Support rewriting status codes in error page middleware

pkg/config/dynamic/middlewares.go

@@ -222,10 +222,15 @@ type ErrorPage struct {
 	// as ranges by separating two codes with a dash (500-599),
 	// or a combination of the two (404,418,500-599).
 	Status []string `json:"status,omitempty" toml:"status,omitempty" yaml:"status,omitempty" export:"true"`
+	// StatusRewrites defines a mapping of status codes that should be returned instead of the original error status codes.
+	// For example: "418": 404 or "410-418": 404
+	StatusRewrites map[string]int `json:"statusRewrites,omitempty" toml:"statusRewrites,omitempty" yaml:"statusRewrites,omitempty" export:"true"`
 	// Service defines the name of the service that will serve the error page.
 	Service string `json:"service,omitempty" toml:"service,omitempty" yaml:"service,omitempty" export:"true"`
 	// Query defines the URL for the error page (hosted by service).
 	// The {status} variable can be used in order to insert the status code in the URL.
+	// The {originalStatus} variable can be used in order to insert the upstream status code in the URL.
+	// The {url} variable can be used in order to insert the escaped request URL.
 	Query string `json:"query,omitempty" toml:"query,omitempty" yaml:"query,omitempty" export:"true"`
 }
 

pkg/config/dynamic/zz_generated.deepcopy.go

@@ -313,6 +313,13 @@ func (in *ErrorPage) DeepCopyInto(out *ErrorPage) {
 		*out = make([]string, len(*in))
 		copy(*out, *in)
 	}
+	if in.StatusRewrites != nil {
+		in, out := &in.StatusRewrites, &out.StatusRewrites
+		*out = make(map[string]int, len(*in))
+		for key, val := range *in {
+			(*out)[key] = val
+		}
+	}
 	return
 }
 

pkg/middlewares/customerrors/custom_errors.go

@@ -37,6 +37,12 @@ type customErrors struct {
 	backendHandler http.Handler
 	httpCodeRanges types.HTTPCodeRanges
 	backendQuery   string
+	statusRewrites []statusRewrite
+}
+
+type statusRewrite struct {
+	fromCodes types.HTTPCodeRanges
+	toCode    int
 }
 
 // New creates a new custom error pages middleware.
@@ -53,12 +59,27 @@ func New(ctx context.Context, next http.Handler, config dynamic.ErrorPage, servi
 		return nil, err
 	}
 
+	// Parse StatusRewrites
+	statusRewrites := make([]statusRewrite, 0, len(config.StatusRewrites))
+	for k, v := range config.StatusRewrites {
+		ranges, err := types.NewHTTPCodeRanges([]string{k})
+		if err != nil {
+			return nil, err
+		}
+
+		statusRewrites = append(statusRewrites, statusRewrite{
+			fromCodes: ranges,
+			toCode:    v,
+		})
+	}
+
 	return &customErrors{
 		name:           name,
 		next:           next,
 		backendHandler: backend,
 		httpCodeRanges: httpCodeRanges,
 		backendQuery:   config.Query,
+		statusRewrites: statusRewrites,
 	}, nil
 }
 
@@ -84,12 +105,28 @@ func (c *customErrors) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
 
 	// check the recorder code against the configured http status code ranges
 	code := catcher.getCode()
-	logger.Debug().Msgf("Caught HTTP Status Code %d, returning error page", code)
+
+	originalCode := code
+
+	// Check if we need to rewrite the status code
+	for _, rsc := range c.statusRewrites {
+		if rsc.fromCodes.Contains(code) {
+			code = rsc.toCode
+			break
+		}
+	}
+
+	if code != originalCode {
+		logger.Debug().Msgf("Caught HTTP Status Code %d (rewritten to %d), returning error page", originalCode, code)
+	} else {
+		logger.Debug().Msgf("Caught HTTP Status Code %d, returning error page", code)
+	}
 
 	var query string
 	if len(c.backendQuery) > 0 {
 		query = "/" + strings.TrimPrefix(c.backendQuery, "/")
 		query = strings.ReplaceAll(query, "{status}", strconv.Itoa(code))
+		query = strings.ReplaceAll(query, "{originalStatus}", strconv.Itoa(originalCode))
 		query = strings.ReplaceAll(query, "{url}", url.QueryEscape(req.URL.String()))
 	}
 

pkg/provider/kubernetes/crd/fixtures/with_error_page.yml

@@ -9,6 +9,8 @@ spec:
     status:
     - "404"
     - "500"
+    statusRewrites:
+      404: 200
     query: query
     service:
       name: whoami

pkg/provider/kubernetes/crd/kubernetes.go

@@ -737,8 +737,9 @@ func (p *Provider) createErrorPageMiddleware(client Client, namespace string, er
 	}
 
 	errorPageMiddleware := &dynamic.ErrorPage{
-		Status: errorPage.Status,
-		Query:  errorPage.Query,
+		Status:         errorPage.Status,
+		StatusRewrites: errorPage.StatusRewrites,
+		Query:          errorPage.Query,
 	}
 
 	cb := configBuilder{

pkg/provider/kubernetes/crd/kubernetes_test.go

@@ -4160,7 +4160,10 @@ func TestLoadIngressRoutes(t *testing.T) {
 					Middlewares: map[string]*dynamic.Middleware{
 						"default-errorpage": {
 							Errors: &dynamic.ErrorPage{
-								Status:  []string{"404", "500"},
+								Status: []string{"404", "500"},
+								StatusRewrites: map[string]int{
+									"404": 200,
+								},
 								Service: "default-errorpage-errorpage-service",
 								Query:   "query",
 							},

pkg/provider/kubernetes/crd/traefikio/v1alpha1/middleware.go

@@ -68,11 +68,16 @@ type ErrorPage struct {
 	// as ranges by separating two codes with a dash (500-599),
 	// or a combination of the two (404,418,500-599).
 	Status []string `json:"status,omitempty"`
+	// StatusRewrites defines a mapping of status codes that should be returned instead of the original error status codes.
+	// For example: "418": 404 or "410-418": 404
+	StatusRewrites map[string]int `json:"statusRewrites,omitempty"`
 	// Service defines the reference to a Kubernetes Service that will serve the error page.
 	// More info: https://doc.traefik.io/traefik/v3.3/middlewares/http/errorpages/#service
 	Service Service `json:"service,omitempty"`
 	// Query defines the URL for the error page (hosted by service).
 	// The {status} variable can be used in order to insert the status code in the URL.
+	// The {originalStatus} variable can be used in order to insert the upstream status code in the URL.
+	// The {url} variable can be used in order to insert the escaped request URL.
 	Query string `json:"query,omitempty"`
 }
 

pkg/provider/kubernetes/crd/traefikio/v1alpha1/zz_generated.deepcopy.go

@@ -229,6 +229,13 @@ func (in *ErrorPage) DeepCopyInto(out *ErrorPage) {
 		*out = make([]string, len(*in))
 		copy(*out, *in)
 	}
+	if in.StatusRewrites != nil {
+		in, out := &in.StatusRewrites, &out.StatusRewrites
+		*out = make(map[string]int, len(*in))
+		for key, val := range *in {
+			(*out)[key] = val
+		}
+	}
 	in.Service.DeepCopyInto(&out.Service)
 	return
 }