first working PoC

2019-03-25 01:02:10 +01:00
parent 902372ed9b
commit 5e01de00c1
8 changed files with 606 additions and 0 deletions
--- a/.gitignore
+++ b/.gitignore
@@ -4,9 +4,14 @@
 *.dll
 *.so
 *.dylib
+wesher
+wg

 # Test binary, build with `go test -c`
 *.test

 # Output of the go coverage tool, specifically when used with LiteIDE
 *.out
+
+# Misc
+*.tmp
--- a/README.md
+++ b/README.md
@@ -0,0 +1,60 @@
+# wesher
+
+Mesh overlay network manager, using [wireguard](https://www.wireguard.com/).
+
+**⚠ WARNING**: since mesh membership is controlled by a mesh-wide pre-shared key, this effectively downgrades some of the
+security benefits from wireguard. See "security considerations" below for more info.
+
+## Quickstart
+
+Before starting, make sure [wireguard](https://www.wireguard.com/) is installed on all nodes.
+
+Install `wesher` on all nodes with:
+```
+$ go get github.com/costela/wesher
+```
+
+On the first node (assuming `$GOPATH/bin` is in the `$PATH`):
+```
+# wesher
+```
+
+Running the command above on a terminal will currently output a generated cluster key, like:
+```
+new cluster key generated: XXXXX
+```
+
+Then, on any further node:
+```
+# wesher --clusterkey XXXXX --joinaddrs x.x.x.x
+```
+
+Where `XXXXX` is the base64 encoded 32 bit key printed by the step above and `x.x.x.x` is the hostname or IP of any of
+the nodes already joined to the mesh cluster.
+
+*Note*: `wireguard`, and therefore `wesher`, need root access.
+
+## Overview
+
+## Configuration options
+
+## Security considerations
+
+The decision of whom to allow in the mesh is made by [memberlist](github.com/hashicorp/memberlist) and is secured by a
+cluster-wide pre-shared key.
+Compromise of this key will allow an attacker to:
+- access services exposed on the overlay network
+- impersonate and/or disrupt traffic to/from other nodes
+It will not, however, allow the attacker access to decrypt the traffic between other nodes.
+
+This pre-shared key is currently static, set up during cluster bootstrapping, but will - in a future version - be
+rotated.
+
+## Current known limitations
+
+### Overlay IP collisions
+
+Since the assignment of IPs on the overlay network is currently decided by the individual node and implemented as a
+naive hashing of the hostname, there can be no guarantee two hosts will not generate the same overlay IPs.
+This limitation may be worked around in a future version.
+
--- a/cluster.go
+++ b/cluster.go
@@ -0,0 +1,239 @@
+package main
+
+import (
+	"bytes"
+	"crypto/rand"
+	"encoding/base64"
+	"encoding/gob"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"net"
+	"os"
+	"path"
+	"time"
+
+	"github.com/mattn/go-isatty"
+
+	"github.com/hashicorp/errwrap"
+
+	"github.com/hashicorp/go-multierror"
+
+	"github.com/hashicorp/memberlist"
+	"github.com/sirupsen/logrus"
+)
+
+// ClusterState keeps track of information needed to rejoin the cluster
+type ClusterState struct {
+	ClusterKey []byte
+	Nodes      []node
+}
+
+type cluster struct {
+	localName string // used to avoid LocalNode(); should not change
+	ml        *memberlist.Memberlist
+	wg        *wgState
+	state     *ClusterState
+	events    chan memberlist.NodeEvent
+}
+
+const statePath = "/var/lib/wesher/state.json"
+
+func newCluster(config *config, wg *wgState) (*cluster, error) {
+	clusterKey := config.ClusterKey
+
+	state := loadState()
+	if len(clusterKey) == 0 {
+		clusterKey = state.ClusterKey
+	}
+
+	if len(clusterKey) == 0 {
+		clusterKey = make([]byte, clusterKeyLen)
+		_, err := rand.Read(clusterKey)
+		if err != nil {
+			return nil, err
+		}
+		// TODO: refactor this into subcommand ("showkey"?)
+		if isatty.IsTerminal(os.Stdout.Fd()) {
+			fmt.Printf("new cluster key generated: %s\n", base64.StdEncoding.EncodeToString(clusterKey))
+		}
+	}
+	state.ClusterKey = clusterKey
+
+	mlConfig := memberlist.DefaultWANConfig()
+	mlConfig.LogOutput = logrus.StandardLogger().WriterLevel(logrus.DebugLevel)
+	mlConfig.SecretKey = clusterKey
+	mlConfig.BindAddr = config.BindAddr
+	mlConfig.BindPort = config.ClusterPort
+	mlConfig.AdvertisePort = config.ClusterPort
+	if config.UseIPAsName && config.BindAddr != "0.0.0.0" {
+		mlConfig.Name = config.BindAddr
+	}
+
+	ml, err := memberlist.Create(mlConfig)
+	if err != nil {
+		return nil, err
+	}
+
+	cluster := cluster{
+		localName: ml.LocalNode().Name,
+		ml:        ml,
+		wg:        wg,
+		events:    make(chan memberlist.NodeEvent, 1),
+		state:     state,
+	}
+	mlConfig.Conflict = &cluster
+	mlConfig.Events = &memberlist.ChannelEventDelegate{Ch: cluster.events}
+	mlConfig.Delegate = &cluster
+
+	wg.assignIP((*net.IPNet)(config.OverlayNet), cluster.localName)
+
+	ml.UpdateNode(1 * time.Second) // we currently do not update after creation
+	return &cluster, nil
+}
+
+func (c *cluster) NotifyConflict(node, other *memberlist.Node) {
+	logrus.Errorf("node name conflict detected: %s", other.Name)
+}
+
+// none if these are used
+func (c *cluster) NotifyMsg([]byte)                           {}
+func (c *cluster) GetBroadcasts(overhead, limit int) [][]byte { return nil }
+func (c *cluster) LocalState(join bool) []byte                { return nil }
+func (c *cluster) MergeRemoteState(buf []byte, join bool)     {}
+
+type nodeMeta struct {
+	OverlayAddr net.IP
+	PubKey      string
+}
+
+func (c *cluster) NodeMeta(limit int) []byte {
+	buf := &bytes.Buffer{}
+	if err := gob.NewEncoder(buf).Encode(nodeMeta{
+		OverlayAddr: c.wg.OverlayAddr,
+		PubKey:      c.wg.PubKey,
+	}); err != nil {
+		logrus.Errorf("could not encode local state: %s", err)
+		return nil
+	}
+	if buf.Len() > limit {
+		logrus.Errorf("could not fit node metadata into %d bytes", limit)
+		return nil
+	}
+	return buf.Bytes()
+}
+
+func decodeNodeMeta(b []byte) (nodeMeta, error) {
+	nm := nodeMeta{}
+	if err := gob.NewDecoder(bytes.NewReader(b)).Decode(&nm); err != nil {
+		return nm, errwrap.Wrapf("could not decode: {{err}}", err)
+	}
+	return nm, nil
+}
+
+func (c *cluster) join(addrs []string) error {
+	if len(addrs) == 0 {
+		for _, n := range c.state.Nodes {
+			addrs = append(addrs, n.Addr.String())
+		}
+	}
+
+	if _, err := c.ml.Join(addrs); err != nil {
+		return err
+	} else if len(addrs) > 0 && c.ml.NumMembers() < 2 {
+		return errors.New("could not join to any of the provided addresses")
+	}
+	return nil
+}
+
+func (c *cluster) leave() {
+	c.saveState()
+	c.ml.Leave(10 * time.Second)
+	c.ml.Shutdown() // ignore errors
+}
+
+func (c *cluster) members() (<-chan []node, <-chan error) {
+	changes := make(chan []node)
+	errc := make(chan error, 1)
+	go func() {
+		for {
+			event := <-c.events
+			if event.Node.Name == c.localName {
+				// ignore events about ourselves
+				continue
+			}
+			switch event.Event {
+			case memberlist.NodeJoin:
+				logrus.Infof("node %s joined", event.Node)
+			case memberlist.NodeUpdate:
+				logrus.Infof("node %s updated", event.Node)
+			case memberlist.NodeLeave:
+				logrus.Infof("node %s left", event.Node)
+			}
+
+			nodes := make([]node, 0)
+			var errs error
+			for _, n := range c.ml.Members() {
+				if n.Name == c.localName {
+					continue
+				}
+				meta, err := decodeNodeMeta(n.Meta)
+				if err != nil {
+					errs = multierror.Append(errs, err)
+					continue
+				}
+				nodes = append(nodes, node{
+					Addr:     n.Addr,
+					nodeMeta: meta,
+				})
+			}
+			c.state.Nodes = nodes
+			changes <- nodes
+			if errs != nil {
+				errc <- errs
+			}
+			c.saveState()
+		}
+	}()
+	return changes, errc
+}
+
+type node struct {
+	Addr net.IP
+	nodeMeta
+}
+
+func (n *node) String() string {
+	return n.Addr.String()
+}
+
+func (c *cluster) saveState() error {
+	if err := os.MkdirAll(path.Dir(statePath), 0700); err != nil {
+		return err
+	}
+
+	stateOut, err := json.MarshalIndent(c.state, "", "  ")
+	if err != nil {
+		return err
+	}
+
+	return ioutil.WriteFile(statePath, stateOut, 0700)
+}
+
+func loadState() *ClusterState {
+	content, err := ioutil.ReadFile(statePath)
+	if err != nil {
+		if !os.IsNotExist(err) {
+			logrus.Warnf("could not open state in %s: %s", statePath, err)
+		}
+		return &ClusterState{}
+	}
+
+	s := &ClusterState{}
+	if err := json.Unmarshal(content, s); err != nil {
+		logrus.Warnf("could not decode state: %s", err)
+		return &ClusterState{} // avoid partially unmarshalled content
+	}
+	return s
+}
--- a/config.go
+++ b/config.go
@@ -0,0 +1,55 @@
+package main
+
+import (
+	"fmt"
+	"net"
+
+	"github.com/stevenroose/gonfig"
+)
+
+const clusterKeyLen = 32
+
+type config struct {
+	LogLevel      string   `desc:"set the verbosity (debug/info/warn/error)" default:"warn"`
+	ClusterKey    []byte   `desc:"shared key for cluster membership; must be 32 bytes base64 encoded; will be generated if not provided"`
+	JoinAddrs     []string `desc:"comma separated list of IP addresses to at least one existing cluster member; if not provided, will attempt resuming any known state or otherwise wait for further members."`
+	BindAddr      string   `desc:"IP address to bind to for cluster membership" default:"0.0.0.0"`
+	ClusterPort   int      `desc:"port used for membership gossip traffic (both TCP and UDP); must be the same across cluster" default:"7946"`
+	WireguardPort int      `desc:"port used for wireguard traffic (UDP); must be the same across cluster" default:"51820"`
+	OverlayNet    *network `desc:"the network in which to allocate addresses for the overlay mesh network (CIDR format); smaller networks increase the chance of IP collision" default:"10.0.0.0/8"`
+	InterfaceName string   `desc:"name of the wireguard interface to create and manage" default:"wgoverlay"`
+
+	// for easier local testing
+	UseIPAsName bool `default:"false" opts:"hidden"`
+}
+
+func loadConfig() (*config, error) {
+	var config config
+	err := gonfig.Load(&config, gonfig.Conf{EnvPrefix: "WESHER_"})
+	if err != nil {
+		return nil, err
+	}
+
+	// perform some validation
+	if len(config.ClusterKey) != 0 && len(config.ClusterKey) != clusterKeyLen {
+		return nil, fmt.Errorf("unsupported cluster key length; expected %d, got %d", clusterKeyLen, len(config.ClusterKey))
+	}
+
+	if bits, _ := ((*net.IPNet)(config.OverlayNet)).Mask.Size(); bits%8 != 0 {
+		return nil, fmt.Errorf("unsupported overlay network size; net mask must be multiple of 8, got %d", bits)
+	}
+
+	return &config, nil
+}
+
+type network net.IPNet
+
+// UnmarshalText parses the provided byte array into the network receiver
+func (n *network) UnmarshalText(data []byte) error {
+	_, ipnet, err := net.ParseCIDR(string(data))
+	if err != nil {
+		return err
+	}
+	*n = network(*ipnet)
+	return nil
+}
--- a/go.mod
+++ b/go.mod
@@ -0,0 +1,10 @@
+module github.com/costela/wesher
+
+require (
+	github.com/hashicorp/errwrap v1.0.0
+	github.com/hashicorp/go-multierror v1.0.0
+	github.com/hashicorp/memberlist v0.1.3
+	github.com/mattn/go-isatty v0.0.7
+	github.com/sirupsen/logrus v1.3.0
+	github.com/stevenroose/gonfig v0.1.4
+)
--- a/go.sum
+++ b/go.sum
@@ -0,0 +1,57 @@
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--- a/main.go
+++ b/main.go
@@ -0,0 +1,63 @@
+package main // import "github.com/costela/wesher"
+
+import (
+	"os"
+	"os/signal"
+	"syscall"
+
+	"github.com/sirupsen/logrus"
+)
+
+func main() {
+	config, err := loadConfig()
+	if err != nil {
+		logrus.Fatal(err)
+	}
+	logLevel, err := logrus.ParseLevel(config.LogLevel)
+	if err != nil {
+		logrus.Fatalf("could not parse loglevel: %s", err)
+	}
+	logrus.SetLevel(logLevel)
+
+	wg, err := newWGConfig(config.InterfaceName, config.WireguardPort)
+	if err != nil {
+		logrus.Fatal(err)
+	}
+
+	cluster, err := newCluster(config, wg)
+	if err != nil {
+		logrus.Fatalf("could not create cluster: %s", err)
+	}
+
+	nodec, errc := cluster.members() // avoid deadlocks by starting before join
+	if err := cluster.join(config.JoinAddrs); err != nil {
+		logrus.Fatalf("could not join cluster: %s", err)
+	}
+
+	incomingSigs := make(chan os.Signal, 1)
+	signal.Notify(incomingSigs, syscall.SIGTERM, os.Interrupt)
+	for {
+		select {
+		case nodes := <-nodec:
+			logrus.Info("cluster members:\n")
+			for _, node := range nodes {
+				logrus.Infof("\taddr: %s, overlay: %s, pubkey: %s", node.Addr, node.OverlayAddr, node.PubKey)
+			}
+			if err := wg.downInterface(); err != nil {
+				logrus.Errorf("could not down interface: %s", err)
+			}
+			if err := wg.writeConf(nodes); err != nil {
+				logrus.Errorf("could not write config: %s", err)
+			}
+			if err := wg.upInterface(); err != nil {
+				logrus.Errorf("could not up interface: %s", err)
+			}
+		case errs := <-errc:
+			logrus.Errorf("could not receive node info: %s", errs)
+		case <-incomingSigs:
+			logrus.Info("terminating...")
+			cluster.leave()
+			os.Exit(0)
+		}
+	}
+}
--- a/wireguard.go
+++ b/wireguard.go
@@ -0,0 +1,117 @@
+package main
+
+import (
+	"crypto/md5"
+	"fmt"
+	"net"
+	"os"
+	"os/exec"
+	"strings"
+	"text/template"
+)
+
+const wgConfPath = "/etc/wireguard/%s.conf"
+const wgConfTpl = `
+# this file was generated automatically by wesher - DO NOT MODIFY
+[Interface]
+PrivateKey = {{ .PrivKey }}
+Address = {{ .OverlayAddr }}
+ListenPort = {{ .Port }}
+
+{{ range .Nodes }}
+[Peer]
+PublicKey = {{ .PubKey }}
+Endpoint = {{ .Addr }}:{{ $.Port }}
+AllowedIPs = {{ .OverlayAddr }}/32
+{{ end }}`
+
+type wgState struct {
+	iface       string
+	OverlayAddr net.IP
+	Port        int
+	PrivKey     string
+	PubKey      string
+}
+
+func newWGConfig(iface string, port int) (*wgState, error) {
+	if err := exec.Command("wg").Run(); err != nil {
+		return nil, fmt.Errorf("could not exec wireguard: %s", err)
+	}
+
+	privKey, pubKey, err := wgKeyPair()
+	if err != nil {
+		return nil, err
+	}
+
+	wgState := wgState{
+		iface:   iface,
+		Port:    port,
+		PrivKey: privKey,
+		PubKey:  pubKey,
+	}
+	return &wgState, nil
+}
+
+func (wg *wgState) assignIP(ipnet *net.IPNet, name string) {
+	// TODO: this is way too brittle and opaque
+	ip := []byte(ipnet.IP)
+	bits, size := ipnet.Mask.Size()
+
+	h := md5.New()
+	h.Write([]byte(name))
+	hb := h.Sum(nil)
+
+	for i := 0; i < (size-bits)/8; i++ {
+		ip[size/8-i-1] = hb[i]
+	}
+	wg.OverlayAddr = net.IP(ip)
+}
+
+func (wg *wgState) writeConf(nodes []node) error {
+	tpl := template.Must(template.New("wgconf").Parse(wgConfTpl))
+	out, err := os.OpenFile(
+		fmt.Sprintf(wgConfPath, wg.iface),
+		os.O_WRONLY|os.O_CREATE|os.O_TRUNC,
+		0600,
+	)
+	if err != nil {
+		return err
+	}
+	return tpl.Execute(out, struct {
+		*wgState
+		Nodes []node
+	}{wg, nodes})
+}
+
+func (wg *wgState) downInterface() error {
+	if err := exec.Command("wg-quick", "down", wg.iface).Run(); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (wg *wgState) upInterface() error {
+	if err := exec.Command("wg-quick", "up", wg.iface).Run(); err != nil {
+		return err
+	}
+	return nil
+}
+
+func wgKeyPair() (string, string, error) {
+	cmd := exec.Command("wg", "genkey")
+	outPriv := strings.Builder{}
+	cmd.Stdout = &outPriv
+	if err := cmd.Run(); err != nil {
+		return "", "", err
+	}
+
+	cmd = exec.Command("wg", "pubkey")
+	outPub := strings.Builder{}
+	cmd.Stdout = &outPub
+	cmd.Stdin = strings.NewReader(outPriv.String())
+	if err := cmd.Run(); err != nil {
+		return "", "", err
+	}
+
+	return strings.TrimSpace(outPriv.String()), strings.TrimSpace(outPub.String()), nil
+}