Merge pull request #947 from lucas-clemente/fix-header-parsing

fix parsing of the Header type byte

internal/wire/header.go

@@ -41,13 +41,14 @@ func ParseHeaderSentByServer(b *bytes.Reader, version protocol.VersionNumber) (*
 
 	var isPublicHeader bool
 	// As a client, we know the version of the packet that the server sent, except for Version Negotiation Packets.
-	// Both gQUIC and IETF QUIC Version Negotiation Packets have 0x1 set.
+	if typeByte == 0x81 { // IETF draft Version Negotiation Packet
-	if typeByte&0x1 > 0 {
+		isPublicHeader = false
+	} else if typeByte&0xcf == 0x9 { // gQUIC Version Negotiation Packet
 		// IETF QUIC Version Negotiation Packets are sent with the Long Header (indicated by the 0x80 bit)
 		// gQUIC always has 0x80 unset
-		isPublicHeader = typeByte&0x80 == 0
+		isPublicHeader = true
-	} else {
+	} else { // not a Version Negotiation Packet
-		// For all packets that are not Version Negotiation Packets, the client knows the version that this packet was sent with
+		// the client knows the version that this packet was sent with
 		isPublicHeader = !version.UsesTLS()
 	}
 	return parsePacketHeader(b, protocol.PerspectiveServer, isPublicHeader)

internal/wire/header_test.go

@@ -19,7 +19,7 @@ var _ = Describe("Header", func() {
 	)
 
 	Context("parsing", func() {
-		It("parses an IETF draft header, when the QUIC version supports TLS", func() {
+		It("parses an IETF draft Short Header, when the QUIC version supports TLS", func() {
 			buf := &bytes.Buffer{}
 			// use a short header, which isn't distinguishable from the gQUIC Public Header when looking at the type byte
 			err := (&Header{
@@ -51,6 +51,21 @@ var _ = Describe("Header", func() {
 			Expect(hdr.isPublicHeader).To(BeFalse())
 		})
 
+		It("doens't mistake packets with a Short Header for Version Negotiation Packets", func() {
+			// make sure this packet could be mistaken for a Version Negotiation Packet, if we only look at the 0x1 bit
+			buf := &bytes.Buffer{}
+			err := (&Header{
+				IsLongHeader:    false,
+				PacketNumberLen: protocol.PacketNumberLen1,
+				PacketNumber:    0x42,
+			}).writeHeader(buf)
+			Expect(err).ToNot(HaveOccurred())
+			Expect(buf.Bytes()[0] & 0x1).To(BeEquivalentTo(0x1))
+			hdr, err := ParseHeaderSentByServer(bytes.NewReader(buf.Bytes()), versionIETFHeader)
+			Expect(err).ToNot(HaveOccurred())
+			Expect(hdr.isPublicHeader).To(BeFalse())
+		})
+
 		It("parses a gQUIC Public Header, when the version is not known", func() {
 			buf := &bytes.Buffer{}
 			err := (&Header{