Improve Make2023BootableMedia.ps1: auto-download oscdimg, path handling, boot.stl, NTFS enforcement

[ballsop]

Description

• Add Download-Oscdimg function to download oscdimg.exe from the Microsoft public symbol server when not found locally, with architecture detection (AMD64/ARM64/x86) and user confirmation prompt. Previously downloaded copies in %TEMP% are reused automatically. Addresses [Feature]: Make2023BootableMedia should have an option to download oscdimg if not present #333.

• Fix path handling errors found in testing: normalize ISOPath to absolute early via ConvertTo-AbsolutePath to prevent crash when bare filenames are passed. Replace fragile Substring/LastIndexOf with Split-Path in Create-ISOMedia. Replace unsafe Substring(0,1) drive letter extraction with Split-Path -Qualifier in Initialize-StagingDirectory and Validate-Parameters. Add null/empty input guard and use TrimEnd in ConvertTo-AbsolutePath.

• Copy boot.stl from boot.wim (Windows\Boot\EFI\boot.stl) to staged media (EFI\Microsoft\Boot\boot.stl) when present and not already at destination. Recent OS servicing introduced a new dependency on boot.stl.

• Require NTFS for StagingDir and NewMediaPath since WIM mounting relies on reparse points not fully supported on ReFS.

• Impacts functionality?

• Impacts security?

• Breaking change?

• Includes tests?

• Includes documentation?

How This Was Tested

Tested on ISO, USB, and LOCAL media creation flows on both X64 and ARM64 systems.

Integration Instructions

N/A

[Copilot]

Pull request overview

Updates the Windows media update PowerShell script to be more robust in real-world usage by improving dependency handling (oscdimg), fixing path normalization edge cases, and ensuring media staging works reliably with newer Windows boot requirements and filesystem constraints.

Changes:

• Add Download-Oscdimg and prompt-driven fallback to download oscdimg.exe when missing.
• Normalize and harden path handling (absolute ISOPath, safer Split-Path usage, drive qualifier parsing, null/empty guards).
• Enforce NTFS for staging/LOCAL media paths and copy boot.stl from boot.wim when present.

Comments suppressed due to low confidence (1)

scripts/windows/Make2023BootableMedia.ps1:711

• ConvertTo-AbsolutePath trims trailing backslashes and then returns early for any ^[a-zA-Z]: path. This turns a drive root like C:\ into C:, which in PowerShell is drive-relative (current directory on that drive) and can cause staging/output paths to resolve unexpectedly. Handle drive roots explicitly (e.g., normalize ^[A-Za-z]:\\?$ to X:\) and avoid returning drive-relative paths like C:foo without expanding them to a fully qualified path.

    $tmpPath = $Path.TrimEnd('\')

    # If a root drive path (C:\), return as-is
    if ($tmpPath -match "^[a-zA-Z]:") {
        return $tmpPath
    }

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