gcsfileserver

Want to serve non-public files off Google Cloud Storage over https to a select group of people? Then Google Cloud Storage File Server may be for you.

Uses App Engine to keep costs very low (as long as your request volume is low, which it usually is when serving files to a small group of people) or can be served as a container in a kubernetes cluster.
Uses Google Cloud Identity Aware Proxy, which lets you specify which Google Apps or gmail emails should have access
HTTPS provided by App Engine for no added cost
If you have no requests in a month, your cost is probably $0.00 (excluding Google Cloud Storage costs to store your files)
Your GCS bucket is not open to the public
GCS files are read-only through gcsfileserver

Caveat: not intended for very high request rates. That use case would require implementing caching of some objects to reduce the network round trips to GCS.

Setup

Set up IAP
Optional, set up custom domain in App Engine > Settings. This gets you free SSL to a custom domain name.
In the root of your repository create an app.yaml and specify the GCS bucket you want to serve files from:

runtime: go114
main: ./
handlers:
- url: /.*
  script: auto

env_variables:
  BUCKET: "rchapman.appspot.com"

Make sure your bucket is created and is not publicly accessible.
Find your app engine service account in Google Cloud Console > IAM For this example, I'll use mine, rchapman@appspot.gserviceaccount.com
In the Google Cloud Console, go to your GCS bucket and give your app engine service account (rchapman@appspot.gserviceaccount.com in the previous example) the roles "Storage Object Viewer" and "Storage Legacy Bucket Reader"
Create main.go in the same directory as your app.yaml file:

package main

import (
	"log"
	"net/http"
	"os"

	"github.com/rchapman/gcsfileserver/server"
)

func main() {
	port := os.Getenv("PORT")
	if port == "" {
		port = "8080"
	}
	s := server.Server{
		DirListPageSize: 100,
	}
	http.Handle("/", &s)

	log.Fatal(http.ListenAndServe(":"+port, nil))

}

Run go mod init github.com/rchapman/gcsfileserver from the root of the project.
Deploy the app with gcloud app deploy --project=YOUR_GCP_PROJECT (for example gcloud app deploy --project=rchapman)
Open web browser with gcloud app browse --project=YOUR_GCP_PROJECT

caulagi/gcsfileserver

gcsfileserver

Setup