Add option to specify the tls-min-version for the server

docs/docs/configuration/alpha_config.md

@@ -349,18 +349,20 @@ Server represents the configuration for an HTTP(S) server
 | ----- | ---- | ----------- |
 | `BindAddress` | _string_ | BindAddress is the address on which to serve traffic.<br/>Leave blank or set to "-" to disable. |
 | `SecureBindAddress` | _string_ | SecureBindAddress is the address on which to serve secure traffic.<br/>Leave blank or set to "-" to disable. |
-| `TLS` | _[TLS](#tls)_ | TLS contains the information for loading the certificate and key for the<br/>secure traffic. |
+| `TLS` | _[TLS](#tls)_ | TLS contains the information for loading the certificate and key for the<br/>secure traffic and further configuration for the TLS server. |
 
 ### TLS
 
 (**Appears on:** [Server](#server))
 
-TLS contains the information for loading a TLS certifcate and key.
+TLS contains the information for loading a TLS certificate and key
+as well as an optional minimal TLS version that is acceptable.
 
 | Field | Type | Description |
 | ----- | ---- | ----------- |
 | `Key` | _[SecretSource](#secretsource)_ | Key is the TLS key data to use.<br/>Typically this will come from a file. |
 | `Cert` | _[SecretSource](#secretsource)_ | Cert is the TLS certificate data to use.<br/>Typically this will come from a file. |
+| `MinVersion` | _string_ | MinVersion is the minimal TLS version that is acceptable.<br/>E.g. Set to "TLS1.3" to select TLS version 1.3 |
 
 ### Upstream
 

docs/docs/configuration/overview.md

@@ -191,6 +191,7 @@ An example [oauth2-proxy.cfg](https://github.com/oauth2-proxy/oauth2-proxy/blob/
 | `--standard-logging-format` | string | Template for standard log lines | see [Logging Configuration](#logging-configuration) |
 | `--tls-cert-file` | string | path to certificate file | |
 | `--tls-key-file` | string | path to private key file | |
+| `--tls-min-version` | string | minimum TLS version that is acceptable, either `"TLS1.2"` or `"TLS1.3"` | `"TLS1.2"` |
 | `--upstream` | string \| list | the http url(s) of the upstream endpoint, file:// paths for static files or `static://<status_code>` for static response. Routing is based on the path | |
 | `--allowed-group` | string \| list | restrict logins to members of this group (may be given multiple times) | |
 | `--allowed-role` | string \| list | restrict logins to users with this role (may be given multiple times). Only works with the keycloak-oidc provider. | |

docs/docs/configuration/tls.md

@@ -3,7 +3,11 @@ id: tls
 title: TLS Configuration
 ---
 
-There are two recommended configurations.
+There are two recommended configurations:
+- [At OAuth2 Proxy](#terminate-tls-at-oauth2-proxy)
+- [At Reverse Proxy](#terminate-tls-at-reverse-proxy-eg-nginx)
+
+### Terminate TLS at OAuth2 Proxy
 
 1.  Configure SSL Termination with OAuth2 Proxy by providing a `--tls-cert-file=/path/to/cert.pem` and `--tls-key-file=/path/to/cert.key`.
 
@@ -22,7 +26,18 @@ There are two recommended configurations.
         --client-secret=...
     ```
 
-2.  Configure SSL Termination with [Nginx](http://nginx.org/) (example config below), Amazon ELB, Google Cloud Platform Load Balancing, or ....
+2.  With this configuration approach the customization of the TLS settings is limited.
+
+    The minimal acceptable TLS version can be set with `--tls-min-version=TLS1.3`. 
+    The defaults set `TLS1.2` as the minimal version. 
+    Regardless of the minimum version configured, `TLS1.3` is currently always used as the maximal version.
+
+    The server side cipher suites are the defaults from [`crypto/tls`](https://pkg.go.dev/crypto/tls#CipherSuites) of 
+    the currently used `go` version for building `oauth2-proxy`.
+
+### Terminate TLS at Reverse Proxy, e.g. Nginx
+
+1.  Configure SSL Termination with [Nginx](http://nginx.org/) (example config below), Amazon ELB, Google Cloud Platform Load Balancing, or ...
 
     Because `oauth2-proxy` listens on `127.0.0.1:4180` by default, to listen on all interfaces (needed when using an
     external load balancer like Amazon ELB or Google Platform Load Balancing) use `--http-address="0.0.0.0:4180"` or
@@ -55,7 +70,7 @@ There are two recommended configurations.
     }
     ```
 
-    The command line to run `oauth2-proxy` in this configuration would look like this:
+2.  The command line to run `oauth2-proxy` in this configuration would look like this:
 
     ```bash
     ./oauth2-proxy \

pkg/apis/options/legacy_options.go

@@ -448,6 +448,7 @@ type LegacyServer struct {
 	HTTPSAddress         string `flag:"https-address" cfg:"https_address"`
 	TLSCertFile          string `flag:"tls-cert-file" cfg:"tls_cert_file"`
 	TLSKeyFile           string `flag:"tls-key-file" cfg:"tls_key_file"`
+	TLSMinVersion        string `flag:"tls-min-version" cfg:"tls_min_version"`
 }
 
 func legacyServerFlagset() *pflag.FlagSet {
@@ -461,6 +462,7 @@ func legacyServerFlagset() *pflag.FlagSet {
 	flagSet.String("https-address", ":443", "<addr>:<port> to listen on for HTTPS clients")
 	flagSet.String("tls-cert-file", "", "path to certificate file")
 	flagSet.String("tls-key-file", "", "path to private key file")
+	flagSet.String("tls-min-version", "", "minimal TLS version for HTTPS clients (either \"TLS1.2\" or \"TLS1.3\")")
 
 	return flagSet
 }
@@ -582,6 +584,7 @@ func (l LegacyServer) convert() (Server, Server) {
 			Cert: &SecretSource{
 				FromFile: l.TLSCertFile,
 			},
+			MinVersion: l.TLSMinVersion,
 		}
 		// Preserve backwards compatibility, only run one server
 		appServer.BindAddress = ""

pkg/apis/options/legacy_options_test.go

@@ -785,6 +785,7 @@ var _ = Describe("Legacy Options", func() {
 			secureMetricsAddr   = ":9443"
 			crtPath             = "tls.crt"
 			keyPath             = "tls.key"
+			minVersion          = "TLS1.3"
 		)
 
 		var tlsConfig = &TLS{
@@ -796,6 +797,12 @@ var _ = Describe("Legacy Options", func() {
 			},
 		}
 
+		var tlsConfigMinVersion = &TLS{
+			Cert:       tlsConfig.Cert,
+			Key:        tlsConfig.Key,
+			MinVersion: minVersion,
+		}
+
 		DescribeTable("should convert to app and metrics servers",
 			func(in legacyServersTableInput) {
 				appServer, metricsServer := in.legacyServer.convert()
@@ -823,6 +830,19 @@ var _ = Describe("Legacy Options", func() {
 					TLS:               tlsConfig,
 				},
 			}),
+			Entry("with TLS options specified with MinVersion", legacyServersTableInput{
+				legacyServer: LegacyServer{
+					HTTPAddress:   insecureAddr,
+					HTTPSAddress:  secureAddr,
+					TLSKeyFile:    keyPath,
+					TLSCertFile:   crtPath,
+					TLSMinVersion: minVersion,
+				},
+				expectedAppServer: Server{
+					SecureBindAddress: secureAddr,
+					TLS:               tlsConfigMinVersion,
+				},
+			}),
 			Entry("with metrics HTTP and HTTPS addresses", legacyServersTableInput{
 				legacyServer: LegacyServer{
 					HTTPAddress:          insecureAddr,

pkg/apis/options/server.go

@@ -11,11 +11,12 @@ type Server struct {
 	SecureBindAddress string
 
 	// TLS contains the information for loading the certificate and key for the
-	// secure traffic.
+	// secure traffic and further configuration for the TLS server.
 	TLS *TLS
 }
 
-// TLS contains the information for loading a TLS certifcate and key.
+// TLS contains the information for loading a TLS certificate and key
+// as well as an optional minimal TLS version that is acceptable.
 type TLS struct {
 	// Key is the TLS key data to use.
 	// Typically this will come from a file.
@@ -24,4 +25,8 @@ type TLS struct {
 	// Cert is the TLS certificate data to use.
 	// Typically this will come from a file.
 	Cert *SecretSource
+
+	// MinVersion is the minimal TLS version that is acceptable.
+	// E.g. Set to "TLS1.3" to select TLS version 1.3
+	MinVersion string
 }

pkg/http/server.go

@@ -91,7 +91,7 @@ func (s *server) setupTLSListener(opts Opts) error {
 	}
 
 	config := &tls.Config{
-		MinVersion: tls.VersionTLS12,
+		MinVersion: tls.VersionTLS12, // default, override below
 		MaxVersion: tls.VersionTLS13,
 		NextProtos: []string{"http/1.1"},
 	}
@@ -104,6 +104,17 @@ func (s *server) setupTLSListener(opts Opts) error {
 	}
 	config.Certificates = []tls.Certificate{cert}
 
+	if len(opts.TLS.MinVersion) > 0 {
+		switch opts.TLS.MinVersion {
+		case "TLS1.2":
+			config.MinVersion = tls.VersionTLS12
+		case "TLS1.3":
+			config.MinVersion = tls.VersionTLS13
+		default:
+			return errors.New("unknown TLS MinVersion config provided")
+		}
+	}
+
 	listenAddr := getListenAddress(opts.SecureBindAddress)
 
 	listener, err := net.Listen("tcp", listenAddr)

pkg/http/server_test.go

@@ -233,6 +233,34 @@ var _ = Describe("Server", func() {
 				expectHTTPListener: false,
 				expectTLSListener:  true,
 			}),
+			Entry("with a valid https bind address, and valid TLS config with MinVersion", &newServerTableInput{
+				opts: Opts{
+					Handler:           handler,
+					SecureBindAddress: "127.0.0.1:0",
+					TLS: &options.TLS{
+						Key:        &keyDataSource,
+						Cert:       &certDataSource,
+						MinVersion: "TLS1.3",
+					},
+				},
+				expectedErr:        nil,
+				expectHTTPListener: false,
+				expectTLSListener:  true,
+			}),
+			Entry("with a valid https bind address, and invalid TLS config with unknown MinVersion", &newServerTableInput{
+				opts: Opts{
+					Handler:           handler,
+					SecureBindAddress: "127.0.0.1:0",
+					TLS: &options.TLS{
+						Key:        &keyDataSource,
+						Cert:       &certDataSource,
+						MinVersion: "TLS1.42",
+					},
+				},
+				expectedErr:        errors.New("error setting up TLS listener: unknown TLS MinVersion config provided"),
+				expectHTTPListener: false,
+				expectTLSListener:  true,
+			}),
 		)
 	})