mirror of
https://github.com/netbirdio/netbird.git
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1d9feab2d9
Works only with userspace implementation: 1. Configure host to solve DNS requests via a fake DSN server address in the Netbird network. 2. Add to firewall catch rule for these DNS requests. 3. Resolve these DNS requests and respond by writing directly to wireguard device.
100 lines
2.3 KiB
Go
100 lines
2.3 KiB
Go
package iface
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import (
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"net"
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"sync"
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"golang.zx2c4.com/wireguard/tun"
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)
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// PacketFilter interface for firewall abilities
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type PacketFilter interface {
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// DropOutgoing filter outgoing packets from host to external destinations
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DropOutgoing(packetData []byte) bool
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// DropIncoming filter incoming packets from external sources to host
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DropIncoming(packetData []byte) bool
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// AddUDPPacketHook calls hook when UDP packet from given direction matched
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//
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// Hook function returns flag which indicates should be the matched package dropped or not.
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// Hook function receives raw network packet data as argument.
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AddUDPPacketHook(in bool, ip net.IP, dPort uint16, hook func(packet []byte) bool) string
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// RemovePacketHook removes hook by ID
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RemovePacketHook(hookID string) error
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// SetNetwork of the wireguard interface to which filtering applied
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SetNetwork(*net.IPNet)
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}
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// DeviceWrapper to override Read or Write of packets
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type DeviceWrapper struct {
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tun.Device
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filter PacketFilter
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mutex sync.RWMutex
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}
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// newDeviceWrapper constructor function
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func newDeviceWrapper(device tun.Device) *DeviceWrapper {
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return &DeviceWrapper{
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Device: device,
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}
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}
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// Read wraps read method with filtering feature
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func (d *DeviceWrapper) Read(bufs [][]byte, sizes []int, offset int) (n int, err error) {
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if n, err = d.Device.Read(bufs, sizes, offset); err != nil {
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return 0, err
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}
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d.mutex.RLock()
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filter := d.filter
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d.mutex.RUnlock()
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if filter == nil {
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return
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}
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for i := 0; i < n; i++ {
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if filter.DropOutgoing(bufs[i][offset : offset+sizes[i]]) {
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bufs = append(bufs[:i], bufs[i+1:]...)
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sizes = append(sizes[:i], sizes[i+1:]...)
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n--
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i--
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}
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}
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return n, nil
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}
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// Write wraps write method with filtering feature
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func (d *DeviceWrapper) Write(bufs [][]byte, offset int) (int, error) {
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d.mutex.RLock()
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filter := d.filter
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d.mutex.RUnlock()
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if filter == nil {
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return d.Device.Write(bufs, offset)
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}
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filteredBufs := make([][]byte, 0, len(bufs))
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dropped := 0
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for _, buf := range bufs {
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if !filter.DropIncoming(buf[offset:]) {
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filteredBufs = append(filteredBufs, buf)
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dropped++
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}
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}
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n, err := d.Device.Write(filteredBufs, offset)
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n += dropped
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return n, err
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}
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// SetFilter sets packet filter to device
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func (d *DeviceWrapper) SetFilter(filter PacketFilter) {
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d.mutex.Lock()
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d.filter = filter
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d.mutex.Unlock()
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}
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