misc: small fix or general refactoring i did not bother commenting

modules/packet_proxy_linux.go

@@ -0,0 +1,219 @@
+// +build !arm
+// +build !mips
+// +build !mipsle
+// +build !mips64
+// +build !mips64le
+package modules
+
+import (
+	"fmt"
+	"io/ioutil"
+	golog "log"
+	"plugin"
+	"strings"
+	"syscall"
+
+	"github.com/bettercap/bettercap/core"
+	"github.com/bettercap/bettercap/log"
+	"github.com/bettercap/bettercap/session"
+
+	"github.com/chifflier/nfqueue-go/nfqueue"
+)
+
+type PacketProxy struct {
+	session.SessionModule
+	done       chan bool
+	chainName  string
+	rule       string
+	queue      *nfqueue.Queue
+	queueNum   int
+	queueCb    nfqueue.Callback
+	pluginPath string
+	plugin     *plugin.Plugin
+}
+
+// this is ugly, but since we can only pass a function
+// (not a struct function) as a callback to nfqueue,
+// we need this in order to recover the state.
+var mod *PacketProxy
+
+func NewPacketProxy(s *session.Session) *PacketProxy {
+	mod = &PacketProxy{
+		SessionModule: session.NewSessionModule("packet.proxy", s),
+		done:          make(chan bool),
+		queue:         nil,
+		queueCb:       nil,
+		queueNum:      0,
+		chainName:     "OUTPUT",
+	}
+
+	mod.AddHandler(session.NewModuleHandler("packet.proxy on", "",
+		"Start the NFQUEUE based packet proxy.",
+		func(args []string) error {
+			return mod.Start()
+		}))
+
+	mod.AddHandler(session.NewModuleHandler("packet.proxy off", "",
+		"Stop the NFQUEUE based packet proxy.",
+		func(args []string) error {
+			return mod.Stop()
+		}))
+
+	mod.AddParam(session.NewIntParameter("packet.proxy.queue.num",
+		"0",
+		"NFQUEUE number to bind to."))
+
+	mod.AddParam(session.NewStringParameter("packet.proxy.chain",
+		"OUTPUT",
+		"",
+		"Chain name of the iptables rule."))
+
+	mod.AddParam(session.NewStringParameter("packet.proxy.plugin",
+		"",
+		"",
+		"Go plugin file to load and call for every packet."))
+
+	mod.AddParam(session.NewStringParameter("packet.proxy.rule",
+		"",
+		"",
+		"Any additional iptables rule to make the queue more selective (ex. --destination 8.8.8.8)."))
+
+	return mod
+}
+
+func (pp PacketProxy) Name() string {
+	return "packet.proxy"
+}
+
+func (pp PacketProxy) Description() string {
+	return "A Linux only module that relies on NFQUEUEs in order to filter packets."
+}
+
+func (pp PacketProxy) Author() string {
+	return "Simone Margaritelli <evilsocket@protonmail.com>"
+}
+
+func (pp *PacketProxy) destroyQueue() {
+	if pp.queue == nil {
+		return
+	}
+
+	pp.queue.DestroyQueue()
+	pp.queue.Close()
+	pp.queue = nil
+}
+
+func (pp *PacketProxy) runRule(enable bool) (err error) {
+	action := "-A"
+	if enable == false {
+		action = "-D"
+	}
+
+	args := []string{
+		action, pp.chainName,
+	}
+
+	if pp.rule != "" {
+		rule := strings.Split(pp.rule, " ")
+		args = append(args, rule...)
+	}
+
+	args = append(args, []string{
+		"-j", "NFQUEUE",
+		"--queue-num", fmt.Sprintf("%d", pp.queueNum),
+	}...)
+
+	log.Debug("iptables %s", args)
+
+	_, err = core.Exec("iptables", args)
+	return
+}
+
+func (pp *PacketProxy) Configure() (err error) {
+	golog.SetOutput(ioutil.Discard)
+
+	pp.destroyQueue()
+
+	if err, pp.queueNum = pp.IntParam("packet.proxy.queue.num"); err != nil {
+		return
+	} else if err, pp.chainName = pp.StringParam("packet.proxy.chain"); err != nil {
+		return
+	} else if err, pp.rule = pp.StringParam("packet.proxy.rule"); err != nil {
+		return
+	} else if err, pp.pluginPath = pp.StringParam("packet.proxy.plugin"); err != nil {
+		return
+	}
+
+	if pp.pluginPath == "" {
+		return fmt.Errorf("The parameter %s can not be empty.", core.Bold("packet.proxy.plugin"))
+	} else if core.Exists(pp.pluginPath) == false {
+		return fmt.Errorf("%s does not exist.", pp.pluginPath)
+	}
+
+	log.Info("Loading packet proxy plugin from %s ...", pp.pluginPath)
+
+	var ok bool
+	var sym plugin.Symbol
+
+	if pp.plugin, err = plugin.Open(pp.pluginPath); err != nil {
+		return
+	} else if sym, err = pp.plugin.Lookup("OnPacket"); err != nil {
+		return
+	} else if pp.queueCb, ok = sym.(func(*nfqueue.Payload) int); ok == false {
+		return fmt.Errorf("Symbol OnPacket is not a valid callback function.")
+	}
+
+	pp.queue = new(nfqueue.Queue)
+	if err = pp.queue.SetCallback(dummyCallback); err != nil {
+		return
+	} else if err = pp.queue.Init(); err != nil {
+		return
+	} else if err = pp.queue.Unbind(syscall.AF_INET); err != nil {
+		return
+	} else if err = pp.queue.Bind(syscall.AF_INET); err != nil {
+		return
+	} else if err = pp.queue.CreateQueue(pp.queueNum); err != nil {
+		return
+	} else if err = pp.queue.SetMode(nfqueue.NFQNL_COPY_PACKET); err != nil {
+		return
+	} else if err = pp.runRule(true); err != nil {
+		return
+	}
+
+	return nil
+}
+
+// we need this because for some reason we can't directly
+// pass the symbol loaded from the plugin as a direct
+// CGO callback ... ¯\_(ツ)_/¯
+func dummyCallback(payload *nfqueue.Payload) int {
+	return mod.queueCb(payload)
+}
+
+func (pp *PacketProxy) Start() error {
+	if pp.Running() == true {
+		return session.ErrAlreadyStarted
+	} else if err := pp.Configure(); err != nil {
+		return err
+	}
+
+	return pp.SetRunning(true, func() {
+		log.Info("%s started on queue number %d", core.Green("packet.proxy"), pp.queueNum)
+
+		defer pp.destroyQueue()
+
+		pp.queue.Loop()
+
+		pp.done <- true
+	})
+
+	return nil
+}
+
+func (pp *PacketProxy) Stop() error {
+	return pp.SetRunning(false, func() {
+		pp.queue.StopLoop()
+		pp.runRule(false)
+		<-pp.done
+	})
+}