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Heroku buildpack Stunnel

This is a Heroku buildpack that allows an application to use an stunnel to connect securely to any service that has its own stunnel server configured.

Usage

First, ensure that the service to which you'd like to connect has stunnel configured and running.

Then set this buildpack as your initial buildpack with:

$ heroku buildpacks:add https://github.com/Baremetrics/heroku-buildpack-stunnel.git -a <your-app-name>

Then confirm you are using this buildpack as well as your language buildpack like so:

heroku buildpacks -a baremetrics-stage                             
=== baremetrics-stage Buildpack URLs
1. https://github.com/Baremetrics/heroku-buildpack-stunnel.git
2. https://github.com/DataDog/heroku-buildpack-datadog.git
3. heroku/nodejs
4. heroku/ruby

For more information on using multiple buildpacks check out this devcenter article.

Next, for each process that should connect to a server securely, you will need to preface the command in your Procfile with bin/start-stunnel. In this example, we want the web process to use a secure connection to a server. The worker process doesn't interact with our DB server, so bin/start-stunnel was not included:

$ cat Procfile
web:    bin/start-stunnel bundle exec unicorn -p $PORT -c ./config/unicorn.rb -E $RACK_ENV
worker: bundle exec rake worker

We're then ready to deploy to Heroku with an encrypted connection between the dynos and our DB server.

Configuration

The buildpack will install and configure stunnel to connect to one or more servers configured as a list in the STUNNEL_URLS variable over a SSL connection. Prepend bin/start-stunnel to any process in the Procfile to run stunnel alongside that process. e.g. $ heroku config:add STUNNEL_URLS="MYSQL_DATABASE_URL PG_DATABASE_URL"

Note that stunnel will use whatever port you have condigured in your MYSQL_DATABASE_URL as a refernce for the stunnel connection. The formula to decide ont he stunnel server port is [port in connection string] - 1 The following parameters are required in the db connection string: schema://:password@host:port/dbname It is also possible (and advised) to pass the username, e.g. schema://username:password@host:port/dbname Note that all query params that would appeat after the dbname would pass as is Example of connection string and how will it translated in the stunnel configuration:

MYSQL_DATABASE_URL=mysql2://username:password@host:3306/dbname

Will set the following configuration on the stunnel client:

[MYSQL_DATABASE_URL]
   client = yes
   accept = 127.0.0.1:43421
   connect = host:3305
   retry = no

Make sure the port 3305 is open on your server.

Stunnel settings

Some settings are configurable through app config vars at runtime:

  • STUNNEL_ENABLED: Default to true, enable or disable stunnel.
  • STUNNEL_LOGLEVEL: Default is notice, set to info or debug for more verbose log output.