Merge pull request #9801 from gyuho/cipher-suites

*: support TLS cipher suite whitelist

CHANGELOG-3.2.md

@@ -3,6 +3,23 @@
 Previous change logs can be found at [CHANGELOG-3.1](https://github.com/coreos/etcd/blob/master/CHANGELOG-3.1.md).
 
 
+## [v3.2.22](https://github.com/coreos/etcd/releases/tag/v3.2.22) (TBD 2018-06)
+
+See [code changes](https://github.com/coreos/etcd/compare/v3.2.21...v3.2.22) and [v3.2 upgrade guide](https://github.com/coreos/etcd/blob/master/Documentation/upgrades/upgrade_3_2.md) for any breaking changes. **Again, before running upgrades from any previous release, please make sure to read change logs below and [v3.2 upgrade guide](https://github.com/coreos/etcd/blob/master/Documentation/upgrades/upgrade_3_2.md).**
+
+### etcd server
+
+- Support TLS cipher suite whitelisting.
+  - To block [weak cipher suites](https://github.com/coreos/etcd/issues/8320).
+  - TLS handshake fails when client hello is requested with invalid cipher suites.
+  - Add [`etcd --cipher-suites`](https://github.com/coreos/etcd/pull/9801) flag.
+  - If empty, Go auto-populates the list.
+
+### Go
+
+- Compile with [*Go 1.8.7*](https://golang.org/doc/devel/release.html#go1.8).
+
+
 ## [v3.2.21](https://github.com/coreos/etcd/releases/tag/v3.2.21) (2018-05-31)
 
 See [code changes](https://github.com/coreos/etcd/compare/v3.2.20...v3.2.21) and [v3.2 upgrade guide](https://github.com/coreos/etcd/blob/master/Documentation/upgrades/upgrade_3_2.md) for any breaking changes. **Again, before running upgrades from any previous release, please make sure to read change logs below and [v3.2 upgrade guide](https://github.com/coreos/etcd/blob/master/Documentation/upgrades/upgrade_3_2.md).**

CHANGELOG-3.3.md

@@ -3,6 +3,23 @@
 Previous change logs can be found at [CHANGELOG-3.2](https://github.com/coreos/etcd/blob/master/CHANGELOG-3.2.md).
 
 
+## [v3.3.7](https://github.com/coreos/etcd/releases/tag/v3.3.7) (TBD 2018-06)
+
+See [code changes](https://github.com/coreos/etcd/compare/v3.3.6...v3.3.7) and [v3.3 upgrade guide](https://github.com/coreos/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md) for any breaking changes. **Again, before running upgrades from any previous release, please make sure to read change logs below and [v3.3 upgrade guide](https://github.com/coreos/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md).**
+
+### etcd server
+
+- Support TLS cipher suite whitelisting.
+  - To block [weak cipher suites](https://github.com/coreos/etcd/issues/8320).
+  - TLS handshake fails when client hello is requested with invalid cipher suites.
+  - Add [`etcd --cipher-suites`](https://github.com/coreos/etcd/pull/9801) flag.
+  - If empty, Go auto-populates the list.
+
+### Go
+
+- Compile with [*Go 1.9.6*](https://golang.org/doc/devel/release.html#go1.9).
+
+
 ## [v3.3.6](https://github.com/coreos/etcd/releases/tag/v3.3.6) (2018-05-31)
 
 See [code changes](https://github.com/coreos/etcd/compare/v3.3.5...v3.3.6) and [v3.3 upgrade guide](https://github.com/coreos/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md) for any breaking changes. **Again, before running upgrades from any previous release, please make sure to read change logs below and [v3.3 upgrade guide](https://github.com/coreos/etcd/blob/master/Documentation/upgrades/upgrade_3_3.md).**

CHANGELOG-3.4.md

@@ -156,6 +156,12 @@ See [code changes](https://github.com/coreos/etcd/compare/v3.3.0...v3.4.0) and [
 
 See [security doc](https://github.com/coreos/etcd/blob/master/Documentation/op-guide/security.md) for more details.
 
+- Support TLS cipher suite whitelisting.
+  - To block [weak cipher suites](https://github.com/coreos/etcd/issues/8320).
+  - TLS handshake fails when client hello is requested with invalid cipher suites.
+  - Add [`etcd --client-cipher-suites`](https://github.com/coreos/etcd/pull/9801) flag.
+  - Add [`etcd --peer-cipher-suites`](https://github.com/coreos/etcd/pull/9801) flag.
+  - If empty, Go auto-populates the list.
 - Add [`etcd --host-whitelist`](https://github.com/coreos/etcd/pull/9372) flag, [`etcdserver.Config.HostWhitelist`](https://github.com/coreos/etcd/pull/9372), and [`embed.Config.HostWhitelist`](https://github.com/coreos/etcd/pull/9372), to prevent ["DNS Rebinding"](https://en.wikipedia.org/wiki/DNS_rebinding) attack.
   - Any website can simply create an authorized DNS name, and direct DNS to `"localhost"` (or any other address). Then, all HTTP endpoints of etcd server listening on `"localhost"` becomes accessible, thus vulnerable to [DNS rebinding attacks (CVE-2018-5702)](https://bugs.chromium.org/p/project-zero/issues/detail?id=1447#c2).
   - Client origin enforce policy works as follow:
@@ -166,7 +172,6 @@ See [security doc](https://github.com/coreos/etcd/blob/master/Documentation/op-g
   - When specifying hostnames, loopback addresses are not added automatically. To allow loopback interfaces, add them to whitelist manually (e.g. `"localhost"`, `"127.0.0.1"`, etc.).
   - e.g. `etcd --host-whitelist example.com`, then the server will reject all HTTP requests whose Host field is not `example.com` (also rejects requests to `"localhost"`).
 - Support [`etcd --cors`](https://github.com/coreos/etcd/pull/9490) in v3 HTTP requests (gRPC gateway).
-- Support [TLS cipher suite lists](TODO).
 - Support [`ttl` field for `etcd` Authentication JWT token](https://github.com/coreos/etcd/pull/8302).
   - e.g. `etcd --auth-token jwt,pub-key=<pub key path>,priv-key=<priv key path>,sign-method=<sign method>,ttl=5m`.
 - Allow empty token provider in [`etcdserver.ServerConfig.AuthToken`](https://github.com/coreos/etcd/pull/9369).
@@ -207,6 +212,11 @@ See [security doc](https://github.com/coreos/etcd/blob/master/Documentation/op-g
   - If not given, etcd queries `_etcd-server-ssl._tcp.[YOUR_HOST]` and `_etcd-server._tcp.[YOUR_HOST]`.
   - If `--discovery-srv-name="foo"`, then query `_etcd-server-ssl-foo._tcp.[YOUR_HOST]` and `_etcd-server-foo._tcp.[YOUR_HOST]`.
   - Useful for operating multiple etcd clusters under the same domain.
+- Support TLS cipher suite whitelisting.
+  - To block [weak cipher suites](https://github.com/coreos/etcd/issues/8320).
+  - TLS handshake fails when client hello is requested with invalid cipher suites.
+  - Add [`etcd --cipher-suites`](https://github.com/coreos/etcd/pull/9801) flag.
+  - If empty, Go auto-populates the list.
 - Support [`etcd --cors`](https://github.com/coreos/etcd/pull/9490) in v3 HTTP requests (gRPC gateway).
 - Rename [`etcd --log-output` to `--log-outputs`](https://github.com/coreos/etcd/pull/9624) to support multiple log outputs.
   - **`etcd --log-output` will be deprecated in v3.5**.
@@ -271,6 +281,10 @@ Note: **v3.5 will deprecate `etcd --log-package-levels` flag for `capnslog`**; `
 
 ### Package `embed`
 
+- Add [`embed.Config.CipherSuites`](https://github.com/coreos/etcd/pull/9801) to specify a list of supported cipher suites for TLS handshake between client/server  and peers.
+  - If empty, Go auto-populates the list.
+  - Both `embed.Config.ClientTLSInfo.CipherSuites` and `embed.Config.CipherSuites` cannot be non-empty at the same time.
+  - If not empty, specify either `embed.Config.ClientTLSInfo.CipherSuites` or `embed.Config.CipherSuites`.
 - Add [`embed.Config.InitialElectionTickAdvance`](https://github.com/coreos/etcd/pull/9591) to enable/disable initial election tick fast-forward.
   - `embed.NewConfig()` would return `*embed.Config` with `InitialElectionTickAdvance` as true by default.
 - Define [`embed.CompactorModePeriodic`](https://godoc.org/github.com/coreos/etcd/embed#pkg-variables) for `compactor.ModePeriodic`.

Documentation/op-guide/security.md

@@ -38,6 +38,8 @@ The peer options work the same way as the client-to-server options:
 
 If either a client-to-server or peer certificate is supplied the key must also be set. All of these configuration options are also available through the environment variables, `ETCD_CA_FILE`, `ETCD_PEER_CA_FILE` and so on.
 
+`--cipher-suites`: Comma-separated list of supported TLS cipher suites between server/client and peers (empty will be auto-populated by Go). Available from v3.2.22+, v3.3.7+, and v3.4+.
+
 ## Example 1: Client-to-server transport security with HTTPS
 
 For this, have a CA certificate (`ca.crt`) and signed key pair (`server.crt`, `server.key`) ready.
@@ -122,6 +124,49 @@ And also the response from the server:
 }
 ```
 
+Specify cipher suites to block [weak TLS cipher suites](https://github.com/coreos/etcd/issues/8320).
+
+TLS handshake would fail when client hello is requested with invalid cipher suites.
+
+For instance:
+
+```bash
+$ etcd \
+  --cert-file ./server.crt \
+  --key-file ./server.key \
+  --trusted-ca-file ./ca.crt \
+  --cipher-suites TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
+```
+
+Then, client requests must specify one of the cipher suites specified in the server:
+
+```bash
+# valid cipher suite
+$ curl \
+  --cacert ./ca.crt \
+  --cert ./server.crt \
+  --key ./server.key \
+  -L [CLIENT-URL]/metrics \
+  --ciphers ECDHE-RSA-AES128-GCM-SHA256
+
+# request succeeds
+etcd_server_version{server_version="3.2.22"} 1
+...
+```
+
+```bash
+# invalid cipher suite
+$ curl \
+  --cacert ./ca.crt \
+  --cert ./server.crt \
+  --key ./server.key \
+  -L [CLIENT-URL]/metrics \
+  --ciphers ECDHE-RSA-DES-CBC3-SHA
+
+# request fails with
+(35) error:14094410:SSL routines:ssl3_read_bytes:sslv3 alert handshake failure
+```
+
 ## Example 3: Transport security & client certificates in a cluster
 
 etcd supports the same model as above for **peer communication**, that means the communication between etcd members in a cluster.

embed/config.go

@@ -32,6 +32,7 @@ import (
 	"github.com/coreos/etcd/pkg/flags"
 	"github.com/coreos/etcd/pkg/netutil"
 	"github.com/coreos/etcd/pkg/srv"
+	"github.com/coreos/etcd/pkg/tlsutil"
 	"github.com/coreos/etcd/pkg/transport"
 	"github.com/coreos/etcd/pkg/types"
 
@@ -175,6 +176,11 @@ type Config struct {
 	PeerTLSInfo    transport.TLSInfo
 	PeerAutoTLS    bool
 
+	// CipherSuites is a list of supported TLS cipher suites between
+	// client/server and peers. If empty, Go auto-populates the list.
+	// Note that cipher suites are prioritized in the given order.
+	CipherSuites []string `json:"cipher-suites"`
+
 	ClusterState          string `json:"initial-cluster-state"`
 	DNSCluster            string `json:"discovery-srv"`
 	DNSClusterServiceName string `json:"discovery-srv-name"`
@@ -510,6 +516,24 @@ func (cfg *configYAML) configFromFile(path string) error {
 	return cfg.Validate()
 }
 
+func updateCipherSuites(tls *transport.TLSInfo, ss []string) error {
+	if len(tls.CipherSuites) > 0 && len(ss) > 0 {
+		return fmt.Errorf("TLSInfo.CipherSuites is already specified (given %v)", ss)
+	}
+	if len(ss) > 0 {
+		cs := make([]uint16, len(ss))
+		for i, s := range ss {
+			var ok bool
+			cs[i], ok = tlsutil.GetCipherSuite(s)
+			if !ok {
+				return fmt.Errorf("unexpected TLS cipher suite %q", s)
+			}
+		}
+		tls.CipherSuites = cs
+	}
+	return nil
+}
+
 // Validate ensures that '*embed.Config' fields are properly configured.
 func (cfg *Config) Validate() error {
 	if err := cfg.setupLogging(); err != nil {
@@ -703,39 +727,49 @@ func (cfg Config) defaultClientHost() bool {
 }
 
 func (cfg *Config) ClientSelfCert() (err error) {
-	if cfg.ClientAutoTLS && cfg.ClientTLSInfo.Empty() {
-		chosts := make([]string, len(cfg.LCUrls))
-		for i, u := range cfg.LCUrls {
-			chosts[i] = u.Host
-		}
-		cfg.ClientTLSInfo, err = transport.SelfCert(cfg.logger, filepath.Join(cfg.Dir, "fixtures", "client"), chosts)
-		return err
-	} else if cfg.ClientAutoTLS {
+	if !cfg.ClientAutoTLS {
+		return nil
+	}
+	if !cfg.ClientTLSInfo.Empty() {
 		if cfg.logger != nil {
 			cfg.logger.Warn("ignoring client auto TLS since certs given")
 		} else {
 			plog.Warningf("ignoring client auto TLS since certs given")
 		}
+		return nil
 	}
-	return nil
+	chosts := make([]string, len(cfg.LCUrls))
+	for i, u := range cfg.LCUrls {
+		chosts[i] = u.Host
+	}
+	cfg.ClientTLSInfo, err = transport.SelfCert(cfg.logger, filepath.Join(cfg.Dir, "fixtures", "client"), chosts)
+	if err != nil {
+		return err
+	}
+	return updateCipherSuites(&cfg.ClientTLSInfo, cfg.CipherSuites)
 }
 
 func (cfg *Config) PeerSelfCert() (err error) {
-	if cfg.PeerAutoTLS && cfg.PeerTLSInfo.Empty() {
-		phosts := make([]string, len(cfg.LPUrls))
-		for i, u := range cfg.LPUrls {
-			phosts[i] = u.Host
-		}
-		cfg.PeerTLSInfo, err = transport.SelfCert(cfg.logger, filepath.Join(cfg.Dir, "fixtures", "peer"), phosts)
-		return err
-	} else if cfg.PeerAutoTLS {
+	if !cfg.PeerAutoTLS {
+		return nil
+	}
+	if !cfg.PeerTLSInfo.Empty() {
 		if cfg.logger != nil {
 			cfg.logger.Warn("ignoring peer auto TLS since certs given")
 		} else {
 			plog.Warningf("ignoring peer auto TLS since certs given")
 		}
+		return nil
 	}
-	return nil
+	phosts := make([]string, len(cfg.LPUrls))
+	for i, u := range cfg.LPUrls {
+		phosts[i] = u.Host
+	}
+	cfg.PeerTLSInfo, err = transport.SelfCert(cfg.logger, filepath.Join(cfg.Dir, "fixtures", "peer"), phosts)
+	if err != nil {
+		return err
+	}
+	return updateCipherSuites(&cfg.PeerTLSInfo, cfg.CipherSuites)
 }
 
 // UpdateDefaultClusterFromName updates cluster advertise URLs with, if available, default host,

embed/etcd.go

@@ -375,6 +375,9 @@ func stopServers(ctx context.Context, ss *servers) {
 func (e *Etcd) Err() <-chan error { return e.errc }
 
 func configurePeerListeners(cfg *Config) (peers []*peerListener, err error) {
+	if err = updateCipherSuites(&cfg.PeerTLSInfo, cfg.CipherSuites); err != nil {
+		return nil, err
+	}
 	if err = cfg.PeerSelfCert(); err != nil {
 		if cfg.logger != nil {
 			cfg.logger.Fatal("failed to get peer self-signed certs", zap.Error(err))
@@ -384,7 +387,11 @@ func configurePeerListeners(cfg *Config) (peers []*peerListener, err error) {
 	}
 	if !cfg.PeerTLSInfo.Empty() {
 		if cfg.logger != nil {
-			cfg.logger.Info("starting with peer TLS", zap.String("tls-info", fmt.Sprintf("%+v", cfg.PeerTLSInfo)))
+			cfg.logger.Info(
+				"starting with peer TLS",
+				zap.String("tls-info", fmt.Sprintf("%+v", cfg.PeerTLSInfo)),
+				zap.Strings("cipher-suites", cfg.CipherSuites),
+			)
 		} else {
 			plog.Infof("peerTLS: %s", cfg.PeerTLSInfo)
 		}
@@ -505,6 +512,9 @@ func (e *Etcd) servePeers() (err error) {
 }
 
 func configureClientListeners(cfg *Config) (sctxs map[string]*serveCtx, err error) {
+	if err = updateCipherSuites(&cfg.ClientTLSInfo, cfg.CipherSuites); err != nil {
+		return nil, err
+	}
 	if err = cfg.ClientSelfCert(); err != nil {
 		if cfg.logger != nil {
 			cfg.logger.Fatal("failed to get client self-signed certs", zap.Error(err))
@@ -623,6 +633,7 @@ func (e *Etcd) serveClients() (err error) {
 			e.cfg.logger.Info(
 				"starting with client TLS",
 				zap.String("tls-info", fmt.Sprintf("%+v", e.cfg.ClientTLSInfo)),
+				zap.Strings("cipher-suites", e.cfg.CipherSuites),
 			)
 		} else {
 			plog.Infof("ClientTLS: %s", e.cfg.ClientTLSInfo)

etcdmain/config.go

@@ -208,6 +208,7 @@ func newConfig() *config {
 	fs.BoolVar(&cfg.ec.PeerAutoTLS, "peer-auto-tls", false, "Peer TLS using generated certificates")
 	fs.StringVar(&cfg.ec.PeerTLSInfo.CRLFile, "peer-crl-file", "", "Path to the peer certificate revocation list file.")
 	fs.StringVar(&cfg.ec.PeerTLSInfo.AllowedCN, "peer-cert-allowed-cn", "", "Allowed CN 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.Var(
 		flags.NewUniqueURLsWithExceptions("*", "*"),
@@ -309,6 +310,8 @@ func (cfg *config) configFromCmdLine() error {
 	cfg.ec.CORS = flags.UniqueURLsMapFromFlag(cfg.cf.flagSet, "cors")
 	cfg.ec.HostWhitelist = flags.UniqueStringsMapFromFlag(cfg.cf.flagSet, "host-whitelist")
 
+	cfg.ec.CipherSuites = flags.StringsFromFlag(cfg.cf.flagSet, "cipher-suites")
+
 	// TODO: remove this in v3.5
 	output := flags.UniqueStringsMapFromFlag(cfg.cf.flagSet, "log-output")
 	oss1 := make([]string, 0, len(output))

etcdmain/help.go

@@ -142,6 +142,8 @@ Security:
     Peer TLS using self-generated certificates if --peer-key-file and --peer-cert-file are not provided.
   --peer-crl-file ''
     Path to the peer certificate revocation list file.
+  --cipher-suites ''
+    Comma-separated list of supported TLS cipher suites between client/server and peers (empty will be auto-populated by Go).
   --cors '*'
     Comma-separated whitelist of origins for CORS, or cross-origin resource sharing, (empty or * means allow all).
   --host-whitelist '*'

integration/v3_tls_test.go

@@ -0,0 +1,71 @@
+// Copyright 2018 The etcd Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package integration
+
+import (
+	"context"
+	"crypto/tls"
+	"testing"
+	"time"
+
+	"github.com/coreos/etcd/clientv3"
+	"github.com/coreos/etcd/pkg/testutil"
+)
+
+func TestTLSClientCipherSuitesValid(t *testing.T)    { testTLSCipherSuites(t, true) }
+func TestTLSClientCipherSuitesMismatch(t *testing.T) { testTLSCipherSuites(t, false) }
+
+// testTLSCipherSuites ensures mismatching client-side cipher suite
+// fail TLS handshake with the server.
+func testTLSCipherSuites(t *testing.T, valid bool) {
+	defer testutil.AfterTest(t)
+
+	cipherSuites := []uint16{
+		tls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
+		tls.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
+		tls.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
+		tls.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
+		tls.TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,
+		tls.TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305,
+	}
+	srvTLS, cliTLS := testTLSInfo, testTLSInfo
+	if valid {
+		srvTLS.CipherSuites, cliTLS.CipherSuites = cipherSuites, cipherSuites
+	} else {
+		srvTLS.CipherSuites, cliTLS.CipherSuites = cipherSuites[:2], cipherSuites[2:]
+	}
+
+	clus := NewClusterV3(t, &ClusterConfig{Size: 1, ClientTLS: &srvTLS})
+	defer clus.Terminate(t)
+
+	cc, err := cliTLS.ClientConfig()
+	if err != nil {
+		t.Fatal(err)
+	}
+	cli, cerr := clientv3.New(clientv3.Config{
+		Endpoints:   []string{clus.Members[0].GRPCAddr()},
+		DialTimeout: time.Second,
+		TLS:         cc,
+	})
+	if cli != nil {
+		cli.Close()
+	}
+	if !valid && cerr != context.DeadlineExceeded {
+		t.Fatalf("expected %v with TLS handshake failure, got %v", context.DeadlineExceeded, cerr)
+	}
+	if valid && cerr != nil {
+		t.Fatalf("expected TLS handshake success, got %v", cerr)
+	}
+}

pkg/tlsutil/cipher_suites.go

@@ -0,0 +1,51 @@
+// Copyright 2018 The etcd Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tlsutil
+
+import "crypto/tls"
+
+// cipher suites implemented by Go
+// https://github.com/golang/go/blob/dev.boringcrypto.go1.10/src/crypto/tls/cipher_suites.go
+var cipherSuites = map[string]uint16{
+	"TLS_RSA_WITH_RC4_128_SHA":                tls.TLS_RSA_WITH_RC4_128_SHA,
+	"TLS_RSA_WITH_3DES_EDE_CBC_SHA":           tls.TLS_RSA_WITH_3DES_EDE_CBC_SHA,
+	"TLS_RSA_WITH_AES_128_CBC_SHA":            tls.TLS_RSA_WITH_AES_128_CBC_SHA,
+	"TLS_RSA_WITH_AES_256_CBC_SHA":            tls.TLS_RSA_WITH_AES_256_CBC_SHA,
+	"TLS_RSA_WITH_AES_128_CBC_SHA256":         tls.TLS_RSA_WITH_AES_128_CBC_SHA256,
+	"TLS_RSA_WITH_AES_128_GCM_SHA256":         tls.TLS_RSA_WITH_AES_128_GCM_SHA256,
+	"TLS_RSA_WITH_AES_256_GCM_SHA384":         tls.TLS_RSA_WITH_AES_256_GCM_SHA384,
+	"TLS_ECDHE_ECDSA_WITH_RC4_128_SHA":        tls.TLS_ECDHE_ECDSA_WITH_RC4_128_SHA,
+	"TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA":    tls.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA,
+	"TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA":    tls.TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA,
+	"TLS_ECDHE_RSA_WITH_RC4_128_SHA":          tls.TLS_ECDHE_RSA_WITH_RC4_128_SHA,
+	"TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA":     tls.TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA,
+	"TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA":      tls.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA,
+	"TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA":      tls.TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA,
+	"TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256": tls.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256,
+	"TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256":   tls.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256,
+	"TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256":   tls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
+	"TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256": tls.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
+	"TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384":   tls.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
+	"TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384": tls.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
+	"TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305":    tls.TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,
+	"TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305":  tls.TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305,
+}
+
+// GetCipherSuite returns the corresponding cipher suite,
+// and boolean value if it is supported.
+func GetCipherSuite(s string) (uint16, bool) {
+	v, ok := cipherSuites[s]
+	return v, ok
+}

pkg/tlsutil/cipher_suites_test.go

@@ -0,0 +1,42 @@
+// Copyright 2018 The etcd Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tlsutil
+
+import (
+	"go/importer"
+	"reflect"
+	"strings"
+	"testing"
+)
+
+func TestGetCipherSuites(t *testing.T) {
+	pkg, err := importer.For("source", nil).Import("crypto/tls")
+	if err != nil {
+		t.Fatal(err)
+	}
+	cm := make(map[string]uint16)
+	for _, s := range pkg.Scope().Names() {
+		if strings.HasPrefix(s, "TLS_RSA_") || strings.HasPrefix(s, "TLS_ECDHE_") {
+			v, ok := GetCipherSuite(s)
+			if !ok {
+				t.Fatalf("Go implements missing cipher suite %q (%v)", s, v)
+			}
+			cm[s] = v
+		}
+	}
+	if !reflect.DeepEqual(cm, cipherSuites) {
+		t.Fatalf("found unmatched cipher suites %v (Go) != %v", cm, cipherSuites)
+	}
+}

pkg/transport/listener.go

@@ -74,6 +74,11 @@ type TLSInfo struct {
 	// connection will be closed immediately afterwards.
 	HandshakeFailure func(*tls.Conn, error)
 
+	// CipherSuites is a list of supported cipher suites.
+	// If empty, Go auto-populates it by default.
+	// Note that cipher suites are prioritized in the given order.
+	CipherSuites []uint16
+
 	selfCert bool
 
 	// parseFunc exists to simplify testing. Typically, parseFunc
@@ -243,6 +248,10 @@ func (info TLSInfo) baseConfig() (*tls.Config, error) {
 		ServerName: info.ServerName,
 	}
 
+	if len(info.CipherSuites) > 0 {
+		cfg.CipherSuites = info.CipherSuites
+	}
+
 	if info.AllowedCN != "" {
 		cfg.VerifyPeerCertificate = func(rawCerts [][]byte, verifiedChains [][]*x509.Certificate) error {
 			for _, chains := range verifiedChains {

pkg/transport/transport_test.go

@@ -0,0 +1,73 @@
+// Copyright 2018 The etcd Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package transport
+
+import (
+	"crypto/tls"
+	"net/http"
+	"strings"
+	"testing"
+	"time"
+)
+
+// TestNewTransportTLSInvalidCipherSuites expects a client with invalid
+// cipher suites fail to handshake with the server.
+func TestNewTransportTLSInvalidCipherSuites(t *testing.T) {
+	tlsInfo, del, err := createSelfCert()
+	if err != nil {
+		t.Fatalf("unable to create cert: %v", err)
+	}
+	defer del()
+
+	cipherSuites := []uint16{
+		tls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
+		tls.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
+		tls.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
+		tls.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
+		tls.TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,
+		tls.TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305,
+	}
+
+	// make server and client have unmatched cipher suites
+	srvTLS, cliTLS := *tlsInfo, *tlsInfo
+	srvTLS.CipherSuites, cliTLS.CipherSuites = cipherSuites[:2], cipherSuites[2:]
+
+	ln, err := NewListener("127.0.0.1:0", "https", &srvTLS)
+	if err != nil {
+		t.Fatalf("unexpected NewListener error: %v", err)
+	}
+	defer ln.Close()
+
+	donec := make(chan struct{})
+	go func() {
+		ln.Accept()
+		donec <- struct{}{}
+	}()
+	go func() {
+		tr, err := NewTransport(cliTLS, 3*time.Second)
+		if err != nil {
+			t.Fatalf("unexpected NewTransport error: %v", err)
+		}
+		cli := &http.Client{Transport: tr}
+		_, gerr := cli.Get("https://" + ln.Addr().String())
+		if gerr == nil || !strings.Contains(gerr.Error(), "tls: handshake failure") {
+			t.Fatal("expected client TLS handshake error")
+		}
+		ln.Close()
+		donec <- struct{}{}
+	}()
+	<-donec
+	<-donec
+}

tests/e2e/cluster_test.go

@@ -117,6 +117,8 @@ type etcdProcessClusterConfig struct {
 	isClientAutoTLS       bool
 	isClientCRL           bool
 
+	cipherSuites []string
+
 	forceNewCluster     bool
 	initialToken        string
 	quotaBackendBytes   int64
@@ -307,6 +309,10 @@ func (cfg *etcdProcessClusterConfig) tlsArgs() (args []string) {
 		args = append(args, "--client-crl-file", crlPath, "--client-cert-auth")
 	}
 
+	if len(cfg.cipherSuites) > 0 {
+		args = append(args, "--cipher-suites", strings.Join(cfg.cipherSuites, ","))
+	}
+
 	return args
 }
 

tests/e2e/v2_curl_test.go

@@ -130,6 +130,8 @@ type cURLReq struct {
 	header   string
 
 	metricsURLScheme string
+
+	ciphers string
 }
 
 // cURLPrefixArgs builds the beginning of a curl command for a given key
@@ -168,6 +170,10 @@ func cURLPrefixArgs(clus *etcdProcessCluster, method string, req cURLReq) []stri
 		cmdArgs = append(cmdArgs, "-H", req.header)
 	}
 
+	if req.ciphers != "" {
+		cmdArgs = append(cmdArgs, "--ciphers", req.ciphers)
+	}
+
 	switch method {
 	case "POST", "PUT":
 		dt := req.value

tests/e2e/v3_curl_test.go

@@ -26,6 +26,7 @@ import (
 	"github.com/coreos/etcd/etcdserver/api/v3rpc/rpctypes"
 	pb "github.com/coreos/etcd/etcdserver/etcdserverpb"
 	"github.com/coreos/etcd/pkg/testutil"
+	"github.com/coreos/etcd/version"
 
 	"github.com/grpc-ecosystem/grpc-gateway/runtime"
 )
@@ -349,6 +350,48 @@ func testV3CurlResignMissiongLeaderKey(cx ctlCtx) {
 	}
 }
 
+func TestV3CurlCipherSuitesValid(t *testing.T)    { testV3CurlCipherSuites(t, true) }
+func TestV3CurlCipherSuitesMismatch(t *testing.T) { testV3CurlCipherSuites(t, false) }
+func testV3CurlCipherSuites(t *testing.T, valid bool) {
+	cc := configClientTLS
+	cc.clusterSize = 1
+	cc.cipherSuites = []string{
+		"TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256",
+		"TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384",
+		"TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256",
+		"TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384",
+		"TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305",
+		"TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305",
+	}
+	testFunc := cipherSuiteTestValid
+	if !valid {
+		testFunc = cipherSuiteTestMismatch
+	}
+	testCtl(t, testFunc, withCfg(cc))
+}
+
+func cipherSuiteTestValid(cx ctlCtx) {
+	if err := cURLGet(cx.epc, cURLReq{
+		endpoint:         "/metrics",
+		expected:         fmt.Sprintf(`etcd_server_version{server_version="%s"} 1`, version.Version),
+		metricsURLScheme: cx.cfg.metricsURLScheme,
+		ciphers:          "ECDHE-RSA-AES128-GCM-SHA256", // TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
+	}); err != nil {
+		cx.t.Fatalf("failed get with curl (%v)", err)
+	}
+}
+
+func cipherSuiteTestMismatch(cx ctlCtx) {
+	if err := cURLGet(cx.epc, cURLReq{
+		endpoint:         "/metrics",
+		expected:         "alert handshake failure",
+		metricsURLScheme: cx.cfg.metricsURLScheme,
+		ciphers:          "ECDHE-RSA-DES-CBC3-SHA", // TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA
+	}); err != nil {
+		cx.t.Fatalf("failed get with curl (%v)", err)
+	}
+}
+
 // to manually decode; JSON marshals integer fields with
 // string types, so can't unmarshal with epb.CampaignResponse
 type campaignResponse struct {