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|
/* SPDX-License-Identifier: MIT
*
* Copyright (C) 2019 WireGuard LLC. All Rights Reserved.
*/
package firewall
import (
"errors"
"net"
"unsafe"
"golang.org/x/sys/windows"
)
type wfpObjectInstaller func(uintptr) error
//
// Fundamental WireGuard specific WFP objects.
//
type baseObjects struct {
provider windows.GUID
filters windows.GUID
}
var wfpSession uintptr
func createWfpSession() (uintptr, error) {
sessionDisplayData, err := createWtFwpmDisplayData0("WireGuard", "WireGuard dynamic session")
if err != nil {
return 0, wrapErr(err)
}
session := wtFwpmSession0{
displayData: *sessionDisplayData,
flags: cFWPM_SESSION_FLAG_DYNAMIC,
txnWaitTimeoutInMSec: windows.INFINITE,
}
sessionHandle := uintptr(0)
err = fwpmEngineOpen0(nil, cRPC_C_AUTHN_WINNT, nil, &session, unsafe.Pointer(&sessionHandle))
if err != nil {
return 0, wrapErr(err)
}
return sessionHandle, nil
}
func registerBaseObjects(session uintptr) (*baseObjects, error) {
// {48E29F38-7492-4436-8F92-29D78A8D29D3}
providerGUID := windows.GUID{
Data1: 0x48e29f38,
Data2: 0x7492,
Data3: 0x4436,
Data4: [8]byte{0x8f, 0x92, 0x29, 0xd7, 0x8a, 0x8d, 0x29, 0xd3},
}
// {FE3DB7F8-4658-4DE5-8DA9-CE5086A8266B}
filtersGUID := windows.GUID{
Data1: 0xfe3db7f8,
Data2: 0x4658,
Data3: 0x4de5,
Data4: [8]byte{0x8d, 0xa9, 0xce, 0x50, 0x86, 0xa8, 0x26, 0x6b},
}
//
// Register provider.
//
{
displayData, err := createWtFwpmDisplayData0("WireGuard", "The WireGuard provider")
if err != nil {
return nil, wrapErr(err)
}
provider := wtFwpmProvider0{
providerKey: providerGUID,
displayData: *displayData,
}
err = fwpmProviderAdd0(session, &provider, 0)
if err != nil {
//TODO: cleanup entire call chain of these if failure?
return nil, wrapErr(err)
}
}
//
// Register filters sublayer.
//
{
displayData, err := createWtFwpmDisplayData0("WireGuard filters", "Permissive and blocking filters")
if err != nil {
return nil, wrapErr(err)
}
sublayer := wtFwpmSublayer0{
subLayerKey: filtersGUID,
displayData: *displayData,
providerKey: &providerGUID,
weight: ^uint16(0),
}
err = fwpmSubLayerAdd0(session, &sublayer, 0)
if err != nil {
return nil, wrapErr(err)
}
}
return &baseObjects{
providerGUID,
filtersGUID,
}, nil
}
func EnableFirewall(luid uint64, restrictToDNSServers []net.IP, restrictAll bool) error {
if wfpSession != 0 {
return errors.New("The firewall has already been enabled")
}
session, err := createWfpSession()
if err != nil {
return wrapErr(err)
}
objectInstaller := func(session uintptr) error {
baseObjects, err := registerBaseObjects(session)
if err != nil {
return wrapErr(err)
}
err = permitWireGuardService(session, baseObjects, 15)
if err != nil {
return wrapErr(err)
}
if len(restrictToDNSServers) > 0 {
err = blockDNS(restrictToDNSServers, session, baseObjects, 15, 14)
if err != nil {
return wrapErr(err)
}
}
if restrictAll {
err = permitLoopback(session, baseObjects, 13)
if err != nil {
return wrapErr(err)
}
}
err = permitTunInterface(session, baseObjects, 12, luid)
if err != nil {
return wrapErr(err)
}
if restrictAll {
err = permitDHCPIPv4(session, baseObjects, 12)
if err != nil {
return wrapErr(err)
}
err = permitDHCPIPv6(session, baseObjects, 12)
if err != nil {
return wrapErr(err)
}
err = permitNdp(session, baseObjects, 12)
if err != nil {
return wrapErr(err)
}
/* TODO: actually evaluate if this does anything and if we need this. It's layer 2; our other rules are layer 3.
* In other words, if somebody complains, try enabling it. For now, keep it off.
err = permitHyperV(session, baseObjects, 12)
if err != nil {
return wrapErr(err)
}
*/
}
if restrictAll {
err = blockAll(session, baseObjects, 0)
if err != nil {
return wrapErr(err)
}
}
return nil
}
err = runTransaction(session, objectInstaller)
if err != nil {
fwpmEngineClose0(session)
return wrapErr(err)
}
wfpSession = session
return nil
}
func DisableFirewall() {
if wfpSession != 0 {
fwpmEngineClose0(wfpSession)
wfpSession = 0
}
}
|
