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tunnel_endpoint.go
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tunnel_endpoint.go
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package base
import (
"context"
"encoding/binary"
"github.com/sirupsen/logrus"
"io"
"net/http"
)
// TunnelEndpoint is initially designed for common parts of stub and agent.
type TunnelEndpoint struct {
Component
}
const (
SessionIDHeaderKey = "X-Tunnel-Session-ID"
BufferSize = 4096
)
func NewTunnelEndpoint(ctx context.Context, logger *logrus.Logger) TunnelEndpoint {
return TunnelEndpoint{
Component: NewComponent(ctx, logger),
}
}
// CheckAndStartPipe will check request header and response status code to see if there is a successful upgrade negotiation.
// The order of endpointA and endpointB only affect to log, A2B is forward and B2A is backward. X2Y means read from X and write to Y.
// This pipe is a full duplex pipe. The close of this pipe is caused by either context done or any error from any connection.
// The data is read in SPDY format where the auxiliary function `readSPDYFrame` does.
// Reference: https://www.chromium.org/spdy/spdy-protocol/spdy-protocol-draft3-1 section 2.2.
func (endpoint *TunnelEndpoint) CheckAndStartPipe(request *http.Request, response *http.Response, endpointA io.ReadWriter, endpointB io.ReadWriter) {
if request.Header.Get("Upgrade") == "SPDY/3.1" && response.StatusCode == 101 {
logger := endpoint.Logger.WithField(SessionIDHeaderKey, request.Header.Get(SessionIDHeaderKey))
logger.Tracef("Upgrade to protocol %s, SPDY pipe start", request.Header.Get("Upgrade"))
ctx, cancel := context.WithCancel(endpoint.Context)
pipe := func(r io.Reader, w io.Writer, log *logrus.Entry) {
log.Tracef("Start pipe")
defer cancel()
for {
select {
case <-ctx.Done():
log.Tracef("Exit")
return
default:
log.Tracef("Reading")
bytes, err := endpoint.readSPDYFrame(r, log)
if err != nil {
log.Tracef("Read failed: ", err)
return
}
log.Tracef("Read completed")
n, err := w.Write(bytes)
if err != nil {
log.Tracef("Write failed: ", err)
return
}
log.Tracef("Write completed, %d bytes transferred.", n)
}
}
}
go pipe(endpointA, endpointB, logger.WithField("pipe", "forward"))
go pipe(endpointB, endpointA, logger.WithField("pipe", "backward"))
<-ctx.Done()
}
if request.Header.Get("Upgrade") == "websocket" && response.StatusCode == 101 {
logger := endpoint.Logger.WithField(SessionIDHeaderKey, request.Header.Get(SessionIDHeaderKey))
logger.Tracef("Upgrade to protocol %s, websocket pipe start", request.Header.Get("Upgrade"))
ctx, cancel := context.WithCancel(endpoint.Context)
pipe := func(r io.Reader, w io.Writer, log *logrus.Entry) {
defer cancel()
for {
select {
case <-ctx.Done():
log.Debugf("Exit")
return
default:
log.Tracef("Reading")
bytes, err := endpoint.readWebsocketFrame(r, log)
if err != nil {
log.Tracef("Read failed: ", err)
return
}
log.Tracef("Read completed")
n, err := w.Write(bytes)
if err != nil {
log.Tracef("Write failed: ", err)
return
}
log.Tracef("Write completed, %d bytes transferred.", n)
}
}
}
go pipe(endpointA, endpointB, logger.WithField("pipe", "forward"))
go pipe(endpointB, endpointA, logger.WithField("pipe", "backward"))
<-ctx.Done()
}
}
func (endpoint *TunnelEndpoint) readSPDYFrame(reader io.Reader, log *logrus.Entry) ([]byte, error) {
log.Debugf("[ReadFrame] start read SPDY Frame")
header := make([]byte, 8)
cnt := 0
log.Debugf("[ReadFrame] reading header")
for cnt < 8 {
n, err := reader.Read(header[cnt:])
if err != nil {
return nil, err
}
log.Debugf("[ReadFrame] reading head %d bytes", n)
cnt += n
}
log.Debugf("[ReadFrame] header read complete")
length := int(binary.BigEndian.Uint32(append([]byte{0}, header[5:8]...))) + 8
frame := make([]byte, length)
copy(frame, header)
log.Debugf("[ReadFrame] reading body [%d bytes]", length-8)
for cnt < length {
n, err := reader.Read(frame[cnt:])
if err != nil {
return nil, err
}
cnt += n
}
log.Debugf("[ReadFrame] body read complete")
return frame, nil
}
func readFrame(size int, reader io.Reader, log *logrus.Entry) ([]byte, error) {
data := make([]byte, 0)
for {
if len(data) == size {
break
}
// Temporary slice to read chunk
sz := BufferSize
remaining := size - len(data)
if sz > remaining {
sz = remaining
}
temp := make([]byte, sz)
n, err := reader.Read(temp)
if err != nil && err != io.EOF {
return data, err
}
data = append(data, temp[:n]...)
}
return data, nil
}
func (endpoint *TunnelEndpoint) readWebsocketFrame(reader io.Reader, log *logrus.Entry) ([]byte, error) {
log.Tracef("[ReadFrame] start")
head, err := readFrame(2, reader, log)
if err != nil {
return nil, err
}
result := make([]byte, 0)
result = append(result, head[:2]...)
IsMasked := (head[1] & 0x80) == 0x80
var length uint64
length = uint64(head[1] & 0x7F)
if length == 126 {
lenBytes, err := readFrame(2, reader, log)
if err != nil {
return nil, err
}
length = uint64(binary.BigEndian.Uint16(lenBytes))
result = append(result, lenBytes[:2]...)
} else if length == 127 {
lenBytes, err := readFrame(8, reader, log)
if err != nil {
return nil, err
}
length = binary.BigEndian.Uint64(lenBytes)
result = append(result, lenBytes[:8]...)
}
if IsMasked {
maskKey, err := readFrame(4, reader, log)
if err != nil {
return nil, err
}
result = append(result, maskKey[:4]...)
}
payload, err := readFrame(int(length), reader, log) // possible data loss
if err != nil {
log.Errorf("[ReadFrame] payload err: %v", err)
return nil, err
}
result = append(result, payload[:length]...)
log.Tracef("[ReadFrame] payload append")
return result, err
}