TUN-7700: Implement feature selector to determine if connections will prefer post quantum cryptography

cmd/cloudflared/tunnel/cmd.go

@@ -392,7 +392,7 @@ func StartServer(
 		observer.SendURL(quickTunnelURL)
 	}
 
-	tunnelConfig, orchestratorConfig, err := prepareTunnelConfig(c, info, log, logTransport, observer, namedTunnel)
+	tunnelConfig, orchestratorConfig, err := prepareTunnelConfig(ctx, c, info, log, logTransport, observer, namedTunnel)
 	if err != nil {
 		log.Err(err).Msg("Couldn't start tunnel")
 		return err

cmd/cloudflared/tunnel/config_test.go

@@ -4,10 +4,12 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/require"
+
+	"github.com/cloudflare/cloudflared/features"
 )
 
 func TestDedup(t *testing.T) {
 	expected := []string{"a", "b"}
-	actual := dedup([]string{"a", "b", "a"})
+	actual := features.Dedup([]string{"a", "b", "a"})
 	require.ElementsMatch(t, expected, actual)
 }

cmd/cloudflared/tunnel/configuration.go

@@ -1,6 +1,7 @@
 package tunnel
 
 import (
+	"context"
 	"crypto/tls"
 	"fmt"
 	"net"
@@ -112,6 +113,7 @@ func dnsProxyStandAlone(c *cli.Context, namedTunnel *connection.NamedTunnelPrope
 }
 
 func prepareTunnelConfig(
+	ctx context.Context,
 	c *cli.Context,
 	info *cliutil.BuildInfo,
 	log, logTransport *zerolog.Logger,
@@ -131,22 +133,36 @@ func prepareTunnelConfig(
 	tags = append(tags, tunnelpogs.Tag{Name: "ID", Value: clientID.String()})
 
 	transportProtocol := c.String("protocol")
-	needPQ := c.Bool("post-quantum")
-	if needPQ {
+
+	clientFeatures := features.Dedup(append(c.StringSlice("features"), features.DefaultFeatures...))
+
+	staticFeatures := features.StaticFeatures{}
+	if c.Bool("post-quantum") {
 		if FipsEnabled {
 			return nil, nil, fmt.Errorf("post-quantum not supported in FIPS mode")
 		}
+		pqMode := features.PostQuantumStrict
+		staticFeatures.PostQuantumMode = &pqMode
+	}
+	featureSelector, err := features.NewFeatureSelector(ctx, namedTunnel.Credentials.AccountTag, staticFeatures, log)
+	if err != nil {
+		return nil, nil, errors.Wrap(err, "Failed to create feature selector")
+	}
+	pqMode := featureSelector.PostQuantumMode()
+	if pqMode == features.PostQuantumStrict {
 		// Error if the user tries to force a non-quic transport protocol
 		if transportProtocol != connection.AutoSelectFlag && transportProtocol != connection.QUIC.String() {
 			return nil, nil, fmt.Errorf("post-quantum is only supported with the quic transport")
 		}
 		transportProtocol = connection.QUIC.String()
+		clientFeatures = append(clientFeatures, features.FeaturePostQuantum)
+
+		log.Info().Msgf(
+			"Using hybrid post-quantum key agreement %s",
+			supervisor.PQKexName,
+		)
 	}
 
-	clientFeatures := dedup(append(c.StringSlice("features"), features.DefaultFeatures...))
-	if needPQ {
-		clientFeatures = append(clientFeatures, features.FeaturePostQuantum)
-	}
 	namedTunnel.Client = tunnelpogs.ClientInfo{
 		ClientID: clientID[:],
 		Features: clientFeatures,
@@ -202,13 +218,6 @@ func prepareTunnelConfig(
 		log.Warn().Str("edgeIPVersion", edgeIPVersion.String()).Err(err).Msg("Overriding edge-ip-version")
 	}
 
-	if needPQ {
-		log.Info().Msgf(
-			"Using hybrid post-quantum key agreement %s",
-			supervisor.PQKexName,
-		)
-	}
-
 	tunnelConfig := &supervisor.TunnelConfig{
 		GracePeriod:     gracePeriod,
 		ReplaceExisting: c.Bool("force"),
@@ -233,7 +242,7 @@ func prepareTunnelConfig(
 		NamedTunnel:                 namedTunnel,
 		ProtocolSelector:            protocolSelector,
 		EdgeTLSConfigs:              edgeTLSConfigs,
-		NeedPQ:                      needPQ,
+		FeatureSelector:             featureSelector,
 		MaxEdgeAddrRetries:          uint8(c.Int("max-edge-addr-retries")),
 		UDPUnregisterSessionTimeout: c.Duration(udpUnregisterSessionTimeoutFlag),
 		DisableQUICPathMTUDiscovery: c.Bool(quicDisablePathMTUDiscovery),
@@ -276,25 +285,6 @@ func isRunningFromTerminal() bool {
 	return term.IsTerminal(int(os.Stdout.Fd()))
 }
 
-// Remove any duplicates from the slice
-func dedup(slice []string) []string {
-
-	// Convert the slice into a set
-	set := make(map[string]bool, 0)
-	for _, str := range slice {
-		set[str] = true
-	}
-
-	// Convert the set back into a slice
-	keys := make([]string, len(set))
-	i := 0
-	for str := range set {
-		keys[i] = str
-		i++
-	}
-	return keys
-}
-
 // ParseConfigIPVersion returns the IP version from possible expected values from config
 func parseConfigIPVersion(version string) (v allregions.ConfigIPVersion, err error) {
 	switch version {