103 lines
2.9 KiB
Go
103 lines
2.9 KiB
Go
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package quic
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import (
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"bytes"
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"fmt"
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"github.com/lucas-clemente/quic-go/internal/handshake"
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"github.com/lucas-clemente/quic-go/internal/protocol"
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"github.com/lucas-clemente/quic-go/internal/utils"
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"github.com/lucas-clemente/quic-go/internal/wire"
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)
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type unpackedPacket struct {
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packetNumber protocol.PacketNumber // the decoded packet number
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hdr *wire.ExtendedHeader
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encryptionLevel protocol.EncryptionLevel
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data []byte
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}
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// The packetUnpacker unpacks QUIC packets.
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type packetUnpacker struct {
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cs handshake.CryptoSetup
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largestRcvdPacketNumber protocol.PacketNumber
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version protocol.VersionNumber
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}
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var _ unpacker = &packetUnpacker{}
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func newPacketUnpacker(cs handshake.CryptoSetup, version protocol.VersionNumber) unpacker {
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return &packetUnpacker{
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cs: cs,
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version: version,
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}
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}
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func (u *packetUnpacker) Unpack(hdr *wire.Header, data []byte) (*unpackedPacket, error) {
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r := bytes.NewReader(data)
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var encLevel protocol.EncryptionLevel
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switch hdr.Type {
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case protocol.PacketTypeInitial:
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encLevel = protocol.EncryptionInitial
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case protocol.PacketTypeHandshake:
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encLevel = protocol.EncryptionHandshake
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default:
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if hdr.IsLongHeader {
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return nil, fmt.Errorf("unknown packet type: %s", hdr.Type)
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}
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encLevel = protocol.Encryption1RTT
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}
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opener, err := u.cs.GetOpener(encLevel)
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if err != nil {
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return nil, err
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}
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hdrLen := int(hdr.ParsedLen())
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if len(data) < hdrLen+4+16 {
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return nil, fmt.Errorf("Packet too small. Expected at least 20 bytes after the header, got %d", len(data)-hdrLen)
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}
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// The packet number can be up to 4 bytes long, but we won't know the length until we decrypt it.
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// 1. save a copy of the 4 bytes
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origPNBytes := make([]byte, 4)
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copy(origPNBytes, data[hdrLen:hdrLen+4])
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// 2. decrypt the header, assuming a 4 byte packet number
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opener.DecryptHeader(
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data[hdrLen+4:hdrLen+4+16],
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&data[0],
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data[hdrLen:hdrLen+4],
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)
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// 3. parse the header (and learn the actual length of the packet number)
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extHdr, err := hdr.ParseExtended(r, u.version)
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if err != nil {
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return nil, fmt.Errorf("error parsing extended header: %s", err)
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}
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extHdrLen := hdrLen + int(extHdr.PacketNumberLen)
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// 4. if the packet number is shorter than 4 bytes, replace the remaining bytes with the copy we saved earlier
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if extHdr.PacketNumberLen != protocol.PacketNumberLen4 {
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copy(data[extHdrLen:hdrLen+4], origPNBytes[int(extHdr.PacketNumberLen):])
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}
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pn := protocol.DecodePacketNumber(
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extHdr.PacketNumberLen,
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u.largestRcvdPacketNumber,
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extHdr.PacketNumber,
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)
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decrypted, err := opener.Open(data[extHdrLen:extHdrLen], data[extHdrLen:], pn, data[:extHdrLen])
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if err != nil {
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return nil, err
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}
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// Only do this after decrypting, so we are sure the packet is not attacker-controlled
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u.largestRcvdPacketNumber = utils.MaxPacketNumber(u.largestRcvdPacketNumber, pn)
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return &unpackedPacket{
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hdr: extHdr,
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packetNumber: pn,
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encryptionLevel: encLevel,
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data: decrypted,
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}, nil
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}
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