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package letscloud

import ""

Package letscloud provides a mechanism for caching letsencrypt data in Google Cloud Storage. It is for use with

Setting up signed URLs

This package uses signed Cloud Storage URLs to read from and write to a Google Cloud Storage bucket. The following instructions describe how to set up a bucket, a service account for accessing the bucket, and a pair of signed URLS to GET and PUT a specific object in that bucket.

Unless you know what you are doing, it is recommended that you create a new bucket specifically for letsencrypt cache files. This will ensure that you use the default (secure) ACLs for the bucket, and protect your TLS certificates from being stolen.

Create a Service Account to access your bucket

1. Visit
2. Click 'Create service account'.
3. Give it a name (eg "myproject-letsencrypt").
4. Check 'Furnish a new private key' (and leave 'Key type' as 'JSON').
5. Click 'Create'.
6. Put the downloaded private key somewhere safe and note its ID.

Create a Cloud Storage bucket for your letsencrypt cache

1. Visit
2. Click 'Create bucket'.
3. Give it a name (eg "myproject-letsencrypt").
4. Click 'Create'.
5. You're now looking at your new bucket. Click 'Buckets' to go back.
6. Click the icon to the right of the new bucket,
   and click 'Edit bucket permissions'.
7. Click 'Add item' and add a 'User' with the Service Account ID and
   'Owner' permissions.
8. Click 'Save'.

Create signed GET and PUT URLs

1. Install the Google Cloud SDK:
2. Create the signed PUT URL:
   $ gsutil signurl -m PUT -d 3650d /path/to/key.json gs://$BUCKET/$OBJECT
   (Where $BUCKET is the storage bucket you created, and $OBJECT
   is some unique string that identifies this particular service.)
3. Populate the PUT URL with an empty file:
   $ curl -H 'Content-length: 0' -X PUT '$PUT_URL'
   (Where $PUT_URL is the URL that gsutil just printed.)
4. Create the signed GET URL:
   $ gsutil signurl -m PUT -d 3650d /path/to/key.json gs://$BUCKET/$OBJECT
5. Make a note of both the PUT and GET URLs for use with this package's
   Cache function.

Storing the signed URLs securely

If you're using Google Compute Engine, a convenient and secure place to store the Signed URLs is in the metadata of your compute instance. The following code fetches the signed URLs from the "letscloud-get-url" and "letscloud-put-url" instance attributes and sets up a letsencrypt.Manager that stores its cache in the object specified by those URLs.

var m letsencrypt.Manager
v := func(key string) string {
	v, err := metadata.InstanceAttributeValue(key)
	if err != nil {
		log.Fatalf("Couldn't read %q metadata value: %v", key, err)
	return v
if err := letscloud.Cache(&m, v("letscloud-get-url"), v("letscloud-put-url")); err != nil {

(Package metadata is "".)


Package Files


func Cache Uses

func Cache(m *letsencrypt.Manager, getURL, putURL string) error

Cache caches letsencrypt data for the given Manager in the Google Cloud Storage object identified by the getURL and putURL values. See the package comment for details on obtaining these values.

Package letscloud imports 6 packages (graph) and is imported by 1 packages. Updated 2016-07-20. Refresh now. Tools for package owners.