Add lighthouse.{remoteAllowList,localAllowList} (#217)

These settings make it possible to blacklist / whitelist IP addresses
that are used for remote connections.

`lighthouse.remoteAllowList` filters which remote IPs are allow when
fetching from the lighthouse (or, if you are the lighthouse, which IPs
you store and forward to querying hosts). By default, any remote IPs are
allowed. You can provide CIDRs here with `true` to allow and `false` to
deny. The most specific CIDR rule applies to each remote.  If all rules
are "allow", the default will be "deny", and vice-versa. If both "allow"
and "deny" rules are present, then you MUST set a rule for "0.0.0.0/0"
as the default.

    lighthouse:
      remoteAllowList:
        # Example to block IPs from this subnet from being used for remote IPs.
        "172.16.0.0/12": false

        # A more complicated example, allow public IPs but only private IPs from a specific subnet
        "0.0.0.0/0": true
        "10.0.0.0/8": false
        "10.42.42.0/24": true

`lighthouse.localAllowList` has the same logic as above, but it applies
to the local addresses we advertise to the lighthouse. Additionally, you
can specify an `interfaces` map of regular expressions to match against
interface names. The regexp must match the entire name. All interface
rules must be either true or false (and the default rule will be the
inverse). CIDR rules are matched after interface name rules.

Default is all local IP addresses.

    lighthouse:
      localAllowList:
        # Example to blacklist docker interfaces.
        interfaces:
          'docker.*': false

        # Example to only advertise IPs in this subnet to the lighthouse.
        "10.0.0.0/8": true

allow_list.go

@@ -0,0 +1,48 @@
+package nebula
+
+import (
+	"fmt"
+	"regexp"
+)
+
+type AllowList struct {
+	// The values of this cidrTree are `bool`, signifying allow/deny
+	cidrTree *CIDRTree
+
+	// To avoid ambiguity, all rules must be true, or all rules must be false.
+	nameRules []AllowListNameRule
+}
+
+type AllowListNameRule struct {
+	Name  *regexp.Regexp
+	Allow bool
+}
+
+func (al *AllowList) Allow(ip uint32) bool {
+	if al == nil {
+		return true
+	}
+
+	result := al.cidrTree.MostSpecificContains(ip)
+	switch v := result.(type) {
+	case bool:
+		return v
+	default:
+		panic(fmt.Errorf("invalid state, allowlist returned: %T %v", result, result))
+	}
+}
+
+func (al *AllowList) AllowName(name string) bool {
+	if al == nil || len(al.nameRules) == 0 {
+		return true
+	}
+
+	for _, rule := range al.nameRules {
+		if rule.Name.MatchString(name) {
+			return rule.Allow
+		}
+	}
+
+	// If no rules match, return the default, which is the inverse of the rules
+	return !al.nameRules[0].Allow
+}

allow_list_test.go

@@ -0,0 +1,47 @@
+package nebula
+
+import (
+	"net"
+	"regexp"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestAllowList_Allow(t *testing.T) {
+	assert.Equal(t, true, ((*AllowList)(nil)).Allow(ip2int(net.ParseIP("1.1.1.1"))))
+
+	tree := NewCIDRTree()
+	tree.AddCIDR(getCIDR("0.0.0.0/0"), true)
+	tree.AddCIDR(getCIDR("10.0.0.0/8"), false)
+	tree.AddCIDR(getCIDR("10.42.42.0/24"), true)
+	al := &AllowList{cidrTree: tree}
+
+	assert.Equal(t, true, al.Allow(ip2int(net.ParseIP("1.1.1.1"))))
+	assert.Equal(t, false, al.Allow(ip2int(net.ParseIP("10.0.0.4"))))
+	assert.Equal(t, true, al.Allow(ip2int(net.ParseIP("10.42.42.42"))))
+}
+
+func TestAllowList_AllowName(t *testing.T) {
+	assert.Equal(t, true, ((*AllowList)(nil)).AllowName("docker0"))
+
+	rules := []AllowListNameRule{
+		{Name: regexp.MustCompile("^docker.*$"), Allow: false},
+		{Name: regexp.MustCompile("^tun.*$"), Allow: false},
+	}
+	al := &AllowList{nameRules: rules}
+
+	assert.Equal(t, false, al.AllowName("docker0"))
+	assert.Equal(t, false, al.AllowName("tun0"))
+	assert.Equal(t, true, al.AllowName("eth0"))
+
+	rules = []AllowListNameRule{
+		{Name: regexp.MustCompile("^eth.*$"), Allow: true},
+		{Name: regexp.MustCompile("^ens.*$"), Allow: true},
+	}
+	al = &AllowList{nameRules: rules}
+
+	assert.Equal(t, false, al.AllowName("docker0"))
+	assert.Equal(t, true, al.AllowName("eth0"))
+	assert.Equal(t, true, al.AllowName("ens5"))
+}

config.go

@@ -6,9 +6,11 @@ import (
 	"github.com/sirupsen/logrus"
 	"gopkg.in/yaml.v2"
 	"io/ioutil"
+	"net"
 	"os"
 	"os/signal"
 	"path/filepath"
+	"regexp"
 	"sort"
 	"strconv"
 	"strings"
@@ -213,6 +215,129 @@ func (c *Config) GetDuration(k string, d time.Duration) time.Duration {
 	return v
 }
 
+func (c *Config) GetAllowList(k string, allowInterfaces bool) (*AllowList, error) {
+	r := c.Get(k)
+	if r == nil {
+		return nil, nil
+	}
+
+	rawMap, ok := r.(map[interface{}]interface{})
+	if !ok {
+		return nil, fmt.Errorf("config `%s` has invalid type: %T", k, r)
+	}
+
+	tree := NewCIDRTree()
+	var nameRules []AllowListNameRule
+
+	firstValue := true
+	allValuesMatch := true
+	defaultSet := false
+	var allValues bool
+
+	for rawKey, rawValue := range rawMap {
+		rawCIDR, ok := rawKey.(string)
+		if !ok {
+			return nil, fmt.Errorf("config `%s` has invalid key (type %T): %v", k, rawKey, rawKey)
+		}
+
+		// Special rule for interface names
+		if rawCIDR == "interfaces" {
+			if !allowInterfaces {
+				return nil, fmt.Errorf("config `%s` does not support `interfaces`", k)
+			}
+			var err error
+			nameRules, err = c.getAllowListInterfaces(k, rawValue)
+			if err != nil {
+				return nil, err
+			}
+
+			continue
+		}
+
+		value, ok := rawValue.(bool)
+		if !ok {
+			return nil, fmt.Errorf("config `%s` has invalid value (type %T): %v", k, rawValue, rawValue)
+		}
+
+		_, cidr, err := net.ParseCIDR(rawCIDR)
+		if err != nil {
+			return nil, fmt.Errorf("config `%s` has invalid CIDR: %s", k, rawCIDR)
+		}
+
+		// TODO: should we error on duplicate CIDRs in the config?
+		tree.AddCIDR(cidr, value)
+
+		if firstValue {
+			allValues = value
+			firstValue = false
+		} else {
+			if value != allValues {
+				allValuesMatch = false
+			}
+		}
+
+		// Check if this is 0.0.0.0/0
+		bits, size := cidr.Mask.Size()
+		if bits == 0 && size == 32 {
+			defaultSet = true
+		}
+	}
+
+	if !defaultSet {
+		if allValuesMatch {
+			_, zeroCIDR, _ := net.ParseCIDR("0.0.0.0/0")
+			tree.AddCIDR(zeroCIDR, !allValues)
+		} else {
+			return nil, fmt.Errorf("config `%s` contains both true and false rules, but no default set for 0.0.0.0/0", k)
+		}
+	}
+
+	return &AllowList{cidrTree: tree, nameRules: nameRules}, nil
+}
+
+func (c *Config) getAllowListInterfaces(k string, v interface{}) ([]AllowListNameRule, error) {
+	var nameRules []AllowListNameRule
+
+	rawRules, ok := v.(map[interface{}]interface{})
+	if !ok {
+		return nil, fmt.Errorf("config `%s.interfaces` is invalid (type %T): %v", k, v, v)
+	}
+
+	firstEntry := true
+	var allValues bool
+	for rawName, rawAllow := range rawRules {
+		name, ok := rawName.(string)
+		if !ok {
+			return nil, fmt.Errorf("config `%s.interfaces` has invalid key (type %T): %v", k, rawName, rawName)
+		}
+		allow, ok := rawAllow.(bool)
+		if !ok {
+			return nil, fmt.Errorf("config `%s.interfaces` has invalid value (type %T): %v", k, rawAllow, rawAllow)
+		}
+
+		nameRE, err := regexp.Compile("^" + name + "$")
+		if err != nil {
+			return nil, fmt.Errorf("config `%s.interfaces` has invalid key: %s: %v", k, name, err)
+		}
+
+		nameRules = append(nameRules, AllowListNameRule{
+			Name:  nameRE,
+			Allow: allow,
+		})
+
+		if firstEntry {
+			allValues = allow
+			firstEntry = false
+		} else {
+			if allow != allValues {
+				return nil, fmt.Errorf("config `%s.interfaces` values must all be the same true/false value", k)
+			}
+		}
+	}
+
+	return nameRules, nil
+}
+
 func (c *Config) Get(k string) interface{} {
 	return c.get(k, c.Settings)
 }

config_test.go

@@ -86,6 +86,76 @@ func TestConfig_GetBool(t *testing.T) {
 	assert.Equal(t, false, c.GetBool("bool", true))
 }
 
+func TestConfig_GetAllowList(t *testing.T) {
+	c := NewConfig()
+	c.Settings["allowlist"] = map[interface{}]interface{}{
+		"192.168.0.0": true,
+	}
+	r, err := c.GetAllowList("allowlist", false)
+	assert.EqualError(t, err, "config `allowlist` has invalid CIDR: 192.168.0.0")
+	assert.Nil(t, r)
+
+	c.Settings["allowlist"] = map[interface{}]interface{}{
+		"192.168.0.0/16": "abc",
+	}
+	r, err = c.GetAllowList("allowlist", false)
+	assert.EqualError(t, err, "config `allowlist` has invalid value (type string): abc")
+
+	c.Settings["allowlist"] = map[interface{}]interface{}{
+		"192.168.0.0/16": true,
+		"10.0.0.0/8":     false,
+	}
+	r, err = c.GetAllowList("allowlist", false)
+	assert.EqualError(t, err, "config `allowlist` contains both true and false rules, but no default set for 0.0.0.0/0")
+
+	c.Settings["allowlist"] = map[interface{}]interface{}{
+		"0.0.0.0/0":     true,
+		"10.0.0.0/8":    false,
+		"10.42.42.0/24": true,
+	}
+	r, err = c.GetAllowList("allowlist", false)
+	if assert.NoError(t, err) {
+		assert.NotNil(t, r)
+	}
+
+	// Test interface names
+
+	c.Settings["allowlist"] = map[interface{}]interface{}{
+		"interfaces": map[interface{}]interface{}{
+			`docker.*`: false,
+		},
+	}
+	r, err = c.GetAllowList("allowlist", false)
+	assert.EqualError(t, err, "config `allowlist` does not support `interfaces`")
+
+	c.Settings["allowlist"] = map[interface{}]interface{}{
+		"interfaces": map[interface{}]interface{}{
+			`docker.*`: "foo",
+		},
+	}
+	r, err = c.GetAllowList("allowlist", true)
+	assert.EqualError(t, err, "config `allowlist.interfaces` has invalid value (type string): foo")
+
+	c.Settings["allowlist"] = map[interface{}]interface{}{
+		"interfaces": map[interface{}]interface{}{
+			`docker.*`: false,
+			`eth.*`:    true,
+		},
+	}
+	r, err = c.GetAllowList("allowlist", true)
+	assert.EqualError(t, err, "config `allowlist.interfaces` values must all be the same true/false value")
+
+	c.Settings["allowlist"] = map[interface{}]interface{}{
+		"interfaces": map[interface{}]interface{}{
+			`docker.*`: false,
+		},
+	}
+	r, err = c.GetAllowList("allowlist", true)
+	if assert.NoError(t, err) {
+		assert.NotNil(t, r)
+	}
+}
+
 func TestConfig_HasChanged(t *testing.T) {
 	// No reload has occurred, return false
 	c := NewConfig()

examples/config.yml

@@ -40,6 +40,37 @@ lighthouse:
   hosts:
     - "192.168.100.1"
 
+  # remoteAllowList allows you to control ip ranges that this node will
+  # consider when handshaking to another node. By default, any remote IPs are
+  # allowed. You can provide CIDRs here with `true` to allow and `false` to
+  # deny. The most specific CIDR rule applies to each remote. If all rules are
+  # "allow", the default will be "deny", and vice-versa. If both "allow" and
+  # "deny" rules are present, then you MUST set a rule for "0.0.0.0/0" as the
+  # default.
+  #remoteAllowList:
+    # Example to block IPs from this subnet from being used for remote IPs.
+    #"172.16.0.0/12": false
+
+    # A more complicated example, allow public IPs but only private IPs from a specific subnet
+    #"0.0.0.0/0": true
+    #"10.0.0.0/8": false
+    #"10.42.42.0/24": true
+
+  # localAllowList allows you to filter which local IP addresses we advertise
+  # to the lighthouses. This uses the same logic as `remoteAllowList`, but
+  # additionally, you can specify an `interfaces` map of regular expressions
+  # to match against interface names. The regexp must match the entire name.
+  # All interface rules must be either true or false (and the default will be
+  # the inverse). CIDR rules are matched after interface name rules.
+  # Default is all local IP addresses.
+  #localAllowList:
+    # Example to blacklist tun0 and all docker interfaces.
+    #interfaces:
+      #tun0: false
+      #'docker.*': false
+    # Example to only advertise this subnet to the lighthouse.
+    #"10.0.0.0/8": true
+
 # Port Nebula will be listening on. The default here is 4242. For a lighthouse node, the port should be defined,
 # however using port 0 will dynamically assign a port and is recommended for roaming nodes.
 listen:

handshake.go

@@ -13,6 +13,11 @@ func HandleIncomingHandshake(f *Interface, addr *udpAddr, packet []byte, h *Head
 	//	return
 	//}
 
+	if !f.lightHouse.remoteAllowList.Allow(udp2ipInt(addr)) {
+		l.WithField("udpAddr", addr).Debug("lighthouse.remoteAllowList denied incoming handshake")
+		return
+	}
+
 	tearDown := false
 	switch h.Subtype {
 	case handshakeIXPSK0:

hostmap.go

@@ -755,11 +755,16 @@ func (d *HostInfoDest) ProbeReceived(probeCount int) {
 
 // Utility functions
 
-func localIps() *[]net.IP {
+func localIps(allowList *AllowList) *[]net.IP {
 	//FIXME: This function is pretty garbage
 	var ips []net.IP
 	ifaces, _ := net.Interfaces()
 	for _, i := range ifaces {
+		allow := allowList.AllowName(i.Name)
+		l.WithField("interfaceName", i.Name).WithField("allow", allow).Debug("localAllowList.AllowName")
+		if !allow {
+			continue
+		}
 		addrs, _ := i.Addrs()
 		for _, addr := range addrs {
 			var ip net.IP
@@ -771,6 +776,12 @@ func localIps() *[]net.IP {
 				ip = v.IP
 			}
 			if ip.To4() != nil && ip.IsLoopback() == false {
+				allow := allowList.Allow(ip2int(ip))
+				l.WithField("localIp", ip).WithField("allow", allow).Debug("localAllowList.Allow")
+				if !allow {
+					continue
+				}
+
 				ips = append(ips, ip)
 			}
 		}

lighthouse.go

@@ -19,6 +19,16 @@ type LightHouse struct {
 	// Local cache of answers from light houses
 	addrMap map[uint32][]udpAddr
 
+	// filters remote addresses allowed for each host
+	// - When we are a lighthouse, this filters what addresses we store and
+	// respond with.
+	// - When we are not a lighthouse, this filters which addresses we accept
+	// from lighthouses.
+	remoteAllowList *AllowList
+
+	// filters local addresses that we advertise to lighthouses
+	localAllowList *AllowList
+
 	// staticList exists to avoid having a bool in each addrMap entry
 	// since static should be rare
 	staticList  map[uint32]struct{}
@@ -55,6 +65,20 @@ func NewLightHouse(amLighthouse bool, myIp uint32, ips []uint32, interval int, n
 	return &h
 }
 
+func (lh *LightHouse) SetRemoteAllowList(allowList *AllowList) {
+	lh.Lock()
+	defer lh.Unlock()
+
+	lh.remoteAllowList = allowList
+}
+
+func (lh *LightHouse) SetLocalAllowList(allowList *AllowList) {
+	lh.Lock()
+	defer lh.Unlock()
+
+	lh.localAllowList = allowList
+}
+
 func (lh *LightHouse) ValidateLHStaticEntries() error {
 	for lhIP, _ := range lh.lighthouses {
 		if _, ok := lh.staticList[lhIP]; !ok {
@@ -135,6 +159,13 @@ func (lh *LightHouse) AddRemote(vpnIP uint32, toIp *udpAddr, static bool) {
 			return
 		}
 	}
+
+	allow := lh.remoteAllowList.Allow(udp2ipInt(toIp))
+	l.WithField("remoteIp", toIp).WithField("allow", allow).Debug("remoteAllowList.Allow")
+	if !allow {
+		return
+	}
+
 	//l.Debugf("Adding reply of %s as %s\n", IntIp(vpnIP), toIp)
 	if static {
 		lh.staticList[vpnIP] = struct{}{}
@@ -203,7 +234,7 @@ func (lh *LightHouse) LhUpdateWorker(f EncWriter) {
 	for {
 		ipp := []*IpAndPort{}
 
-		for _, e := range *localIps() {
+		for _, e := range *localIps(lh.localAllowList) {
 			// Only add IPs that aren't my VPN/tun IP
 			if ip2int(e) != lh.myIp {
 				ipp = append(ipp, &IpAndPort{Ip: ip2int(e), Port: uint32(lh.nebulaPort)})

main.go

@@ -228,6 +228,18 @@ func Main(configPath string, configTest bool, buildVersion string) {
 		punchy.Delay,
 	)
 
+	remoteAllowList, err := config.GetAllowList("lighthouse.remoteAllowList", false)
+	if err != nil {
+		l.WithError(err).Fatal("Invalid lighthouse.remoteAllowList")
+	}
+	lightHouse.SetRemoteAllowList(remoteAllowList)
+
+	localAllowList, err := config.GetAllowList("lighthouse.localAllowList", true)
+	if err != nil {
+		l.WithError(err).Fatal("Invalid lighthouse.localAllowList")
+	}
+	lightHouse.SetLocalAllowList(localAllowList)
+
 	//TODO: Move all of this inside functions in lighthouse.go
 	for k, v := range config.GetMap("static_host_map", map[interface{}]interface{}{}) {
 		vpnIp := net.ParseIP(fmt.Sprintf("%v", k))

outside.go

@@ -142,6 +142,10 @@ func (f *Interface) closeTunnel(hostInfo *HostInfo) {
 
 func (f *Interface) handleHostRoaming(hostinfo *HostInfo, addr *udpAddr) {
 	if hostDidRoam(hostinfo.remote, addr) {
+		if !f.lightHouse.remoteAllowList.Allow(udp2ipInt(addr)) {
+			hostinfo.logger().WithField("newAddr", addr).Debug("lighthouse.remoteAllowList denied roaming")
+			return
+		}
 		if !hostinfo.lastRoam.IsZero() && addr.Equals(hostinfo.lastRoamRemote) && time.Since(hostinfo.lastRoam) < RoamingSupressSeconds*time.Second {
 			if l.Level >= logrus.DebugLevel {
 				hostinfo.logger().WithField("udpAddr", hostinfo.remote).WithField("newAddr", addr).