadType {
+	return payloadTypeRAND
+}
+
+func (p *PayloadRAND) marshalSize() int {
+	return 2 + len(p.Data)
+}
+
+func (p *PayloadRAND) marshalTo(buf []byte) (int, error) {
+	buf[1] = uint8(len(p.Data))
+	n := 2
+	n += copy(buf[2:], p.Data)
+	return n, nil
+}