Add JWT authentication

README.md

@@ -1,2 +1,14 @@
 # realtime-messaging
 Real time pubsub messaging with Golang and Websockets
+
+### Build and run the project
+```
+docker compose up --build
+```
+
+### Obtain a JWT token
+```
+docker compose run auth-cli /app/auth-cli-bin -action create -username demo-user
+```
+
+### Access Grafana dashboard: localhost:3002/d/realtime-metrics-dashboard

auth-cli/main.go

@@ -0,0 +1,50 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"log"
+	"os"
+	"time"
+
+	"github.com/golang-jwt/jwt/v5"
+	"github.com/iulian509/realtime-messaging/config"
+)
+
+func main() {
+	action := flag.String("action", "", "Action to perform (create)")
+	username := flag.String("username", "", "Username for the token")
+
+	flag.Parse()
+
+	if *action != "create" {
+		flag.Usage()
+		os.Exit(1)
+	}
+
+	if *username == "" {
+		log.Fatal("username is required for create action")
+	}
+
+	token, err := generateJWT(*username)
+	if err != nil {
+		log.Fatalf("failed to generate JWT: %v", err)
+	}
+
+	fmt.Printf("generated JWT for user %s: %s\n", *username, token)
+}
+
+func generateJWT(username string) (string, error) {
+	config, err := config.LoadConfig()
+	if err != nil {
+		log.Fatalf("failed to load YAML configuration")
+	}
+
+	claims := jwt.MapClaims{
+		"username": username,
+		"exp":      time.Now().Add(time.Hour * 1).Unix(),
+	}
+
+	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
+	return token.SignedString([]byte(config.JWT.SecretKey))
+}

config/config-dev.yml

@@ -1,2 +1,5 @@
 nats:
   host: 'nats://realtime-messaging-nats:4222'
+
+jwt:
+  secretKey: "your-very-secure-secret-key" # Do not store real keys here

config/config.go

@@ -12,6 +12,9 @@ type Config struct {
 	Nats struct {
 		Host string `yaml:"host"`
 	}
+	JWT struct {
+		SecretKey string `yaml:"secretKey"`
+	}
 }
 
 func LoadConfig() (*Config, error) {

docker-compose.yml

@@ -42,3 +42,7 @@ services:
     volumes:
       - ./grafana/provisioning:/etc/grafana/provisioning
       - ./grafana/dashboards:/var/lib/grafana/dashboards
+  auth-cli:
+    build:
+      context: .
+      dockerfile: docker/auth-cli/Dockerfile

docker/auth-cli/Dockerfile

@@ -0,0 +1,11 @@
+FROM golang:1.24.2-alpine
+
+WORKDIR /app
+
+COPY config/ ./config/
+COPY auth-cli/ ./auth-cli
+COPY go.mod go.sum ./
+
+RUN go mod download
+
+RUN CGO_ENABLED=0 GOOS=linux go build -o auth-cli-bin -ldflags "-s -w" ./auth-cli/

go.mod

@@ -4,6 +4,7 @@ go 1.24.2
 
 require (
 	github.com/goccy/go-yaml v1.17.1
+	github.com/golang-jwt/jwt/v5 v5.2.2
 	github.com/gorilla/websocket v1.5.3
 	github.com/nats-io/nats.go v1.40.1
 	github.com/prometheus/client_golang v1.21.1

go.sum

@@ -7,6 +7,8 @@ github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/goccy/go-yaml v1.17.1 h1:LI34wktB2xEE3ONG/2Ar54+/HJVBriAGJ55PHls4YuY=
 github.com/goccy/go-yaml v1.17.1/go.mod h1:XBurs7gK8ATbW4ZPGKgcbrY1Br56PdM69F7LkFRi1kA=
+github.com/golang-jwt/jwt/v5 v5.2.2 h1:Rl4B7itRWVtYIHFrSNd7vhTiz9UpLdi6gZhZ3wEeDy8=
+github.com/golang-jwt/jwt/v5 v5.2.2/go.mod h1:pqrtFR0X4osieyHYxtmOUWsAWrfe1Q5UVIyoH402zdk=
 github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
 github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/gorilla/websocket v1.5.3 h1:saDtZ6Pbx/0u+bgYQ3q96pZgCzfhKXGPqt7kZ72aNNg=

internal/auth/auth.go

@@ -0,0 +1,46 @@
+package auth
+
+import (
+	"fmt"
+	"log"
+	"net/http"
+
+	"github.com/golang-jwt/jwt/v5"
+	"github.com/iulian509/realtime-messaging/config"
+)
+
+func AuthMiddleware(next http.HandlerFunc) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		authHeader := r.Header.Get("Authorization")
+		if authHeader == "" {
+			http.Error(w, "missing Authorization header", http.StatusUnauthorized)
+			return
+		}
+
+		const bearerPrefix = "Bearer "
+		if len(authHeader) < len(bearerPrefix) || authHeader[:len(bearerPrefix)] != bearerPrefix {
+			http.Error(w, "invalid Authorization header format", http.StatusUnauthorized)
+			return
+		}
+
+		tokenString := authHeader[len(bearerPrefix):]
+		config, err := config.LoadConfig()
+		if err != nil {
+			log.Fatalf("failed to load YAML configuration")
+		}
+
+		token, err := jwt.Parse(tokenString, func(token *jwt.Token) (interface{}, error) {
+			if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
+				return nil, fmt.Errorf("unexpected signing method: %v", token.Header["alg"])
+			}
+			return []byte(config.JWT.SecretKey), nil
+		})
+
+		if err != nil || !token.Valid {
+			http.Error(w, "invalid or expired token", http.StatusUnauthorized)
+			return
+		}
+
+		next.ServeHTTP(w, r)
+	}
+}

publisher/cmd/publisher/main.go

@@ -5,6 +5,7 @@ import (
 	"net/http"
 
 	"github.com/iulian509/realtime-messaging/config"
+	"github.com/iulian509/realtime-messaging/internal/auth"
 	"github.com/iulian509/realtime-messaging/internal/metrics"
 	"github.com/iulian509/realtime-messaging/publisher/internal/handlers"
 	"github.com/iulian509/realtime-messaging/publisher/internal/mq"
@@ -28,7 +29,7 @@ func main() {
 	}
 
 	http.HandleFunc("/metrics", metrics.PromHandler())
-	http.HandleFunc("/publish", metrics.PrometheusMiddleware(deps.PublisherHandler))
+	http.HandleFunc("/publish", metrics.PrometheusMiddleware(auth.AuthMiddleware(deps.PublisherHandler)))
 
 	err = http.ListenAndServe(":3000", nil)
 	log.Println("publisher service running on :3000")

subscriber/cmd/subscriber/main.go

@@ -5,6 +5,7 @@ import (
 	"net/http"
 
 	"github.com/iulian509/realtime-messaging/config"
+	"github.com/iulian509/realtime-messaging/internal/auth"
 	"github.com/iulian509/realtime-messaging/internal/metrics"
 	"github.com/iulian509/realtime-messaging/subscriber/internal/handlers"
 	"github.com/iulian509/realtime-messaging/subscriber/internal/mq"
@@ -28,7 +29,7 @@ func main() {
 	}
 
 	http.HandleFunc("/metrics", metrics.PromHandler())
-	http.HandleFunc("/subscribe", metrics.PrometheusMiddleware(deps.SubscriberHandler))
+	http.HandleFunc("/subscribe", metrics.PrometheusMiddleware(auth.AuthMiddleware(deps.SubscriberHandler)))
 
 	err = http.ListenAndServe(":3001", nil)
 	log.Println("subscriber service running on :3001")