autocert

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Golang Library for automatic LetsEncrypt SSL Certificates

Obtains certificates automatically, and manages renewal and hot reload for your Golang application. It uses the awesome LEGO Library to perform ACME challenges. Lego is vendored with dep, in case of any breaking API changes.

CAUTION: Beta, use with care.

You need to supply the following data to autocert: Domains, Contact Email and a Directory to store the certs in (CacheDir). On startup, call the autocert.Init() function and pass your config. You will receive a certReloader instance, that has a GetCertificateFunc to allow hot reloading the cert upon renewal. See Usage for a detailed example.

For more advanced usage, see the config section for all configuration options.

Install

go get -u -v github.com/foomo/autocert

Usage

autocert has a default configuration available: autocert.Default

You will need to update the Domains, CacheDir and SSLEmail and you are ready to go.

// do the cert magic
cfg := autocert.Default
cfg.Domains = []string{"yourdomain.com", "www.yourdomain.com"}
cfg.CacheDir = "/etc/letsencrypt/live/yourdomain.com"
cfg.SSLEmail = "you@emailprovider.com"
certReloader, err := autocert.Init(cfg)
if err != nil {
	log.Fatal("autocert init failed: ", err)
}

// redirect HTTP to HTTPS
// CAUTION: This has to be done AFTER autocert setup
// Otherwise Port 80 will be blocked and cert registration fails!
cLog.Info("starting HTTP Listener on Port 80")
go http.ListenAndServe(":80", http.HandlerFunc(redirect))

// init strict tlsConfig with certReloader
// you could also use a default &tls.Config{}, but be warned this is highly insecure
tlsconf := tlsconfig.NewServerTLSConfig(tlsconfig.TLSModeServerStrict)

// now set GetCertificate to the reloaders GetCertificateFunc to enable hot reload
tlsconf.GetCertificate = certReloader.GetCertificateFunc()

// init server
s := &http.Server{
	Addr:      ":443",
	TLSConfig: tlsconf,
}

// lets go
log.Fatal(s.ListenAndServeTLS("", ""))

Configuration

You can pass a custom config to suit your needs.

Parameters are explained below.

// Config allows configuration of autocert
type Config struct {

	// renew the certificate X hours before it expires
	// LetsEncrypt Certs are valid for 90 Days
	RenewBefore int

	// Interval for checking if cert is closer to expiration than RenewBefore
	CheckInterval time.Duration

	// SSLEmail for contact
	SSLEmail string

	// ACME Directory URL. Can be set to https://acme-staging.api.letsencrypt.org/directory for testing
	DirectoryURL string

	// Endpoints for webroot challenge
	// CAUTION: challenge must be received on port 80 and 443
	// if you choose different ports here you must redirect the traffic
	HTTPAddress string
	TLSAddress  string

	// UNIX Permission for the CacheDir and all files inside
	CacheDirPerm os.FileMode

	// Domains for which to obtain the certificate
	Domains []string

	// Path of the CacheDir
	CacheDir string
}

License

MIT