init

.traefik.yml

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+displayName: UsersBlocker
+
+type: middleware
+
+import: github.com/ditkrg/traefik-response-header-forward-plugin
+
+summary: A middleware to add headers from request to response.
+
+testData:
+  requestHeaders:
+    - userId1
+    - userId2

README.md

@@ -0,0 +1 @@
+# Traefik Response header forward plugin

docker-compose.yaml

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+version: '3'
+
+services:
+  reverse-proxy:
+    image: traefik:v3.0
+    command:
+      - --api.insecure=true
+      - --providers.docker
+      - "--experimental.localPlugins.responseHeaderForward.moduleName=github.com/ditkrg/traefik-response-header-forward-plugin"
+    ports:
+      - "9090:80"
+      - "9091:8080"
+    volumes:
+      # So that Traefik can listen to the Docker events
+      - /var/run/docker.sock:/var/run/docker.sock
+      - ./:/plugins-local/src/github.com/ditkrg/traefik-response-header-forward-plugin

go.mod

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+module github.com/ditkrg/traefik-response-header-forward-plugin
+
+go 1.21.3

main.go

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+package traefik_response_header_forward_plugin
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+)
+
+type RequestHeader struct {
+	Name string `json:"name,omitempty"`
+}
+
+type Config struct {
+	RequestHeaders []RequestHeader `json:"requestHeaders,omitempty"`
+}
+
+func CreateConfig() *Config {
+	return &Config{
+		RequestHeaders: make([]RequestHeader, 0),
+	}
+}
+
+type ResponseHeaderForward struct {
+	next           http.Handler
+	name           string
+	requestHeaders []RequestHeader
+}
+
+func New(ctx context.Context, next http.Handler, config *Config, name string) (http.Handler, error) {
+	if len(config.RequestHeaders) == 0 {
+		return nil, fmt.Errorf("RequestHeaders cannot be empty")
+
+	}
+
+	for _, headerName := range config.RequestHeaders {
+		if headerName.Name == "" {
+			return nil, fmt.Errorf("RequestHeaders.Name cannot be empty")
+		}
+	}
+	return &ResponseHeaderForward{
+		next:           next,
+		name:           name,
+		requestHeaders: config.RequestHeaders,
+	}, nil
+}
+
+func (a *ResponseHeaderForward) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
+	a.next.ServeHTTP(rw, req)
+
+	for _, requestHeader := range a.requestHeaders {
+		headerValue := req.Header.Get(requestHeader.Name)
+		if headerValue == "" {
+			continue
+		}
+
+		rw.Header().Set(requestHeader.Name, headerValue)
+	}
+}