Backport tls 1.3 support.

Signed-off-by: James Blair <mail@jamesblair.net>

server/embed/config.go

@@ -15,6 +15,7 @@
 package embed
 
 import (
+	"crypto/tls"
 	"fmt"
 	"io/ioutil"
 	"math"
@@ -220,6 +221,11 @@ type Config struct {
 	// Note that cipher suites are prioritized in the given order.
 	CipherSuites []string `json:"cipher-suites"`
 
+	// TlsMinVersion is the minimum accepted TLS version between client/server and peers.
+	TlsMinVersion string `json:"tls-min-version"`
+	// TlsMaxVersion is the maximum accepted TLS version between client/server and peers.
+	TlsMaxVersion string `json:"tls-max-version"`
+
 	ClusterState          string `json:"initial-cluster-state"`
 	DNSCluster            string `json:"discovery-srv"`
 	DNSClusterServiceName string `json:"discovery-srv-name"`
@@ -628,6 +634,17 @@ func updateCipherSuites(tls *transport.TLSInfo, ss []string) error {
 	return nil
 }
 
+func updateMinMaxVersions(info *transport.TLSInfo, min, max string) {
+	// Validate() has been called to check the user input, so it should never fail.
+	var err error
+	if info.MinVersion, err = tlsutil.GetTLSVersion(min); err != nil {
+		panic(err)
+	}
+	if info.MaxVersion, err = tlsutil.GetTLSVersion(max); err != nil {
+		panic(err)
+	}
+}
+
 // Validate ensures that '*embed.Config' fields are properly configured.
 func (cfg *Config) Validate() error {
 	if err := cfg.setupLogging(); err != nil {
@@ -703,6 +720,25 @@ func (cfg *Config) Validate() error {
 		return fmt.Errorf("--experimental-compact-hash-check-time must be >0 (set to %v)", cfg.ExperimentalCompactHashCheckTime)
 	}
 
+	minVersion, err := tlsutil.GetTLSVersion(cfg.TlsMinVersion)
+	if err != nil {
+		return err
+	}
+	maxVersion, err := tlsutil.GetTLSVersion(cfg.TlsMaxVersion)
+	if err != nil {
+		return err
+	}
+
+	// maxVersion == 0 means that Go selects the highest available version.
+	if maxVersion != 0 && minVersion > maxVersion {
+		return fmt.Errorf("min version (%s) is greater than max version (%s)", cfg.TlsMinVersion, cfg.TlsMaxVersion)
+	}
+
+	// Check if user attempted to configure ciphers for TLS1.3 only: Go does not support that currently.
+	if minVersion == tls.VersionTLS13 && len(cfg.CipherSuites) > 0 {
+		return fmt.Errorf("cipher suites cannot be configured when only TLS1.3 is enabled")
+	}
+
 	return nil
 }
 

server/embed/config_test.go

@@ -15,6 +15,7 @@
 package embed
 
 import (
+	"crypto/tls"
 	"errors"
 	"fmt"
 	"io/ioutil"
@@ -24,6 +25,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/stretchr/testify/assert"
 	"go.etcd.io/etcd/client/pkg/v3/srv"
 	"go.etcd.io/etcd/client/pkg/v3/transport"
 	"go.etcd.io/etcd/client/pkg/v3/types"
@@ -422,3 +424,80 @@ func TestLogRotation(t *testing.T) {
 		})
 	}
 }
+
+func TestTLSVersionMinMax(t *testing.T) {
+	tests := []struct {
+		name                  string
+		givenTLSMinVersion    string
+		givenTLSMaxVersion    string
+		givenCipherSuites     []string
+		expectError           bool
+		expectedMinTLSVersion uint16
+		expectedMaxTLSVersion uint16
+	}{
+		{
+			name:                  "Minimum TLS version is set",
+			givenTLSMinVersion:    "TLS1.3",
+			expectedMinTLSVersion: tls.VersionTLS13,
+			expectedMaxTLSVersion: 0,
+		},
+		{
+			name:                  "Maximum TLS version is set",
+			givenTLSMaxVersion:    "TLS1.2",
+			expectedMinTLSVersion: 0,
+			expectedMaxTLSVersion: tls.VersionTLS12,
+		},
+		{
+			name:                  "Minimum and Maximum TLS versions are set",
+			givenTLSMinVersion:    "TLS1.3",
+			givenTLSMaxVersion:    "TLS1.3",
+			expectedMinTLSVersion: tls.VersionTLS13,
+			expectedMaxTLSVersion: tls.VersionTLS13,
+		},
+		{
+			name:               "Minimum and Maximum TLS versions are set in reverse order",
+			givenTLSMinVersion: "TLS1.3",
+			givenTLSMaxVersion: "TLS1.2",
+			expectError:        true,
+		},
+		{
+			name:               "Invalid minimum TLS version",
+			givenTLSMinVersion: "invalid version",
+			expectError:        true,
+		},
+		{
+			name:               "Invalid maximum TLS version",
+			givenTLSMaxVersion: "invalid version",
+			expectError:        true,
+		},
+		{
+			name:               "Cipher suites configured for TLS 1.3",
+			givenTLSMinVersion: "TLS1.3",
+			givenCipherSuites:  []string{"TLS_AES_128_GCM_SHA256"},
+			expectError:        true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			cfg := NewConfig()
+			cfg.TlsMinVersion = tt.givenTLSMinVersion
+			cfg.TlsMaxVersion = tt.givenTLSMaxVersion
+			cfg.CipherSuites = tt.givenCipherSuites
+
+			err := cfg.Validate()
+			if err != nil {
+				assert.True(t, tt.expectError, "Validate() returned error while expecting success: %v", err)
+				return
+			}
+
+			updateMinMaxVersions(&cfg.PeerTLSInfo, cfg.TlsMinVersion, cfg.TlsMaxVersion)
+			updateMinMaxVersions(&cfg.ClientTLSInfo, cfg.TlsMinVersion, cfg.TlsMaxVersion)
+
+			assert.Equal(t, tt.expectedMinTLSVersion, cfg.PeerTLSInfo.MinVersion)
+			assert.Equal(t, tt.expectedMaxTLSVersion, cfg.PeerTLSInfo.MaxVersion)
+			assert.Equal(t, tt.expectedMinTLSVersion, cfg.ClientTLSInfo.MinVersion)
+			assert.Equal(t, tt.expectedMaxTLSVersion, cfg.ClientTLSInfo.MaxVersion)
+		})
+	}
+}

server/embed/etcd.go

@@ -480,6 +480,9 @@ func configurePeerListeners(cfg *Config) (peers []*peerListener, err error) {
 	if err = cfg.PeerSelfCert(); err != nil {
 		cfg.logger.Fatal("failed to get peer self-signed certs", zap.Error(err))
 	}
+
+	updateMinMaxVersions(&cfg.PeerTLSInfo, cfg.TlsMinVersion, cfg.TlsMaxVersion)
+
 	if !cfg.PeerTLSInfo.Empty() {
 		cfg.logger.Info(
 			"starting with peer TLS",
@@ -600,6 +603,9 @@ func configureClientListeners(cfg *Config) (sctxs map[string]*serveCtx, err erro
 	if err = cfg.ClientSelfCert(); err != nil {
 		cfg.logger.Fatal("failed to get client self-signed certs", zap.Error(err))
 	}
+
+	updateMinMaxVersions(&cfg.ClientTLSInfo, cfg.TlsMinVersion, cfg.TlsMaxVersion)
+
 	if cfg.EnablePprof {
 		cfg.logger.Info("pprof is enabled", zap.String("path", debugutil.HTTPPrefixPProf))
 	}

server/etcdmain/config.go

@@ -26,6 +26,7 @@ import (
 
 	"go.etcd.io/etcd/api/v3/version"
 	"go.etcd.io/etcd/client/pkg/v3/logutil"
+	"go.etcd.io/etcd/client/pkg/v3/tlsutil"
 	"go.etcd.io/etcd/pkg/v3/flags"
 	cconfig "go.etcd.io/etcd/server/v3/config"
 	"go.etcd.io/etcd/server/v3/embed"
@@ -237,6 +238,8 @@ func newConfig() *config {
 	fs.StringVar(&cfg.ec.PeerTLSInfo.AllowedHostname, "peer-cert-allowed-hostname", "", "Allowed TLS hostname for inter peer authentication.")
 	fs.Var(flags.NewStringsValue(""), "cipher-suites", "Comma-separated list of supported TLS cipher suites between client/server and peers (empty will be auto-populated by Go).")
 	fs.BoolVar(&cfg.ec.PeerTLSInfo.SkipClientSANVerify, "experimental-peer-skip-client-san-verification", false, "Skip verification of SAN field in client certificate for peer connections.")
+	fs.StringVar(&cfg.ec.TlsMinVersion, "tls-min-version", string(tlsutil.TLSVersion12), "Minimum TLS version supported by etcd. Possible values: TLS1.2, TLS1.3.")
+	fs.StringVar(&cfg.ec.TlsMaxVersion, "tls-max-version", string(tlsutil.TLSVersionDefault), "Maximum TLS version supported by etcd. Possible values: TLS1.2, TLS1.3 (empty defers to Go).")
 
 	fs.Var(
 		flags.NewUniqueURLsWithExceptions("*", "*"),

server/etcdmain/help.go

@@ -174,6 +174,10 @@ Security:
     Comma-separated whitelist of origins for CORS, or cross-origin resource sharing, (empty or * means allow all).
   --host-whitelist '*'
     Acceptable hostnames from HTTP client requests, if server is not secure (empty or * means allow all).
+  --tls-min-version 'TLS1.2'
+    Minimum TLS version supported by etcd. Possible values: TLS1.2, TLS1.3.
+  --tls-max-version ''
+    Maximum TLS version supported by etcd. Possible values: TLS1.2, TLS1.3 (empty will be auto-populated by Go).
 
 Auth:
   --auth-token 'simple'