feat: add custom base url (#858)

Co-authored-by: Stephan Höhn <me@steph.ovh>
Co-authored-by: Kyle Mendell <ksm@ofkm.us>

backend/internal/common/env_config.go

@@ -27,6 +27,7 @@ const (
 	DbProviderPostgres      DbProvider = "postgres"
 	MaxMindGeoLiteCityUrl   string     = "https://download.maxmind.com/app/geoip_download?edition_id=GeoLite2-City&license_key=%s&suffix=tar.gz"
 	defaultSqliteConnString string     = "data/pocket-id.db"
+	AppUrl                  string     = "http://localhost:1411"
 )
 
 type EnvConfigSchema struct {
@@ -53,6 +54,7 @@ type EnvConfigSchema struct {
 	TrustProxy         bool       `env:"TRUST_PROXY"`
 	AnalyticsDisabled  bool       `env:"ANALYTICS_DISABLED"`
 	AllowDowngrade     bool       `env:"ALLOW_DOWNGRADE"`
+	InternalAppURL     string     `env:"INTERNAL_APP_URL"`
 }
 
 var EnvConfig = defaultConfig()
@@ -74,7 +76,7 @@ func defaultConfig() EnvConfigSchema {
 		KeysPath:           "data/keys",
 		KeysStorage:        "", // "database" or "file"
 		EncryptionKey:      nil,
-		AppURL:             "http://localhost:1411",
+		AppURL:             AppUrl,
 		Port:               "1411",
 		Host:               "0.0.0.0",
 		UnixSocket:         "",
@@ -89,6 +91,7 @@ func defaultConfig() EnvConfigSchema {
 		TrustProxy:         false,
 		AnalyticsDisabled:  false,
 		AllowDowngrade:     false,
+		InternalAppURL:     "",
 	}
 }
 
@@ -133,6 +136,19 @@ func parseEnvConfig() error {
 		return errors.New("APP_URL must not contain a path")
 	}
 
+	// Derive INTERNAL_APP_URL from APP_URL if not set; validate only when provided
+	if EnvConfig.InternalAppURL == "" {
+		EnvConfig.InternalAppURL = EnvConfig.AppURL
+	} else {
+		parsedInternalAppUrl, err := url.Parse(EnvConfig.InternalAppURL)
+		if err != nil {
+			return errors.New("INTERNAL_APP_URL is not a valid URL")
+		}
+		if parsedInternalAppUrl.Path != "" {
+			return errors.New("INTERNAL_APP_URL must not contain a path")
+		}
+	}
+
 	switch EnvConfig.KeysStorage {
 	// KeysStorage defaults to "file" if empty
 	case "":

backend/internal/common/env_config_test.go

@@ -91,6 +91,28 @@ func TestParseEnvConfig(t *testing.T) {
 		assert.ErrorContains(t, err, "APP_URL must not contain a path")
 	})
 
+	t.Run("should fail with invalid INTERNAL_APP_URL", func(t *testing.T) {
+		EnvConfig = defaultConfig()
+		t.Setenv("DB_PROVIDER", "sqlite")
+		t.Setenv("DB_CONNECTION_STRING", "file:test.db")
+		t.Setenv("INTERNAL_APP_URL", "€://not-a-valid-url")
+
+		err := parseEnvConfig()
+		require.Error(t, err)
+		assert.ErrorContains(t, err, "INTERNAL_APP_URL is not a valid URL")
+	})
+
+	t.Run("should fail when INTERNAL_APP_URL contains path", func(t *testing.T) {
+		EnvConfig = defaultConfig()
+		t.Setenv("DB_PROVIDER", "sqlite")
+		t.Setenv("DB_CONNECTION_STRING", "file:test.db")
+		t.Setenv("INTERNAL_APP_URL", "http://localhost:3000/path")
+
+		err := parseEnvConfig()
+		require.Error(t, err)
+		assert.ErrorContains(t, err, "INTERNAL_APP_URL must not contain a path")
+	})
+
 	t.Run("should default KEYS_STORAGE to 'file' when empty", func(t *testing.T) {
 		EnvConfig = defaultConfig()
 		t.Setenv("DB_PROVIDER", "sqlite")

backend/internal/controller/well_known_controller.go

@@ -67,6 +67,9 @@ func (wkc *WellKnownController) openIDConfigurationHandler(c *gin.Context) {
 
 func (wkc *WellKnownController) computeOIDCConfiguration() ([]byte, error) {
 	appUrl := common.EnvConfig.AppURL
+
+	internalAppUrl := common.EnvConfig.InternalAppURL
+
 	alg, err := wkc.jwtService.GetKeyAlg()
 	if err != nil {
 		return nil, fmt.Errorf("failed to get key algorithm: %w", err)
@@ -74,12 +77,12 @@ func (wkc *WellKnownController) computeOIDCConfiguration() ([]byte, error) {
 	config := map[string]any{
 		"issuer":                                         appUrl,
 		"authorization_endpoint":                         appUrl + "/authorize",
-		"token_endpoint":                                 appUrl + "/api/oidc/token",
+		"token_endpoint":                                 internalAppUrl + "/api/oidc/token",
-		"userinfo_endpoint":                              appUrl + "/api/oidc/userinfo",
+		"userinfo_endpoint":                              internalAppUrl + "/api/oidc/userinfo",
 		"end_session_endpoint":                           appUrl + "/api/oidc/end-session",
-		"introspection_endpoint":                         appUrl + "/api/oidc/introspect",
+		"introspection_endpoint":                         internalAppUrl + "/api/oidc/introspect",
 		"device_authorization_endpoint":                  appUrl + "/api/oidc/device/authorize",
-		"jwks_uri":                                       appUrl + "/.well-known/jwks.json",
+		"jwks_uri":                                       internalAppUrl + "/.well-known/jwks.json",
 		"grant_types_supported":                          []string{service.GrantTypeAuthorizationCode, service.GrantTypeRefreshToken, service.GrantTypeDeviceCode},
 		"scopes_supported":                               []string{"openid", "profile", "email", "groups"},
 		"claims_supported":                               []string{"sub", "given_name", "family_name", "name", "email", "email_verified", "preferred_username", "picture", "groups"},