Add warning when AuthenticodeCheck is used on non-Windows platforms

[Copilot]

Summary

Fixes an issue where the AuthenticodeCheck parameter on Install-PSResource, Save-PSResource, and Update-PSResource cmdlets would silently do nothing on Linux and MacOS platforms, leaving users unaware that signature verification was not being performed.

Changes

This PR adds a user-facing warning message when the AuthenticodeCheck parameter is used on non-Windows platforms:

WARNING: Authenticode check cannot be performed on Linux or MacOS.

The warning appears once per operation and informs users that while the operation will complete successfully, authenticode signature verification is only supported on Windows platforms.

Implementation Details

• Modified CheckAuthenticodeSignature method in Utils.cs to emit a warning before returning true on non-Windows platforms
• The fix automatically applies to all three cmdlets (Install-PSResource, Save-PSResource, Update-PSResource) since they all share the same code path through InstallHelper
• Added comprehensive test coverage with three new test cases (one per cmdlet) that verify the warning is displayed on non-Windows systems
• All tests use -Skip:(Get-IsWindows) to ensure they only run on Linux/MacOS

Testing

# Before: No warning displayed
Install-PSResource -Name MyModule -AuthenticodeCheck -Repository PSGallery -TrustRepository

# After: Warning is displayed
Install-PSResource -Name MyModule -AuthenticodeCheck -Repository PSGallery -TrustRepository
# WARNING: Authenticode check cannot be performed on Linux or MacOS.

The operation still completes successfully, but users are now properly informed about the platform limitation.

Resolves #2020

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• 1k9vsblobprodcus379.vsblob.vsassets.io
  • Triggering command: /usr/bin/dotnet publish --configuration Debug --framework net472 --output bin/Debug/net472/publish (dns block)
• 37cvsblobprodcus359.vsblob.vsassets.io
  • Triggering command: /usr/bin/dotnet publish --configuration Debug --framework net472 --output bin/Debug/net472/publish (dns block)
• 4myvsblobprodcus32.vsblob.vsassets.io
  • Triggering command: /usr/bin/dotnet publish --configuration Debug --framework net472 --output bin/Debug/net472/publish (dns block)
• 51yvsblobprodcus36.vsblob.vsassets.io
  • Triggering command: /usr/bin/dotnet publish --configuration Debug --framework net472 --output bin/Debug/net472/publish (dns block)
• 5dkvsblobprodcus355.vsblob.vsassets.io
  • Triggering command: /usr/bin/dotnet publish --configuration Debug --framework net472 --output bin/Debug/net472/publish (dns block)
• 7devsblobprodcus323.vsblob.vsassets.io
  • Triggering command: /usr/bin/dotnet publish --configuration Debug --framework net472 --output bin/Debug/net472/publish (dns block)
• 7k6vsblobprodcus337.vsblob.vsassets.io
  • Triggering command: /usr/bin/dotnet publish --configuration Debug --framework net472 --output bin/Debug/net472/publish (dns block)
• 7tjvsblobprodcus341.vsblob.vsassets.io
  • Triggering command: /usr/bin/dotnet publish --configuration Debug --framework net472 --output bin/Debug/net472/publish (dns block)
• bcnvsblobprodcus378.vsblob.vsassets.io
  • Triggering command: /usr/bin/dotnet publish --configuration Debug --framework net472 --output bin/Debug/net472/publish (dns block)
• c50vsblobprodcus330.vsblob.vsassets.io
  • Triggering command: /usr/bin/dotnet publish --configuration Debug --framework net472 --output bin/Debug/net472/publish (dns block)
• c78vsblobprodcus322.vsblob.vsassets.io
  • Triggering command: /usr/bin/dotnet publish --configuration Debug --framework net472 --output bin/Debug/net472/publish (dns block)
• dlbvsblobprodcus316.vsblob.vsassets.io
  • Triggering command: /usr/bin/dotnet publish --configuration Debug --framework net472 --output bin/Debug/net472/publish (dns block)
• fdpvsblobprodcus345.vsblob.vsassets.io
  • Triggering command: /usr/bin/dotnet publish --configuration Debug --framework net472 --output bin/Debug/net472/publish (dns block)
• gbsvsblobprodcus365.vsblob.vsassets.io
  • Triggering command: /usr/bin/dotnet publish --configuration Debug --framework net472 --output bin/Debug/net472/publish (dns block)
• kh4vsblobprodcus325.vsblob.vsassets.io
  • Triggering command: /usr/bin/dotnet publish --configuration Debug --framework net472 --output bin/Debug/net472/publish (dns block)
• kmuvsblobprodcus389.vsblob.vsassets.io
  • Triggering command: /usr/bin/dotnet publish --configuration Debug --framework net472 --output bin/Debug/net472/publish (dns block)
• l49vsblobprodcus358.vsblob.vsassets.io
  • Triggering command: /usr/bin/dotnet publish --configuration Debug --framework net472 --output bin/Debug/net472/publish (dns block)
• m6xvsblobprodcus342.vsblob.vsassets.io
  • Triggering command: /usr/bin/dotnet publish --configuration Debug --framework net472 --output bin/Debug/net472/publish (dns block)
• pkvvsblobprodcus321.vsblob.vsassets.io
  • Triggering command: /usr/bin/dotnet publish --configuration Debug --framework net472 --output bin/Debug/net472/publish (dns block)
• s4uvsblobprodcus326.vsblob.vsassets.io
  • Triggering command: /usr/bin/dotnet publish --configuration Debug --framework net472 --output bin/Debug/net472/publish (dns block)
• tphvsblobprodcus375.vsblob.vsassets.io
  • Triggering command: /usr/bin/dotnet publish --configuration Debug --framework net472 --output bin/Debug/net472/publish (dns block)
• uy6vsblobprodcus34.vsblob.vsassets.io
  • Triggering command: /usr/bin/dotnet publish --configuration Debug --framework net472 --output bin/Debug/net472/publish (dns block)
• yttvsblobprodcus357.vsblob.vsassets.io
  • Triggering command: /usr/bin/dotnet publish --configuration Debug --framework net472 --output bin/Debug/net472/publish (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>AuthenticodeCheck should warn/error on non-Windows</issue_title>
<issue_description>### Prerequisites

• Write a descriptive title.
• Make sure you are able to repro it on the latest released version
• Search the existing issues.

Steps to reproduce

If you use AuthenticodeCheck parameter on non-Windows it silently passes instead of writing a message to the user that signatures wasn't actually checked.

PSResourceGet/src/code/Utils.cs

Lines 2005 to 2009 in 949c26a

	// Because authenticode and catalog verifications are only applicable on Windows, we allow all packages by default to be installed on unix systems.
	if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
	{
	return true;
	}

Expected behavior

Write warning/error that parameter isn't supported on non-Windows.

Actual behavior

Nothing

Error details

No response

Environment data

n/a

Visuals

No response</issue_description>

<agent_instructions>Instead of just 'return true' here, add a warning that that "Authenticode check cannot be preformed on Linux or MacOS": // Because authenticode and catalog verifications are only applicable on Windows, we allow all packages by default to be installed on unix systems.
if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
{
return true;
}
</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@SydneyhSmith A warning seems appropriate here

Fixes #1754

---

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[alerickson]

/azp run PowerShell.PSResourceGet

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[alerickson]

/azp run PowerShell.PSResourceGet

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[anamnavi]

LGTM