First commit

set-calendar-perms.ps1

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+$TenantID = '538b9b1c-23fa-4102-b36e-a4d83fc9c4c1'
+$ClientID = '6914cac7-e824-44e2-94af-1d5165121a11'
+$CertThumb = '190ee98caf1003ef10fbfc05ded771f5940ab837'
+
+$DefaultUserID = 'RGVmYXVsdA==' # I think this is equivalent to the "default" group in previous Calendars.
+$365SKU = @('O365_BUSINESS_ESSENTIALS', 'O365_BUSINESS_PREMIUM', 'EXCHANGESTANDARD') # Licenses with mailboxes
+$GroupsToIgnore = '^MPE Office Managers$|^CEO|Accounting$|^HR$' #Regex Format, match DisplayName
+$GroupIDtoIgnore = Get-MgGroup -all -ConsistencyLevel eventual | where DisplayName -Match $GroupsToIgnore
+$specialusersToIgnore = '#EXT#@mpe' #RegEx Format please
+$specialusersToIgnore_IDs = @() # used to revert accidental changes to the permissions. 
+$upnToAdd = ''
+$usersToIgnore = ''
+
+# extract users from groups, merge with users to ignore. 
+$usersToIgnore = $specialusersToIgnore
+
+foreach ($group in $GroupIDtoIgnore) {
+    $memberIDs = Get-MgGroupMember -GroupId $group.Id 
+    foreach ($member in $memberIDs) {
+        $upnToAdd = Get-MgUser -UserId $member.Id
+        $specialusersToIgnore_IDs += $upnToAdd #adds for later usage
+        $usersToIgnore = $usersToIgnore + '|^' + $upnToAdd.UserPrincipalName + '$'
+    }
+}
+
+# Get full user list, then remove anything in $usersToIgnore variable. This should remove any guest accounts, as well as anyone in the $GroupsToIgnore
+$users = get-mguser -all -Sort displayname | Where-Object UserPrincipalName -NotMatch $usersToIgnore 
+
+# $specialusersToIgnore_IDs =  $specialusersToIgnore_IDs | sort -Unique -Descending #clears duplicates
+
+#loop through all users in $users to set permissions to "read". 
+
+foreach ($user in $users) { 
+    $UserLicense = get-mguserlicensedetail -UserId $user.id | where SkuPartNumber -in $365SKU # Only need to look at calendar perms if the user has a valid license. Returns Null / False if there's no match
+    if ($UserLicense) {
+        $currentPerms = Get-MgUserCalendarPermission -UserId $user.id 
+        if ($currentPerms.Role -eq 'read' -and $currentPerms.id -eq $DefaultUserID) {
+            Write-Host -ForegroundColor blue Checked $($user.displayname)...
+        }
+        else {
+            Write-Host -ForegroundColor green Setting permission for $($user.displayname)... 
+            Update-MgUserCalendarPermission -UserId $user.id -Role read -CalendarPermissionId $DefaultUserID
+        }
+    }
+   
+}
+
+# Loop through ignored users in $specialusersToIgnore_ID's array, and reset Perms to "default"
+foreach ($spec_id in $specialusersToIgnore_IDs) {
+    $currentPerms = Get-MgUserCalendarPermission -UserId $spec_id.Id
+    if ($currentPerms.Role -eq 'read' -and $currentPerms.id -eq $DefaultUserID) {
+        Write-Host -ForegroundColor Magenta Correcting $($spec_id.DisplayName)...
+        Update-MgUserCalendarPermission -UserId $spec_id.id -Role freeBusyRead -CalendarPermissionId $DefaultUserID
+    }
+    else {
+        
+        
+    }
+}
+
+
+Disconnect-MgGraph