Allow PreferServerCipherSuites as a TLS Option

docs/content/https/tls.md

@@ -347,6 +347,39 @@ spec:
   sniStrict: true
 ```
 
+### Prefer Server Cipher Suites
+
+This option allows the server to choose its most preferred cipher suite instead of the client's.
+Please note that this is enabled automatically when `minVersion` or `maxVersion` are set.
+
+```toml tab="File (TOML)"
+# Dynamic configuration
+
+[tls.options]
+  [tls.options.default]
+    preferServerCipherSuites = true
+```
+
+```yaml tab="File (YAML)"
+# Dynamic configuration
+
+tls:
+  options:
+    default:
+      preferServerCipherSuites: true
+```
+
+```yaml tab="Kubernetes"
+apiVersion: traefik.containo.us/v1alpha1
+kind: TLSOption
+metadata:
+  name: default
+  namespace: default
+
+spec:
+  preferServerCipherSuites: true
+```
+
 ### Client Authentication (mTLS)
 
 Traefik supports mutual authentication, through the `clientAuth` section.

docs/content/reference/dynamic-configuration/file.toml

@@ -357,6 +357,7 @@
       cipherSuites = ["foobar", "foobar"]
       curvePreferences = ["foobar", "foobar"]
       sniStrict = true
+      preferServerCipherSuites = true
       [tls.options.Options0.clientAuth]
         caFiles = ["foobar", "foobar"]
         clientAuthType = "foobar"
@@ -366,6 +367,7 @@
       cipherSuites = ["foobar", "foobar"]
       curvePreferences = ["foobar", "foobar"]
       sniStrict = true
+      preferServerCipherSuites = true
       [tls.options.Options1.clientAuth]
         caFiles = ["foobar", "foobar"]
         clientAuthType = "foobar"

docs/content/reference/dynamic-configuration/file.yaml

@@ -397,6 +397,7 @@ tls:
         - foobar
         clientAuthType: foobar
       sniStrict: true
+      preferServerCipherSuites: true
     Options1:
       minVersion: foobar
       maxVersion: foobar
@@ -412,6 +413,7 @@ tls:
         - foobar
         clientAuthType: foobar
       sniStrict: true
+      preferServerCipherSuites: true
   stores:
     Store0:
       defaultCertificate:

docs/content/reference/dynamic-configuration/kubernetes-crd-resource.yml

@@ -155,3 +155,27 @@ spec:
     options:
       name: myTLSOption
       namespace: default
+
+---
+apiVersion: traefik.containo.us/v1alpha1
+kind: TLSOption
+metadata:
+  name: tlsoption
+  namespace: default
+
+spec:
+  minVersion: foobar
+  maxVersion: foobar
+  cipherSuites:
+    - foobar
+    - foobar
+  curvePreferences:
+    - foobar
+    - foobar
+  clientAuth:
+    caFiles:
+      - foobar
+      - foobar
+    clientAuthType: foobar
+  sniStrict: true
+  preferServerCipherSuites: true

docs/content/reference/dynamic-configuration/kubernetes-crd.yml

@@ -230,3 +230,27 @@ spec:
     options:
       name: myTLSOption
       namespace: default
+
+---
+apiVersion: traefik.containo.us/v1alpha1
+kind: TLSOption
+metadata:
+  name: tlsoption
+  namespace: default
+
+spec:
+  minVersion: foobar
+  maxVersion: foobar
+  cipherSuites:
+    - foobar
+    - foobar
+  curvePreferences:
+    - foobar
+    - foobar
+  clientAuth:
+    caFiles:
+      - foobar
+      - foobar
+    clientAuthType: foobar
+  sniStrict: true
+  preferServerCipherSuites: true

docs/content/reference/dynamic-configuration/kv-ref.md

@@ -233,6 +233,7 @@
 | `traefik/tls/options/Options0/curvePreferences/1` | `foobar` |
 | `traefik/tls/options/Options0/maxVersion` | `foobar` |
 | `traefik/tls/options/Options0/minVersion` | `foobar` |
+| `traefik/tls/options/Options0/preferServerCipherSuites` | `true` |
 | `traefik/tls/options/Options0/sniStrict` | `true` |
 | `traefik/tls/options/Options1/cipherSuites/0` | `foobar` |
 | `traefik/tls/options/Options1/cipherSuites/1` | `foobar` |
@@ -243,6 +244,7 @@
 | `traefik/tls/options/Options1/curvePreferences/1` | `foobar` |
 | `traefik/tls/options/Options1/maxVersion` | `foobar` |
 | `traefik/tls/options/Options1/minVersion` | `foobar` |
+| `traefik/tls/options/Options1/preferServerCipherSuites` | `true` |
 | `traefik/tls/options/Options1/sniStrict` | `true` |
 | `traefik/tls/stores/Store0/defaultCertificate/certFile` | `foobar` |
 | `traefik/tls/stores/Store0/defaultCertificate/keyFile` | `foobar` |

pkg/provider/kubernetes/crd/fixtures/tcp/with_tls_options.yml

@@ -35,7 +35,7 @@ spec:
       - secretCA1
       - secretCA2
     clientAuthType: VerifyClientCertIfGiven
-
+  preferServerCipherSuites: true
 ---
 apiVersion: v1
 kind: Secret

pkg/provider/kubernetes/crd/fixtures/with_tls_options.yml

@@ -35,6 +35,7 @@ spec:
       - secretCA1
       - secretCA2
     clientAuthType: VerifyClientCertIfGiven
+  preferServerCipherSuites: true
 
 ---
 apiVersion: traefik.containo.us/v1alpha1

pkg/provider/kubernetes/crd/kubernetes.go

@@ -502,6 +502,7 @@ func buildTLSOptions(ctx context.Context, client Client) map[string]tls.Options
 				ClientAuthType: tlsOption.Spec.ClientAuth.ClientAuthType,
 			},
 			SniStrict:                tlsOption.Spec.SniStrict,
+			PreferServerCipherSuites: tlsOption.Spec.PreferServerCipherSuites,
 		}
 	}
 	return tlsOptions

pkg/provider/kubernetes/crd/kubernetes_test.go

@@ -424,6 +424,7 @@ func TestLoadIngressRouteTCPs(t *testing.T) {
 								ClientAuthType: "VerifyClientCertIfGiven",
 							},
 							SniStrict:                true,
+							PreferServerCipherSuites: true,
 						},
 					},
 				},
@@ -1897,6 +1898,7 @@ func TestLoadIngressRoutes(t *testing.T) {
 								ClientAuthType: "VerifyClientCertIfGiven",
 							},
 							SniStrict:                true,
+							PreferServerCipherSuites: true,
 						},
 					},
 				},

pkg/provider/kubernetes/crd/traefik/v1alpha1/tlsoption.go

@@ -25,6 +25,7 @@ type TLSOptionSpec struct {
 	CurvePreferences         []string   `json:"curvePreferences,omitempty"`
 	ClientAuth               ClientAuth `json:"clientAuth,omitempty"`
 	SniStrict                bool       `json:"sniStrict,omitempty"`
+	PreferServerCipherSuites bool       `json:"preferServerCipherSuites,omitempty"`
 }
 
 // +k8s:deepcopy-gen=true

pkg/tls/tls.go

@@ -22,6 +22,7 @@ type Options struct {
 	CurvePreferences         []string   `json:"curvePreferences,omitempty" toml:"curvePreferences,omitempty" yaml:"curvePreferences,omitempty"`
 	ClientAuth               ClientAuth `json:"clientAuth,omitempty" toml:"clientAuth,omitempty" yaml:"clientAuth,omitempty"`
 	SniStrict                bool       `json:"sniStrict,omitempty" toml:"sniStrict,omitempty" yaml:"sniStrict,omitempty" export:"true"`
+	PreferServerCipherSuites bool       `json:"preferServerCipherSuites,omitempty" toml:"preferServerCipherSuites,omitempty" yaml:"preferServerCipherSuites,omitempty" export:"true"`
 }
 
 // +k8s:deepcopy-gen=true

pkg/tls/tlsmanager.go

@@ -219,6 +219,9 @@ func buildTLSConfig(tlsOption Options) (*tls.Config, error) {
 		}
 	}
 
+	// Set PreferServerCipherSuites.
+	conf.PreferServerCipherSuites = tlsOption.PreferServerCipherSuites
+
 	// Set the minimum TLS version if set in the config
 	if minConst, exists := MinVersion[tlsOption.MinVersion]; exists {
 		conf.PreferServerCipherSuites = true