List the Windows Service Hardening firewall rules

I’ve seen recently the following knowledge base article http://support.microsoft.com/kb/2761899 about Hyper-V VMM service fails and Event ID 14050 is logged when dynamicportrange is changed in Windows Server 2012

I was surprised that not everybody uses Powershell especially when running on Windows 2012 server.

I’ll show how to replace the following vbscript from KB2761899…

'This VBScript adds a port range from 9000 to 9999 for outgoing traffic
'run as cscript addportrange.vbs on the hyper-v host

option explicit

'IP protocols
const NET_FW_IP_PROTOCOL_TCP = 6
const NET_FW_IP_PROTOCOL_UDP = 17

'Action
const NET_FW_ACTION_BLOCK = 0
const NET_FW_ACTION_ALLOW = 1

'Direction
const NET_FW_RULE_DIR_IN = 1
const NET_FW_RULE_DIR_OUT = 2

'Create the FwPolicy2 object.
Dim fwPolicy2
Set fwPolicy2 = CreateObject("HNetCfg.FwPolicy2")

'Get the Service Restriction object for the local firewall policy.
Dim ServiceRestriction
Set ServiceRestriction = fwPolicy2.ServiceRestriction

'If the service requires sending/receiving certain type of traffic, then add "allow" WSH rules as follows
'Get the collection of Windows Service Hardening networking rules

Dim wshRules
Set wshRules = ServiceRestriction.Rules

'Add outbound WSH allow rules
Dim NewOutboundRule
Set NewOutboundRule = CreateObject("HNetCfg.FWRule")
NewOutboundRule.Name = "Allow outbound traffic from service to TCP 9000 to 9999"
NewOutboundRule.ApplicationName = "%systemDrive%\WINDOWS\system32\vmms.exe"
NewOutboundRule.ServiceName = "vmms"
NewOutboundRule.Protocol = NET_FW_IP_PROTOCOL_TCP
NewOutboundRule.RemotePorts = "9000-9999"
NewOutboundRule.Action = NET_FW_ACTION_ALLOW
NewOutboundRule.Direction = NET_FW_RULE_DIR_OUT
NewOutboundRule.Enabled = true
wshRules.Add NewOutboundRule

'end of script

…with a 3 lines Powershell script using the exact same approach.

$rule = New-Object -ComObject HNetCfg.FWRule -Property @{
    Name = "Allow outbound traffic from service to TCP 9000 to 9999"
    Direction = 2
    Enabled = $true
    ApplicationName = "$($env:systemdrive)\WINDOWS\system32\vmms.exe"
    ServiceName = "vmms"
    Protocol = 6
} 
$rule.RemotePorts = "9000-9999"
(New-Object -ComObject HNetCfg.FwPolicy2).ServiceRestriction.Rules.Add($rule)

It isn’t actually done in 2 lines because of the intricacies related to the INetFwRule interface comobject

Now that I created the rule how do I list these new firewall rules?

There are actually two ways.
Either using ComObject

(New-Object -ComObject HNetCfg.FwPolicy2).ServiceRestriction.Rules

…or using the built-in Powershell commands of the NetSecurity module as we run on a Windows Server 2012 😀

Get-NetFirewallRule -PolicyStore ConfigurableServiceStore

If there’s a way to query these rules, there must be a way to create these rules.

And…here’s the one-liner (split in two lines using splatting for a better readability)

$HT = @{
    DisplayName = "Allow outbound traffic from service to TCP 9000 to 9999"
    Direction = "Outbound"
    InterfaceType = "Any"
    Action =  "Allow"
    Protocol =  "TCP"
    Service = "vmms"
    Program = "$($env:systemdrive)\WINDOWS\system32\vmms.exe"
    Enabled = "TRUE"
    RemotePort = "9000-9999"
    PolicyStore = "ConfigurableServiceStore"
}
New-NetFirewallRule @HT

Note that you can see the rule added in the registry as well under the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\SharedAccess\Parameters\FirewallPolicy\RestrictedServices\Configurable\System key (Source: http://blogs.technet.com/b/voy/archive/2007/04/02/network-restrictions-for-service-hardening.aspx )

Let’s have a look at the PolicyStore parameter.

Get-Help Get-NetFirewallRule -ParameterName PolicyStore

While the help states that …

— ActiveStore: This store contains the currently active policy, which is the sum of all policy stores that apply to the computer. This is the resultant set of policy (RSOP) for the local computer (the sum of all GPOs that apply to the computer), and the local stores (the PersistentStore, the static Windows service hardening (WSH), and the configurable WSH).

…my experience shows that the static and configurable WSH are not part of the ActiveStore.
Maybe that’s why these 2 stores are at same level as the Persistent and ActiveStore.

# "VMMSAllowRDPIn" isn't in ActiveStore            
Get-NetFirewallRule -Name "VMMSAllowRDPIn" -PolicyStore ActiveStore            
            
# but it's in the ConfigurableServiceStore            
Get-NetFirewallRule -Name "VMMSAllowRDPIn" -PolicyStore configurableServiceStore            
            
# And you cannot get it like like this...            
Get-CimInstance -Namespace root/StandardCimv2 -ClassName MSFT_NetFirewallRule |            
? InstanceID -match "VMMSAllowRDPIn"