Allow users to set min and max TLS versions (#3591)

* Allow users to set min and max TLS versions

Users want to be to choose the min and max versions they want to allow. Introduce two new settings to make the version range configurable.

* Make linter happy

config/configtls/README.md

@@ -34,6 +34,12 @@ won't use TLS at all.
 - `insecure_skip_verify` (default = false): whether to skip verifying the
   certificate or not.
 
+Minimum and maximum TLS version can be set:
+
+- `min_version` (default = "1.0"): Minimum acceptable TLS version.
+
+- `max_version` (default = "1.3"): Maximum acceptable TLS version.
+
 How TLS/mTLS is configured depends on whether configuring the client or server.
 See below for examples.
 
@@ -63,6 +69,8 @@ exporters:
     ca_file: server.crt
     cert_file: client.crt
     key_file: client.key
+    min_version: "1.1"
+    max_version: "1.2"
   otlp/insecure:
     endpoint: myserver.local:55690
     insecure: true

config/configtls/configtls.go

@@ -30,10 +30,20 @@ type TLSSetting struct {
 	// For a server this verifies client certificates. If empty uses system root CA.
 	// (optional)
 	CAFile string `mapstructure:"ca_file"`
+
 	// Path to the TLS cert to use for TLS required connections. (optional)
 	CertFile string `mapstructure:"cert_file"`
+
 	// Path to the TLS key to use for TLS required connections. (optional)
 	KeyFile string `mapstructure:"key_file"`
+
+	// MinVersion sets the minimum TLS version that is acceptable.
+	// If not set, TLS 1.0 is used. (optional)
+	MinVersion string `mapstructure:"min_version"`
+
+	// MaxVersion sets the maximum TLS version that is acceptable.
+	// If not set, TLS 1.3 is used. (optional)
+	MaxVersion string `mapstructure:"max_version"`
 }
 
 // TLSClientSetting contains TLS configurations that are specific to client
@@ -96,16 +106,28 @@ func (c TLSSetting) loadTLSConfig() (*tls.Config, error) {
 
 	var certificates []tls.Certificate
 	if c.CertFile != "" && c.KeyFile != "" {
-		tlsCert, err := tls.LoadX509KeyPair(filepath.Clean(c.CertFile), filepath.Clean(c.KeyFile))
+		var tlsCert tls.Certificate
+		tlsCert, err = tls.LoadX509KeyPair(filepath.Clean(c.CertFile), filepath.Clean(c.KeyFile))
 		if err != nil {
 			return nil, fmt.Errorf("failed to load TLS cert and key: %w", err)
 		}
 		certificates = append(certificates, tlsCert)
 	}
 
+	minTLS, err := convertVersion(c.MinVersion)
+	if err != nil {
+		return nil, fmt.Errorf("invalid TLS min_version: %w", err)
+	}
+	maxTLS, err := convertVersion(c.MaxVersion)
+	if err != nil {
+		return nil, fmt.Errorf("invalid TLS max_version: %w", err)
+	}
+
 	return &tls.Config{
 		RootCAs:      certPool,
 		Certificates: certificates,
+		MinVersion:   minTLS,
+		MaxVersion:   maxTLS,
 	}, nil
 }
 
@@ -153,3 +175,21 @@ func (c TLSServerSetting) LoadTLSConfig() (*tls.Config, error) {
 	}
 	return tlsCfg, nil
 }
+
+func convertVersion(v string) (uint16, error) {
+	if v == "" {
+		return 0, nil // default
+	}
+	val, ok := tlsVersions[v]
+	if !ok {
+		return 0, fmt.Errorf("unsupported TLS version: %q", v)
+	}
+	return val, nil
+}
+
+var tlsVersions = map[string]uint16{
+	"1.0": tls.VersionTLS10,
+	"1.1": tls.VersionTLS11,
+	"1.2": tls.VersionTLS12,
+	"1.3": tls.VersionTLS13,
+}

config/configtls/configtls_test.go

@@ -107,6 +107,27 @@ func TestOptionsToConfig(t *testing.T) {
 				CAFile: "testdata/testCA.pem",
 			},
 		},
+		{
+			name: "should pass with valid min and max version",
+			options: TLSSetting{
+				MinVersion: "1.1",
+				MaxVersion: "1.2",
+			},
+		},
+		{
+			name: "should pass with invalid min",
+			options: TLSSetting{
+				MinVersion: "1.7",
+			},
+			expectError: "invalid TLS min_",
+		},
+		{
+			name: "should pass with invalid max",
+			options: TLSSetting{
+				MaxVersion: "1.7",
+			},
+			expectError: "invalid TLS max_",
+		},
 	}
 
 	for _, test := range tests {