feat: support CORS Private Network Access (#350)

README.md

@@ -152,6 +152,8 @@ cors:
   # Whether or not CORS configuration should be applied. Default is 'false'.
   enabled: true
   credentials: true
+  # Allow Private Network Access preflight requests. Default is 'false'.
+  allow_private_network: false
   # The following are the default CORS settings when it is enabled.
   allowed_hosts:
     - '*'
@@ -240,7 +242,7 @@ A `regex` rule is matched literally against the path, and gets none of the above
 
 ### CORS
 
-The `allowed_*` properties are optional, the default value for each of them will be `*`. `exposed_headers` is optional as well, but is not set if not defined. Setting `credentials` to `true` will allow you to:
+The `allowed_*` properties are optional, the default value for each of them will be `*`. `exposed_headers` is optional as well, but is not set if not defined. Setting `allow_private_network` to `true` to allow Private-Network-Access preflight requests. Setting `credentials` to `true` will allow you to:
 
 1. Use `withCredentials = true` in javascript.
 2. Use the `username:password@host` syntax.

lib/config.go

@@ -383,10 +383,11 @@ type Log struct {
 }
 
 type CORS struct {
-	Enabled        bool
-	Credentials    bool
-	AllowedHeaders []string `mapstructure:"allowed_headers"`
-	AllowedHosts   []string `mapstructure:"allowed_hosts"`
-	AllowedMethods []string `mapstructure:"allowed_methods"`
-	ExposedHeaders []string `mapstructure:"exposed_headers"`
+	Enabled             bool
+	Credentials         bool
+	AllowPrivateNetwork bool     `mapstructure:"allow_private_network"`
+	AllowedHeaders      []string `mapstructure:"allowed_headers"`
+	AllowedHosts        []string `mapstructure:"allowed_hosts"`
+	AllowedMethods      []string `mapstructure:"allowed_methods"`
+	ExposedHeaders      []string `mapstructure:"exposed_headers"`
 }

lib/config_test.go

@@ -55,6 +55,7 @@ func TestConfigDefaults(t *testing.T) {
 	require.EqualValues(t, []string{"*"}, cfg.CORS.AllowedHosts)
 	require.EqualValues(t, []string{"Authorization", "Content-Type", "Content-Range", "Depth", "Destination", "If", "Lock-Token", "Overwrite", "X-Update-Range"}, cfg.CORS.AllowedHeaders)
 	require.EqualValues(t, []string{"COPY", "DELETE", "GET", "HEAD", "LOCK", "MKCOL", "MOVE", "OPTIONS", "PATCH", "POST", "PROPFIND", "PROPPATCH", "PUT", "UNLOCK"}, cfg.CORS.AllowedMethods)
+	require.False(t, cfg.CORS.AllowPrivateNetwork)
 }
 
 func TestConfigCascade(t *testing.T) {
@@ -356,6 +357,7 @@ func TestConfigKeys(t *testing.T) {
 cors:
   enabled: true
   credentials: true
+  allow_private_network: true
   allowed_headers:
     - Depth
   allowed_hosts:
@@ -369,6 +371,7 @@ cors:
 
 	require.True(t, cfg.CORS.Enabled)
 	require.True(t, cfg.CORS.Credentials)
+	require.True(t, cfg.CORS.AllowPrivateNetwork)
 	require.EqualValues(t, []string{"Content-Length", "Content-Range"}, cfg.CORS.ExposedHeaders)
 	require.EqualValues(t, []string{"Depth"}, cfg.CORS.AllowedHeaders)
 	require.EqualValues(t, []string{"http://localhost:8080"}, cfg.CORS.AllowedHosts)

lib/handler.go

@@ -48,12 +48,13 @@ func NewHandler(c *Config) (http.Handler, error) {
 
 	if c.CORS.Enabled {
 		return cors.New(cors.Options{
-			AllowCredentials:   c.CORS.Credentials,
-			AllowedOrigins:     c.CORS.AllowedHosts,
-			AllowedMethods:     c.CORS.AllowedMethods,
-			AllowedHeaders:     c.CORS.AllowedHeaders,
-			ExposedHeaders:     c.CORS.ExposedHeaders,
-			OptionsPassthrough: false,
+			AllowCredentials:    c.CORS.Credentials,
+			AllowPrivateNetwork: c.CORS.AllowPrivateNetwork,
+			AllowedOrigins:      c.CORS.AllowedHosts,
+			AllowedMethods:      c.CORS.AllowedMethods,
+			AllowedHeaders:      c.CORS.AllowedHeaders,
+			ExposedHeaders:      c.CORS.ExposedHeaders,
+			OptionsPassthrough:  false,
 		}).Handler(h), nil
 	}
 

lib/handler_test.go

@@ -86,6 +86,29 @@ func TestServerDefaults(t *testing.T) {
 	require.ErrorContains(t, client.Write("/foo.txt", []byte("hello world 2"), 0666), "403")
 }
 
+func TestServerCORSPrivateNetwork(t *testing.T) {
+	t.Parallel()
+
+	srv := makeTestServer(t, `
+cors:
+  enabled: true
+  allow_private_network: true`)
+	defer srv.Close()
+
+	req, err := http.NewRequest(http.MethodOptions, srv.URL, nil)
+	require.NoError(t, err)
+	req.Header.Set("Origin", "https://example.com")
+	req.Header.Set("Access-Control-Request-Method", http.MethodGet)
+	req.Header.Set("Access-Control-Request-Private-Network", "true")
+
+	resp, err := http.DefaultClient.Do(req)
+	require.NoError(t, err)
+	defer func() { _ = resp.Body.Close() }()
+
+	require.Equal(t, http.StatusNoContent, resp.StatusCode)
+	require.Equal(t, "true", resp.Header.Get("Access-Control-Allow-Private-Network"))
+}
+
 func TestServerPartialUpdateOptions(t *testing.T) {
 	t.Parallel()