Set-Acl: Do not fail on untranslatable SID

[jborean93]

PR Summary

Fix up error when attempting to set a SecurityDescriptor that contains a SACL, Owner, or Group entry with a SecurityIdentifier that cannot be translated. For example the existing SD or SD to set owner has a SecurityIdentifier set to a user that doesn't exist on the current machine or is a domain account where the host isn't domain joined.

PR Context

Fixes: #21095

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[SteveL-MSFT]

@jborean93 with this change, does it mean that someone could set an ACL with an invalid SID?

[jborean93]

That is already technicality possible if you are running as Administrator as the code changed here is only hit when you are a non-admin without the SeRestorePrivilege or SeBackupPrivilege present. This change makes the non-admin scenarios more consistent with the admin scenarios and while yes it does allow you to set a SID that is invalid/untranslatable that's only if you manually supply a SecurityIdentifier object (you probably know what you are doing here).

The most important reason for this change though is it allows you to use Set-Acl with an existing object that contains a SID that is untranslatable. Before the code would unnecessarily change the identity to an NTAccount for comparison when in reality it only needs to compare it with the SecurityIdentifier here which avoids any translation steps.

It's also not just an invalid SID, there are a few cases where the SecurityIdentifier class cannot translate a SID

• Network share that's contains a local account in the SD
• Offline or unreachable DC
• Local user has been removed
• Dealing with things like an NT SERVICE\... account or APPX/MSIX application privileges

[jborean93]

@anmenaga any chance for a review on this one, has been waiting on some action for 2 and half months now.