reject packets with version 0 sent by the client

Version 0 is an invalid version. For packets sent by the server, it is
used to identify the Version Negotiation Packet.

internal/wire/ietf_header.go

@@ -42,6 +42,9 @@ func parseLongHeader(b *bytes.Reader, sentBy protocol.Perspective, typeByte byte
 		Version:         protocol.VersionNumber(v),
 	}
 	if v == 0 { // version negotiation packet
+		if sentBy == protocol.PerspectiveClient {
+			return nil, qerr.InvalidVersion
+		}
 		if b.Len() == 0 {
 			return nil, qerr.Error(qerr.InvalidVersionNegotiationPacket, "empty version list")
 		}

internal/wire/ietf_header_test.go

@@ -93,6 +93,17 @@ var _ = Describe("IETF draft Header", func() {
 				Expect(err).To(MatchError("InvalidPacketHeader: Received packet with invalid packet type: 42"))
 			})
 
+			It("rejects version 0 for packets sent by the client", func() {
+				data := []byte{
+					0x80 ^ uint8(protocol.PacketTypeInitial),
+					0xde, 0xad, 0xbe, 0xef, 0xca, 0xfe, 0x13, 0x37, // connection ID
+					0x0, 0x0, 0x0, 0x0, // version number
+					0xde, 0xca, 0xfb, 0xad, // packet number
+				}
+				_, err := parseHeader(bytes.NewReader(data), protocol.PerspectiveClient)
+				Expect(err).To(MatchError(qerr.InvalidVersion))
+			})
+
 			It("errors on EOF", func() {
 				data := generatePacket(protocol.PacketTypeInitial)
 				for i := 0; i < len(data); i++ {