tls: enable the selection of more TLS settings

Signed-off-by: Julien Pivotto <[email protected]>

https/README.md

@@ -15,17 +15,47 @@ The config file should be written in YAML format, and is reloaded on each connec
 
 ```
 tls_config:
-  # Certificate and key files for server to use to authenticate to client
+  # Certificate and key files for server to use to authenticate to client.
   cert_file: <filename>
   key_file: <filename>
 
-  # Server policy for client authentication. Maps to ClientAuth Policies
+  # Server policy for client authentication. Maps to ClientAuth Policies.
   # For more detail on clientAuth options: [ClientAuthType](https://golang.org/pkg/crypto/tls/#ClientAuthType)
   [ client_auth_type: <string> | default = "NoClientCert" ]
 
-  # CA certificate for client certificate authentication to the server
+  # CA certificate for client certificate authentication to the server.
   [ client_ca_file: <filename> ]
 
+  # Minimum TLS version that is acceptable.
+  [ min_version: <string> | default = "TLS1.2" ]
+
+  # Maximum TLS version that is acceptable.
+  [ max_version: <string> | default = "TLS1.3" ]
+
+  # List of supported cipher suites for TLS versions up to TLS 1.2. If empty,
+  # Go default cipher suites are used. Available cipher suites are documented
+  # below.
+  [ cipher_suites:
+    - <string> ] ]
+
+  # Disable HTTP/2 support. This can not be toggled on the fly.
+  [ disable_http2: <bool> | default = false ]
+
+  # prefer_server_cipher_suites controls whether the server selects the
+  # client's most preferred ciphersuite, or the server's most preferred
+  # ciphersuite. If true then the server's preference, as expressed in
+  # the order of elements in CipherSuites, is used.
+  [ prefer_server_cipher_suites: <bool> | default = false ]
+
+  # session_tickets_disabled may be set to true to disable session ticket and
+  # PSK (resumption) support.
+  [ session_tickets_disabled: <bool> | default = false ]
+
+  # Elliptic curves that will be used in an ECDHE handshake, in preference
+  # order. Available supported groups are documented below.
+  [ supported_groups:
+    - <string> ] ]
+
 # List of usernames and hashed passwords that have full access to the web
 # server via basic authentication. If empty, no basic authentication is
 # required. Passwords are hashed with bcrypt.
@@ -49,3 +79,40 @@ hash. A higher cost will en up slowing down the authentication process.
 Depending on the machine, a cost of 10 will take about ~70ms where a cost of
 18 can take up to a few seconds. That hash will be computed on every
 password-protected request.
+
+
+## Available cipher suites
+
+List of available cipher suites for TLS up to 1.2 (we only permit
+ciphersuites marked by go as 'secure'):
+
+- TLS_RSA_WITH_3DES_EDE_CBC_SHA
+- TLS_RSA_WITH_AES_128_CBC_SHA
+- TLS_RSA_WITH_AES_256_CBC_SHA
+- TLS_RSA_WITH_AES_128_GCM_SHA256
+- TLS_RSA_WITH_AES_256_GCM_SHA384
+- TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA
+- TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA
+- TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA
+- TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA
+- TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA
+- TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256
+- TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384
+- TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
+- TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
+- TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256
+- TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256
+
+List of available cipher suites for TLS 1.3 (TLS 1.3 ciphersuites are not
+configurable):
+
+- TLS_AES_128_GCM_SHA256
+- TLS_AES_256_GCM_SHA384
+- TLS_CHACHA20_POLY1305_SHA256
+
+## Available supported groups
+
+- CurveP256
+- CurveP384
+- CurveP521
+- X25519

https/testdata/tls_config_noAuth_allCiphers.good.yml

@@ -0,0 +1,26 @@
+tls_config :
+  cert_file : "testdata/server.crt"
+  key_file : "testdata/server.key"
+  client_auth_type : "VerifyClientCertIfGiven"
+  client_ca_file : "testdata/tls-ca-chain.pem"
+  cipher_suites:
+  - TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256
+  - TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384
+  - TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
+  - TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
+  - TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256
+  - TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256
+  - TLS_AES_128_GCM_SHA256
+  - TLS_AES_256_GCM_SHA384
+  - TLS_CHACHA20_POLY1305_SHA256
+  - TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA
+  - TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA
+  - TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA
+  - TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA
+  - TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA
+  - TLS_RSA_WITH_3DES_EDE_CBC_SHA
+  - TLS_RSA_WITH_AES_128_CBC_SHA
+  - TLS_RSA_WITH_AES_256_CBC_SHA
+  - TLS_RSA_WITH_AES_128_GCM_SHA256
+  - TLS_RSA_WITH_AES_256_GCM_SHA384
+

https/testdata/tls_config_noAuth_allCurves.good.yml

@@ -0,0 +1,10 @@
+tls_config :
+  cert_file : "testdata/server.crt"
+  key_file : "testdata/server.key"
+  client_auth_type : "VerifyClientCertIfGiven"
+  client_ca_file : "testdata/tls-ca-chain.pem"
+  supported_groups:
+    - CurveP256
+    - CurveP384
+    - CurveP521
+    - X25519

https/testdata/tls_config_noAuth_inventedCiphers.bad.yml

@@ -0,0 +1,8 @@
+tls_config :
+  cert_file : "testdata/server.crt"
+  key_file : "testdata/server.key"
+  client_auth_type : "VerifyClientCertIfGiven"
+  client_ca_file : "testdata/tls-ca-chain.pem"
+  cipher_suites:
+  - TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA2048
+

https/testdata/tls_config_noAuth_inventedCurves.bad.yml

@@ -0,0 +1,7 @@
+tls_config :
+  cert_file : "testdata/server.crt"
+  key_file : "testdata/server.key"
+  client_auth_type : "VerifyClientCertIfGiven"
+  client_ca_file : "testdata/tls-ca-chain.pem"
+  supported_groups:
+    - CurveP257

https/testdata/tls_config_noAuth_noHTTP2.good.yml

@@ -0,0 +1,9 @@
+tls_config :
+  cert_file : "testdata/server.crt"
+  key_file : "testdata/server.key"
+  client_auth_type : "VerifyClientCertIfGiven"
+  client_ca_file : "testdata/tls-ca-chain.pem"
+  cipher_suites:
+    - TLS_RSA_WITH_AES_128_CBC_SHA
+  max_version: TLS1.2
+  disable_http2: true

https/testdata/tls_config_noAuth_noHTTP2Cipher.bad.yml

@@ -0,0 +1,8 @@
+tls_config :
+  cert_file : "testdata/server.crt"
+  key_file : "testdata/server.key"
+  client_auth_type : "VerifyClientCertIfGiven"
+  client_ca_file : "testdata/tls-ca-chain.pem"
+  cipher_suites:
+    - TLS_RSA_WITH_AES_128_CBC_SHA
+  max_version: TLS1.2

https/testdata/tls_config_noAuth_someCiphers.good.yml

@@ -0,0 +1,11 @@
+tls_config :
+  cert_file : "testdata/server.crt"
+  key_file : "testdata/server.key"
+  client_auth_type : "VerifyClientCertIfGiven"
+  client_ca_file : "testdata/tls-ca-chain.pem"
+  cipher_suites:
+  - TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384
+  - TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
+  - TLS_CHACHA20_POLY1305_SHA256
+  min_version: TLS1.2
+  max_version: TLS1.2

https/testdata/tls_config_noAuth_someCurves.good.yml

@@ -0,0 +1,8 @@
+tls_config :
+  cert_file : "testdata/server.crt"
+  key_file : "testdata/server.key"
+  client_auth_type : "VerifyClientCertIfGiven"
+  client_ca_file : "testdata/tls-ca-chain.pem"
+  min_version: TLS1.3
+  supported_groups:
+  - CurveP521

https/tls_ciphers.go

@@ -0,0 +1,43 @@
+// Copyright 2020 The Prometheus 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.
+
+// +build go1.14
+
+package https
+
+import (
+	"crypto/tls"
+	"strings"
+
+	"github.com/pkg/errors"
+)
+
+func (c *cipher) UnmarshalYAML(unmarshal func(interface{}) error) error {
+	var s string
+	err := unmarshal((*string)(&s))
+	if err != nil {
+		return err
+	}
+	s = strings.ToUpper(s)
+	for _, cs := range tls.CipherSuites() {
+		if cs.Name == s {
+			*c = (cipher)(cs.ID)
+			return nil
+		}
+	}
+	return errors.New("unknown cipher: " + s)
+}
+
+func (c cipher) MarshalYAML() (interface{}, error) {
+	return tls.CipherSuiteName((uint16)(c)), nil
+}

https/tls_config.go

@@ -17,8 +17,10 @@ package https
 import (
 	"crypto/tls"
 	"crypto/x509"
+	"fmt"
 	"io/ioutil"
 	"net/http"
+	"strings"
 
 	"github.com/go-kit/kit/log"
 	"github.com/go-kit/kit/log/level"
@@ -37,10 +39,17 @@ type Config struct {
 }
 
 type TLSStruct struct {
-	TLSCertPath string `yaml:"cert_file"`
-	TLSKeyPath  string `yaml:"key_file"`
-	ClientAuth  string `yaml:"client_auth_type"`
-	ClientCAs   string `yaml:"client_ca_file"`
+	TLSCertPath              string   `yaml:"cert_file"`
+	TLSKeyPath               string   `yaml:"key_file"`
+	ClientAuth               string   `yaml:"client_auth_type"`
+	ClientCAs                string   `yaml:"client_ca_file"`
+	CipherSuites             []cipher `yaml:"cipher_suites"`
+	CurveIDs                 []curve  `yaml:"supported_groups"`
+	MinVersion               string   `yaml:"min_version"`
+	MaxVersion               string   `yaml:"max_version"`
+	PreferServerCipherSuites bool     `yaml:"prefer_server_cipher_suites"`
+	DisableHTTP2             bool     `yaml:"disable_http2"`
+	SessionTicketsDisabled   bool     `yaml:"session_tickets_disabled"`
 }
 
 func getConfig(configPath string) (*Config, error) {
@@ -73,16 +82,32 @@ func ConfigToTLSConfig(c *TLSStruct) (*tls.Config, error) {
 	if c.TLSKeyPath == "" {
 		return nil, errors.New("missing key_file")
 	}
-	cfg := &tls.Config{
-		MinVersion: tls.VersionTLS12,
-	}
+
 	loadCert := func() (*tls.Certificate, error) {
 		cert, err := tls.LoadX509KeyPair(c.TLSCertPath, c.TLSKeyPath)
 		if err != nil {
 			return nil, errors.Wrap(err, "failed to load X509KeyPair")
 		}
 		return &cert, nil
 	}
+
+	minVersion, err := pickMinVersion(c.MinVersion)
+	if err != nil {
+		return nil, err
+	}
+
+	maxVersion, err := pickMaxVersion(c.MaxVersion)
+	if err != nil {
+		return nil, err
+	}
+
+	cfg := &tls.Config{
+		MinVersion:               minVersion,
+		MaxVersion:               maxVersion,
+		PreferServerCipherSuites: c.PreferServerCipherSuites,
+		SessionTicketsDisabled:   c.SessionTicketsDisabled,
+	}
+
 	// Confirm that certificate and key paths are valid.
 	if _, err := loadCert(); err != nil {
 		return nil, err
@@ -91,6 +116,22 @@ func ConfigToTLSConfig(c *TLSStruct) (*tls.Config, error) {
 		return loadCert()
 	}
 
+	var cf []uint16
+	for _, c := range c.CipherSuites {
+		cf = append(cf, (uint16)(c))
+	}
+	if len(cf) > 0 {
+		cfg.CipherSuites = cf
+	}
+
+	var sg []tls.CurveID
+	for _, c := range c.CurveIDs {
+		sg = append(sg, (tls.CurveID)(c))
+	}
+	if len(sg) > 0 {
+		cfg.CurvePreferences = sg
+	}
+
 	if c.ClientCAs != "" {
 		clientCAPool := x509.NewCertPool()
 		clientCAFile, err := ioutil.ReadFile(c.ClientCAs)
@@ -145,11 +186,20 @@ func Listen(server *http.Server, tlsConfigPath string, logger log.Logger) error
 		handler:       handler,
 	}
 
-	config, err := getTLSConfig(tlsConfigPath)
+	c, err := getConfig(tlsConfigPath)
+	if err != nil {
+		return err
+	}
+	config, err := ConfigToTLSConfig(&c.TLSConfig)
 	switch err {
 	case nil:
+		withHTTP2 := "with HTTP/2 support"
+		if c.TLSConfig.DisableHTTP2 {
+			withHTTP2 = "without HTTP/2 support"
+			server.TLSNextProto = make(map[string]func(*http.Server, *tls.Conn, http.Handler))
+		}
 		// Valid TLS config.
-		level.Info(logger).Log("msg", "TLS is enabled and it cannot be disabled on the fly.")
+		level.Info(logger).Log("msg", "TLS "+withHTTP2+" is enabled and it cannot be disabled on the fly.")
 	case errNoTLSConfig:
 		// No TLS config, back to plain HTTP.
 		level.Info(logger).Log("msg", "TLS is disabled and it cannot be enabled on the fly.")
@@ -168,3 +218,44 @@ func Listen(server *http.Server, tlsConfigPath string, logger log.Logger) error
 	}
 	return server.ListenAndServeTLS("", "")
 }
+
+// For go1.14, unmarshalling is done properly in tls_ciphers.go.
+type cipher uint16
+
+type curve tls.CurveID
+
+func (c *curve) UnmarshalYAML(unmarshal func(interface{}) error) error {
+	var s string
+	err := unmarshal((*string)(&s))
+	if err != nil {
+		return err
+	}
+	switch strings.ToUpper(s) {
+	case "CURVEP256":
+		*c = (curve)(tls.CurveP256)
+	case "CURVEP384":
+		*c = (curve)(tls.CurveP384)
+	case "CURVEP521":
+		*c = (curve)(tls.CurveP521)
+	case "X25519":
+		*c = (curve)(tls.X25519)
+	default:
+		return errors.New("unknown supported group: " + s)
+	}
+	return nil
+}
+
+func (c curve) MarshalYAML() (interface{}, error) {
+	switch c {
+	case (curve)(tls.CurveP256):
+		return "CurveP256", nil
+	case (curve)(tls.CurveP384):
+		return "CurveP384", nil
+	case (curve)(tls.CurveP521):
+		return "CurveP521", nil
+	case (curve)(tls.X25519):
+		return "X25519", nil
+	default:
+		return fmt.Sprintf("%v", c), nil
+	}
+}