fix decoding of packet numbers in different packet number spaces

internal/handshake/aead.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/lucas-clemente/quic-go/internal/protocol"
 	"github.com/lucas-clemente/quic-go/internal/qtls"
+	"github.com/lucas-clemente/quic-go/internal/utils"
 )
 
 func createAEAD(suite *qtls.CipherSuiteTLS13, trafficSecret []byte) cipher.AEAD {
@@ -50,6 +51,7 @@ func (s *longHeaderSealer) Overhead() int {
 type longHeaderOpener struct {
 	aead            cipher.AEAD
 	headerProtector headerProtector
+	highestRcvdPN   protocol.PacketNumber // highest packet number received (which could be successfully unprotected)
 
 	// use a single slice to avoid allocations
 	nonceBuf []byte
@@ -65,12 +67,18 @@ func newLongHeaderOpener(aead cipher.AEAD, headerProtector headerProtector) Long
 	}
 }
 
+func (o *longHeaderOpener) DecodePacketNumber(wirePN protocol.PacketNumber, wirePNLen protocol.PacketNumberLen) protocol.PacketNumber {
+	return protocol.DecodePacketNumber(wirePNLen, o.highestRcvdPN, wirePN)
+}
+
 func (o *longHeaderOpener) Open(dst, src []byte, pn protocol.PacketNumber, ad []byte) ([]byte, error) {
 	binary.BigEndian.PutUint64(o.nonceBuf[len(o.nonceBuf)-8:], uint64(pn))
 	// The AEAD we're using here will be the qtls.aeadAESGCM13.
 	// It uses the nonce provided here and XOR it with the IV.
 	dec, err := o.aead.Open(dst, o.nonceBuf, src, ad)
-	if err != nil {
+	if err == nil {
+		o.highestRcvdPN = utils.MaxPacketNumber(o.highestRcvdPN, pn)
+	} else {
 		err = ErrDecryptionFailed
 	}
 	return dec, err

internal/handshake/aead_test.go

@@ -58,6 +58,22 @@ var _ = Describe("Long Header AEAD", func() {
 					_, err := opener.Open(nil, encrypted, 0x42, ad)
 					Expect(err).To(MatchError(ErrDecryptionFailed))
 				})
+
+				It("decodes the packet number", func() {
+					sealer, opener := getSealerAndOpener()
+					encrypted := sealer.Seal(nil, msg, 0x1337, ad)
+					_, err := opener.Open(nil, encrypted, 0x1337, ad)
+					Expect(err).ToNot(HaveOccurred())
+					Expect(opener.DecodePacketNumber(0x38, protocol.PacketNumberLen1)).To(BeEquivalentTo(0x1338))
+				})
+
+				It("ignores packets it can't decrypt for packet number derivation", func() {
+					sealer, opener := getSealerAndOpener()
+					encrypted := sealer.Seal(nil, msg, 0x1337, ad)
+					_, err := opener.Open(nil, encrypted[:len(encrypted)-1], 0x1337, ad)
+					Expect(err).To(HaveOccurred())
+					Expect(opener.DecodePacketNumber(0x38, protocol.PacketNumberLen1)).To(BeEquivalentTo(0x38))
+				})
 			})
 
 			Context("header encryption", func() {

internal/handshake/interface.go

@@ -33,12 +33,14 @@ type headerDecryptor interface {
 // LongHeaderOpener opens a long header packet
 type LongHeaderOpener interface {
 	headerDecryptor
+	DecodePacketNumber(wirePN protocol.PacketNumber, wirePNLen protocol.PacketNumberLen) protocol.PacketNumber
 	Open(dst, src []byte, pn protocol.PacketNumber, associatedData []byte) ([]byte, error)
 }
 
 // ShortHeaderOpener opens a short header packet
 type ShortHeaderOpener interface {
 	headerDecryptor
+	DecodePacketNumber(wirePN protocol.PacketNumber, wirePNLen protocol.PacketNumberLen) protocol.PacketNumber
 	Open(dst, src []byte, rcvTime time.Time, pn protocol.PacketNumber, kp protocol.KeyPhaseBit, associatedData []byte) ([]byte, error)
 }
 

internal/handshake/updatable_aead.go

@@ -37,6 +37,7 @@ type updatableAEAD struct {
 
 	firstRcvdWithCurrentKey protocol.PacketNumber
 	firstSentWithCurrentKey protocol.PacketNumber
+	highestRcvdPN           protocol.PacketNumber // highest packet number received (which could be successfully unprotected)
 	numRcvdWithCurrentKey   uint64
 	numSentWithCurrentKey   uint64
 	rcvAEAD                 cipher.AEAD
@@ -153,6 +154,10 @@ func (a *updatableAEAD) setAEADParameters(aead cipher.AEAD, suite *qtls.CipherSu
 	}
 }
 
+func (a *updatableAEAD) DecodePacketNumber(wirePN protocol.PacketNumber, wirePNLen protocol.PacketNumberLen) protocol.PacketNumber {
+	return protocol.DecodePacketNumber(wirePNLen, a.highestRcvdPN, wirePN)
+}
+
 func (a *updatableAEAD) Open(dst, src []byte, rcvTime time.Time, pn protocol.PacketNumber, kp protocol.KeyPhaseBit, ad []byte) ([]byte, error) {
 	dec, err := a.open(dst, src, rcvTime, pn, kp, ad)
 	if err == ErrDecryptionFailed {
@@ -161,6 +166,9 @@ func (a *updatableAEAD) Open(dst, src []byte, rcvTime time.Time, pn protocol.Pac
 			return nil, qerr.AEADLimitReached
 		}
 	}
+	if err == nil {
+		a.highestRcvdPN = utils.MaxPacketNumber(a.highestRcvdPN, pn)
+	}
 	return dec, err
 }
 

internal/handshake/updatable_aead_test.go

@@ -117,6 +117,20 @@ var _ = Describe("Updatable AEAD", func() {
 					Expect(err).To(MatchError(ErrDecryptionFailed))
 				})
 
+				It("decodes the packet number", func() {
+					encrypted := server.Seal(nil, msg, 0x1337, ad)
+					_, err := client.Open(nil, encrypted, time.Now(), 0x1337, protocol.KeyPhaseZero, ad)
+					Expect(err).ToNot(HaveOccurred())
+					Expect(client.DecodePacketNumber(0x38, protocol.PacketNumberLen1)).To(BeEquivalentTo(0x1338))
+				})
+
+				It("ignores packets it can't decrypt for packet number derivation", func() {
+					encrypted := server.Seal(nil, msg, 0x1337, ad)
+					_, err := client.Open(nil, encrypted[:len(encrypted)-1], time.Now(), 0x1337, protocol.KeyPhaseZero, ad)
+					Expect(err).To(HaveOccurred())
+					Expect(client.DecodePacketNumber(0x38, protocol.PacketNumberLen1)).To(BeEquivalentTo(0x38))
+				})
+
 				It("returns an AEAD_LIMIT_REACHED error when reaching the AEAD limit", func() {
 					client.invalidPacketLimit = 10
 					for i := 0; i < 9; i++ {

packet_unpacker.go

@@ -7,7 +7,6 @@ import (
 
 	"github.com/lucas-clemente/quic-go/internal/handshake"
 	"github.com/lucas-clemente/quic-go/internal/protocol"
-	"github.com/lucas-clemente/quic-go/internal/utils"
 	"github.com/lucas-clemente/quic-go/internal/wire"
 )
 
@@ -44,8 +43,6 @@ type unpackedPacket struct {
 type packetUnpacker struct {
 	cs handshake.CryptoSetup
 
-	largestRcvdPacketNumber protocol.PacketNumber
-
 	version protocol.VersionNumber
 }
 
@@ -112,9 +109,6 @@ func (u *packetUnpacker) Unpack(hdr *wire.Header, rcvTime time.Time, data []byte
 		}
 	}
 
-	// Only do this after decrypting, so we are sure the packet is not attacker-controlled
-	u.largestRcvdPacketNumber = utils.MaxPacketNumber(u.largestRcvdPacketNumber, extHdr.PacketNumber)
-
 	return &unpackedPacket{
 		hdr:             extHdr,
 		packetNumber:    extHdr.PacketNumber,
@@ -132,6 +126,7 @@ func (u *packetUnpacker) unpackLongHeaderPacket(opener handshake.LongHeaderOpene
 		return nil, nil, parseErr
 	}
 	extHdrLen := extHdr.ParsedLen()
+	extHdr.PacketNumber = opener.DecodePacketNumber(extHdr.PacketNumber, extHdr.PacketNumberLen)
 	decrypted, err := opener.Open(data[extHdrLen:extHdrLen], data[extHdrLen:], extHdr.PacketNumber, data[:extHdrLen])
 	if err != nil {
 		return nil, nil, err
@@ -155,6 +150,7 @@ func (u *packetUnpacker) unpackShortHeaderPacket(
 	if parseErr != nil && parseErr != wire.ErrInvalidReservedBits {
 		return nil, nil, parseErr
 	}
+	extHdr.PacketNumber = opener.DecodePacketNumber(extHdr.PacketNumber, extHdr.PacketNumberLen)
 	extHdrLen := extHdr.ParsedLen()
 	decrypted, err := opener.Open(data[extHdrLen:extHdrLen], data[extHdrLen:], rcvTime, extHdr.PacketNumber, extHdr.KeyPhase, data[:extHdrLen])
 	if err != nil {
@@ -172,11 +168,6 @@ func (u *packetUnpacker) unpackHeader(hd headerDecryptor, hdr *wire.Header, data
 	if err != nil && err != wire.ErrInvalidReservedBits {
 		return nil, &headerParseError{err: err}
 	}
-	extHdr.PacketNumber = protocol.DecodePacketNumber(
-		extHdr.PacketNumberLen,
-		u.largestRcvdPacketNumber,
-		extHdr.PacketNumber,
-	)
 	return extHdr, err
 }
 

packet_unpacker_test.go

@@ -5,14 +5,14 @@ import (
 	"errors"
 	"time"
 
-	"github.com/lucas-clemente/quic-go/internal/qerr"
-
-	"github.com/golang/mock/gomock"
 	"github.com/lucas-clemente/quic-go/internal/handshake"
 	"github.com/lucas-clemente/quic-go/internal/mocks"
 	"github.com/lucas-clemente/quic-go/internal/protocol"
+	"github.com/lucas-clemente/quic-go/internal/qerr"
 	"github.com/lucas-clemente/quic-go/internal/wire"
 
+	"github.com/golang/mock/gomock"
+
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
 )
@@ -97,9 +97,12 @@ var _ = Describe("Packet Unpacker", func() {
 		}
 		hdr, hdrRaw := getHeader(extHdr)
 		opener := mocks.NewMockLongHeaderOpener(mockCtrl)
-		cs.EXPECT().GetInitialOpener().Return(opener, nil)
-		opener.EXPECT().DecryptHeader(gomock.Any(), gomock.Any(), gomock.Any())
-		opener.EXPECT().Open(gomock.Any(), payload, extHdr.PacketNumber, hdrRaw).Return([]byte("decrypted"), nil)
+		gomock.InOrder(
+			cs.EXPECT().GetInitialOpener().Return(opener, nil),
+			opener.EXPECT().DecryptHeader(gomock.Any(), gomock.Any(), gomock.Any()),
+			opener.EXPECT().DecodePacketNumber(protocol.PacketNumber(2), protocol.PacketNumberLen3).Return(protocol.PacketNumber(1234)),
+			opener.EXPECT().Open(gomock.Any(), payload, protocol.PacketNumber(1234), hdrRaw).Return([]byte("decrypted"), nil),
+		)
 		packet, err := unpacker.Unpack(hdr, time.Now(), append(hdrRaw, payload...))
 		Expect(err).ToNot(HaveOccurred())
 		Expect(packet.encryptionLevel).To(Equal(protocol.EncryptionInitial))
@@ -115,20 +118,45 @@ var _ = Describe("Packet Unpacker", func() {
 				DestConnectionID: connID,
 				Version:          version,
 			},
-			PacketNumber:    2,
-			PacketNumberLen: 3,
+			PacketNumber:    20,
+			PacketNumberLen: 2,
 		}
 		hdr, hdrRaw := getHeader(extHdr)
 		opener := mocks.NewMockLongHeaderOpener(mockCtrl)
-		cs.EXPECT().Get0RTTOpener().Return(opener, nil)
-		opener.EXPECT().DecryptHeader(gomock.Any(), gomock.Any(), gomock.Any())
-		opener.EXPECT().Open(gomock.Any(), payload, extHdr.PacketNumber, hdrRaw).Return([]byte("decrypted"), nil)
+		gomock.InOrder(
+			cs.EXPECT().Get0RTTOpener().Return(opener, nil),
+			opener.EXPECT().DecryptHeader(gomock.Any(), gomock.Any(), gomock.Any()),
+			opener.EXPECT().DecodePacketNumber(protocol.PacketNumber(20), protocol.PacketNumberLen2).Return(protocol.PacketNumber(321)),
+			opener.EXPECT().Open(gomock.Any(), payload, protocol.PacketNumber(321), hdrRaw).Return([]byte("decrypted"), nil),
+		)
 		packet, err := unpacker.Unpack(hdr, time.Now(), append(hdrRaw, payload...))
 		Expect(err).ToNot(HaveOccurred())
 		Expect(packet.encryptionLevel).To(Equal(protocol.Encryption0RTT))
 		Expect(packet.data).To(Equal([]byte("decrypted")))
 	})
 
+	It("opens short header packets", func() {
+		extHdr := &wire.ExtendedHeader{
+			Header:          wire.Header{DestConnectionID: connID},
+			KeyPhase:        protocol.KeyPhaseOne,
+			PacketNumber:    99,
+			PacketNumberLen: protocol.PacketNumberLen4,
+		}
+		hdr, hdrRaw := getHeader(extHdr)
+		opener := mocks.NewMockShortHeaderOpener(mockCtrl)
+		now := time.Now()
+		gomock.InOrder(
+			cs.EXPECT().Get1RTTOpener().Return(opener, nil),
+			opener.EXPECT().DecryptHeader(gomock.Any(), gomock.Any(), gomock.Any()),
+			opener.EXPECT().DecodePacketNumber(protocol.PacketNumber(99), protocol.PacketNumberLen4).Return(protocol.PacketNumber(321)),
+			opener.EXPECT().Open(gomock.Any(), payload, now, protocol.PacketNumber(321), protocol.KeyPhaseOne, hdrRaw).Return([]byte("decrypted"), nil),
+		)
+		packet, err := unpacker.Unpack(hdr, now, append(hdrRaw, payload...))
+		Expect(err).ToNot(HaveOccurred())
+		Expect(packet.encryptionLevel).To(Equal(protocol.Encryption1RTT))
+		Expect(packet.data).To(Equal([]byte("decrypted")))
+	})
+
 	It("returns the error when getting the sealer fails", func() {
 		extHdr := &wire.ExtendedHeader{
 			Header:          wire.Header{DestConnectionID: connID},
@@ -157,6 +185,7 @@ var _ = Describe("Packet Unpacker", func() {
 		opener := mocks.NewMockLongHeaderOpener(mockCtrl)
 		cs.EXPECT().GetHandshakeOpener().Return(opener, nil)
 		opener.EXPECT().DecryptHeader(gomock.Any(), gomock.Any(), gomock.Any())
+		opener.EXPECT().DecodePacketNumber(gomock.Any(), gomock.Any())
 		opener.EXPECT().Open(gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any()).Return(nil, qerr.CryptoBufferExceeded)
 		_, err := unpacker.Unpack(hdr, time.Now(), append(hdrRaw, payload...))
 		Expect(err).To(MatchError(qerr.CryptoBufferExceeded))
@@ -178,6 +207,7 @@ var _ = Describe("Packet Unpacker", func() {
 		opener := mocks.NewMockLongHeaderOpener(mockCtrl)
 		opener.EXPECT().DecryptHeader(gomock.Any(), gomock.Any(), gomock.Any())
 		cs.EXPECT().GetHandshakeOpener().Return(opener, nil)
+		opener.EXPECT().DecodePacketNumber(gomock.Any(), gomock.Any())
 		opener.EXPECT().Open(gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any()).Return([]byte("payload"), nil)
 		_, err := unpacker.Unpack(hdr, time.Now(), append(hdrRaw, payload...))
 		Expect(err).To(MatchError(wire.ErrInvalidReservedBits))
@@ -194,6 +224,7 @@ var _ = Describe("Packet Unpacker", func() {
 		opener := mocks.NewMockShortHeaderOpener(mockCtrl)
 		opener.EXPECT().DecryptHeader(gomock.Any(), gomock.Any(), gomock.Any())
 		cs.EXPECT().Get1RTTOpener().Return(opener, nil)
+		opener.EXPECT().DecodePacketNumber(gomock.Any(), gomock.Any())
 		opener.EXPECT().Open(gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any()).Return([]byte("payload"), nil)
 		_, err := unpacker.Unpack(hdr, time.Now(), append(hdrRaw, payload...))
 		Expect(err).To(MatchError(wire.ErrInvalidReservedBits))
@@ -210,6 +241,7 @@ var _ = Describe("Packet Unpacker", func() {
 		opener := mocks.NewMockShortHeaderOpener(mockCtrl)
 		opener.EXPECT().DecryptHeader(gomock.Any(), gomock.Any(), gomock.Any())
 		cs.EXPECT().Get1RTTOpener().Return(opener, nil)
+		opener.EXPECT().DecodePacketNumber(gomock.Any(), gomock.Any())
 		opener.EXPECT().Open(gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any()).Return(nil, handshake.ErrDecryptionFailed)
 		_, err := unpacker.Unpack(hdr, time.Now(), append(hdrRaw, payload...))
 		Expect(err).To(MatchError(handshake.ErrDecryptionFailed))
@@ -247,46 +279,15 @@ var _ = Describe("Packet Unpacker", func() {
 					pnBytes[i] ^= 0xff // invert the packet number bytes
 				}
 			}),
-			opener.EXPECT().Open(gomock.Any(), gomock.Any(), protocol.PacketNumber(0x1337), origHdrRaw).Return([]byte{0}, nil),
+			opener.EXPECT().DecodePacketNumber(protocol.PacketNumber(0x1337), protocol.PacketNumberLen2).Return(protocol.PacketNumber(0x7331)),
+			opener.EXPECT().Open(gomock.Any(), gomock.Any(), protocol.PacketNumber(0x7331), origHdrRaw).Return([]byte{0}, nil),
 		)
 		data := hdrRaw
 		for i := 1; i <= 100; i++ {
 			data = append(data, uint8(i))
 		}
 		packet, err := unpacker.Unpack(hdr, time.Now(), data)
 		Expect(err).ToNot(HaveOccurred())
-		Expect(packet.packetNumber).To(Equal(protocol.PacketNumber(0x1337)))
-	})
-
-	It("decodes the packet number", func() {
-		rcvTime := time.Now().Add(-time.Hour)
-		firstHdr := &wire.ExtendedHeader{
-			Header:          wire.Header{DestConnectionID: connID},
-			PacketNumber:    0x1337,
-			PacketNumberLen: 2,
-			KeyPhase:        protocol.KeyPhaseOne,
-		}
-		opener := mocks.NewMockShortHeaderOpener(mockCtrl)
-		cs.EXPECT().Get1RTTOpener().Return(opener, nil).Times(2)
-		opener.EXPECT().DecryptHeader(gomock.Any(), gomock.Any(), gomock.Any())
-		opener.EXPECT().Open(gomock.Any(), gomock.Any(), rcvTime, firstHdr.PacketNumber, protocol.KeyPhaseOne, gomock.Any()).Return([]byte{0}, nil)
-		hdr, hdrRaw := getHeader(firstHdr)
-		packet, err := unpacker.Unpack(hdr, rcvTime, append(hdrRaw, payload...))
-		Expect(err).ToNot(HaveOccurred())
-		Expect(packet.packetNumber).To(Equal(protocol.PacketNumber(0x1337)))
-		// the real packet number is 0x1338, but only the last byte is sent
-		secondHdr := &wire.ExtendedHeader{
-			Header:          wire.Header{DestConnectionID: connID},
-			PacketNumber:    0x38,
-			PacketNumberLen: 1,
-			KeyPhase:        protocol.KeyPhaseZero,
-		}
-		// expect the call with the decoded packet number
-		opener.EXPECT().DecryptHeader(gomock.Any(), gomock.Any(), gomock.Any())
-		opener.EXPECT().Open(gomock.Any(), gomock.Any(), rcvTime, protocol.PacketNumber(0x1338), protocol.KeyPhaseZero, gomock.Any()).Return([]byte{0}, nil)
-		hdr, hdrRaw = getHeader(secondHdr)
-		packet, err = unpacker.Unpack(hdr, rcvTime, append(hdrRaw, payload...))
-		Expect(err).ToNot(HaveOccurred())
-		Expect(packet.packetNumber).To(Equal(protocol.PacketNumber(0x1338)))
+		Expect(packet.packetNumber).To(Equal(protocol.PacketNumber(0x7331)))
 	})
 })