letsencrypt

Automatic Let's Encrypt HTTPS Certificates for node.js

• Automatic HTTPS with ExpressJS
• Automatic live renewal
• On-the-fly HTTPS certificates for Dynamic DNS (in-process, no server restart)
• Works with node cluster out of the box
• usable via commandline as well
• Free SSL (HTTPS Certificates for TLS)
• 90-day certificates

See Also

• See the node-letsencrypt Examples
• Let's Encrypt in (exactly) 90 seconds with Caddy
• lego: Let's Encrypt for golang

Install

npm install --save letsencrypt
npm install --global letsencrypt-cli

Usage

letsencrypt-cli

See more at letsencrypt-cli

letsencrypt certonly \
  --agree-tos --email user@example.com \
  --standalone \
  --domains example.com,www.example.com \
  --config-dir ~/letsencrypt/etc \
  --server https://acme-staging.api.letsencrypt.org/directory \

ls ~/letsencrypt/etc/live

letsencrypt-express

'use strict';

// Note: using staging server url, remove .testing() for production
var lex = require('letsencrypt-express').testing();
var express = require('express');
var app = express();

app.use('/', function (req, res) {
  res.send({ success: true });
});

lex.create('./letsencrypt.config', app).listen([80], [443, 5001], function () {
  console.log("ENCRYPT __ALL__ THE DOMAINS!");
});

See more at letsencrypt-express

letsencrypt (the library)

There are NO DEFAULTS. A number of constants (such as LE.stagingServerUrl and LE.configDir) are exported for your convenience, but all required options must be specified by the library invoking the call.

Open an issue if you need a variable for something that isn't there yet.

var LE = require('letsencrypt');


var config = {
, server: LE.stagingServerUrl                               // or LE.productionServerUrl

, configDir: require('homedir')() + '/letsencrypt/etc'      // or /etc/letsencrypt or wherever

, privkeyPath: ':config/live/:hostname/privkey.pem'         //
, fullchainPath: ':config/live/:hostname/fullchain.pem'     // Note: both that :config and :hostname
, certPath: ':config/live/:hostname/cert.pem'               //       will be templated as expected
, chainPath: ':config/live/:hostname/chain.pem'             //

, debug: false
};


var handlers = {
  setChallenge: function (opts, hostname, key, val, cb) {}  // called during the ACME server handshake, before validation
, removeChallenge: function (opts, hostname, key, cb) {}    // called after validation on both success and failure
, getChallenge: function (opts, hostname, key, cb) {}       // this is special because it is called by the webserver
                                                            // (see letsencrypt-cli/bin & letsencrypt-express/standalone),
                                                            // not by the library itself

, agreeToTerms: function (tosUrl, cb) {}                    // gives you an async way to expose the legal agreement
                                                            // (terms of use) to your users before accepting
};


var le = LE.create(config, handlers);

                                                              // checks :conf/renewal/:hostname.conf
le.register({                                                 // and either renews or registers

  domains: ['example.com']                                    // CHANGE TO YOUR DOMAIN
, email: 'user@email.com'                                     // CHANGE TO YOUR EMAIL
, agreeTos: false                                             // set to true to automatically accept an agreement
                                                              // which you have pre-approved (not recommended)
}, function (err) {

  if (err) {
    // Note: you must have a webserver running
    // and expose handlers.getChallenge to it
    // in order to pass validation
    // See letsencrypt-cli and or letsencrypt-express
    console.error('[Error]: node-letsencrypt/examples/standalone');
    console.error(err.stack);
  } else {
    console.log('success');
  }
});

However, due to the nature of what this library does, it has a few more "moving parts" than what makes sense to show in a minimal snippet.

Examples

The simplest example of setting up a webserver appropriately is probably letsencrypt-cli (~120 lines of code):

• letsencrypt-cli//lib/standalone.js

Similary, letsencrypt-cli's usage of le.register() is fairly simple (~75 lines of code):

• letsencrypt-cli/bin/letsencrypt.js

One-Time Registration

Register a 90-day certificate manually, on a whim

Note: We've been running a fast development cycle and this example may be out of date. The API shouldn't have changed much but, we probably need to come back and update it.

Snippets

commandline-minimal:

Part 1: the Let's Encrypt client:

'use strict';

var LE = require('letsencrypt');
var config = require('./config-minimal');

// Note: you should make this special dir in your product and leave it empty
config.le.webrootPath = __dirname + '/../tests/acme-challenge';
config.le.server = LE.stagingServer;


//
// Manual Registration
//
var le = LE.create(config.backend, config.le);
le.register({
  agreeTos: true
, domains: ['example.com']          // CHANGE TO YOUR DOMAIN
, email: 'user@email.com'           // CHANGE TO YOUR EMAIL
}, function (err) {
  if (err) {
    console.error('[Error]: node-letsencrypt/examples/standalone');
    console.error(err.stack);
  } else {
    console.log('success');
  }

  plainServer.close();
  tlsServer.close();
});

Part 2: Express Web Server:

//
// Express App
//
var app = require('express')();
app.use('/', le.middleware());  // TODO le.middleware was moved to letsencrypt-express, we need to update the docs here


//
// HTTP & HTTPS servers
// (required for domain validation)
//
var plainServer = require('http').createServer(app).listen(config.plainPort, function () {
  console.log('Listening http', this.address());
});

var tlsServer = require('https').createServer({
  key: config.tlsKey
, cert: config.tlsCert
, SNICallback: le.sniCallback
}, app).listen(config.tlsPort, function () {
  console.log('Listening http', this.address());
});

Runnable Demo

• commandline (standalone with "webroot")

# manual standalone registration via commandline
# (runs against testing server on tls port 5001)
node examples/commandline.js example.com,www.example.com user@example.net agree

Express

Fully Automatic HTTPS with ExpressJS using Free SSL certificates from Let's Encrypt

Snippets

• Minimal ExpressJS Example

'use strict';

var LE = require('letsencrypt');
var config = require('./config-minimal');

// Note: you should make this special dir in your product and leave it empty
config.le.webrootPath = __dirname + '/../tests/acme-challenge';
config.le.server = LE.stagingServer;

//
// Automatically Register / Renew Domains
//
var le = LE.create(config.backend, config.le, {
  sniRegisterCallback: function (args, expiredCert, cb) {
    // Security: check that this is actually a subdomain we allow
    // (otherwise an attacker can cause you to rate limit against the LE server)

    var hostname = args.domains[0];
    if (!/\.example\.com$/.test(hostname)) {
      console.error("bad domain '" + hostname + "', not a subdomain of example.com");
      cb(nul, null);
    }

    // agree to the LE TOS for this domain
    args.agreeTos = true;
    args.email = 'user@example.com';

    // use the cert even though it's expired
    if (expiredCert) {
      cb(null, expiredCert);
      cb = function () { /*ignore*/ };
    }

    // register / renew the certificate in the background
    le.register(args, cb);
  }
});


//
// Express App
//
var app = require('express')();
app.use('/', le.middleware());


//
// HTTP & HTTPS servers
//
require('http').createServer(app).listen(config.plainPort, function () {
  console.log('Listening http', this.address());
});

require('https').createServer({
  key: config.tlsKey
, cert: config.tlsCert
, SNICallback: le.sniCallback
}, app).listen(config.tlsPort, function () {
  console.log('Listening http', this.address());
});

Runnable Example

• Full ExpressJS Example

# clear out the certificates
rm -rf tests/letsencrypt.*

# automatic registration and renewal (certs install as you visit the site for the first time)
# (runs against testing server on tls port 5001)
node examples/express.js example.com,www.example.com user@example.net agree

# this will take a moment because it won't respond to the tls sni header until it gets the certs
curl https://example.com/

non-root

If you want to run this as non-root, you can.

You just have to set node to be allowed to use root ports

# node
sudo setcap cap_net_bind_service=+ep /usr/local/bin/node

and then make sure to set all of of the following to a directory that your user is permitted to write to

• webrootPath
• configDir

API

LetsEncrypt.init(leConfig, handlers)                      // wraps a given
LetsEncrypt.create(backend, leConfig, handlers)           // wraps a given "backend" (the python or node client)
LetsEncrypt.stagingServer                                 // string of staging server for testing

le.middleware()                                           // middleware for serving webrootPath to /.well-known/acme-challenge
le.sniCallback(hostname, function (err, tlsContext) {})   // uses fetch (below) and formats for https.SNICallback
le.register({ domains, email, agreeTos, ... }, cb)        // registers or renews certs for a domain
le.fetch({domains, email, agreeTos, ... }, cb)            // fetches certs from in-memory cache, occasionally refreshes from disk
le.validate(domains, cb)                                  // do some sanity checks before attempting to register
le.registrationFailureCallback(err, args, certInfo, cb)   // called when registration fails (not implemented yet)

LetsEncrypt.create(backend, leConfig, handlers)

leConfig

The arguments passed here (typically webpathRoot, configDir, etc) will be merged with any args (typically domains, email, and agreeTos) and passed to the backend whenever it is called.

Typically the backend wrapper will already merge any necessary backend-specific arguments.

Example:

{ webrootPath: __dirname, '/acme-challenge'
, fullchainTpl: '/live/:hostname/fullchain.pem'
, privkeyTpl: '/live/:hostname/fullchain.pem'
, configDir: '/etc/letsencrypt'
}

Note: webrootPath can be set as a default, semi-locally with webrootPathTpl, or per registration as webrootPath (which overwrites leConfig.webrootPath).

handlers optional

h.setChallenge(hostnames, name, value, cb):

default is to write to fs

h.getChallenge(hostnames, value cb)

default is to read from fs

h.sniRegisterCallback(args, currentCerts, cb)

The default is to immediately call cb(null, null) and register (or renew) in the background during the SNICallback phase. Right now it isn't reasonable to renew during SNICallback, but around February when it is possible to use ECDSA keys (as opposed to RSA at present), registration will take very little time.

This will not be called while another registration is already in progress.

SECURITY WARNING: If you use this option with a custom h.validate(), make sure that args.domains refers to domains you expect, otherwise an attacker will spoof SNI and cause your server to rate-limit letsencrypt.org and get blocked. Note that le.validate() will check A records before attempting to register to help prevent such possible attacks.

h.validate(domains, cb)

When specified this will override le.validate(). You will need to do this if the ip address of this server is not one specified in the A records for your domain.

le.middleware()

An express handler for /.well-known/acme-challenge/<challenge>. Will call getChallenge([hostname], key, cb) if present or otherwise read challenge from disk.

Example:

app.use('/', le.middleware())

le.sniCallback(hostname, function (err, tlsContext) {});

Will call fetch. If fetch does not return certificates or returns expired certificates it will call sniRegisterCallback(args, currentCerts, cb) and then return the error, the new certificates, or call fetch a final time.

Example:

var server = require('https').createServer({ SNICallback: le.sniCallback, cert: '...', key: '...' });
server.on('request', app);

le.register({ domains, email, agreeTos, ... }, cb)

Get certificates for a domain

Example:

le.register({
  domains: ['example.com', 'www.example.com']
, email: 'user@example.com'
, webrootPath: '/srv/www/example.com/public'
, agreeTos: true
}, function (err, certs) {
  // err is some error

  console.log(certs);
  /*
  { cert: "contents of fullchain.pem"
  , key: "contents of privkey.pem"
  , renewedAt: <date in milliseconds>
  , duration: <duration in milliseconds (90-days)>
  }
  */
});

le.isValidDomain(hostname)

returns true if hostname is a valid ascii or punycode domain name.

(also exposed on the main exported module as LetsEncrypt.isValidDomain())

le.validate(args, cb)

Used internally, but exposed for convenience. Checks LetsEncrypt.isValidDomain() and then checks to see that the current server

Called before backend.register() to validate the following:

• the hostnames don't use any illegal characters
• the server's actual public ip (via api.apiify.org)
• the A records for said hostnames

le.fetch(args, cb)

Used internally, but exposed for convenience.

Checks in-memory cache of certificates for args.domains and calls then calls backend.fetch(args, cb) after merging args if necessary.

le.registrationFailureCallback(err, args, certInfo, cb)

Not yet implemented

This is what args looks like:

{ domains: ['example.com', 'www.example.com']
, email: 'user@email.com'
, agreeTos: true
, configDir: '/etc/letsencrypt'
, fullchainTpl: '/live/:hostname/fullchain.pem'  // :hostname will be replaced with the domainname
, privkeyTpl: '/live/:hostname/privkey.pem'
, webrootPathTpl: '/srv/www/:hostname/public'
, webrootPath: '/srv/www/example.com/public'    // templated from webrootPathTpl
}

This is what the implementation should look like:

(it's expected that the client will follow the same conventions as the python client, but it's not necessary)

Change History

• v1.1.0 Added letiny-core, removed node-letsencrypt-python
• v1.0.2 Works with node-letsencrypt-python
• v1.0.0 Thar be dragons

LICENSE

Dual-licensed MIT and Apache-2.0

See LICENSE