Convert an Azure Active Directory / MS Entra / AAD SID to Object Id. Entra doesn't store the SID natively (the OnPremiseSecurityIdentifier is the AD SID in hybrid environments, but has no comptable link to the Entra SID), so if given a SID we need to convert it to an ObjectId before we can use that to find the correspnding Entra object (could be…

Convert-EntraSidToObjectId.ps1

# Thanks to https://github.com/okieselbach/Intune/blob/master/Convert-AzureAdSidToObjectId.ps1
Function Convert-EntraSidToObjectId {
	[CmdletBinding()]
	Param(
		[Parameter(ValueFromPipeline)]
		[String]$Sid
	)
	Process {
		$text = $sid.Replace('S-1-12-1-', '')
		$array = [UInt32[]]$text.Split('-')
		$bytes = New-Object 'Byte[]' 16
		[Buffer]::BlockCopy($array, 0, $bytes, 0, 16)
		([PSCustomObject]@{
			SID = $Sid
			ObjectId = [Guid]$bytes
		})
	}
}

 $sid = 'S-1-12-1-#########-##########-##########-##########'
 $x = Convert-EntraSidToObjectId $sid
 $x | Format-Table -AutoSize
 Get-AzAdUser -ObjectId $x.ObjectId -ErrorAction SilentlyContinue
 Get-AzAdGroup -ObjectId $x.ObjectId -ErrorAction SilentlyContinue