EtherGuard-VPN/tun_windows.go
Jason A. Donenfeld 2326d6a4d7 Odds and ends
2018-05-13 19:34:28 +02:00

483 lines
9.9 KiB
Go

/* SPDX-License-Identifier: GPL-2.0
*
* Copyright (C) 2017-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
*/
package main
import (
"encoding/binary"
"errors"
"fmt"
"golang.org/x/sys/windows"
"golang.org/x/sys/windows/registry"
"net"
"sync"
"syscall"
"time"
"unsafe"
)
/* Relies on the OpenVPN TAP-Windows driver (NDIS 6 version)
*
* https://github.com/OpenVPN/tap-windows
*/
type NativeTUN struct {
fd windows.Handle
rl sync.Mutex
wl sync.Mutex
ro *windows.Overlapped
wo *windows.Overlapped
events chan TUNEvent
name string
}
const (
METHOD_BUFFERED = 0
ComponentID = "tap0901" // tap0801
)
func ctl_code(device_type, function, method, access uint32) uint32 {
return (device_type << 16) | (access << 14) | (function << 2) | method
}
func TAP_CONTROL_CODE(request, method uint32) uint32 {
return ctl_code(file_device_unknown, request, method, 0)
}
var (
errIfceNameNotFound = errors.New("Failed to find the name of interface")
TAP_IOCTL_GET_MAC = TAP_CONTROL_CODE(1, METHOD_BUFFERED)
TAP_IOCTL_GET_VERSION = TAP_CONTROL_CODE(2, METHOD_BUFFERED)
TAP_IOCTL_GET_MTU = TAP_CONTROL_CODE(3, METHOD_BUFFERED)
TAP_IOCTL_GET_INFO = TAP_CONTROL_CODE(4, METHOD_BUFFERED)
TAP_IOCTL_CONFIG_POINT_TO_POINT = TAP_CONTROL_CODE(5, METHOD_BUFFERED)
TAP_IOCTL_SET_MEDIA_STATUS = TAP_CONTROL_CODE(6, METHOD_BUFFERED)
TAP_IOCTL_CONFIG_DHCP_MASQ = TAP_CONTROL_CODE(7, METHOD_BUFFERED)
TAP_IOCTL_GET_LOG_LINE = TAP_CONTROL_CODE(8, METHOD_BUFFERED)
TAP_IOCTL_CONFIG_DHCP_SET_OPT = TAP_CONTROL_CODE(9, METHOD_BUFFERED)
TAP_IOCTL_CONFIG_TUN = TAP_CONTROL_CODE(10, METHOD_BUFFERED)
file_device_unknown = uint32(0x00000022)
nCreateEvent,
nResetEvent,
nGetOverlappedResult uintptr
)
func init() {
k32, err := windows.LoadLibrary("kernel32.dll")
if err != nil {
panic("LoadLibrary " + err.Error())
}
defer windows.FreeLibrary(k32)
nCreateEvent = getProcAddr(k32, "CreateEventW")
nResetEvent = getProcAddr(k32, "ResetEvent")
nGetOverlappedResult = getProcAddr(k32, "GetOverlappedResult")
}
/* implementation of the read/write/closer interface */
func getProcAddr(lib windows.Handle, name string) uintptr {
addr, err := windows.GetProcAddress(lib, name)
if err != nil {
panic(name + " " + err.Error())
}
return addr
}
func resetEvent(h windows.Handle) error {
r, _, err := syscall.Syscall(nResetEvent, 1, uintptr(h), 0, 0)
if r == 0 {
return err
}
return nil
}
func getOverlappedResult(h windows.Handle, overlapped *windows.Overlapped) (int, error) {
var n int
r, _, err := syscall.Syscall6(
nGetOverlappedResult,
4,
uintptr(h),
uintptr(unsafe.Pointer(overlapped)),
uintptr(unsafe.Pointer(&n)), 1, 0, 0)
if r == 0 {
return n, err
}
return n, nil
}
func newOverlapped() (*windows.Overlapped, error) {
var overlapped windows.Overlapped
r, _, err := syscall.Syscall6(nCreateEvent, 4, 0, 1, 0, 0, 0, 0)
if r == 0 {
return nil, err
}
overlapped.HEvent = windows.Handle(r)
return &overlapped, nil
}
func (f *NativeTUN) Events() chan TUNEvent {
return f.events
}
func (f *NativeTUN) Close() error {
close(f.events)
err := windows.Close(f.fd)
return err
}
func (f *NativeTUN) Write(b []byte) (int, error) {
f.wl.Lock()
defer f.wl.Unlock()
if err := resetEvent(f.wo.HEvent); err != nil {
return 0, err
}
var n uint32
err := windows.WriteFile(f.fd, b, &n, f.wo)
if err != nil && err != windows.ERROR_IO_PENDING {
return int(n), err
}
return getOverlappedResult(f.fd, f.wo)
}
func (f *NativeTUN) Read(b []byte) (int, error) {
f.rl.Lock()
defer f.rl.Unlock()
if err := resetEvent(f.ro.HEvent); err != nil {
return 0, err
}
var done uint32
err := windows.ReadFile(f.fd, b, &done, f.ro)
if err != nil && err != windows.ERROR_IO_PENDING {
return int(done), err
}
return getOverlappedResult(f.fd, f.ro)
}
func getdeviceid(
targetComponentId string,
targetDeviceName string,
) (deviceid string, err error) {
getName := func(instanceId string) (string, error) {
path := fmt.Sprintf(
`SYSTEM\CurrentControlSet\Control\Network\{4D36E972-E325-11CE-BFC1-08002BE10318}\%s\Connection`,
instanceId,
)
key, err := registry.OpenKey(
registry.LOCAL_MACHINE,
path,
registry.READ,
)
if err != nil {
return "", err
}
defer key.Close()
val, _, err := key.GetStringValue("Name")
key.Close()
return val, err
}
getInstanceId := func(keyName string) (string, string, error) {
path := fmt.Sprintf(
`SYSTEM\CurrentControlSet\Control\Class\{4D36E972-E325-11CE-BFC1-08002BE10318}\%s`,
keyName,
)
key, err := registry.OpenKey(
registry.LOCAL_MACHINE,
path,
registry.READ,
)
if err != nil {
return "", "", err
}
defer key.Close()
componentId, _, err := key.GetStringValue("ComponentId")
if err != nil {
return "", "", err
}
instanceId, _, err := key.GetStringValue("NetCfgInstanceId")
return componentId, instanceId, err
}
// find list of all network devices
k, err := registry.OpenKey(
registry.LOCAL_MACHINE,
`SYSTEM\CurrentControlSet\Control\Class\{4D36E972-E325-11CE-BFC1-08002BE10318}`,
registry.READ,
)
if err != nil {
return "", fmt.Errorf("Failed to open the adapter registry, TAP driver may be not installed, %v", err)
}
defer k.Close()
keys, err := k.ReadSubKeyNames(-1)
if err != nil {
return "", err
}
// look for matching component id and name
var componentFound bool
for _, v := range keys {
componentId, instanceId, err := getInstanceId(v)
if err != nil || componentId != targetComponentId {
continue
}
componentFound = true
deviceName, err := getName(instanceId)
if err != nil || deviceName != targetDeviceName {
continue
}
return instanceId, nil
}
// provide a descriptive error message
if componentFound {
return "", fmt.Errorf("Unable to find tun/tap device with name = %s", targetDeviceName)
}
return "", fmt.Errorf(
"Unable to find device in registry with ComponentId = %s, is tap-windows installed?",
targetComponentId,
)
}
// setStatus is used to bring up or bring down the interface
func setStatus(fd windows.Handle, status bool) error {
var code [4]byte
if status {
binary.LittleEndian.PutUint32(code[:], 1)
}
var bytesReturned uint32
rdbbuf := make([]byte, windows.MAXIMUM_REPARSE_DATA_BUFFER_SIZE)
return windows.DeviceIoControl(
fd,
TAP_IOCTL_SET_MEDIA_STATUS,
&code[0],
uint32(4),
&rdbbuf[0],
uint32(len(rdbbuf)),
&bytesReturned,
nil,
)
}
/* When operating in TUN mode we must assign an ip address & subnet to the device.
*
*/
func setTUN(fd windows.Handle, network string) error {
var bytesReturned uint32
rdbbuf := make([]byte, windows.MAXIMUM_REPARSE_DATA_BUFFER_SIZE)
localIP, remoteNet, err := net.ParseCIDR(network)
if err != nil {
return fmt.Errorf("Failed to parse network CIDR in config, %v", err)
}
if localIP.To4() == nil {
return fmt.Errorf("Provided network(%s) is not a valid IPv4 address", network)
}
var param [12]byte
copy(param[0:4], localIP.To4())
copy(param[4:8], remoteNet.IP.To4())
copy(param[8:12], remoteNet.Mask)
return windows.DeviceIoControl(
fd,
TAP_IOCTL_CONFIG_TUN,
&param[0],
uint32(12),
&rdbbuf[0],
uint32(len(rdbbuf)),
&bytesReturned,
nil,
)
}
func (tun *NativeTUN) MTU() (int, error) {
var mtu [4]byte
var bytesReturned uint32
err := windows.DeviceIoControl(
tun.fd,
TAP_IOCTL_GET_MTU,
&mtu[0],
uint32(len(mtu)),
&mtu[0],
uint32(len(mtu)),
&bytesReturned,
nil,
)
val := binary.LittleEndian.Uint32(mtu[:])
return int(val), err
}
func (tun *NativeTUN) Name() string {
return tun.name
}
func CreateTUN(name string) (TUNDevice, error) {
// find the device in registry.
deviceid, err := getdeviceid(ComponentID, name)
if err != nil {
return nil, err
}
path := "\\\\.\\Global\\" + deviceid + ".tap"
pathp, err := windows.UTF16PtrFromString(path)
if err != nil {
return nil, err
}
// create TUN device
handle, err := windows.CreateFile(
pathp,
windows.GENERIC_READ|windows.GENERIC_WRITE,
0,
nil,
windows.OPEN_EXISTING,
windows.FILE_ATTRIBUTE_SYSTEM|windows.FILE_FLAG_OVERLAPPED,
0,
)
if err != nil {
return nil, err
}
ro, err := newOverlapped()
if err != nil {
windows.Close(handle)
return nil, err
}
wo, err := newOverlapped()
if err != nil {
windows.Close(handle)
return nil, err
}
tun := &NativeTUN{
fd: handle,
name: name,
ro: ro,
wo: wo,
events: make(chan TUNEvent, 5),
}
// find addresses of interface
// TODO: fix this hack, the question is how
inter, err := net.InterfaceByName(name)
if err != nil {
windows.Close(handle)
return nil, err
}
addrs, err := inter.Addrs()
if err != nil {
windows.Close(handle)
return nil, err
}
var ip net.IP
for _, addr := range addrs {
ip = func() net.IP {
switch v := addr.(type) {
case *net.IPNet:
return v.IP.To4()
case *net.IPAddr:
return v.IP.To4()
}
return nil
}()
if ip != nil {
break
}
}
if ip == nil {
windows.Close(handle)
return nil, errors.New("No IPv4 address found for interface")
}
// bring up device.
if err := setStatus(handle, true); err != nil {
windows.Close(handle)
return nil, err
}
// set tun mode
mask := ip.String() + "/0"
if err := setTUN(handle, mask); err != nil {
windows.Close(handle)
return nil, err
}
// start listener
go func(native *NativeTUN, ifname string) {
// TODO: Fix this very niave implementation
var (
statusUp bool
statusMTU int
)
for ; ; time.Sleep(time.Second) {
intr, err := net.InterfaceByName(name)
if err != nil {
// TODO: handle
return
}
// Up / Down event
up := (intr.Flags & net.FlagUp) != 0
if up != statusUp && up {
native.events <- TUNEventUp
}
if up != statusUp && !up {
native.events <- TUNEventDown
}
statusUp = up
// MTU changes
if intr.MTU != statusMTU {
native.events <- TUNEventMTUUpdate
}
statusMTU = intr.MTU
}
}(tun, name)
return tun, nil
}