How To Add a DNSimple SSL Certificate to Heroku
1. Buy an SSL Cert from DNSimple
The first thing to do is to buy an SSL cert from DNSimple (I usually only buy wildcard certs nowadays). Go to the manage interface for the domain that you want to buy the SSL cert, and click “Buy an SSL Certificate.” The interface will walk you through the rest of the steps. As long as you’re not super paranoid, you can even let DNSimple generate the private key and certificate signing request for you. Don’t worry, you can delete the private key from the DNSimple servers immediately after you save it to a secure place.
After a few minutes, you should receive some emails with your new SSL cert (a resulting wildcard certificate will actually come from Comodo).
2. Build the Public Certificate Chain PEM file
Along with your SSL certificate, Comodo will send a zip file containing the Root CA Certificate and some Intermediate CA Certificates. Before we can upload our certificate to Heroku, we need to concatenate these files together to form the certificate chain.
$ cat STAR_yourdomain_com.crt EssentialSSLCA_2.crt \ ComodoUTNSGCCA.crt UTNAddTrustSGCCA.crt \ AddTrustExternalCARoot.crt > STAR_yourdomain_com-bundle.pem
Make sure you concatenate these files in the correct order, starting with your cert and ending at the root cert; otherwise, Heroku will not be able to recognize the result as a public key certificate.
This example shows the chain for a wildcard certificate (from Comodo). Your chain might be different if you purchased a single subdomain certificate from DNSimple (I think those come from RapidSSL, which might deliver root certs).
Note: To make sure Heroku can automatically start your server, you must not have a passphrase assigned to the certficate. If you let DNSimple do all the work for you, you should already have a passphrase-free cert.
3. Add the SSL Endpoint Add-on to Your App
$ heroku addons:add ssl:endpoint
Read more about the SSL Endpoint Add-on.
4. Upload your SSL Cert and Private Key to Heroku
$ heroku certs:add STAR_yourdomain_com-bundle.pem STAR_yourdomain_com-private.key
That’s it! You can find more information and instructions on what to do after this from the Heroku Dev Center.