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pad Initial packets to the required minimum size (1200 bytes)

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This commit is contained in:
Marten Seemann 2017-12-08 11:23:12 +07:00
parent 62a664f5f4
commit 6019634286
3 changed files with 35 additions and 3 deletions
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3
internal/protocol/protocol.go
View file

@ -77,6 +77,9 @@ const DefaultTCPMSS ByteCount = 1460
// ClientHelloMinimumSize is the minimum size the server expects an inchoate CHLO to have.
const ClientHelloMinimumSize = 1024
// MinInitialPacketSize is the minimum size an Initial packet (in IETF QUIC) is requried to have.
const MinInitialPacketSize = 1200
// MaxClientHellos is the maximum number of times we'll send a client hello
// The value 3 accounts for:
// * one failure due to an incorrect or missing source-address token

20
packet_packer.go
View file

@ -290,7 +290,6 @@ func (p *packetPacker) getHeader(encLevel protocol.EncryptionLevel) *wire.Header
header.IsLongHeader = true
if !p.hasSentPacket && p.perspective == protocol.PerspectiveClient {
header.Type = protocol.PacketTypeInitial
// TODO(#886): add padding
} else {
header.Type = protocol.PacketTypeHandshake
}
@ -327,12 +326,27 @@ func (p *packetPacker) writeAndSealPacket(
return nil, err
}
payloadStartIndex := buffer.Len()
// the Initial packet needs to be padded, so the last STREAM frame must have the data length present
if header.Type == protocol.PacketTypeInitial {
lastFrame := payloadFrames[len(payloadFrames)-1]
if sf, ok := lastFrame.(*wire.StreamFrame); ok {
sf.DataLenPresent = true
}
}
for _, frame := range payloadFrames {
err := frame.Write(buffer, p.version)
if err != nil {
if err := frame.Write(buffer, p.version); err != nil {
return nil, err
}
}
// if this is an IETF QUIC Initial packet, we need to pad it to fulfill the minimum size requirement
// in gQUIC, padding is handled in the CHLO
if header.Type == protocol.PacketTypeInitial {
paddingLen := protocol.MinInitialPacketSize - sealer.Overhead() - buffer.Len()
if paddingLen > 0 {
buffer.Write(bytes.Repeat([]byte{0}, paddingLen))
}
}
if protocol.ByteCount(buffer.Len()+sealer.Overhead()) > protocol.MaxPacketSize {
return nil, errors.New("PacketPacker BUG: packet too large")
}

15
packet_packer_test.go
View file

@ -767,6 +767,21 @@ var _ = Describe("Packet packer", func() {
Expect(err).To(MatchError("PacketPacker BUG: packet too large"))
})
It("pads Initial packets to the required minimum packet size", func() {
packer.version = protocol.VersionTLS
packer.hasSentPacket = false
packer.perspective = protocol.PerspectiveClient
packer.cryptoSetup.(*mockCryptoSetup).encLevelSealCrypto = protocol.EncryptionUnencrypted
cryptoStream.dataForWriting = []byte("foobar")
packet, err := packer.PackPacket()
Expect(err).ToNot(HaveOccurred())
Expect(packet.raw).To(HaveLen(protocol.MinInitialPacketSize))
Expect(packet.frames).To(HaveLen(1))
sf := packet.frames[0].(*wire.StreamFrame)
Expect(sf.Data).To(Equal([]byte("foobar")))
Expect(sf.DataLenPresent).To(BeTrue())
})
It("refuses to retransmit packets that were sent with forward-secure encryption", func() {
p := &ackhandler.Packet{
EncryptionLevel: protocol.EncryptionForwardSecure,