Add ability to overwrite the default scopes in the settings file

README.md

@@ -67,7 +67,8 @@ The middleware supports the following configuration options:
 |-----------|-------------|---------|---------|
 | `logoutURL` | The path for handling logout requests | `callbackURL + "/logout"` | `/oauth2/logout` |
 | `postLogoutRedirectURI` | The URL to redirect to after logout | `/` | `/logged-out-page` |
-| `scopes` | Additional OAuth 2.0 scopes to append to defaults | `["openid", "profile", "email"]` (always included) | `["roles", "custom_scope"]` (appended to defaults) |
+| `scopes` | OAuth 2.0 scopes to use for authentication | `["openid", "profile", "email"]` (always included by default) | `["roles", "custom_scope"]` (appended to defaults) |
+| `overrideScopes` | When true, replaces default scopes with provided scopes instead of appending | `false` | `true` (use only the scopes explicitly provided) |
 | `logLevel` | Sets the logging verbosity | `info` | `debug`, `info`, `error` |
 | `forceHTTPS` | Forces the use of HTTPS for all URLs | `true` | `true`, `false` |
 | `rateLimit` | Sets the maximum number of requests per second | `100` | `500` |
@@ -83,23 +84,35 @@ The middleware supports the following configuration options:
 
 ## Scope Configuration
 
-### Scope Append Behavior
+### Scope Behavior
 
-The middleware uses an **append** behavior for OAuth 2.0 scopes, not replacement. This means:
+The middleware supports two modes for handling OAuth 2.0 scopes, controlled by the `overrideScopes` parameter:
+
+#### Default Append Mode (`overrideScopes: false`)
+
+By default, the middleware uses an **append** behavior for OAuth 2.0 scopes:
 
 - **Default scopes** are always included: `["openid", "profile", "email"]`
 - **User-provided scopes** are appended to the defaults with automatic deduplication
 - The final scope list maintains the order: defaults first, then user scopes
 
-#### Examples:
+#### Override Mode (`overrideScopes: true`)
 
-**No custom scopes specified:**
+When `overrideScopes` is set to `true`, the middleware uses **replacement** behavior:
+
+- Default scopes are **not** automatically included
+- Only the scopes explicitly provided in the `scopes` field are used
+- You must include all required scopes explicitly, including `openid` if needed
+
+### Examples:
+
+**Default behavior (no custom scopes):**
 ```yaml
 # No scopes field specified
 # Result: ["openid", "profile", "email"]
 ```
 
-**Custom scopes appended:**
+**Default append behavior:**
 ```yaml
 scopes:
   - roles
@@ -107,7 +120,7 @@ scopes:
 # Result: ["openid", "profile", "email", "roles", "custom_scope"]
 ```
 
-**Overlapping scopes (automatic deduplication):**
+**Overlapping scopes with append (automatic deduplication):**
 ```yaml
 scopes:
   - openid      # Duplicate - will be deduplicated
@@ -117,13 +130,30 @@ scopes:
 # Result: ["openid", "profile", "email", "roles", "permissions"]
 ```
 
-**Empty scopes list:**
+**Using override mode:**
+```yaml
+overrideScopes: true
+scopes:
+  - openid
+  - profile
+  - custom_scope
+# Result: ["openid", "profile", "custom_scope"]
+```
+
+**Empty scopes list with default behavior:**
 ```yaml
 scopes: []
 # Result: ["openid", "profile", "email"]
 ```
 
-This append behavior ensures that essential OIDC scopes are always present while allowing you to add provider-specific or application-specific scopes as needed.
+**Empty scopes list with override mode:**
+```yaml
+overrideScopes: true
+scopes: []
+# Result: [] (Warning: empty scopes may cause authentication to fail)
+```
+
+The default append behavior ensures essential OIDC scopes are always present, while the override mode gives you complete control over the exact scopes requested from the provider.
 
 ## Usage Examples
 

main.go

@@ -240,6 +240,7 @@ type TraefikOidc struct {
 	shutdownOnce               sync.Once
 	forceHTTPS                 bool
 	enablePKCE                 bool
+	overrideScopes             bool
 	suppressDiagnosticLogs     bool
 }
 
@@ -652,14 +653,20 @@ func New(ctx context.Context, next http.Handler, config *Config, name string) (h
 			}
 			return config.PostLogoutRedirectURI
 		}(),
-		tokenBlacklist:        cacheManager.GetSharedTokenBlacklist(),
-		jwkCache:              cacheManager.GetSharedJWKCache(),
-		metadataCache:         cacheManager.GetSharedMetadataCache(),
-		clientID:              config.ClientID,
-		clientSecret:          config.ClientSecret,
-		forceHTTPS:            config.ForceHTTPS,
-		enablePKCE:            config.EnablePKCE,
-		scopes:                mergeScopes([]string{"openid", "profile", "email"}, config.Scopes),
+		tokenBlacklist: cacheManager.GetSharedTokenBlacklist(),
+		jwkCache:       cacheManager.GetSharedJWKCache(),
+		metadataCache:  cacheManager.GetSharedMetadataCache(),
+		clientID:       config.ClientID,
+		clientSecret:   config.ClientSecret,
+		forceHTTPS:     config.ForceHTTPS,
+		enablePKCE:     config.EnablePKCE,
+		overrideScopes: config.OverrideScopes,
+		scopes: func() []string {
+			if config.OverrideScopes {
+				return append([]string(nil), config.Scopes...)
+			}
+			return mergeScopes([]string{"openid", "profile", "email"}, config.Scopes)
+		}(),
 		limiter:               rate.NewLimiter(rate.Every(time.Second), config.RateLimit),
 		tokenCache:            cacheManager.GetSharedTokenCache(),
 		httpClient:            httpClient,

scopes_test.go

@@ -0,0 +1,124 @@
+package traefikoidc
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestMergeScopes(t *testing.T) {
+	testCases := []struct {
+		name           string
+		defaultScopes  []string
+		userScopes     []string
+		expectedScopes []string
+	}{
+		{
+			name:           "Empty user scopes",
+			defaultScopes:  []string{"openid", "profile", "email"},
+			userScopes:     []string{},
+			expectedScopes: []string{"openid", "profile", "email"},
+		},
+		{
+			name:           "Non-overlapping scopes",
+			defaultScopes:  []string{"openid", "profile", "email"},
+			userScopes:     []string{"roles", "custom_scope"},
+			expectedScopes: []string{"openid", "profile", "email", "roles", "custom_scope"},
+		},
+		{
+			name:           "Overlapping scopes",
+			defaultScopes:  []string{"openid", "profile", "email"},
+			userScopes:     []string{"openid", "roles", "profile", "permissions"},
+			expectedScopes: []string{"openid", "profile", "email", "roles", "permissions"},
+		},
+		{
+			name:           "Nil user scopes",
+			defaultScopes:  []string{"openid", "profile", "email"},
+			userScopes:     nil,
+			expectedScopes: []string{"openid", "profile", "email"},
+		},
+		{
+			name:           "Nil default scopes",
+			defaultScopes:  nil,
+			userScopes:     []string{"roles", "custom_scope"},
+			expectedScopes: []string{"roles", "custom_scope"},
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			result := mergeScopes(tc.defaultScopes, tc.userScopes)
+			if !reflect.DeepEqual(result, tc.expectedScopes) {
+				t.Errorf("Expected %v, got %v", tc.expectedScopes, result)
+			}
+		})
+	}
+}
+
+func TestScopesConfiguration(t *testing.T) {
+	defaultScopes := []string{"openid", "profile", "email"}
+	userScopes := []string{"roles", "custom_scope"}
+
+	t.Run("Default Append Behavior", func(t *testing.T) {
+		// Create config with user scopes but overrideScopes=false
+		config := &Config{
+			Scopes:         userScopes,
+			OverrideScopes: false,
+		}
+
+		// Simulate middleware initialization
+		var result []string
+		if config.OverrideScopes {
+			result = append([]string(nil), config.Scopes...)
+		} else {
+			result = mergeScopes(defaultScopes, config.Scopes)
+		}
+
+		// Expect defaultScopes + userScopes with deduplication
+		expectedScopes := []string{"openid", "profile", "email", "roles", "custom_scope"}
+		if !reflect.DeepEqual(result, expectedScopes) {
+			t.Errorf("Expected %v, got %v", expectedScopes, result)
+		}
+	})
+
+	t.Run("Override Behavior", func(t *testing.T) {
+		// Create config with user scopes and overrideScopes=true
+		config := &Config{
+			Scopes:         userScopes,
+			OverrideScopes: true,
+		}
+
+		// Simulate middleware initialization
+		var result []string
+		if config.OverrideScopes {
+			result = append([]string(nil), config.Scopes...)
+		} else {
+			result = mergeScopes(defaultScopes, config.Scopes)
+		}
+
+		// Expect only userScopes
+		if !reflect.DeepEqual(result, userScopes) {
+			t.Errorf("Expected %v, got %v", userScopes, result)
+		}
+	})
+
+	t.Run("Empty Scopes with Override", func(t *testing.T) {
+		// Create config with empty scopes and overrideScopes=true
+		config := &Config{
+			Scopes:         []string{},
+			OverrideScopes: true,
+		}
+
+		// Simulate middleware initialization
+		var result []string
+		if config.OverrideScopes {
+			result = append([]string(nil), config.Scopes...)
+		} else {
+			result = mergeScopes(defaultScopes, config.Scopes)
+		}
+
+		// Expect empty scopes - check length instead of DeepEqual
+		if len(result) != 0 {
+			t.Errorf("Expected empty slice, got %v with length %d", result, len(result))
+		}
+	})
+}

settings.go

@@ -47,6 +47,7 @@ type Config struct {
 	RefreshGracePeriodSeconds int               `json:"refreshGracePeriodSeconds"`
 	ForceHTTPS                bool              `json:"forceHTTPS"`
 	EnablePKCE                bool              `json:"enablePKCE"`
+	OverrideScopes            bool              `json:"overrideScopes"`
 }
 
 const (
@@ -87,6 +88,7 @@ func CreateConfig() *Config {
 		RateLimit:                 DefaultRateLimit,
 		ForceHTTPS:                true,  // Secure by default
 		EnablePKCE:                false, // PKCE is opt-in
+		OverrideScopes:            false, // Default to appending scopes, not overriding
 		RefreshGracePeriodSeconds: 60,    // Default grace period of 60 seconds
 	}
 

settings_test.go

@@ -49,6 +49,11 @@ func TestCreateConfig(t *testing.T) {
 		if !config.ForceHTTPS {
 			t.Error("Expected ForceHTTPS to be true by default")
 		}
+
+		// Check OverrideScopes default
+		if config.OverrideScopes {
+			t.Error("Expected OverrideScopes to be false by default")
+		}
 	})
 
 	t.Run("Config Can Hold Custom Values", func(t *testing.T) {
@@ -57,6 +62,7 @@ func TestCreateConfig(t *testing.T) {
 		config.LogLevel = "debug"
 		config.RateLimit = 50
 		config.ForceHTTPS = false
+		config.OverrideScopes = true
 
 		// Verify config struct can hold custom values
 		if len(config.Scopes) != 1 || config.Scopes[0] != "custom_scope" {
@@ -71,6 +77,9 @@ func TestCreateConfig(t *testing.T) {
 		if config.ForceHTTPS {
 			t.Error("Config struct cannot hold custom ForceHTTPS value")
 		}
+		if !config.OverrideScopes {
+			t.Error("Config struct cannot hold custom OverrideScopes value")
+		}
 	})
 }