Firebase Middleware for Echo framework

authMiddleware.go

package auth

import (
	"context"
	firebase "firebase.google.com/go"
	"github.com/labstack/echo/v4"
	"google.golang.org/api/option"
	"net/http"
	"strings"
)

func Client() *firebase.App {
	opt := option.WithCredentialsFile("secure/firebase.json")
	app, err := firebase.NewApp(context.Background(), nil, opt)
	if err != nil {
		return nil
	}

	return app
}

func Auth() echo.MiddlewareFunc {
	return auth
}

func auth(next echo.HandlerFunc) echo.HandlerFunc {
	return func(c echo.Context) error {
		fb, err := Client().Auth(context.Background())
		if err != nil {
			return nil
		}

		auth := c.Request().Header.Get("Authorization")
		idToken := strings.Replace(auth, "Bearer ", "", 1)
		token, err := fb.VerifyIDToken(context.Background(), idToken)
		if err != nil {
			return c.NoContent(http.StatusForbidden)
		}

		c.Set("token", token)
		return next(c)
	}
}