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various: create a catch-all NRPT rule when "Override local DNS" is enabled on Windows

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Without this rule, Windows 8.1 and newer devices issue parallel DNS requests to DNS servers
associated with all network adapters, even when "Override local DNS" is enabled and/or
a Mullvad exit node is being used, resulting in DNS leaks.

This also adds "disable-local-dns-override-via-nrpt" nodeAttr that can be used to disable
the new behavior if needed.

Fixes tailscale/corp#20718

Signed-off-by: Nick Khyl <nickk@tailscale.com>
This commit is contained in:
Nick Khyl 2024-06-10 22:05:15 -05:00 committed by Nick Khyl
parent 7354547bd8
commit c32efd9118
11 changed files with 75 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
cmd/tailscaled/tailscaled.go
View File

@ -698,7 +698,7 @@ func tryEngine(logf logger.Logf, sys *tsd.System, name string) (onlyNetstack boo
// configuration being unavailable (from the noop
// manager). More in Issue 4017.
// TODO(bradfitz): add a Synology-specific DNS manager.
conf.DNS, err = dns.NewOSConfigurator(logf, sys.HealthTracker(), "") // empty interface name
conf.DNS, err = dns.NewOSConfigurator(logf, sys.HealthTracker(), sys.ControlKnobs(), "") // empty interface name
if err != nil {
return false, fmt.Errorf("dns.NewOSConfigurator: %w", err)
}
@ -726,7 +726,7 @@ func tryEngine(logf logger.Logf, sys *tsd.System, name string) (onlyNetstack boo
return false, fmt.Errorf("creating router: %w", err)
}
d, err := dns.NewOSConfigurator(logf, sys.HealthTracker(), devName)
d, err := dns.NewOSConfigurator(logf, sys.HealthTracker(), sys.ControlKnobs(), devName)
if err != nil {
dev.Close()
r.Close()

12
control/controlknobs/controlknobs.go
View File

@ -90,6 +90,15 @@ type Knobs struct {
// This is for now (2024-06-06) an iOS-specific battery life optimization,
// and this knob allows us to disable the optimization remotely if needed.
DisableSplitDNSWhenNoCustomResolvers atomic.Bool
// DisableLocalDNSOverrideViaNRPT indicates that the node's DNS manager should not
// create a default (catch-all) Windows NRPT rule when "Override local DNS" is enabled.
// Without this rule, Windows 8.1 and newer devices issue parallel DNS requests to DNS servers
// associated with all network adapters, even when "Override local DNS" is enabled and/or
// a Mullvad exit node is being used, resulting in DNS leaks.
// We began creating this rule on 2024-06-14, and this knob
// allows us to disable the new behavior remotely if needed.
DisableLocalDNSOverrideViaNRPT atomic.Bool
}
// UpdateFromNodeAttributes updates k (if non-nil) based on the provided self
@ -117,6 +126,7 @@ func (k *Knobs) UpdateFromNodeAttributes(capMap tailcfg.NodeCapMap) {
appCStoreRoutes = has(tailcfg.NodeAttrStoreAppCRoutes)
userDialUseRoutes = has(tailcfg.NodeAttrUserDialUseRoutes)
disableSplitDNSWhenNoCustomResolvers = has(tailcfg.NodeAttrDisableSplitDNSWhenNoCustomResolvers)
disableLocalDNSOverrideViaNRPT = has(tailcfg.NodeAttrDisableLocalDNSOverrideViaNRPT)
)
if has(tailcfg.NodeAttrOneCGNATEnable) {
@ -142,6 +152,7 @@ func (k *Knobs) UpdateFromNodeAttributes(capMap tailcfg.NodeCapMap) {
k.AppCStoreRoutes.Store(appCStoreRoutes)
k.UserDialUseRoutes.Store(userDialUseRoutes)
k.DisableSplitDNSWhenNoCustomResolvers.Store(disableSplitDNSWhenNoCustomResolvers)
k.DisableLocalDNSOverrideViaNRPT.Store(disableLocalDNSOverrideViaNRPT)
}
// AsDebugJSON returns k as something that can be marshalled with json.Marshal
@ -168,5 +179,6 @@ func (k *Knobs) AsDebugJSON() map[string]any {
"AppCStoreRoutes": k.AppCStoreRoutes.Load(),
"UserDialUseRoutes": k.UserDialUseRoutes.Load(),
"DisableSplitDNSWhenNoCustomResolvers": k.DisableSplitDNSWhenNoCustomResolvers.Load(),
"DisableLocalDNSOverrideViaNRPT": k.DisableLocalDNSOverrideViaNRPT.Load(),
}
}

2
net/dns/manager.go
View File

@ -485,7 +485,7 @@ func (m *Manager) FlushCaches() error {
// in case the Tailscale daemon terminated without closing the router.
// No other state needs to be instantiated before this runs.
func CleanUp(logf logger.Logf, netMon *netmon.Monitor, interfaceName string) {
oscfg, err := NewOSConfigurator(logf, nil, interfaceName)
oscfg, err := NewOSConfigurator(logf, nil, nil, interfaceName)
if err != nil {
logf("creating dns cleanup: %v", err)
return

6
net/dns/manager_darwin.go
View File

@ -8,12 +8,16 @@
"os"
"go4.org/mem"
"tailscale.com/control/controlknobs"
"tailscale.com/health"
"tailscale.com/types/logger"
"tailscale.com/util/mak"
)
func NewOSConfigurator(logf logger.Logf, health *health.Tracker, ifName string) (OSConfigurator, error) {
// NewOSConfigurator creates a new OS configurator.
//
// The health tracker and the knobs may be nil and are ignored on this platform.
func NewOSConfigurator(logf logger.Logf, _ *health.Tracker, _ *controlknobs.Knobs, ifName string) (OSConfigurator, error) {
return &darwinConfigurator{logf: logf, ifName: ifName}, nil
}

6
net/dns/manager_default.go
View File

@ -6,10 +6,14 @@
package dns
import (
"tailscale.com/control/controlknobs"
"tailscale.com/health"
"tailscale.com/types/logger"
)
func NewOSConfigurator(logger.Logf, *health.Tracker, string) (OSConfigurator, error) {
// NewOSConfigurator creates a new OS configurator.
//
// The health tracker and the knobs may be nil and are ignored on this platform.
func NewOSConfigurator(logger.Logf, *health.Tracker, *controlknobs.Knobs, string) (OSConfigurator, error) {
return NewNoopManager()
}

6
net/dns/manager_freebsd.go
View File

@ -7,11 +7,15 @@
"fmt"
"os"
"tailscale.com/control/controlknobs"
"tailscale.com/health"
"tailscale.com/types/logger"
)
func NewOSConfigurator(logf logger.Logf, health *health.Tracker, _ string) (OSConfigurator, error) {
// NewOSConfigurator creates a new OS configurator.
//
// The health tracker may be nil; the knobs may be nil and are ignored on this platform.
func NewOSConfigurator(logf logger.Logf, health *health.Tracker, _ *controlknobs.Knobs, _ string) (OSConfigurator, error) {
bs, err := os.ReadFile("/etc/resolv.conf")
if os.IsNotExist(err) {
return newDirectManager(logf, health), nil

6
net/dns/manager_linux.go
View File

@ -14,6 +14,7 @@
"time"
"github.com/godbus/dbus/v5"
"tailscale.com/control/controlknobs"
"tailscale.com/health"
"tailscale.com/net/netaddr"
"tailscale.com/types/logger"
@ -31,7 +32,10 @@ func (kv kv) String() string {
var publishOnce sync.Once
func NewOSConfigurator(logf logger.Logf, health *health.Tracker, interfaceName string) (ret OSConfigurator, err error) {
// NewOSConfigurator created a new OS configurator.
//
// The health tracker may be nil; the knobs may be nil and are ignored on this platform.
func NewOSConfigurator(logf logger.Logf, health *health.Tracker, _ *controlknobs.Knobs, interfaceName string) (ret OSConfigurator, err error) {
env := newOSConfigEnv{
fs: directFS{},
dbusPing: dbusPing,

6
net/dns/manager_openbsd.go
View File

@ -8,6 +8,7 @@
"fmt"
"os"
"tailscale.com/control/controlknobs"
"tailscale.com/health"
"tailscale.com/types/logger"
)
@ -20,7 +21,10 @@ func (kv kv) String() string {
return fmt.Sprintf("%s=%s", kv.k, kv.v)
}
func NewOSConfigurator(logf logger.Logf, health *health.Tracker, interfaceName string) (OSConfigurator, error) {
// NewOSConfigurator created a new OS configurator.
//
// The health tracker may be nil; the knobs may be nil and are ignored on this platform.
func NewOSConfigurator(logf logger.Logf, health *health.Tracker, _ *controlknobs.Knobs, interfaceName string) (OSConfigurator, error) {
return newOSConfigurator(logf, health, interfaceName,
newOSConfigEnv{
rcIsResolvd: rcIsResolvd,

26
net/dns/manager_windows.go
View File

@ -22,6 +22,7 @@
"golang.org/x/sys/windows/registry"
"golang.zx2c4.com/wireguard/windows/tunnel/winipcfg"
"tailscale.com/atomicfile"
"tailscale.com/control/controlknobs"
"tailscale.com/envknob"
"tailscale.com/health"
"tailscale.com/types/logger"
@ -38,6 +39,7 @@
type windowsManager struct {
logf logger.Logf
guid string
knobs *controlknobs.Knobs // or nil
nrptDB *nrptRuleDatabase
wslManager *wslManager
@ -45,10 +47,14 @@ type windowsManager struct {
closing bool
}
func NewOSConfigurator(logf logger.Logf, health *health.Tracker, interfaceName string) (OSConfigurator, error) {
// NewOSConfigurator created a new OS configurator.
//
// The health tracker and the knobs may be nil.
func NewOSConfigurator(logf logger.Logf, health *health.Tracker, knobs *controlknobs.Knobs, interfaceName string) (OSConfigurator, error) {
ret := &windowsManager{
logf: logf,
guid: interfaceName,
knobs: knobs,
wslManager: newWSLManager(logf, health),
}
@ -288,6 +294,10 @@ func (m *windowsManager) setPrimaryDNS(resolvers []netip.Addr, domains []dnsname
return nil
}
func (m *windowsManager) disableLocalDNSOverrideViaNRPT() bool {
return m.knobs != nil && m.knobs.DisableLocalDNSOverrideViaNRPT.Load()
}
func (m *windowsManager) SetDNS(cfg OSConfig) error {
// We can configure Windows DNS in one of two ways:
//
@ -322,7 +332,17 @@ func (m *windowsManager) SetDNS(cfg OSConfig) error {
}
if len(cfg.MatchDomains) == 0 {
if err := m.setSplitDNS(nil, nil); err != nil {
var resolvers []netip.Addr
var domains []dnsname.FQDN
if !m.disableLocalDNSOverrideViaNRPT() {
// Create a default catch-all rule to make ourselves the actual primary resolver.
// Without this rule, Windows 8.1 and newer devices issue parallel DNS requests to DNS servers
// associated with all network adapters, even when "Override local DNS" is enabled and/or
// a Mullvad exit node is being used, resulting in DNS leaks.
resolvers = cfg.Nameservers
domains = []dnsname.FQDN{"."}
}
if err := m.setSplitDNS(resolvers, domains); err != nil {
return err
}
if err := m.setHosts(nil); err != nil {
@ -331,8 +351,6 @@ func (m *windowsManager) SetDNS(cfg OSConfig) error {
if err := m.setPrimaryDNS(cfg.Nameservers, cfg.SearchDomains); err != nil {
return err
}
} else if m.nrptDB == nil {
return errors.New("cannot set per-domain resolvers on Windows 7")
} else {
if err := m.setSplitDNS(cfg.Nameservers, cfg.MatchDomains); err != nil {
return err

4
net/dns/manager_windows_test.go
View File

@ -84,7 +84,7 @@ func TestManagerWindowsGPCopy(t *testing.T) {
}
defer delIfKey()
cfg, err := NewOSConfigurator(logf, nil, fakeInterface.String())
cfg, err := NewOSConfigurator(logf, nil, nil, fakeInterface.String())
if err != nil {
t.Fatalf("NewOSConfigurator: %v\n", err)
}
@ -213,7 +213,7 @@ func runTest(t *testing.T, isLocal bool) {
}
defer delIfKey()
cfg, err := NewOSConfigurator(logf, nil, fakeInterface.String())
cfg, err := NewOSConfigurator(logf, nil, nil, fakeInterface.String())
if err != nil {
t.Fatalf("NewOSConfigurator: %v\n", err)
}

12
tailcfg/tailcfg.go
View File

@ -139,7 +139,8 @@
// - 96: 2024-05-29: Client understands NodeAttrSSHBehaviorV1
// - 97: 2024-06-06: Client understands NodeAttrDisableSplitDNSWhenNoCustomResolvers
// - 98: 2024-06-13: iOS/tvOS clients may provide serial number as part of posture information
const CurrentCapabilityVersion CapabilityVersion = 98
// - 99: 2024-06-14: Client understands NodeAttrDisableLocalDNSOverrideViaNRPT
const CurrentCapabilityVersion CapabilityVersion = 99
type StableID string
@ -2306,6 +2307,15 @@ type Oauth2Token struct {
// and this node attribute allows us to disable the optimization remotely
// if needed.
NodeAttrDisableSplitDNSWhenNoCustomResolvers NodeCapability = "disable-split-dns-when-no-custom-resolvers"
// NodeAttrDisableLocalDNSOverrideViaNRPT indicates that the node's DNS manager should not
// create a default (catch-all) Windows NRPT rule when "Override local DNS" is enabled.
// Without this rule, Windows 8.1 and newer devices issue parallel DNS requests to DNS servers
// associated with all network adapters, even when "Override local DNS" is enabled and/or
// a Mullvad exit node is being used, resulting in DNS leaks.
// We began creating this rule on 2024-06-14, and this node attribute
// allows us to disable the new behavior remotely if needed.
NodeAttrDisableLocalDNSOverrideViaNRPT NodeCapability = "disable-local-dns-override-via-nrpt"
)
// SetDNSRequest is a request to add a DNS record.