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hijacker.go
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hijacker.go
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package hijacker
import (
"crypto/tls"
"fmt"
"io"
"net/http"
"os"
"time"
"github.com/concourse/atc"
"github.com/concourse/fly/pty"
"github.com/concourse/fly/rc"
"github.com/concourse/fly/ui"
"github.com/gorilla/websocket"
"github.com/mgutz/ansi"
"github.com/tedsuo/rata"
)
type ProcessIO struct {
In io.Reader
Out io.Writer
Err io.Writer
}
type Hijacker struct {
tlsConfig *tls.Config
requestGenerator *rata.RequestGenerator
token *rc.TargetToken
interval time.Duration
}
func New(tlsConfig *tls.Config, requestGenerator *rata.RequestGenerator, token *rc.TargetToken) *Hijacker {
return &Hijacker{
tlsConfig: tlsConfig,
requestGenerator: requestGenerator,
token: token,
interval: 10 * time.Second,
}
}
func (h *Hijacker) SetHeartbeatInterval(interval time.Duration) {
h.interval = interval
}
func (h *Hijacker) Hijack(handle string, spec atc.HijackProcessSpec, pio ProcessIO) (int, error) {
url, header, err := h.hijackRequestParts(handle)
if err != nil {
return -1, err
}
dialer := websocket.Dialer{
TLSClientConfig: h.tlsConfig,
Proxy: http.ProxyFromEnvironment,
}
conn, _, err := dialer.Dial(url, header)
if err != nil {
return -1, err
}
defer conn.Close()
err = conn.WriteJSON(spec)
if err != nil {
return -1, err
}
inputs := make(chan atc.HijackInput, 1)
finished := make(chan struct{}, 1)
go h.monitorTTYSize(inputs, finished)
go func() {
io.Copy(&stdinWriter{inputs}, pio.In)
inputs <- atc.HijackInput{Closed: true}
}()
go h.handleInput(conn, inputs, finished)
exitStatus := h.handleOutput(conn, pio)
close(finished)
return exitStatus, nil
}
func (h *Hijacker) hijackRequestParts(handle string) (string, http.Header, error) {
hijackReq, _ := h.requestGenerator.CreateRequest(
atc.HijackContainer,
rata.Params{"id": handle},
nil,
)
if h.token != nil {
hijackReq.Header.Add("Authorization", h.token.Type+" "+h.token.Value)
}
wsUrl := hijackReq.URL
var found bool
wsUrl.Scheme, found = websocketSchemeMap[wsUrl.Scheme]
if !found {
return "", nil, fmt.Errorf("unknown target scheme: %s", wsUrl.Scheme)
}
return wsUrl.String(), hijackReq.Header, nil
}
func (h *Hijacker) handleOutput(conn *websocket.Conn, pio ProcessIO) int {
var exitStatus int
for {
var output atc.HijackOutput
err := conn.ReadJSON(&output)
if err != nil {
if !websocket.IsCloseError(err) && !websocket.IsUnexpectedCloseError(err) {
fmt.Println(err)
}
break
}
if output.ExitStatus != nil {
exitStatus = *output.ExitStatus
} else if len(output.Error) > 0 {
fmt.Fprintf(ui.Stderr, "%s\n", ansi.Color(output.Error, "red+b"))
exitStatus = 255
} else if len(output.Stdout) > 0 {
pio.Out.Write(output.Stdout)
} else if len(output.Stderr) > 0 {
pio.Err.Write(output.Stderr)
}
}
return exitStatus
}
func (h *Hijacker) handleInput(conn *websocket.Conn, inputs <-chan atc.HijackInput, finished chan struct{}) {
ticker := time.NewTicker(h.interval)
defer ticker.Stop()
for {
select {
case input := <-inputs:
err := conn.WriteJSON(input)
if err != nil {
fmt.Fprintf(ui.Stderr, "failed to send input: %s", err.Error())
return
}
case t := <-ticker.C:
err := conn.WriteControl(websocket.PingMessage, []byte(t.String()), time.Now().Add(time.Second))
if err != nil {
fmt.Fprintf(ui.Stderr, "failed to send heartbeat: %s", err.Error())
}
case <-finished:
return
}
}
}
func (h *Hijacker) monitorTTYSize(inputs chan<- atc.HijackInput, finished chan struct{}) {
resized := pty.ResizeNotifier()
for {
select {
case <-resized:
rows, cols, err := pty.Getsize(os.Stdin)
if err == nil {
inputs <- atc.HijackInput{
TTYSpec: &atc.HijackTTYSpec{
WindowSize: atc.HijackWindowSize{
Columns: cols,
Rows: rows,
},
},
}
}
case <-finished:
return
}
}
}
type stdinWriter struct {
inputs chan<- atc.HijackInput
}
func (w *stdinWriter) Write(d []byte) (int, error) {
w.inputs <- atc.HijackInput{
Stdin: d,
}
return len(d), nil
}
var websocketSchemeMap = map[string]string{
"http": "ws",
"https": "wss",
}