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tailscale-android/cmd/tailscale/backend.go

474 lines
14 KiB
Go

// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package main
import (
"errors"
"fmt"
"log"
"net/http"
"net/netip"
"path/filepath"
"reflect"
"strings"
"time"
"github.com/tailscale/tailscale-android/jni"
"github.com/tailscale/wireguard-go/tun"
"golang.org/x/sys/unix"
"tailscale.com/ipn"
"tailscale.com/ipn/ipnlocal"
"tailscale.com/logpolicy"
"tailscale.com/logtail"
"tailscale.com/logtail/filch"
"tailscale.com/net/dns"
"tailscale.com/net/netmon"
"tailscale.com/net/tsdial"
"tailscale.com/smallzstd"
"tailscale.com/tsd"
"tailscale.com/types/logger"
"tailscale.com/types/logid"
"tailscale.com/util/clientmetric"
"tailscale.com/util/dnsname"
"tailscale.com/util/must"
"tailscale.com/wgengine"
"tailscale.com/wgengine/netstack"
"tailscale.com/wgengine/router"
)
type backend struct {
engine wgengine.Engine
backend *ipnlocal.LocalBackend
devices *multiTUN
settings settingsFunc
lastCfg *router.Config
lastDNSCfg *dns.OSConfig
logIDPublic string
logger *logtail.Logger
// avoidEmptyDNS controls whether to use fallback nameservers
// when no nameservers are provided by Tailscale.
avoidEmptyDNS bool
jvm *jni.JVM
appCtx jni.Object
}
type settingsFunc func(*router.Config, *dns.OSConfig) error
const defaultMTU = 1280 // minimalMTU from wgengine/userspace.go
const (
logPrefKey = "privatelogid"
loginMethodPrefKey = "loginmethod"
customLoginServerPrefKey = "customloginserver"
)
const (
loginMethodGoogle = "google"
loginMethodWeb = "web"
)
// googleDNSServers are used on ChromeOS, where an empty VpnBuilder DNS setting results
// in erasing the platform DNS servers. The developer docs say this is not supposed to happen,
// but nonetheless it does.
var googleDNSServers = []netip.Addr{
netip.MustParseAddr("8.8.8.8"),
netip.MustParseAddr("8.8.4.4"),
netip.MustParseAddr("2001:4860:4860::8888"),
netip.MustParseAddr("2001:4860:4860::8844"),
}
// errVPNNotPrepared is used when VPNService.Builder.establish returns
// null, either because the VPNService is not yet prepared or because
// VPN status was revoked.
var errVPNNotPrepared = errors.New("VPN service not prepared or was revoked")
// errMultipleUsers is used when we get a "INTERACT_ACROSS_USERS" error, which
// happens due to a bug in Android. See:
//
// https://github.com/tailscale/tailscale/issues/2180
var errMultipleUsers = errors.New("VPN cannot be created on this device due to an Android bug with multiple users")
func newBackend(dataDir string, jvm *jni.JVM, appCtx jni.Object, store *stateStore,
settings settingsFunc) (*backend, error) {
sys := new(tsd.System)
sys.Set(store)
logf := logger.RusagePrefixLog(log.Printf)
b := &backend{
jvm: jvm,
devices: newTUNDevices(),
settings: settings,
appCtx: appCtx,
}
var logID logid.PrivateID
logID.UnmarshalText([]byte("dead0000dead0000dead0000dead0000dead0000dead0000dead0000dead0000"))
storedLogID, err := store.read(logPrefKey)
// In all failure cases we ignore any errors and continue with the dead value above.
if err != nil || storedLogID == nil {
// Read failed or there was no previous log id.
newLogID, err := logid.NewPrivateID()
if err == nil {
logID = newLogID
enc, err := newLogID.MarshalText()
if err == nil {
store.write(logPrefKey, enc)
}
}
} else {
logID.UnmarshalText([]byte(storedLogID))
}
b.SetupLogs(dataDir, logID)
dialer := new(tsdial.Dialer)
cb := &router.CallbackRouter{
SetBoth: b.setCfg,
SplitDNS: false,
GetBaseConfigFunc: b.getDNSBaseConfig,
}
engine, err := wgengine.NewUserspaceEngine(logf, wgengine.Config{
Tun: b.devices,
Router: cb,
DNS: cb,
Dialer: dialer,
SetSubsystem: sys.Set,
})
if err != nil {
return nil, fmt.Errorf("runBackend: NewUserspaceEngine: %v", err)
}
sys.Set(engine)
b.logIDPublic = logID.Public().String()
ns, err := netstack.Create(logf, sys.Tun.Get(), engine, sys.MagicSock.Get(), dialer, sys.DNSManager.Get())
if err != nil {
return nil, fmt.Errorf("netstack.Create: %w", err)
}
ns.ProcessLocalIPs = false // let Android kernel handle it; VpnBuilder sets this up
ns.ProcessSubnets = true // for Android-being-an-exit-node support
sys.NetstackRouter.Set(true)
lb, err := ipnlocal.NewLocalBackend(logf, logID.Public(), sys, 0)
if err != nil {
engine.Close()
return nil, fmt.Errorf("runBackend: NewLocalBackend: %v", err)
}
if err := ns.Start(lb); err != nil {
return nil, fmt.Errorf("startNetstack: %w", err)
}
if b.logger != nil {
lb.SetLogFlusher(b.logger.StartFlush)
}
b.engine = engine
b.backend = lb
return b, nil
}
func (b *backend) Start(notify func(n ipn.Notify)) error {
b.backend.SetNotifyCallback(notify)
return b.backend.Start(ipn.Options{})
}
func (b *backend) LinkChange() {
if b.engine != nil {
b.engine.LinkChange(false)
}
}
func (b *backend) setCfg(rcfg *router.Config, dcfg *dns.OSConfig) error {
return b.settings(rcfg, dcfg)
}
func (b *backend) updateTUN(service jni.Object, rcfg *router.Config, dcfg *dns.OSConfig) error {
if reflect.DeepEqual(rcfg, b.lastCfg) && reflect.DeepEqual(dcfg, b.lastDNSCfg) {
return nil
}
// Close previous tunnel(s).
// This is necessary for ChromeOS, native Android devices
// seem to handle seamless handover between tunnels correctly.
//
// TODO(eliasnaur): If seamless handover becomes a desirable feature, skip
// the closing on ChromeOS.
b.CloseTUNs()
if len(rcfg.LocalAddrs) == 0 {
return nil
}
err := jni.Do(b.jvm, func(env *jni.Env) error {
cls := jni.GetObjectClass(env, service)
// Construct a VPNService.Builder. IPNService.newBuilder calls
// setConfigureIntent, and allowFamily for both IPv4 and IPv6.
m := jni.GetMethodID(env, cls, "newBuilder", "()Landroid/net/VpnService$Builder;")
builder, err := jni.CallObjectMethod(env, service, m)
if err != nil {
return fmt.Errorf("IPNService.newBuilder: %v", err)
}
bcls := jni.GetObjectClass(env, builder)
// builder.setMtu.
setMtu := jni.GetMethodID(env, bcls, "setMtu", "(I)Landroid/net/VpnService$Builder;")
const mtu = defaultMTU
if _, err := jni.CallObjectMethod(env, builder, setMtu, jni.Value(mtu)); err != nil {
return fmt.Errorf("VpnService.Builder.setMtu: %v", err)
}
// builder.addDnsServer
addDnsServer := jni.GetMethodID(env, bcls, "addDnsServer", "(Ljava/lang/String;)Landroid/net/VpnService$Builder;")
// builder.addSearchDomain.
addSearchDomain := jni.GetMethodID(env, bcls, "addSearchDomain", "(Ljava/lang/String;)Landroid/net/VpnService$Builder;")
if dcfg != nil {
nameservers := dcfg.Nameservers
if b.avoidEmptyDNS && len(nameservers) == 0 {
nameservers = googleDNSServers
}
for _, dns := range nameservers {
_, err = jni.CallObjectMethod(env,
builder,
addDnsServer,
jni.Value(jni.JavaString(env, dns.String())),
)
if err != nil {
return fmt.Errorf("VpnService.Builder.addDnsServer(%v): %v", dns, err)
}
}
for _, dom := range dcfg.SearchDomains {
_, err = jni.CallObjectMethod(env,
builder,
addSearchDomain,
jni.Value(jni.JavaString(env, dom.WithoutTrailingDot())),
)
if err != nil {
return fmt.Errorf("VpnService.Builder.addSearchDomain(%v): %v", dom, err)
}
}
}
// builder.addRoute.
addRoute := jni.GetMethodID(env, bcls, "addRoute", "(Ljava/lang/String;I)Landroid/net/VpnService$Builder;")
for _, route := range rcfg.Routes {
// Normalize route address; Builder.addRoute does not accept non-zero masked bits.
route = route.Masked()
_, err = jni.CallObjectMethod(env,
builder,
addRoute,
jni.Value(jni.JavaString(env, route.Addr().String())),
jni.Value(route.Bits()),
)
if err != nil {
return fmt.Errorf("VpnService.Builder.addRoute(%v): %v", route, err)
}
}
// builder.addAddress.
addAddress := jni.GetMethodID(env, bcls, "addAddress", "(Ljava/lang/String;I)Landroid/net/VpnService$Builder;")
for _, addr := range rcfg.LocalAddrs {
_, err = jni.CallObjectMethod(env,
builder,
addAddress,
jni.Value(jni.JavaString(env, addr.Addr().String())),
jni.Value(addr.Bits()),
)
if err != nil {
return fmt.Errorf("VpnService.Builder.addAddress(%v): %v", addr, err)
}
}
// builder.establish.
establish := jni.GetMethodID(env, bcls, "establish", "()Landroid/os/ParcelFileDescriptor;")
parcelFD, err := jni.CallObjectMethod(env, builder, establish)
if err != nil {
if strings.Contains(err.Error(), "INTERACT_ACROSS_USERS") {
return errMultipleUsers
}
return fmt.Errorf("VpnService.Builder.establish: %v", err)
}
if parcelFD == 0 {
return errVPNNotPrepared
}
// detachFd.
parcelCls := jni.GetObjectClass(env, parcelFD)
detachFd := jni.GetMethodID(env, parcelCls, "detachFd", "()I")
tunFD, err := jni.CallIntMethod(env, parcelFD, detachFd)
if err != nil {
return fmt.Errorf("detachFd: %v", err)
}
// Create TUN device.
tunDev, _, err := tun.CreateUnmonitoredTUNFromFD(int(tunFD))
if err != nil {
unix.Close(int(tunFD))
return err
}
b.devices.add(tunDev)
return nil
})
if err != nil {
b.lastCfg = nil
b.CloseTUNs()
return err
}
b.lastCfg = rcfg
b.lastDNSCfg = dcfg
return nil
}
// CloseVPN closes any active TUN devices.
func (b *backend) CloseTUNs() {
b.lastCfg = nil
b.devices.Shutdown()
}
// SetupLogs sets up remote logging.
func (b *backend) SetupLogs(logDir string, logID logid.PrivateID) {
logf := logger.RusagePrefixLog(log.Printf)
netMon, err := netmon.New(func(format string, args ...any) {
logf(format, args...)
})
if err != nil {
log.Printf("netmon.New: %w", err)
}
transport := logpolicy.NewLogtailTransport(logtail.DefaultHost, netMon, log.Printf)
logcfg := logtail.Config{
Collection: logtail.CollectionNode,
PrivateID: logID,
Stderr: log.Writer(),
MetricsDelta: clientmetric.EncodeLogTailMetricsDelta,
IncludeProcID: true,
IncludeProcSequence: true,
NewZstdEncoder: func() logtail.Encoder {
return must.Get(smallzstd.NewEncoder(nil))
},
HTTPC: &http.Client{Transport: transport},
}
logcfg.FlushDelayFn = func() time.Duration { return 2 * time.Minute }
filchOpts := filch.Options{
ReplaceStderr: true,
}
var filchErr error
if logDir != "" {
logPath := filepath.Join(logDir, "ipn.log.")
logcfg.Buffer, filchErr = filch.New(logPath, filchOpts)
}
b.logger = logtail.NewLogger(logcfg, logf)
log.SetFlags(0)
log.SetOutput(b.logger)
log.Printf("goSetupLogs: success")
if logDir == "" {
log.Printf("SetupLogs: no logDir, storing logs in memory")
}
if filchErr != nil {
log.Printf("SetupLogs: filch setup failed: %v", filchErr)
}
}
// We log the result of each of the DNS configuration discovery mechanisms, as we're
// expecting a long tail of obscure Android devices with interesting behavior.
func (b *backend) logDNSConfigMechanisms() {
err := jni.Do(b.jvm, func(env *jni.Env) error {
cls := jni.GetObjectClass(env, b.appCtx)
m := jni.GetMethodID(env, cls, "getDnsConfigObj", "()Lcom/tailscale/ipn/DnsConfig;")
dns, err := jni.CallObjectMethod(env, b.appCtx, m)
if err != nil {
return fmt.Errorf("getDnsConfigObj JNI: %v", err)
}
dnsCls := jni.GetObjectClass(env, dns)
for _, impl := range []string{"getDnsConfigFromLinkProperties",
"getDnsServersFromSystemProperties",
"getDnsServersFromNetworkInfo"} {
m = jni.GetMethodID(env, dnsCls, impl, "()Ljava/lang/String;")
n, err := jni.CallObjectMethod(env, dns, m)
baseConfig := jni.GoString(env, jni.String(n))
if err != nil {
log.Printf("%s JNI: %v", impl, err)
} else {
oneLine := strings.Replace(baseConfig, "\n", ";", -1)
log.Printf("%s: %s", impl, oneLine)
}
}
return nil
})
if err != nil {
log.Printf("logDNSConfigMechanisms: %v", err)
}
}
func (b *backend) getPlatformDNSConfig() string {
var baseConfig string
err := jni.Do(b.jvm, func(env *jni.Env) error {
cls := jni.GetObjectClass(env, b.appCtx)
m := jni.GetMethodID(env, cls, "getDnsConfigObj", "()Lcom/tailscale/ipn/DnsConfig;")
dns, err := jni.CallObjectMethod(env, b.appCtx, m)
if err != nil {
return fmt.Errorf("getDnsConfigObj: %v", err)
}
dnsCls := jni.GetObjectClass(env, dns)
m = jni.GetMethodID(env, dnsCls, "getDnsConfigAsString", "()Ljava/lang/String;")
n, err := jni.CallObjectMethod(env, dns, m)
baseConfig = jni.GoString(env, jni.String(n))
return err
})
if err != nil {
log.Printf("getPlatformDNSConfig JNI: %v", err)
return ""
}
return baseConfig
}
func (b *backend) getDNSBaseConfig() (ret dns.OSConfig, _ error) {
defer func() {
// If we couldn't find any base nameservers, ultimately fall back to
// Google's. Normally Tailscale doesn't ever pick a default nameserver
// for users but in this case Android's APIs for reading the underlying
// DNS config are lacking, and almost all Android phones use Google
// services anyway, so it's a reasonable default: it's an ecosystem the
// user has selected by having an Android device.
if len(ret.Nameservers) == 0 && googleSignInEnabled() {
log.Printf("getDNSBaseConfig: none found; falling back to Google public DNS")
ret.Nameservers = append(ret.Nameservers, googleDNSServers...)
}
}()
b.logDNSConfigMechanisms()
baseConfig := b.getPlatformDNSConfig()
lines := strings.Split(baseConfig, "\n")
if len(lines) == 0 {
return dns.OSConfig{}, nil
}
config := dns.OSConfig{}
addrs := strings.Trim(lines[0], " \n")
for _, addr := range strings.Split(addrs, " ") {
ip, err := netip.ParseAddr(addr)
if err == nil {
config.Nameservers = append(config.Nameservers, ip)
}
}
if len(lines) > 1 {
for _, s := range strings.Split(strings.Trim(lines[1], " \n"), " ") {
domain, err := dnsname.ToFQDN(s)
if err != nil {
log.Printf("getDNSBaseConfig: unable to parse %q: %v", s, err)
continue
}
config.SearchDomains = append(config.SearchDomains, domain)
}
}
return config, nil
}