auth/jwt.go

package auth

import (
	"crypto/rsa"
	"fmt"
	"net/http"
	"strings"

	"github.com/golang-jwt/jwt"
)

type JWTMiddleware struct {
	publicKey *rsa.PublicKey
}

func NewJWTMiddleware(publicKey *rsa.PublicKey) *JWTMiddleware {
	return &JWTMiddleware{publicKey: publicKey}
}

func (m *JWTMiddleware) Middleware(next http.HandlerFunc) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		// Skip auth endpoint
		if r.URL.Path == "/auth" {
			next(w, r)
			return
		}

		authHeader := r.Header.Get("Authorization")
		if authHeader == "" {
			http.Error(w, "Authorization header required", http.StatusUnauthorized)
			return
		}

		tokenString := strings.TrimPrefix(authHeader, "Bearer ")
		token, err := jwt.Parse(tokenString, func(token *jwt.Token) (interface{}, error) {
			if _, ok := token.Method.(*jwt.SigningMethodRSA); !ok {
				return nil, fmt.Errorf("unexpected signing method: %v", token.Header["alg"])
			}
			return m.publicKey, nil
		})

		if err != nil {
			http.Error(w, "Invalid token", http.StatusUnauthorized)
			return
		}

		if !token.Valid {
			http.Error(w, "Invalid token", http.StatusUnauthorized)
			return
		}

		next(w, r)
	})
}