TUN-7700: Implement feature selector to determine if connections will prefer post quantum cryptography
This commit is contained in:
Chung-Ting Huang
Jean Khawand
parent
279e080e7e
commit
76c8ff9d99
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@ -392,7 +392,7 @@ func StartServer(
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observer.SendURL(quickTunnelURL)
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}
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tunnelConfig, orchestratorConfig, err := prepareTunnelConfig(c, info, log, logTransport, observer, namedTunnel)
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tunnelConfig, orchestratorConfig, err := prepareTunnelConfig(ctx, c, info, log, logTransport, observer, namedTunnel)
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if err != nil {
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log.Err(err).Msg("Couldn't start tunnel")
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return err
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@ -4,10 +4,12 @@ import (
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"testing"
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"github.com/stretchr/testify/require"
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"github.com/cloudflare/cloudflared/features"
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)
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func TestDedup(t *testing.T) {
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expected := []string{"a", "b"}
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actual := dedup([]string{"a", "b", "a"})
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actual := features.Dedup([]string{"a", "b", "a"})
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require.ElementsMatch(t, expected, actual)
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}
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@ -1,6 +1,7 @@
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package tunnel
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import (
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"context"
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"crypto/tls"
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"fmt"
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"net"
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@ -112,6 +113,7 @@ func dnsProxyStandAlone(c *cli.Context, namedTunnel *connection.NamedTunnelPrope
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}
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func prepareTunnelConfig(
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ctx context.Context,
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c *cli.Context,
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info *cliutil.BuildInfo,
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log, logTransport *zerolog.Logger,
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@ -131,22 +133,36 @@ func prepareTunnelConfig(
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tags = append(tags, tunnelpogs.Tag{Name: "ID", Value: clientID.String()})
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transportProtocol := c.String("protocol")
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needPQ := c.Bool("post-quantum")
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if needPQ {
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clientFeatures := features.Dedup(append(c.StringSlice("features"), features.DefaultFeatures...))
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staticFeatures := features.StaticFeatures{}
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if c.Bool("post-quantum") {
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if FipsEnabled {
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return nil, nil, fmt.Errorf("post-quantum not supported in FIPS mode")
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}
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pqMode := features.PostQuantumStrict
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staticFeatures.PostQuantumMode = &pqMode
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}
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featureSelector, err := features.NewFeatureSelector(ctx, namedTunnel.Credentials.AccountTag, staticFeatures, log)
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if err != nil {
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return nil, nil, errors.Wrap(err, "Failed to create feature selector")
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}
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pqMode := featureSelector.PostQuantumMode()
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if pqMode == features.PostQuantumStrict {
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// Error if the user tries to force a non-quic transport protocol
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if transportProtocol != connection.AutoSelectFlag && transportProtocol != connection.QUIC.String() {
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return nil, nil, fmt.Errorf("post-quantum is only supported with the quic transport")
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}
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transportProtocol = connection.QUIC.String()
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clientFeatures = append(clientFeatures, features.FeaturePostQuantum)
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log.Info().Msgf(
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"Using hybrid post-quantum key agreement %s",
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supervisor.PQKexName,
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)
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}
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clientFeatures := dedup(append(c.StringSlice("features"), features.DefaultFeatures...))
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if needPQ {
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clientFeatures = append(clientFeatures, features.FeaturePostQuantum)
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}
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namedTunnel.Client = tunnelpogs.ClientInfo{
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ClientID: clientID[:],
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Features: clientFeatures,
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@ -202,13 +218,6 @@ func prepareTunnelConfig(
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log.Warn().Str("edgeIPVersion", edgeIPVersion.String()).Err(err).Msg("Overriding edge-ip-version")
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}
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if needPQ {
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log.Info().Msgf(
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"Using hybrid post-quantum key agreement %s",
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supervisor.PQKexName,
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)
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}
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tunnelConfig := &supervisor.TunnelConfig{
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GracePeriod: gracePeriod,
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ReplaceExisting: c.Bool("force"),
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@ -233,7 +242,7 @@ func prepareTunnelConfig(
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NamedTunnel: namedTunnel,
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ProtocolSelector: protocolSelector,
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EdgeTLSConfigs: edgeTLSConfigs,
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NeedPQ: needPQ,
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FeatureSelector: featureSelector,
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MaxEdgeAddrRetries: uint8(c.Int("max-edge-addr-retries")),
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UDPUnregisterSessionTimeout: c.Duration(udpUnregisterSessionTimeoutFlag),
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DisableQUICPathMTUDiscovery: c.Bool(quicDisablePathMTUDiscovery),
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@ -276,25 +285,6 @@ func isRunningFromTerminal() bool {
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return term.IsTerminal(int(os.Stdout.Fd()))
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}
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// Remove any duplicates from the slice
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func dedup(slice []string) []string {
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// Convert the slice into a set
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set := make(map[string]bool, 0)
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for _, str := range slice {
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set[str] = true
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}
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// Convert the set back into a slice
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keys := make([]string, len(set))
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i := 0
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for str := range set {
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keys[i] = str
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i++
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}
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return keys
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}
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// ParseConfigIPVersion returns the IP version from possible expected values from config
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func parseConfigIPVersion(version string) (v allregions.ConfigIPVersion, err error) {
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switch version {
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@ -28,3 +28,22 @@ func Contains(feature string) bool {
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}
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return false
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}
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// Remove any duplicates from the slice
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func Dedup(slice []string) []string {
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// Convert the slice into a set
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set := make(map[string]bool, 0)
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for _, str := range slice {
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set[str] = true
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}
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// Convert the set back into a slice
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keys := make([]string, len(set))
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i := 0
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for str := range set {
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keys[i] = str
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i++
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}
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return keys
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}
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@ -0,0 +1,164 @@
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package features
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import (
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"context"
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"encoding/json"
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"fmt"
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"hash/fnv"
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"net"
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"sync"
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"time"
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"github.com/rs/zerolog"
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)
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const (
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featureSelectorHostname = "cfd-features.argotunnel.com"
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defaultRefreshFreq = time.Hour * 6
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lookupTimeout = time.Second * 10
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)
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type PostQuantumMode uint8
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const (
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PostQuantumDisabled PostQuantumMode = iota
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// Prefer post quantum, but fallback if connection cannot be established
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PostQuantumPrefer
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// If the user passes the --post-quantum flag, we override
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// CurvePreferences to only support hybrid post-quantum key agreements.
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PostQuantumStrict
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)
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// If the TXT record adds other fields, the umarshal logic will ignore those keys
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// If the TXT record is missing a key, the field will unmarshal to the default Go value
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type featuresRecord struct {
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PostQuantumPercentage int32 `json:"pq"`
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}
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func NewFeatureSelector(ctx context.Context, accountTag string, staticFeatures StaticFeatures, logger *zerolog.Logger) (*FeatureSelector, error) {
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return newFeatureSelector(ctx, accountTag, logger, newDNSResolver(), staticFeatures, defaultRefreshFreq)
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}
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// FeatureSelector determines if this account will try new features. It preiodically queries a DNS TXT record
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// to see which features are turned on
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type FeatureSelector struct {
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accountHash int32
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logger *zerolog.Logger
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resolver resolver
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staticFeatures StaticFeatures
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// lock protects concurrent access to dynamic features
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lock sync.RWMutex
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features featuresRecord
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}
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// Features set by user provided flags
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type StaticFeatures struct {
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PostQuantumMode *PostQuantumMode
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}
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func newFeatureSelector(ctx context.Context, accountTag string, logger *zerolog.Logger, resolver resolver, staticFeatures StaticFeatures, refreshFreq time.Duration) (*FeatureSelector, error) {
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selector := &FeatureSelector{
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accountHash: switchThreshold(accountTag),
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logger: logger,
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resolver: resolver,
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staticFeatures: staticFeatures,
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}
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if err := selector.refresh(ctx); err != nil {
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logger.Err(err).Msg("Failed to fetch features, default to disable")
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}
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go selector.refreshLoop(ctx, refreshFreq)
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return selector, nil
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}
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func (fs *FeatureSelector) PostQuantumMode() PostQuantumMode {
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if fs.staticFeatures.PostQuantumMode != nil {
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return *fs.staticFeatures.PostQuantumMode
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}
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fs.lock.RLock()
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defer fs.lock.RUnlock()
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if fs.features.PostQuantumPercentage > fs.accountHash {
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return PostQuantumPrefer
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}
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return PostQuantumDisabled
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}
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func (fs *FeatureSelector) refreshLoop(ctx context.Context, refreshFreq time.Duration) {
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ticker := time.NewTicker(refreshFreq)
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for {
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select {
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case <-ctx.Done():
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return
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case <-ticker.C:
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err := fs.refresh(ctx)
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if err != nil {
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fs.logger.Err(err).Msg("Failed to refresh feature selector")
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}
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}
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}
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}
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func (fs *FeatureSelector) refresh(ctx context.Context) error {
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record, err := fs.resolver.lookupRecord(ctx)
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if err != nil {
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return err
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}
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var features featuresRecord
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if err := json.Unmarshal(record, &features); err != nil {
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return err
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}
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pq_enabled := features.PostQuantumPercentage > fs.accountHash
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fs.logger.Debug().Int32("account_hash", fs.accountHash).Int32("pq_perct", features.PostQuantumPercentage).Bool("pq_enabled", pq_enabled).Msg("Refreshed feature")
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fs.lock.Lock()
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defer fs.lock.Unlock()
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fs.features = features
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return nil
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}
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// resolver represents an object that can look up featuresRecord
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type resolver interface {
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lookupRecord(ctx context.Context) ([]byte, error)
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}
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type dnsResolver struct {
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resolver *net.Resolver
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}
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func newDNSResolver() *dnsResolver {
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return &dnsResolver{
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resolver: net.DefaultResolver,
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}
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}
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func (dr *dnsResolver) lookupRecord(ctx context.Context) ([]byte, error) {
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ctx, cancel := context.WithTimeout(ctx, lookupTimeout)
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defer cancel()
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records, err := dr.resolver.LookupTXT(ctx, featureSelectorHostname)
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if err != nil {
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return nil, err
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}
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if len(records) == 0 {
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return nil, fmt.Errorf("No TXT record found for %s to determine which features to opt-in", featureSelectorHostname)
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}
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return []byte(records[0]), nil
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}
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func switchThreshold(accountTag string) int32 {
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h := fnv.New32a()
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_, _ = h.Write([]byte(accountTag))
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return int32(h.Sum32() % 100)
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}
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@ -0,0 +1,128 @@
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package features
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import (
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"context"
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"encoding/json"
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"fmt"
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"testing"
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"time"
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"github.com/rs/zerolog"
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"github.com/stretchr/testify/require"
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)
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func TestUnmarshalFeaturesRecord(t *testing.T) {
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tests := []struct {
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record []byte
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expectedPercentage int32
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expectedErr bool
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}{
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{
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record: []byte(`{"pq":0}`),
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expectedPercentage: 0,
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},
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{
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record: []byte(`{"pq":39}`),
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expectedPercentage: 39,
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},
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{
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record: []byte(`{"pq":100}`),
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expectedPercentage: 100,
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},
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{
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record: []byte(`{}`),
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expectedPercentage: 0, // Unmarshal to default struct if key is not present
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},
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{
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record: []byte(`{"kyber":768}`),
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expectedPercentage: 0, // Unmarshal to default struct if key is not present
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},
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{
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record: []byte(`{"pq":"kyber768"}`),
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expectedErr: true,
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},
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}
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for _, test := range tests {
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var features featuresRecord
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err := json.Unmarshal(test.record, &features)
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if test.expectedErr {
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require.Error(t, err, test)
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} else {
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require.NoError(t, err)
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require.Equal(t, test.expectedPercentage, features.PostQuantumPercentage, test)
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}
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}
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}
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func TestRefreshFeaturesRecord(t *testing.T) {
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// The hash of the accountTag is 82
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accountTag := t.Name()
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threshold := switchThreshold(accountTag)
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percentages := []int32{0, 10, 80, 83, 100}
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refreshFreq := time.Millisecond * 10
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selector := newTestSelector(t, percentages, nil, refreshFreq)
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for _, percentage := range percentages {
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if percentage > threshold {
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require.Equal(t, PostQuantumPrefer, selector.PostQuantumMode())
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} else {
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require.Equal(t, PostQuantumDisabled, selector.PostQuantumMode())
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}
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time.Sleep(refreshFreq + time.Millisecond)
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}
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// Make sure error doesn't override the last fetched features
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require.Equal(t, PostQuantumPrefer, selector.PostQuantumMode())
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}
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func TestStaticFeatures(t *testing.T) {
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percentages := []int32{0}
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pqMode := PostQuantumStrict
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selector := newTestSelector(t, percentages, &pqMode, time.Millisecond*10)
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require.Equal(t, PostQuantumStrict, selector.PostQuantumMode())
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}
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// Verify that if the first refresh fails, the selector will use default features
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func TestFailedRefreshInitToDefault(t *testing.T) {
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selector := newTestSelector(t, []int32{}, nil, time.Second)
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require.Equal(t, featuresRecord{}, selector.features)
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require.Equal(t, PostQuantumDisabled, selector.PostQuantumMode())
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}
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func newTestSelector(t *testing.T, percentages []int32, pqMode *PostQuantumMode, refreshFreq time.Duration) *FeatureSelector {
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accountTag := t.Name()
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logger := zerolog.Nop()
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resolver := &mockResolver{
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percentages: percentages,
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}
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staticFeatures := StaticFeatures{
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PostQuantumMode: pqMode,
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}
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selector, err := newFeatureSelector(context.Background(), accountTag, &logger, resolver, staticFeatures, refreshFreq)
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require.NoError(t, err)
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return selector
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}
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type mockResolver struct {
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nextIndex int
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percentages []int32
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}
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func (mr *mockResolver) lookupRecord(ctx context.Context) ([]byte, error) {
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if mr.nextIndex >= len(mr.percentages) {
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return nil, fmt.Errorf("no more record to lookup")
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}
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record, err := json.Marshal(featuresRecord{
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PostQuantumPercentage: mr.percentages[mr.nextIndex],
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})
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mr.nextIndex++
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return record, err
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}
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@ -4,8 +4,11 @@ import (
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"bytes"
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"crypto/tls"
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"encoding/json"
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"fmt"
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"net/http"
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"sync"
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"github.com/cloudflare/cloudflared/features"
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)
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// When experimental post-quantum tunnels are enabled, and we're hitting an
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@ -94,3 +97,32 @@ func submitPQTunnelError(rep error, config *TunnelConfig) {
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}
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resp.Body.Close()
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}
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func curvePreference(pqMode features.PostQuantumMode, currentCurve []tls.CurveID) ([]tls.CurveID, error) {
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switch pqMode {
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case features.PostQuantumStrict:
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// If the user passes the -post-quantum flag, we override
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// CurvePreferences to only support hybrid post-quantum key agreements.
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return []tls.CurveID{PQKex}, nil
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case features.PostQuantumPrefer:
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if len(currentCurve) == 0 {
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return []tls.CurveID{PQKex}, nil
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}
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if currentCurve[0] != PQKex {
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return append([]tls.CurveID{PQKex}, currentCurve...), nil
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}
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return currentCurve, nil
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case features.PostQuantumDisabled:
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curvePref := currentCurve
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// Remove PQ from curve preference
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for i, curve := range currentCurve {
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if curve == PQKex {
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curvePref = append(curvePref[:i], curvePref[i+1:]...)
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}
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}
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return curvePref, nil
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default:
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return nil, fmt.Errorf("Unexpected post quantum mode")
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}
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}
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|
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@ -69,6 +69,8 @@ type TunnelConfig struct {
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UDPUnregisterSessionTimeout time.Duration
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|
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DisableQUICPathMTUDiscovery bool
|
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|
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FeatureSelector *features.FeatureSelector
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}
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func (c *TunnelConfig) registrationOptions(connectionID uint8, OriginLocalIP string, uuid uuid.UUID) *tunnelpogs.RegistrationOptions {
|
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|
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@ -536,7 +538,8 @@ func (e *EdgeTunnelServer) serveHTTP2(
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controlStreamHandler connection.ControlStreamHandler,
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connIndex uint8,
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) error {
|
||||
if e.config.NeedPQ {
|
||||
pqMode := e.config.FeatureSelector.PostQuantumMode()
|
||||
if pqMode == features.PostQuantumStrict {
|
||||
return unrecoverableError{errors.New("HTTP/2 transport does not support post-quantum")}
|
||||
}
|
||||
|
||||
|
|
@ -579,14 +582,18 @@ func (e *EdgeTunnelServer) serveQUIC(
|
|||
) (err error, recoverable bool) {
|
||||
tlsConfig := e.config.EdgeTLSConfigs[connection.QUIC]
|
||||
|
||||
if e.config.NeedPQ {
|
||||
// If the user passes the -post-quantum flag, we override
|
||||
// CurvePreferences to only support hybrid post-quantum key agreements.
|
||||
tlsConfig.CurvePreferences = []tls.CurveID{
|
||||
PQKex,
|
||||
pqMode := e.config.FeatureSelector.PostQuantumMode()
|
||||
if pqMode == features.PostQuantumStrict || pqMode == features.PostQuantumPrefer {
|
||||
connOptions.Client.Features = features.Dedup(append(connOptions.Client.Features, features.FeaturePostQuantum))
|
||||
}
|
||||
|
||||
curvePref, err := curvePreference(pqMode, tlsConfig.CurvePreferences)
|
||||
if err != nil {
|
||||
return err, true
|
||||
}
|
||||
|
||||
tlsConfig.CurvePreferences = curvePref
|
||||
|
||||
quicConfig := &quic.Config{
|
||||
HandshakeIdleTimeout: quicpogs.HandshakeIdleTimeout,
|
||||
MaxIdleTimeout: quicpogs.MaxIdleTimeout,
|
||||
|
|
@ -614,7 +621,7 @@ func (e *EdgeTunnelServer) serveQUIC(
|
|||
e.config.UDPUnregisterSessionTimeout,
|
||||
)
|
||||
if err != nil {
|
||||
if e.config.NeedPQ {
|
||||
if pqMode == features.PostQuantumStrict || pqMode == features.PostQuantumPrefer {
|
||||
handlePQTunnelError(err, e.config)
|
||||
}
|
||||
|
||||
|
|
|
|||
Loading…
Reference in New Issue