Overview

SMCache is a Go library to store certificates from Let's Encrypt in GCP Secret Manager. It is an implementation of the Cache within acme autocert that will store data within Google Cloud's Secret Manager.

This is not an official Google product.

Simple Example

import (
	"github.com/jwendel/smcache"
	"golang.org/x/crypto/acme/autocert"
)

func main() {
  m := &autocert.Manager{
      Cache:      smcache.NewSMCache(smcache.Config{ProjectID: "my-project-id", SecretPrefix: "test-"}),
      Prompt:     autocert.AcceptTOS,
      HostPolicy: autocert.HostWhitelist("example.com", "www.example.com"),
  }
  s := &http.Server{
      Addr:         ":https",
      TLSConfig:    m.TLSConfig(),
  }
  panic(s.ListenAndServeTLS("", ""))
}

Detailed Guide to Setting up SMCache

Permission setup in GCP

SMCache requires admin access to the Secret Manager API to function properly. This is configure in the IAM policy for a resource.

Example of enabling this API for Compute Engine:

1. Go the IAM policy management
2. Edit the <projectId>-compute@developer.gserviceaccount.com (Compute Engine default service account)
3. Click Add Another Role, and select Secret Manager Admin.

Bonus Security: if you're paranoid about this resource getting access to other secrets, you can set a condition on the Role we just added.

4. click Add Condition, then set a name and description for it.
5. For Conditional Type, select Resource -> Name, Operator: Starts With, and set it to whatever value you want, such as "test-".
   • Note: this prefix should be the same as the SecretPrefix you set on the smcache.Config.

Demos

There are 2 demos checked into this repo under example/.

• Autocert+Http Example - shows how to use this library with Autocert and the Go HTTP std server.
• Simple Example - demos how this library interacts with GCP's Secret Manager.

Other notes

• Requires Go >= 1.13.0 (due to use of fmt.Errorf)