Modifying a Binary via Powershell

Creating or modifying a binary files in PowerShell can be done using various methods. One common approach is to use the Set-Content cmdlet along with a byte array.

This approach is useful for creating or modifying binary files directly from PowerShell, especially when dealing with small files or when you need to automate the process in a script.

Writing a Binary File

First, we need to create a byte array in powershell, where each element in this array is a byte to be written to the file.

$bytes = [byte[]](0x01, 0x02, 0x03, 0x04)

This creates an array with four bytes: 1, 2, 3, and 4.

The following Python script will also generate an array from a file in the required format. It reads a binary file and outputs the bytes in the format required ([byte[]](0x01, 0x02, 0x03, 0x04)).

def read_binary_file(file_path): 
  try: with open(file_path, "rb") as file: 
   byte_data = file.read() 
  byte_array = ', '.join(f'0x{byte:02x}' for byte in byte_data) 
   return f'[byte[]]({byte_array})' 
   except 
    Exception as e: return f"Error reading file: {e}" # Example usage: 
output = read_binary_file("path_to_your_file.bin") 
print(output)

Next, we need to use Set-Content to write the byte array to a file.

Set-Content -Path "C:\path\to\your\file.bin" -Value $bytes -Encoding Byte -Force

To use the command we just need to replace "C:\path\to\your\file.bin" with the path where we want to save the file. Note, that the the -Encoding Byte parameter ensures that the content is treated as bytes.

Reading and Modifying a Binary File

To modify a file we need to read the binary file in question, modify its contents, and then write it back.

$bytes = Get-Content -Path "C:\path\to\your\file.bin" -Encoding Byte -Raw

Next, we just change the array elements as required. And, finally we can write the file back to the hard drive.

Set-Content -Path "C:\path\to\your\file.bin" -Value $bytes -Encoding Byte -Force

Creating a Binary File from a String

If you have a string that you want to convert to a binary file (for example, writing a text in UTF-8 encoding), you can do it as follows.

$text = "Hello, world!" $bytes = [System.Text.Encoding]::UTF8.GetBytes($text)

Then just write the bytes to file.

Set-Content -Path "C:\path\to\your\file.bin" -Value $bytes -Encoding Byte -Force

Notes

• Always ensure the path you’re writing to is correct and that you have the necessary permissions to write to that location.
• Be cautious when modifying existing binary files, as incorrect modifications can corrupt the file.