chore: clearer description

- Preserve backward compatibility: wildcard origins allow credentials by default
- Add MINIO_API_CORS_ALLOW_CREDENTIALS_WITH_WILDCARD=off for enhanced security
- Addresses CORS specification compliance while preventing service disruption
- Existing deployments continue working unchanged

cmd/api-router.go

@@ -683,7 +683,8 @@ func corsHandler(handler http.Handler) http.Handler {
 		// Configure CORS dynamically based on current settings
 		// This ensures we handle configuration changes and wildcard security properly
 		hasWildcard := configHasWildcard()
-		
+		allowCredentialsWithWildcard := globalAPIConfig.getCorsAllowCredentialsWithWildcard()
+
 		opts := cors.Options{
 			AllowOriginFunc: func(origin string) bool {
 				for _, allowedOrigin := range globalAPIConfig.getCorsAllowOrigins() {
@@ -702,11 +703,12 @@ func corsHandler(handler http.Handler) http.Handler {
 				http.MethodOptions,
 				http.MethodPatch,
 			},
-			AllowedHeaders:   commonS3Headers,
-			ExposedHeaders:   commonS3Headers,
+			AllowedHeaders: commonS3Headers,
+			ExposedHeaders: commonS3Headers,
 			// CORS spec compliance: disable credentials when wildcard origins are configured
+			// Unless explicitly overridden by administrator (for backward compatibility)
 			// This prevents the security vulnerability where any website can make credentialed requests
-			AllowCredentials: !hasWildcard,
+			AllowCredentials: !hasWildcard || allowCredentialsWithWildcard,
 		}
 
 		// Use rs/cors directly without custom wrapper to avoid interface issues

cmd/api-router_test.go

@@ -27,59 +27,83 @@ import (
 func TestCORSCredentialsWithWildcard(t *testing.T) {
 	// Save original config and restore after test
 	originalOrigins := globalAPIConfig.getCorsAllowOrigins()
+	originalAllowCredentialsWithWildcard := globalAPIConfig.getCorsAllowCredentialsWithWildcard()
 	defer func() {
 		globalAPIConfig.mu.Lock()
 		globalAPIConfig.corsAllowOrigins = originalOrigins
+		globalAPIConfig.corsAllowCredentialsWithWildcard = originalAllowCredentialsWithWildcard
 		globalAPIConfig.mu.Unlock()
 	}()
 
-	// Setup wildcard CORS config
-	globalAPIConfig.mu.Lock()
-	globalAPIConfig.corsAllowOrigins = []string{"*"}
-	globalAPIConfig.mu.Unlock()
+	// Test 1: Default secure behavior (wildcard without credentials)
+	t.Run("Secure Default", func(t *testing.T) {
+		// Setup wildcard CORS config with default secure behavior
+		globalAPIConfig.mu.Lock()
+		globalAPIConfig.corsAllowOrigins = []string{"*"}
+		globalAPIConfig.corsAllowCredentialsWithWildcard = false // default secure behavior
+		globalAPIConfig.mu.Unlock()
 
-	// Create a simple handler
-	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		w.WriteHeader(http.StatusOK)
+		// Create a simple handler
+		handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			w.WriteHeader(http.StatusOK)
+		})
+
+		// Wrap with CORS handler
+		corsWrappedHandler := corsHandler(handler)
+
+		// Test preflight request
+		req := httptest.NewRequest("OPTIONS", "/", nil)
+		req.Header.Set("Origin", "https://example.com")
+		req.Header.Set("Access-Control-Request-Method", "GET")
+
+		rr := httptest.NewRecorder()
+		corsWrappedHandler.ServeHTTP(rr, req)
+
+		// Verify specific origin is echoed back (rs/cors library behavior)
+		if got := rr.Header().Get("Access-Control-Allow-Origin"); got != "https://example.com" {
+			t.Errorf("Expected Access-Control-Allow-Origin: https://example.com, got: %s", got)
+		}
+
+		// Verify credentials header is NOT present (security fix)
+		if got := rr.Header().Get("Access-Control-Allow-Credentials"); got != "" {
+			t.Errorf("Expected no Access-Control-Allow-Credentials header with wildcard origin, got: %s", got)
+		}
 	})
 
-	// Wrap with CORS handler
-	corsWrappedHandler := corsHandler(handler)
+	// Test 2: Backward compatibility opt-out (wildcard with credentials - insecure)
+	t.Run("Backward Compatibility Opt-out", func(t *testing.T) {
+		// Setup wildcard CORS config with explicit opt-out for backward compatibility
+		globalAPIConfig.mu.Lock()
+		globalAPIConfig.corsAllowOrigins = []string{"*"}
+		globalAPIConfig.corsAllowCredentialsWithWildcard = true // explicitly allow insecure behavior
+		globalAPIConfig.mu.Unlock()
 
-	// Test preflight request
-	req := httptest.NewRequest("OPTIONS", "/", nil)
-	req.Header.Set("Origin", "https://example.com")
-	req.Header.Set("Access-Control-Request-Method", "GET")
+		// Create a simple handler
+		handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			w.WriteHeader(http.StatusOK)
+		})
 
-	rr := httptest.NewRecorder()
-	corsWrappedHandler.ServeHTTP(rr, req)
+		// Wrap with CORS handler
+		corsWrappedHandler := corsHandler(handler)
 
-	// Verify specific origin is echoed back (rs/cors library behavior)
-	if got := rr.Header().Get("Access-Control-Allow-Origin"); got != "https://example.com" {
-		t.Errorf("Expected Access-Control-Allow-Origin: https://example.com, got: %s", got)
-	}
+		// Test preflight request
+		req := httptest.NewRequest("OPTIONS", "/", nil)
+		req.Header.Set("Origin", "https://example.com")
+		req.Header.Set("Access-Control-Request-Method", "GET")
 
-	// Verify credentials header is NOT present (security fix)
-	if got := rr.Header().Get("Access-Control-Allow-Credentials"); got != "" {
-		t.Errorf("Expected no Access-Control-Allow-Credentials header with wildcard origin, got: %s", got)
-	}
+		rr := httptest.NewRecorder()
+		corsWrappedHandler.ServeHTTP(rr, req)
 
-	// Test actual GET request
-	req = httptest.NewRequest("GET", "/", nil)
-	req.Header.Set("Origin", "https://example.com")
+		// Verify specific origin is echoed back (rs/cors library behavior)
+		if got := rr.Header().Get("Access-Control-Allow-Origin"); got != "https://example.com" {
+			t.Errorf("Expected Access-Control-Allow-Origin: https://example.com, got: %s", got)
+		}
 
-	rr = httptest.NewRecorder()
-	corsWrappedHandler.ServeHTTP(rr, req)
-
-	// Verify specific origin is echoed back (rs/cors library behavior)
-	if got := rr.Header().Get("Access-Control-Allow-Origin"); got != "https://example.com" {
-		t.Errorf("Expected Access-Control-Allow-Origin: https://example.com, got: %s", got)
-	}
-
-	// Verify credentials header is NOT present
-	if got := rr.Header().Get("Access-Control-Allow-Credentials"); got != "" {
-		t.Errorf("Expected no Access-Control-Allow-Credentials header with wildcard origin, got: %s", got)
-	}
+		// Verify credentials header IS present (backward compatibility)
+		if got := rr.Header().Get("Access-Control-Allow-Credentials"); got != "true" {
+			t.Errorf("Expected Access-Control-Allow-Credentials: true with opt-out enabled, got: %s", got)
+		}
+	})
 }
 
 // Test that CORS credentials are allowed for specific origins
@@ -168,7 +192,7 @@ func TestCORSUnauthorizedOrigin(t *testing.T) {
 
 	// Test preflight request from unauthorized origin
 	req := httptest.NewRequest("OPTIONS", "/", nil)
-	req.Header.Set("Origin", "https://example.org")  // This origin is NOT in the allowed list
+	req.Header.Set("Origin", "https://example.org") // This origin is NOT in the allowed list
 	req.Header.Set("Access-Control-Request-Method", "GET")
 
 	rr := httptest.NewRecorder()
@@ -188,15 +212,18 @@ func TestCORSUnauthorizedOrigin(t *testing.T) {
 func TestCORSMixedConfiguration(t *testing.T) {
 	// Save original config and restore after test
 	originalOrigins := globalAPIConfig.getCorsAllowOrigins()
+	originalAllowCredentialsWithWildcard := globalAPIConfig.getCorsAllowCredentialsWithWildcard()
 	defer func() {
 		globalAPIConfig.mu.Lock()
 		globalAPIConfig.corsAllowOrigins = originalOrigins
+		globalAPIConfig.corsAllowCredentialsWithWildcard = originalAllowCredentialsWithWildcard
 		globalAPIConfig.mu.Unlock()
 	}()
 
-	// Setup mixed CORS config (wildcard + specific origins)
+	// Setup mixed CORS config (wildcard + specific origins) with default secure behavior
 	globalAPIConfig.mu.Lock()
 	globalAPIConfig.corsAllowOrigins = []string{"*", "https://example.com"}
+	globalAPIConfig.corsAllowCredentialsWithWildcard = false // default secure behavior
 	globalAPIConfig.mu.Unlock()
 
 	// Create a simple handler
@@ -220,7 +247,7 @@ func TestCORSMixedConfiguration(t *testing.T) {
 		t.Errorf("Expected Access-Control-Allow-Origin: https://example.com, got: %s", got)
 	}
 
-	// Verify credentials header is NOT present due to wildcard in config
+	// Verify credentials header is NOT present due to wildcard in config (secure default)
 	if got := rr.Header().Get("Access-Control-Allow-Credentials"); got != "" {
 		t.Errorf("Expected no Access-Control-Allow-Credentials header with wildcard in config, got: %s", got)
 	}

cmd/handler-api.go

@@ -49,14 +49,15 @@ type apiConfig struct {
 	replicationMaxLWorkers int
 	transitionWorkers      int
 
-	staleUploadsExpiry          time.Duration
-	staleUploadsCleanupInterval time.Duration
-	deleteCleanupInterval       time.Duration
-	enableODirect               bool
-	gzipObjects                 bool
-	rootAccess                  bool
-	syncEvents                  bool
-	objectMaxVersions           int64
+	staleUploadsExpiry               time.Duration
+	staleUploadsCleanupInterval      time.Duration
+	deleteCleanupInterval            time.Duration
+	enableODirect                    bool
+	gzipObjects                      bool
+	rootAccess                       bool
+	syncEvents                       bool
+	objectMaxVersions                int64
+	corsAllowCredentialsWithWildcard bool
 }
 
 const (
@@ -187,6 +188,7 @@ func (t *apiConfig) init(cfg api.Config, setDriveCounts []int, legacy bool) {
 	t.rootAccess = cfg.RootAccess
 	t.syncEvents = cfg.SyncEvents
 	t.objectMaxVersions = cfg.ObjectMaxVersions
+	t.corsAllowCredentialsWithWildcard = cfg.CorsAllowCredentialsWithWildcard
 
 	if t.staleUploadsCleanupInterval != cfg.StaleUploadsCleanupInterval {
 		t.staleUploadsCleanupInterval = cfg.StaleUploadsCleanupInterval
@@ -244,6 +246,12 @@ func (t *apiConfig) getCorsAllowOrigins() []string {
 	return corsAllowOrigins
 }
 
+func (t *apiConfig) getCorsAllowCredentialsWithWildcard() bool {
+	t.mu.RLock()
+	defer t.mu.RUnlock()
+	return t.corsAllowCredentialsWithWildcard
+}
+
 func (t *apiConfig) getStaleUploadsCleanupInterval() time.Duration {
 	t.mu.RLock()
 	defer t.mu.RUnlock()

internal/config/api/api.go

@@ -32,14 +32,15 @@ import (
 
 // API sub-system constants
 const (
-	apiRequestsMax             = "requests_max"
-	apiClusterDeadline         = "cluster_deadline"
-	apiCorsAllowOrigin         = "cors_allow_origin"
-	apiRemoteTransportDeadline = "remote_transport_deadline"
-	apiListQuorum              = "list_quorum"
-	apiReplicationPriority     = "replication_priority"
-	apiReplicationMaxWorkers   = "replication_max_workers"
-	apiReplicationMaxLWorkers  = "replication_max_lrg_workers"
+	apiRequestsMax                      = "requests_max"
+	apiClusterDeadline                  = "cluster_deadline"
+	apiCorsAllowOrigin                  = "cors_allow_origin"
+	apiCorsAllowCredentialsWithWildcard = "cors_allow_credentials_with_wildcard"
+	apiRemoteTransportDeadline          = "remote_transport_deadline"
+	apiListQuorum                       = "list_quorum"
+	apiReplicationPriority              = "replication_priority"
+	apiReplicationMaxWorkers            = "replication_max_workers"
+	apiReplicationMaxLWorkers           = "replication_max_lrg_workers"
 
 	apiTransitionWorkers           = "transition_workers"
 	apiStaleUploadsCleanupInterval = "stale_uploads_cleanup_interval"
@@ -52,17 +53,18 @@ const (
 	apiSyncEvents                  = "sync_events"
 	apiObjectMaxVersions           = "object_max_versions"
 
-	EnvAPIRequestsMax             = "MINIO_API_REQUESTS_MAX"
-	EnvAPIRequestsDeadline        = "MINIO_API_REQUESTS_DEADLINE"
-	EnvAPIClusterDeadline         = "MINIO_API_CLUSTER_DEADLINE"
-	EnvAPICorsAllowOrigin         = "MINIO_API_CORS_ALLOW_ORIGIN"
-	EnvAPIRemoteTransportDeadline = "MINIO_API_REMOTE_TRANSPORT_DEADLINE"
-	EnvAPITransitionWorkers       = "MINIO_API_TRANSITION_WORKERS"
-	EnvAPIListQuorum              = "MINIO_API_LIST_QUORUM"
-	EnvAPISecureCiphers           = "MINIO_API_SECURE_CIPHERS" // default config.EnableOn
-	EnvAPIReplicationPriority     = "MINIO_API_REPLICATION_PRIORITY"
-	EnvAPIReplicationMaxWorkers   = "MINIO_API_REPLICATION_MAX_WORKERS"
-	EnvAPIReplicationMaxLWorkers  = "MINIO_API_REPLICATION_MAX_LRG_WORKERS"
+	EnvAPIRequestsMax                      = "MINIO_API_REQUESTS_MAX"
+	EnvAPIRequestsDeadline                 = "MINIO_API_REQUESTS_DEADLINE"
+	EnvAPIClusterDeadline                  = "MINIO_API_CLUSTER_DEADLINE"
+	EnvAPICorsAllowOrigin                  = "MINIO_API_CORS_ALLOW_ORIGIN"
+	EnvAPICorsAllowCredentialsWithWildcard = "MINIO_API_CORS_ALLOW_CREDENTIALS_WITH_WILDCARD"
+	EnvAPIRemoteTransportDeadline          = "MINIO_API_REMOTE_TRANSPORT_DEADLINE"
+	EnvAPITransitionWorkers                = "MINIO_API_TRANSITION_WORKERS"
+	EnvAPIListQuorum                       = "MINIO_API_LIST_QUORUM"
+	EnvAPISecureCiphers                    = "MINIO_API_SECURE_CIPHERS" // default config.EnableOn
+	EnvAPIReplicationPriority              = "MINIO_API_REPLICATION_PRIORITY"
+	EnvAPIReplicationMaxWorkers            = "MINIO_API_REPLICATION_MAX_WORKERS"
+	EnvAPIReplicationMaxLWorkers           = "MINIO_API_REPLICATION_MAX_LRG_WORKERS"
 
 	EnvAPIStaleUploadsCleanupInterval = "MINIO_API_STALE_UPLOADS_CLEANUP_INTERVAL"
 	EnvAPIStaleUploadsExpiry          = "MINIO_API_STALE_UPLOADS_EXPIRY"
@@ -100,6 +102,10 @@ var (
 			Key:   apiCorsAllowOrigin,
 			Value: "*",
 		},
+		config.KV{
+			Key:   apiCorsAllowCredentialsWithWildcard,
+			Value: config.EnableOn,
+		},
 		config.KV{
 			Key:   apiRemoteTransportDeadline,
 			Value: "2h",
@@ -166,23 +172,24 @@ var (
 
 // Config storage class configuration
 type Config struct {
-	RequestsMax                 int           `json:"requests_max"`
-	ClusterDeadline             time.Duration `json:"cluster_deadline"`
-	CorsAllowOrigin             []string      `json:"cors_allow_origin"`
-	RemoteTransportDeadline     time.Duration `json:"remote_transport_deadline"`
-	ListQuorum                  string        `json:"list_quorum"`
-	ReplicationPriority         string        `json:"replication_priority"`
-	ReplicationMaxWorkers       int           `json:"replication_max_workers"`
-	ReplicationMaxLWorkers      int           `json:"replication_max_lrg_workers"`
-	TransitionWorkers           int           `json:"transition_workers"`
-	StaleUploadsCleanupInterval time.Duration `json:"stale_uploads_cleanup_interval"`
-	StaleUploadsExpiry          time.Duration `json:"stale_uploads_expiry"`
-	DeleteCleanupInterval       time.Duration `json:"delete_cleanup_interval"`
-	EnableODirect               bool          `json:"enable_odirect"`
-	GzipObjects                 bool          `json:"gzip_objects"`
-	RootAccess                  bool          `json:"root_access"`
-	SyncEvents                  bool          `json:"sync_events"`
-	ObjectMaxVersions           int64         `json:"object_max_versions"`
+	RequestsMax                      int           `json:"requests_max"`
+	ClusterDeadline                  time.Duration `json:"cluster_deadline"`
+	CorsAllowOrigin                  []string      `json:"cors_allow_origin"`
+	CorsAllowCredentialsWithWildcard bool          `json:"cors_allow_credentials_with_wildcard"`
+	RemoteTransportDeadline          time.Duration `json:"remote_transport_deadline"`
+	ListQuorum                       string        `json:"list_quorum"`
+	ReplicationPriority              string        `json:"replication_priority"`
+	ReplicationMaxWorkers            int           `json:"replication_max_workers"`
+	ReplicationMaxLWorkers           int           `json:"replication_max_lrg_workers"`
+	TransitionWorkers                int           `json:"transition_workers"`
+	StaleUploadsCleanupInterval      time.Duration `json:"stale_uploads_cleanup_interval"`
+	StaleUploadsExpiry               time.Duration `json:"stale_uploads_expiry"`
+	DeleteCleanupInterval            time.Duration `json:"delete_cleanup_interval"`
+	EnableODirect                    bool          `json:"enable_odirect"`
+	GzipObjects                      bool          `json:"gzip_objects"`
+	RootAccess                       bool          `json:"root_access"`
+	SyncEvents                       bool          `json:"sync_events"`
+	ObjectMaxVersions                int64         `json:"object_max_versions"`
 }
 
 // UnmarshalJSON - Validate SS and RRS parity when unmarshalling JSON.
@@ -211,11 +218,13 @@ func LookupConfig(kvs config.KVS) (cfg Config, err error) {
 	enableODirect := env.Get(EnvAPIODirect, kvs.Get(apiODirect)) == config.EnableOn
 	gzipObjects := env.Get(EnvAPIGzipObjects, kvs.Get(apiGzipObjects)) == config.EnableOn
 	rootAccess := env.Get(EnvAPIRootAccess, kvs.Get(apiRootAccess)) == config.EnableOn
+	corsAllowCredentialsWithWildcard := env.Get(EnvAPICorsAllowCredentialsWithWildcard, kvs.Get(apiCorsAllowCredentialsWithWildcard)) == config.EnableOn
 
 	cfg = Config{
-		EnableODirect: enableODirect || !disableODirect,
-		GzipObjects:   gzipObjects,
-		RootAccess:    rootAccess,
+		EnableODirect:                    enableODirect || !disableODirect,
+		GzipObjects:                      gzipObjects,
+		RootAccess:                       rootAccess,
+		CorsAllowCredentialsWithWildcard: corsAllowCredentialsWithWildcard,
 	}
 
 	var corsAllowOrigin []string

internal/config/api/help.go

@@ -44,6 +44,12 @@ var (
 			Optional:    true,
 			Type:        "csv",
 		},
+		config.HelpKV{
+			Key:         apiCorsAllowCredentialsWithWildcard,
+			Description: `allow credentials with wildcard CORS origins (default: 'on' for backward compatibility, 'off' for enhanced security compliance)` + defaultHelpPostfix(apiCorsAllowCredentialsWithWildcard),
+			Optional:    true,
+			Type:        "on|off",
+		},
 		config.HelpKV{
 			Key:         apiRemoteTransportDeadline,
 			Description: `set the deadline for API requests on remote transports while proxying between federated instances e.g. "2h"` + defaultHelpPostfix(apiRemoteTransportDeadline),