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Handle legacy server list ping for handshake

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This commit is contained in:
Geoff Bourne 2019-07-13 15:40:34 -05:00
parent 3699931af0
commit 4c99daafa3
4 changed files with 300 additions and 78 deletions
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147
mcproto/read.go
View File

@ -1,20 +1,38 @@
package mcproto
import (
"bufio"
"bytes"
"errors"
"encoding/binary"
"github.com/pkg/errors"
"github.com/sirupsen/logrus"
"golang.org/x/text/encoding/unicode"
"golang.org/x/text/transform"
"io"
"net"
"strings"
"time"
)
func ReadPacket(reader io.Reader, addr net.Addr) (*Packet, error) {
func ReadPacket(reader io.Reader, addr net.Addr, state State) (*Packet, error) {
logrus.
WithField("client", addr).
Debug("Reading packet")
if state == StateHandshaking {
bufReader := bufio.NewReader(reader)
data, err := bufReader.Peek(1)
if err != nil {
return nil, err
}
if data[0] == PacketIdLegacyServerListPing {
return ReadLegacyServerListPing(bufReader, addr)
} else {
reader = bufReader
}
}
frame, err := ReadFrame(reader, addr)
if err != nil {
return nil, err
@ -38,6 +56,97 @@ func ReadPacket(reader io.Reader, addr net.Addr) (*Packet, error) {
return packet, nil
}
func ReadLegacyServerListPing(reader *bufio.Reader, addr net.Addr) (*Packet, error) {
logrus.
WithField("client", addr).
Debug("Reading legacy server list ping")
packetId, err := reader.ReadByte()
if err != nil {
return nil, err
}
if packetId != PacketIdLegacyServerListPing {
return nil, errors.Errorf("expected legacy server listing ping packet ID, got %x", packetId)
}
payload, err := reader.ReadByte()
if err != nil {
return nil, err
}
if payload != 0x01 {
return nil, errors.Errorf("expected payload=1 from legacy server listing ping, got %x", payload)
}
packetIdForPluginMsg, err := reader.ReadByte()
if err != nil {
return nil, err
}
if packetIdForPluginMsg != 0xFA {
return nil, errors.Errorf("expected packetIdForPluginMsg=0xFA from legacy server listing ping, got %x", packetIdForPluginMsg)
}
messageNameShortLen, err := ReadUnsignedShort(reader)
if err != nil {
return nil, err
}
if messageNameShortLen != 11 {
return nil, errors.Errorf("expected messageNameShortLen=11 from legacy server listing ping, got %d", messageNameShortLen)
}
messageName, err := ReadUTF16BEString(reader, messageNameShortLen)
if messageName != "MC|PingHost" {
return nil, errors.Errorf("expected messageName=MC|PingHost, got %s", messageName)
}
remainingLen, err := ReadUnsignedShort(reader)
remainingReader := io.LimitReader(reader, int64(remainingLen))
protocolVersion, err := ReadByte(remainingReader)
if err != nil {
return nil, err
}
hostnameLen, err := ReadUnsignedShort(remainingReader)
if err != nil {
return nil, err
}
hostname, err := ReadUTF16BEString(remainingReader, hostnameLen)
if err != nil {
return nil, err
}
port, err := ReadUnsignedInt(remainingReader)
if err != nil {
return nil, err
}
return &Packet{
PacketID: PacketIdLegacyServerListPing,
Length: 0,
Data: &LegacyServerListPing{
ProtocolVersion: int(protocolVersion),
ServerAddress: hostname,
ServerPort: uint16(port),
},
}, nil
}
func ReadUTF16BEString(reader io.Reader, symbolLen uint16) (string, error) {
bsUtf16be := make([]byte, symbolLen*2)
_, err := io.ReadFull(reader, bsUtf16be)
if err != nil {
return "", err
}
result, _, err := transform.Bytes(unicode.UTF16(unicode.BigEndian, unicode.IgnoreBOM).NewDecoder(), bsUtf16be)
if err != nil {
return "", err
}
return string(result), nil
}
func ReadFrame(reader io.Reader, addr net.Addr) (*Frame, error) {
logrus.
WithField("client", addr).
@ -136,25 +245,43 @@ func ReadString(reader io.Reader) (string, error) {
return strBuilder.String(), nil
}
func ReadByte(reader io.Reader) (byte, error) {
buf := make([]byte, 1)
_, err := reader.Read(buf)
if err != nil {
return 0, err
} else {
return buf[0], nil
}
}
func ReadUnsignedShort(reader io.Reader) (uint16, error) {
upper := make([]byte, 1)
_, err := reader.Read(upper)
var value uint16
err := binary.Read(reader, binary.BigEndian, &value)
if err != nil {
return 0, err
}
lower := make([]byte, 1)
_, err = reader.Read(lower)
return value, nil
}
func ReadUnsignedInt(reader io.Reader) (uint32, error) {
var value uint32
err := binary.Read(reader, binary.BigEndian, &value)
if err != nil {
return 0, err
}
return (uint16(upper[0]) << 8) | uint16(lower[0]), nil
return value, nil
}
func ReadHandshake(data []byte) (*Handshake, error) {
func ReadHandshake(data interface{}) (*Handshake, error) {
dataBytes, ok := data.([]byte)
if !ok {
return nil, errors.New("data is not expected byte slice")
}
handshake := &Handshake{}
buffer := bytes.NewBuffer(data)
buffer := bytes.NewBuffer(dataBytes)
var err error
handshake.ProtocolVersion, err = ReadVarInt(buffer)

36
mcproto/read_test.go Normal file
View File

@ -0,0 +1,36 @@
package mcproto
import (
"bytes"
"github.com/stretchr/testify/assert"
"github.com/stretchr/testify/require"
"testing"
)
func TestReadVarInt(t *testing.T) {
tests := []struct {
Name string
Input []byte
Expected int
}{
{
Name: "Single byte",
Input: []byte{0xFA, 0x00},
Expected: 0x7A,
},
{
Name: "Two byte",
Input: []byte{0x81, 0x04},
Expected: 0x0201,
},
}
for _, tt := range tests {
t.Run(tt.Name, func(t *testing.T) {
result, err := ReadVarInt(bytes.NewBuffer(tt.Input))
require.NoError(t, err)
assert.Equal(t, tt.Expected, result)
})
}
}

26
mcproto/types.go
View File

@ -7,6 +7,12 @@ type Frame struct {
Payload []byte
}
type State int
const (
StateHandshaking = iota
)
var trimLimit = 64
func trimBytes(data []byte) ([]byte, string) {
@ -25,15 +31,23 @@ func (f *Frame) String() string {
type Packet struct {
Length int
PacketID int
Data []byte
// Data is either a byte slice of raw content or a parsed message
Data interface{}
}
func (p *Packet) String() string {
trimmed, cont := trimBytes(p.Data)
if dataBytes, ok := p.Data.([]byte); ok {
trimmed, cont := trimBytes(dataBytes)
return fmt.Sprintf("Frame:[len=%d, packetId=%d, data=%#X%s]", p.Length, p.PacketID, trimmed, cont)
} else {
return fmt.Sprintf("Frame:[len=%d, packetId=%d, data=%+v]", p.Length, p.PacketID, p.Data)
}
}
const PacketIdHandshake = 0x00
const (
PacketIdHandshake = 0x00
PacketIdLegacyServerListPing = 0xFE
)
type Handshake struct {
ProtocolVersion int
@ -42,6 +56,12 @@ type Handshake struct {
NextState int
}
type LegacyServerListPing struct {
ProtocolVersion int
ServerAddress string
ServerPort uint16
}
type ByteReader interface {
ReadByte() (byte, error)
}

135
server/connector.go
View File

@ -12,7 +12,7 @@ import (
)
const (
handshakeTimeout = 2 * time.Second
handshakeTimeout = 5 * time.Second
)
var noDeadline time.Time
@ -21,9 +21,12 @@ type IConnector interface {
StartAcceptingConnections(ctx context.Context, listenAddress string, connRateLimit int) error
}
var Connector IConnector = &connectorImpl{}
var Connector IConnector = &connectorImpl{
state: mcproto.StateHandshaking,
}
type connectorImpl struct {
state mcproto.State
}
func (c *connectorImpl) StartAcceptingConnections(ctx context.Context, listenAddress string, connRateLimit int) error {
@ -70,71 +73,65 @@ func (c *connectorImpl) HandleConnection(ctx context.Context, frontendConn net.C
logrus.
WithField("client", clientAddr).
Info("Got connection")
defer logrus.WithField("client", clientAddr).Debug("Closing frontend connection")
inspectionBuffer := new(bytes.Buffer)
inspectionReader := io.TeeReader(frontendConn, inspectionBuffer)
if err := frontendConn.SetReadDeadline(time.Now().Add(handshakeTimeout)); err != nil {
/* if err := frontendConn.SetReadDeadline(time.Now().Add(handshakeTimeout)); err != nil {
logrus.
WithError(err).
WithField("client", clientAddr).
Error("Failed to set read deadline")
return
}
packet, err := mcproto.ReadPacket(inspectionReader, clientAddr)
*/packet, err := mcproto.ReadPacket(inspectionReader, clientAddr, c.state)
if err != nil {
logrus.WithError(err).WithField("clientAddr", clientAddr).Error("Failed to read packet")
return
}
logrus.WithFields(logrus.Fields{"length": packet.Length, "packetID": packet.PacketID}).Info("Got packet")
logrus.
WithField("client", clientAddr).
WithField("length", packet.Length).
WithField("packetID", packet.PacketID).
Debug("Got packet")
if packet.PacketID == mcproto.PacketIdHandshake {
handshake, err := mcproto.ReadHandshake(packet.Data)
if err != nil {
logrus.WithError(err).WithField("clientAddr", clientAddr).Error("Failed to read handshake")
logrus.WithError(err).WithField("clientAddr", clientAddr).
Error("Failed to read handshake")
return
}
logrus.WithFields(logrus.Fields{
"protocolVersion": handshake.ProtocolVersion,
"server": handshake.ServerAddress,
"serverPort": handshake.ServerPort,
"nextState": handshake.NextState,
}).Info("Got handshake")
backendHostPort := Routes.FindBackendForServerAddress(handshake.ServerAddress)
if backendHostPort == "" {
logrus.WithField("serverAddress", handshake.ServerAddress).Warn("Unable to find registered backend")
return
}
logrus.WithField("backendHostPort", backendHostPort).Info("Connecting to backend")
backendConn, err := net.Dial("tcp", backendHostPort)
if err != nil {
logrus.WithError(err).WithFields(logrus.Fields{
"serverAddress": handshake.ServerAddress,
"backend": backendHostPort,
}).Warn("Unable to connect to backend")
return
}
amount, err := io.Copy(backendConn, inspectionBuffer)
if err != nil {
logrus.WithError(err).Error("Failed to write handshake to backend connection")
return
}
logrus.WithField("amount", amount).Debug("Relayed handshake to backend")
if err = frontendConn.SetReadDeadline(noDeadline); err != nil {
logrus.
WithError(err).
WithField("client", clientAddr).
Error("Failed to clear read deadline")
WithField("handshake", handshake).
Debug("Got handshake")
serverAddress := handshake.ServerAddress
c.findAndConnectBackend(ctx, frontendConn, clientAddr, inspectionBuffer, serverAddress)
} else if packet.PacketID == mcproto.PacketIdLegacyServerListPing {
handshake, ok := packet.Data.(*mcproto.LegacyServerListPing)
if !ok {
logrus.
WithField("client", clientAddr).
WithField("packet", packet).
Warn("Unexpected data type for PacketIdLegacyServerListPing")
return
}
pumpConnections(ctx, frontendConn, backendConn)
logrus.
WithField("client", clientAddr).
WithField("handshake", handshake).
Debug("Got legacy server list ping")
serverAddress := handshake.ServerAddress
c.findAndConnectBackend(ctx, frontendConn, clientAddr, inspectionBuffer, serverAddress)
} else {
logrus.
WithField("client", clientAddr).
@ -144,17 +141,58 @@ func (c *connectorImpl) HandleConnection(ctx context.Context, frontendConn net.C
}
}
func (c *connectorImpl) findAndConnectBackend(ctx context.Context, frontendConn net.Conn,
clientAddr net.Addr, preReadContent io.Reader, serverAddress string) {
backendHostPort := Routes.FindBackendForServerAddress(serverAddress)
if backendHostPort == "" {
logrus.WithField("serverAddress", serverAddress).Warn("Unable to find registered backend")
return
}
logrus.
WithField("client", clientAddr).
WithField("server", serverAddress).
WithField("backendHostPort", backendHostPort).
Info("Connecting to backend")
backendConn, err := net.Dial("tcp", backendHostPort)
if err != nil {
logrus.
WithError(err).
WithField("client", clientAddr).
WithField("serverAddress", serverAddress).
WithField("backend", backendHostPort).
Warn("Unable to connect to backend")
return
}
amount, err := io.Copy(backendConn, preReadContent)
if err != nil {
logrus.WithError(err).Error("Failed to write handshake to backend connection")
return
}
logrus.WithField("amount", amount).Debug("Relayed handshake to backend")
if err = frontendConn.SetReadDeadline(noDeadline); err != nil {
logrus.
WithError(err).
WithField("client", clientAddr).
Error("Failed to clear read deadline")
return
}
pumpConnections(ctx, frontendConn, backendConn)
return
}
func pumpConnections(ctx context.Context, frontendConn, backendConn net.Conn) {
//noinspection GoUnhandledErrorResult
defer backendConn.Close()
clientAddr := frontendConn.RemoteAddr()
defer logrus.WithField("client", clientAddr).Debug("Closing backend connection")
errors := make(chan error, 2)
go pumpFrames(backendConn, frontendConn, errors, "backend", "frontend", clientAddr)
go pumpFrames(frontendConn, backendConn, errors, "frontend", "backend", clientAddr)
for {
select {
case err := <-errors:
if err != io.EOF {
@ -163,21 +201,22 @@ func pumpConnections(ctx context.Context, frontendConn, backendConn net.Conn) {
Error("Error observed on connection relay")
}
return
case <-ctx.Done():
return
}
logrus.Debug("Observed context cancellation")
}
}
func pumpFrames(incoming io.Reader, outgoing io.Writer, errors chan<- error, from, to string, clientAddr net.Addr) {
amount, err := io.Copy(outgoing, incoming)
if err != nil {
errors <- err
}
logrus.
WithField("client", clientAddr).
WithField("amount", amount).
Infof("Finished relay %s->%s", from, to)
if err != nil {
errors <- err
} else {
// successful io.Copy return nil error, not EOF...to simulate that to trigger outer handling
errors <- io.EOF
}
}