Disable anti-amplification limit by address validation token (#3326)

connection.go

@@ -242,6 +242,7 @@ var newConnection = func(
 	tlsConf *tls.Config,
 	tokenGenerator *handshake.TokenGenerator,
 	enable0RTT bool,
+	clientAddressValidated bool,
 	tracer logging.ConnectionTracer,
 	tracingID uint64,
 	logger utils.Logger,
@@ -288,6 +289,7 @@ var newConnection = func(
 		0,
 		getMaxPacketSize(s.conn.RemoteAddr()),
 		s.rttStats,
+		clientAddressValidated,
 		s.perspective,
 		s.tracer,
 		s.logger,
@@ -415,6 +417,7 @@ var newClientConnection = func(
 		initialPacketNumber,
 		getMaxPacketSize(s.conn.RemoteAddr()),
 		s.rttStats,
+		false, /* has no effect */
 		s.perspective,
 		s.tracer,
 		s.logger,

connection_test.go

@@ -107,6 +107,7 @@ var _ = Describe("Connection", func() {
 			nil, // tls.Config
 			tokenGenerator,
 			false,
+			false,
 			tracer,
 			1234,
 			utils.DefaultLogger,

internal/ackhandler/ackhandler.go

@@ -6,16 +6,19 @@ import (
 	"github.com/lucas-clemente/quic-go/logging"
 )
 
-// NewAckHandler creates a new SentPacketHandler and a new ReceivedPacketHandler
+// NewAckHandler creates a new SentPacketHandler and a new ReceivedPacketHandler.
+// clientAddressValidated indicates whether the address was validated beforehand by an address validation token.
+// clientAddressValidated has no effect for a client.
 func NewAckHandler(
 	initialPacketNumber protocol.PacketNumber,
 	initialMaxDatagramSize protocol.ByteCount,
 	rttStats *utils.RTTStats,
+	clientAddressValidated bool,
 	pers protocol.Perspective,
 	tracer logging.ConnectionTracer,
 	logger utils.Logger,
 	version protocol.VersionNumber,
 ) (SentPacketHandler, ReceivedPacketHandler) {
-	sph := newSentPacketHandler(initialPacketNumber, initialMaxDatagramSize, rttStats, pers, tracer, logger)
+	sph := newSentPacketHandler(initialPacketNumber, initialMaxDatagramSize, rttStats, clientAddressValidated, pers, tracer, logger)
 	return sph, newReceivedPacketHandler(sph, rttStats, logger, version)
 }

internal/ackhandler/sent_packet_handler.go

@@ -101,10 +101,13 @@ var (
 	_ sentPacketTracker = &sentPacketHandler{}
 )
 
+// clientAddressValidated indicates whether the address was validated beforehand by an address validation token.
+// If the address was validated, the amplification limit doesn't apply. It has no effect for a client.
 func newSentPacketHandler(
 	initialPN protocol.PacketNumber,
 	initialMaxDatagramSize protocol.ByteCount,
 	rttStats *utils.RTTStats,
+	clientAddressValidated bool,
 	pers protocol.Perspective,
 	tracer logging.ConnectionTracer,
 	logger utils.Logger,
@@ -119,7 +122,7 @@ func newSentPacketHandler(
 
 	return &sentPacketHandler{
 		peerCompletedAddressValidation: pers == protocol.PerspectiveServer,
-		peerAddressValidated:           pers == protocol.PerspectiveClient,
+		peerAddressValidated:           pers == protocol.PerspectiveClient || clientAddressValidated,
 		initialPackets:                 newPacketNumberSpace(initialPN, false, rttStats),
 		handshakePackets:               newPacketNumberSpace(0, false, rttStats),
 		appDataPackets:                 newPacketNumberSpace(0, true, rttStats),

internal/ackhandler/sent_packet_handler_test.go

@@ -29,7 +29,7 @@ var _ = Describe("SentPacketHandler", func() {
 	JustBeforeEach(func() {
 		lostPackets = nil
 		rttStats := utils.NewRTTStats()
-		handler = newSentPacketHandler(42, protocol.InitialPacketSizeIPv4, rttStats, perspective, nil, utils.DefaultLogger)
+		handler = newSentPacketHandler(42, protocol.InitialPacketSizeIPv4, rttStats, false, perspective, nil, utils.DefaultLogger)
 		streamFrame = wire.StreamFrame{
 			StreamID: 5,
 			Data:     []byte{0x13, 0x37},
@@ -944,6 +944,26 @@ var _ = Describe("SentPacketHandler", func() {
 		})
 	})
 
+	Context("amplification limit, for the server, with validated address", func() {
+		JustBeforeEach(func() {
+			rttStats := utils.NewRTTStats()
+			handler = newSentPacketHandler(42, protocol.InitialPacketSizeIPv4, rttStats, true, perspective, nil, utils.DefaultLogger)
+		})
+
+		It("do not limits the window", func() {
+			handler.ReceivedBytes(0)
+			Expect(handler.SendMode()).To(Equal(SendAny))
+			handler.SentPacket(&Packet{
+				PacketNumber:    1,
+				Length:          900,
+				EncryptionLevel: protocol.EncryptionInitial,
+				Frames:          []Frame{{Frame: &wire.PingFrame{}}},
+				SendTime:        time.Now(),
+			})
+			Expect(handler.SendMode()).To(Equal(SendAny))
+		})
+	})
+
 	Context("amplification limit, for the client", func() {
 		BeforeEach(func() {
 			perspective = protocol.PerspectiveClient

internal/handshake/token_generator.go

@@ -26,6 +26,7 @@ type Token struct {
 	RetrySrcConnectionID     protocol.ConnectionID
 }
 
+// ValidateRemoteAddr validates the address, but does not check expiration
 func (t *Token) ValidateRemoteAddr(addr net.Addr) bool {
 	return bytes.Equal(encodeRemoteAddr(addr), t.encodedRemoteAddr)
 }

server.go

@@ -89,6 +89,7 @@ type baseServer struct {
 		*tls.Config,
 		*handshake.TokenGenerator,
 		bool, /* enable 0-RTT */
+		bool, /* client address validated by an address validation token */
 		logging.ConnectionTracer,
 		uint64,
 		utils.Logger,
@@ -375,6 +376,26 @@ func (s *baseServer) handlePacketImpl(p *receivedPacket) bool /* is the buffer s
 	return true
 }
 
+// validateToken returns false if:
+//   - address is invalid
+//   - token is expired
+//   - token is null
+func (s *baseServer) validateToken(token *handshake.Token, addr net.Addr) bool {
+	if token == nil {
+		return false
+	}
+	if !token.ValidateRemoteAddr(addr) {
+		return false
+	}
+	if !token.IsRetryToken && time.Since(token.SentTime) > s.config.MaxTokenAge {
+		return false
+	}
+	if token.IsRetryToken && time.Since(token.SentTime) > s.config.MaxRetryTokenAge {
+		return false
+	}
+	return true
+}
+
 func (s *baseServer) handleInitialImpl(p *receivedPacket, hdr *wire.Header) error {
 	if len(hdr.Token) == 0 && hdr.DestConnectionID.Len() < protocol.MinConnectionIDLenInitial {
 		p.buffer.Release()
@@ -399,23 +420,23 @@ func (s *baseServer) handleInitialImpl(p *receivedPacket, hdr *wire.Header) erro
 			token = tok
 		}
 	}
-	if token != nil {
-		addrIsValid := token.ValidateRemoteAddr(p.remoteAddr)
+
+	clientAddrIsValid := s.validateToken(token, p.remoteAddr)
+
+	if token != nil && !clientAddrIsValid {
 		// For invalid and expired non-retry tokens, we don't send an INVALID_TOKEN error.
 		// We just ignore them, and act as if there was no token on this packet at all.
 		// This also means we might send a Retry later.
-		if !token.IsRetryToken && (time.Since(token.SentTime) > s.config.MaxTokenAge || !addrIsValid) {
+		if !token.IsRetryToken {
 			token = nil
-		} else if token.IsRetryToken && (time.Since(token.SentTime) > s.config.MaxRetryTokenAge || !addrIsValid) {
+		} else {
 			// For Retry tokens, we send an INVALID_ERROR if
 			// * the token is too old, or
 			// * the token is invalid, in case of a retry token.
 			go func() {
 				defer p.buffer.Release()
-				if token != nil && token.IsRetryToken {
-					if err := s.maybeSendInvalidToken(p, hdr); err != nil {
-						s.logger.Debugf("Error sending INVALID_TOKEN error: %s", err)
-					}
+				if err := s.maybeSendInvalidToken(p, hdr); err != nil {
+					s.logger.Debugf("Error sending INVALID_TOKEN error: %s", err)
 				}
 			}()
 			return nil
@@ -476,6 +497,7 @@ func (s *baseServer) handleInitialImpl(p *receivedPacket, hdr *wire.Header) erro
 			s.tlsConf,
 			s.tokenGenerator,
 			s.acceptEarlyConns,
+			clientAddrIsValid,
 			tracer,
 			tracingID,
 			s.logger,

server_test.go

@@ -287,6 +287,7 @@ var _ = Describe("Server", func() {
 					_ *tls.Config,
 					_ *handshake.TokenGenerator,
 					enable0RTT bool,
+					_ bool,
 					_ logging.ConnectionTracer,
 					_ uint64,
 					_ utils.Logger,
@@ -491,6 +492,7 @@ var _ = Describe("Server", func() {
 					_ *tls.Config,
 					_ *handshake.TokenGenerator,
 					enable0RTT bool,
+					_ bool,
 					_ logging.ConnectionTracer,
 					_ uint64,
 					_ utils.Logger,
@@ -550,6 +552,7 @@ var _ = Describe("Server", func() {
 					_ *tls.Config,
 					_ *handshake.TokenGenerator,
 					_ bool,
+					_ bool,
 					_ logging.ConnectionTracer,
 					_ uint64,
 					_ utils.Logger,
@@ -603,6 +606,7 @@ var _ = Describe("Server", func() {
 					_ *tls.Config,
 					_ *handshake.TokenGenerator,
 					_ bool,
+					_ bool,
 					_ logging.ConnectionTracer,
 					_ uint64,
 					_ utils.Logger,
@@ -632,6 +636,7 @@ var _ = Describe("Server", func() {
 					_ *tls.Config,
 					_ *handshake.TokenGenerator,
 					_ bool,
+					_ bool,
 					_ logging.ConnectionTracer,
 					_ uint64,
 					_ utils.Logger,
@@ -702,6 +707,7 @@ var _ = Describe("Server", func() {
 					_ *tls.Config,
 					_ *handshake.TokenGenerator,
 					_ bool,
+					_ bool,
 					_ logging.ConnectionTracer,
 					_ uint64,
 					_ utils.Logger,
@@ -1007,6 +1013,7 @@ var _ = Describe("Server", func() {
 					_ *tls.Config,
 					_ *handshake.TokenGenerator,
 					_ bool,
+					_ bool,
 					_ logging.ConnectionTracer,
 					_ uint64,
 					_ utils.Logger,
@@ -1080,6 +1087,7 @@ var _ = Describe("Server", func() {
 				_ *tls.Config,
 				_ *handshake.TokenGenerator,
 				enable0RTT bool,
+				_ bool,
 				_ logging.ConnectionTracer,
 				_ uint64,
 				_ utils.Logger,
@@ -1122,6 +1130,7 @@ var _ = Describe("Server", func() {
 				_ *tls.Config,
 				_ *handshake.TokenGenerator,
 				_ bool,
+				_ bool,
 				_ logging.ConnectionTracer,
 				_ uint64,
 				_ utils.Logger,
@@ -1184,6 +1193,7 @@ var _ = Describe("Server", func() {
 				_ *tls.Config,
 				_ *handshake.TokenGenerator,
 				_ bool,
+				_ bool,
 				_ logging.ConnectionTracer,
 				_ uint64,
 				_ utils.Logger,