150 lines
3.2 KiB
Go
150 lines
3.2 KiB
Go
// Copyright 2018 Google Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Binary captured streams network packets to wireshark via SSH, replaying
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// buffered packets upon connection for retroactive debugging.
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package main
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import (
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"container/ring"
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"context"
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"flag"
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"log"
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"os"
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"os/signal"
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"sync"
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"syscall"
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"github.com/rtr7/router7/internal/multilisten"
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"github.com/gokrazy/gokrazy"
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"github.com/google/gopacket"
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"github.com/google/gopacket/layers"
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"github.com/google/gopacket/pcapgo"
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_ "net/http/pprof"
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)
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var (
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hostKeyPath = flag.String("host_key",
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"/perm/breakglass.host_key",
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"path to a PEM-encoded RSA, DSA or ECDSA private key (create using e.g. ssh-keygen -f /perm/breakglass.host_key -N '' -t rsa)")
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)
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func capturePackets(ctx context.Context) (chan gopacket.Packet, error) {
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packets := make(chan gopacket.Packet)
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for _, ifname := range []string{"uplink0", "lan0"} {
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handle, err := pcapgo.NewEthernetHandle(ifname)
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if err != nil {
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return nil, err
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}
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if err := handle.SetBPF(instructions); err != nil {
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return nil, err
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}
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pkgsrc := gopacket.NewPacketSource(handle, layers.LayerTypeEthernet)
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go func() {
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defer handle.Close()
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for packet := range pkgsrc.Packets() {
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select {
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case packets <- packet:
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case <-ctx.Done():
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return
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}
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}
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}()
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}
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return packets, nil
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}
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type packetRingBuffer struct {
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sync.Mutex
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r *ring.Ring
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}
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func newPacketRingBuffer(size int) *packetRingBuffer {
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return &packetRingBuffer{
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r: ring.New(size),
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}
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}
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func (prb *packetRingBuffer) writePacket(p gopacket.Packet) {
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prb.Lock()
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defer prb.Unlock()
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prb.r.Value = p
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prb.r = prb.r.Next()
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}
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func (prb *packetRingBuffer) packetsLocked() []gopacket.Packet {
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packets := make([]gopacket.Packet, 0, prb.r.Len())
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prb.r.Do(func(x interface{}) {
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if x != nil {
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packets = append(packets, x.(gopacket.Packet))
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}
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})
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return packets
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}
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var sshListeners = multilisten.NewPool()
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func updateListeners(srv *server) error {
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hosts, err := gokrazy.PrivateInterfaceAddrs()
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if err != nil {
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return err
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}
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sshListeners.ListenAndServe(hosts, func(host string) multilisten.Listener {
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return srv.listenerFor(host)
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})
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return nil
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}
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func logic() error {
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prb := newPacketRingBuffer(50000)
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srv, err := newServer(prb)
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if err != nil {
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return err
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}
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if err := updateListeners(srv); err != nil {
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return err
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}
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go func() {
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ch := make(chan os.Signal, 1)
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signal.Notify(ch, syscall.SIGUSR1)
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for range ch {
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if err := updateListeners(srv); err != nil {
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log.Printf("updateListeners: %v", err)
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}
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}
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}()
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packets, err := capturePackets(context.Background())
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if err != nil {
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return err
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}
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for packet := range packets {
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prb.writePacket(packet)
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}
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return nil
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}
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func main() {
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flag.Parse()
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if err := logic(); err != nil {
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log.Fatal(err)
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}
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}
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