fix(updater): only uses DoH to cloudflare+google

- prevent dns plaintext manipulation both the periodic update and when running in cli mode
- possibly higher reliability on poor connections versus UDP
- drop `-dns` flag in update command
- for now no configuration allowed since it makes everything rather complex

cmd/gluetun/main.go

@@ -16,6 +16,8 @@ import (
 	_ "time/tzdata"
 
 	_ "github.com/breml/rootcerts"
+	"github.com/qdm12/dns/v2/pkg/doh"
+	dnsprovider "github.com/qdm12/dns/v2/pkg/provider"
 	"github.com/qdm12/gluetun/internal/alpine"
 	"github.com/qdm12/gluetun/internal/boringpoll"
 	"github.com/qdm12/gluetun/internal/cli"
@@ -433,10 +435,18 @@ func _main(ctx context.Context, buildInfo models.BuildInformation,
 	go healthcheckServer.Run(healthServerCtx, healthServerDone)
 	healthChecker := healthcheck.NewChecker(healthLogger)
 
+	// Note: we use a separate DoH dialer for the VPN servers data updater, separate from the
+	// main DNS local server to make sure no request is blocked by filters.
+	dohDialer, err := doh.New(doh.Settings{
+		UpstreamResolvers: []dnsprovider.Provider{dnsprovider.Cloudflare(), dnsprovider.Google()},
+	})
+	if err != nil {
+		return fmt.Errorf("creating updater DoH dialer: %w", err)
+	}
 	updaterLogger := logger.New(log.SetComponent("updater"))
 
 	unzipper := unzip.New(httpClient)
-	parallelResolver := resolver.NewParallelResolver(allSettings.Updater.DNSAddress)
+	parallelResolver := resolver.NewParallelResolver(dohDialer)
 	openvpnFileExtractor := extract.New()
 	providers := provider.NewProviders(storage, time.Now, updaterLogger,
 		httpClient, unzipper, parallelResolver, publicIPLooper.Fetcher(),

internal/cli/update.go

@@ -10,6 +10,8 @@ import (
 	"strings"
 	"time"
 
+	"github.com/qdm12/dns/v2/pkg/doh"
+	dnsprovider "github.com/qdm12/dns/v2/pkg/provider"
 	"github.com/qdm12/gluetun/internal/configuration/settings"
 	"github.com/qdm12/gluetun/internal/constants"
 	"github.com/qdm12/gluetun/internal/constants/providers"
@@ -38,12 +40,12 @@ type UpdaterLogger interface {
 func (c *CLI) Update(ctx context.Context, args []string, logger UpdaterLogger) error {
 	options := settings.Updater{}
 	var endUserMode, maintainerMode, updateAll bool
-	var csvProviders, ipToken, protonUsername, protonEmail, protonPassword string
+	var dnsServer, csvProviders, ipToken, protonUsername, protonEmail, protonPassword string
 	flagSet := flag.NewFlagSet("update", flag.ExitOnError)
 	flagSet.BoolVar(&endUserMode, "enduser", false, "Write results to /gluetun/servers.json (for end users)")
 	flagSet.BoolVar(&maintainerMode, "maintainer", false,
 		"Write results to ./internal/storage/servers.json to modify the program (for maintainers)")
-	flagSet.StringVar(&options.DNSAddress, "dns", "8.8.8.8", "DNS resolver address to use")
+	flagSet.StringVar(&dnsServer, "dns", "", "no longer used, your DNS will use DoH with Cloudflare and Google")
 	const defaultMinRatio = 0.8
 	flagSet.Float64Var(&options.MinRatio, "minratio", defaultMinRatio,
 		"Minimum ratio of servers to find for the update to succeed")
@@ -58,6 +60,10 @@ func (c *CLI) Update(ctx context.Context, args []string, logger UpdaterLogger) e
 		return err
 	}
 
+	if dnsServer != "" {
+		logger.Warn("The -dns flag is no longer used, your DNS will use DoH with Cloudflare and Google")
+	}
+
 	if !endUserMode && !maintainerMode {
 		return fmt.Errorf("%w", ErrModeUnspecified)
 	}
@@ -97,10 +103,21 @@ func (c *CLI) Update(ctx context.Context, args []string, logger UpdaterLogger) e
 		return fmt.Errorf("creating servers storage: %w", err)
 	}
 
+	dohSettings := doh.Settings{
+		UpstreamResolvers: []dnsprovider.Provider{
+			dnsprovider.Cloudflare(),
+			dnsprovider.Google(),
+		},
+	}
+	dnsDialer, err := doh.New(dohSettings)
+	if err != nil {
+		return fmt.Errorf("creating DoH dialer: %w", err)
+	}
+
 	const clientTimeout = 10 * time.Second
 	httpClient := &http.Client{Timeout: clientTimeout}
 	unzipper := unzip.New(httpClient)
-	parallelResolver := resolver.NewParallelResolver(options.DNSAddress)
+	parallelResolver := resolver.NewParallelResolver(dnsDialer)
 	nameTokenPairs := []api.NameToken{
 		{Name: string(api.IPInfo), Token: ipToken},
 		{Name: string(api.IP2Location)},

internal/configuration/settings/updater.go

@@ -21,10 +21,6 @@ type Updater struct {
 	// updater. It cannot be nil in the internal state.
 	// TODO change to value and add Enabled field.
 	Period *time.Duration
-	// DNSAddress is the DNS server address to use
-	// to resolve VPN server hostnames to IP addresses.
-	// It cannot be the empty string in the internal state.
-	DNSAddress string
 	// MinRatio is the minimum ratio of servers to
 	// find per provider, compared to the total current
 	// number of servers. It defaults to 0.8.
@@ -76,7 +72,6 @@ func (u Updater) Validate() (err error) {
 func (u *Updater) copy() (copied Updater) {
 	return Updater{
 		Period:         gosettings.CopyPointer(u.Period),
-		DNSAddress:     u.DNSAddress,
 		MinRatio:       u.MinRatio,
 		Providers:      gosettings.CopySlice(u.Providers),
 		ProtonEmail:    gosettings.CopyPointer(u.ProtonEmail),
@@ -89,7 +84,6 @@ func (u *Updater) copy() (copied Updater) {
 // settings.
 func (u *Updater) overrideWith(other Updater) {
 	u.Period = gosettings.OverrideWithPointer(u.Period, other.Period)
-	u.DNSAddress = gosettings.OverrideWithComparable(u.DNSAddress, other.DNSAddress)
 	u.MinRatio = gosettings.OverrideWithComparable(u.MinRatio, other.MinRatio)
 	u.Providers = gosettings.OverrideWithSlice(u.Providers, other.Providers)
 	u.ProtonEmail = gosettings.OverrideWithPointer(u.ProtonEmail, other.ProtonEmail)
@@ -98,7 +92,6 @@ func (u *Updater) overrideWith(other Updater) {
 
 func (u *Updater) SetDefaults(vpnProvider string) {
 	u.Period = gosettings.DefaultPointer(u.Period, 0)
-	u.DNSAddress = gosettings.DefaultComparable(u.DNSAddress, "1.1.1.1:53")
 
 	if u.MinRatio == 0 {
 		const defaultMinRatio = 0.8
@@ -125,7 +118,6 @@ func (u Updater) toLinesNode() (node *gotree.Node) {
 
 	node = gotree.New("Server data updater settings:")
 	node.Appendf("Update period: %s", *u.Period)
-	node.Appendf("DNS address: %s", u.DNSAddress)
 	node.Appendf("Minimum ratio: %.1f", u.MinRatio)
 	node.Appendf("Providers to update: %s", strings.Join(u.Providers, ", "))
 	if slices.Contains(u.Providers, providers.Protonvpn) {
@@ -142,11 +134,6 @@ func (u *Updater) read(r *reader.Reader) (err error) {
 		return err
 	}
 
-	u.DNSAddress, err = readUpdaterDNSAddress()
-	if err != nil {
-		return err
-	}
-
 	u.MinRatio, err = r.Float64("UPDATER_MIN_RATIO")
 	if err != nil {
 		return err
@@ -166,12 +153,3 @@ func (u *Updater) read(r *reader.Reader) (err error) {
 
 	return nil
 }
-
-func readUpdaterDNSAddress() (address string, err error) {
-	// TODO this is currently using Cloudflare in
-	// plaintext to not be blocked by DNS over TLS by default.
-	// If a plaintext address is set in the DNS settings, this one will be used.
-	// use custom future encrypted DNS written in Go without blocking
-	// as it's too much trouble to start another parallel unbound instance for now.
-	return "", nil
-}

internal/updater/resolver/interfaces.go

@@ -0,0 +1,10 @@
+package resolver
+
+import (
+	"context"
+	"net"
+)
+
+type Dialer interface {
+	Dial(ctx context.Context, network, address string) (net.Conn, error)
+}

internal/updater/resolver/net.go

@@ -1,17 +1,12 @@
 package resolver
 
 import (
-	"context"
 	"net"
 )
 
-func newResolver(resolverAddress string) *net.Resolver {
-	d := net.Dialer{}
-	resolverAddress = net.JoinHostPort(resolverAddress, "53")
+func newResolver(d Dialer) *net.Resolver {
 	return &net.Resolver{
 		PreferGo: true,
-		Dial: func(ctx context.Context, _, _ string) (net.Conn, error) {
-			return d.DialContext(ctx, "udp", resolverAddress)
-		},
+		Dial:     d.Dial,
 	}
 }

internal/updater/resolver/parallel.go

@@ -11,9 +11,9 @@ type Parallel struct {
 	repeatResolver *Repeat
 }
 
-func NewParallelResolver(resolverAddress string) *Parallel {
+func NewParallelResolver(dialer Dialer) *Parallel {
 	return &Parallel{
-		repeatResolver: NewRepeat(resolverAddress),
+		repeatResolver: NewRepeat(dialer),
 	}
 }
 

internal/updater/resolver/repeat.go

@@ -14,9 +14,9 @@ type Repeat struct {
 	resolver *net.Resolver
 }
 
-func NewRepeat(resolverAddress string) *Repeat {
+func NewRepeat(dialer Dialer) *Repeat {
 	return &Repeat{
-		resolver: newResolver(resolverAddress),
+		resolver: newResolver(dialer),
 	}
 }