Last updated June 14, 2023

SSL is a cryptographic protocol that provides end-to-end encryption and integrity for all web requests. Apps that transmit sensitive data should enable SSL to ensure all information is transmitted securely.

To enable SSL on a custom domain, for example, www.example.com, use the SSL Endpoint add-on.

SSL Endpoint is a paid add-on service. Please keep this in mind when provisioning the service.

Overview

Because of the unique nature of SSL validation, provisioning SSL for your application is a multi-step process that involves several third parties. You will need to:

1. Purchase an SSL certificate from your SSL provider
2. Provision an SSL endpoint from Heroku
3. Upload the certificate to Heroku
4. Update your DNS settings to reference the new SSL endpoint URL

Acquire SSL certificate

Purchasing an SSL certificate varies in cost and process depending on the vendor. DNSimple and ExpeditedSSL offer simple ways to purchase a certificate and are recommended solutions.

Otherwise, using other SSL providers requires some or all of the following steps.

Generate private key

Before requesting an SSL cert, you need to generate a private key in your local environment using the openssl tool. If you cannot execute the openssl command from the terminal you may need to install it.

Use openssl to generate a new private key.

$ openssl genrsa -aes256 -out server.pass.key 4096
...
Enter pass phrase for server.pass.key:
Verifying - Enter pass phrase for server.pass.key:

The private key needs to be stripped of its password so it can be loaded without manually entering the password.

$ openssl rsa -in server.pass.key -out server.key

You now have a server.key private key file in your current working directory.

Generate CSR

A CSR is a certificate signing request and is also required when purchasing an SSL cert. Using the private key from the previous step, generate the CSR. This will require you to enter identifying information about your organization and domain.

Though most fields are self-explanatory, pay close attention to the following:

Generate the CSR:

$ openssl req -nodes -new -key server.key -out server.csr
...
Country Name (2 letter code) [AU]:US
Common Name (eg, YOUR name) []:www.example.com
...

The result of this operation will be a server.csr file in your local directory (alongside the server.key private key file from the previous step).

Submit CSR to SSL provider

Next, begin the process of creating a new SSL certificate with your chosen certificate provider. This will vary depending on your provider, but at some point you will need to upload the CSR generated in the previous step.

You may also be asked for what web server to create the certificate. If so, select Nginx as the web server for use on Heroku. If Nginx is not an option, Apache 2.x will also suffice.

If you’re given an option of what certificate format to use, such as PKCS or X.509, choose X.509.

If you want to secure more than one subdomain you will need to purchase a wildcard certificate from your provider. While these certificates are typically more expensive, they allow you to serve requests for all subdomains of *.example.com over SSL.

On completion of the SSL certificate purchase process you should have several files including:

• The SSL certificate for the domain specified in your CSR, downloaded from your certificate provider. This file will have either a .pem or .crt extension.
• The private key you generated in the first step, server.key.

Setting up SSL on Heroku

Once you have the SSL certificate file and private key you are ready to configure SSL Endpoint for your app. SSL configuration on Heroku depends slightly on where you are deploying your application.

Create the add-on

This step is only necessary for apps in the Common Runtime. Skip this step for apps in Private Spaces.

Create the add-on with:

$ heroku addons:create ssl:endpoint
Adding ssl:endpoint on example... done, v1 ($20/mo)

Add certificate and intermediaries

Add your certificate, any intermediate certificates, and private key to the endpoint with the certs:add command. Note that you will need to include the --type endpoint argument to this command, as seen below.

$ heroku certs:add server.crt server.key --type endpoint
Adding SSL Endpoint to example... done
example now served by example-12345.ssl.herokudns.com.
Certificate details:
Expires At: 2012-10-31 21:53:18 GMT
Issuer: C=US; ST=CA; L=SF; O=Heroku; CN=www.example.com
Starts At: 2011-11-01 21:53:18 GMT
...

The endpoint URL assigned to your app will be listed in the output, example-12345.ssl.herokudns.com in this example. Visiting this URL will result in a “no such app” message – this is expected. Read further for proper verification steps.

Apps in Private Spaces will have a name in the form of some-name.some-other-name.herokuspace.com In all cases, the output of the certs:add command will accurately reflect this.

Endpoint details

You can verify the details of the SSL configuration with heroku certs.

$ heroku certs

Name         Endpoint                      Common Name(s)     Expires               Trusted  Type
───────────  ─────────────────────────    ──────────────────  ────────────────────  ───────  ────────
example-2121  example-12345.ssl.herokudns.com  www.example.com     2018-06-30 23:59 UTC   False   Endpoint

To get the detailed information about a certificate, use certs:info.

$ heroku certs:info
Fetching SSL Endpoint example-12345.ssl.herokudns.com info for example... done
Certificate details:
Expires At: 2012-10-31 21:53:18 GMT
Issuer: C=US; ST=CA; L=SF; O=Heroku; CN=www.example.com
Starts At: 2011-11-01 21:53:18 GMT
Subject: C=US; ST=CA; L=SF; O=Heroku; CN=www.example.com
...

DNS and domain configuration

Once the SSL endpoint is provisioned and your certificate is confirmed, you must route requests for your secure domain through the endpoint URL. Unless you’ve already done so, add the domain specified when generating the CSR to your app with:

$ heroku domains:add www.example.com
Added www.example.com to example... done

Subdomain

If you’re securing a subdomain, for example, www.example.com, modify your DNS settings and create a CNAME record to the endpoint or modify the CNAME target if you already have a CNAME record.

If you’re using a wildcard certificate your DNS setup will look similar.

Root domain

If you’re securing a root domain, for example, example.com, you must be using a DNS provider that provides CNAME-like functionality at the zone apex.

Modify your DNS settings and create an ALIAS or ANAME record to the endpoint.

Testing SSL

Use a command line utility like curl to test that everything is configured correctly for your secure domain.

$ curl -kvI https://www.example.com
* About to connect() to www.example.com port 443 (#0)
*   Trying 50.16.234.21... connected
* Connected to www.example.com (50.16.234.21) port 443 (#0)
* SSLv3, TLS handshake, Client hello (1):
* SSLv3, TLS handshake, Server hello (2):
* SSLv3, TLS handshake, CERT (11):
* SSLv3, TLS handshake, Server finished (14):
* SSLv3, TLS handshake, Client key exchange (16):
* SSLv3, TLS change cipher, Client hello (1):
* SSLv3, TLS handshake, Finished (20):
* SSLv3, TLS change cipher, Client hello (1):
* SSLv3, TLS handshake, Finished (20):
* SSL connection using AES256-SHA
* Server certificate:
*    subject: C=US; ST=CA; L=SF; O=SFDC; OU=Heroku; CN=www.example.com
*    start date: 2011-11-01 17:18:11 GMT
*    expire date: 2012-10-31 17:18:11 GMT
*    common name: www.example.com (matched)
*    issuer: C=US; ST=CA; L=SF; O=SFDC; OU=Heroku; CN=www.heroku.com
*    SSL certificate verify ok.
> GET / HTTP/1.1
> User-Agent: curl/7.19.7 (universal-apple-darwin10.0) libcurl/7.19.7 OpenSSL/0.9.8r zlib/1.2.3
> Host: www.example.com
> Accept: */*
...

Pay attention to the output. It should print SSL certificate verify ok. If it prints something like common name: www.example.com (does not match 'www.somedomain.com') then something is not configured correctly.

Update certificate

You can update a certificate using the certs:update command with the new certificate and the new or an existing private key:

$ heroku certs:update server.crt server.key --endpoint example-12345.ssl.herokudns.com
Updating SSL Endpoint endpoint example-12345.ssl.herokudns.com for example... done

Remove certificate

You can remove a certificate using the certs:remove command:

$ heroku certs:remove --endpoint example-12345.ssl.herokudns.com
Removing SSL Endpoint endpoint example-12345.ssl.herokudns.com on example... done

Removing a certificate will remove the SSL endpoint so any domain names pointing to it will stop working.

If you try to remove the SSL endpoint add-on before the certificate is removed, you will receive an error.

Client IP address

When an end-client (often the browser) initiates an SSL request, the request must be decrypted before being sent to your app. This extra SSL termination step obfuscates the originating IP address of the request. As a workaround, the IP address of the external client is added to the X-Forwarded-For HTTP request header.

Performance

SSL Endpoint infrastructure is elastic and scales automatically based on historical traffic levels. However, if you plan to switch a lot of traffic to a newly created SSL endpoint or if you expect large spikes, contact Heroku support so we can help with preemptive scaling.

An initial request rate of greater than 150 requests/sec or a doubling of the existing requests/second within a 5 minute period are the thresholds at which you should consider contacting support to pre-warm your endpoint. Please give us at least 2 business days advance notice for these types of requests.

Troubleshooting

Untrusted certificate

In some cases, when running heroku certs it may list your certificate as untrusted.

$ heroku certs
Endpoint                    Common Name         Expires                    Trusted
------------------------    ----------------    -----------------------    -------
example-12345.ssl.herokudns.com    www.example.com    2012-10-31 21:53:18 GMT    False

If this occurs it may be because it is not trusted by Mozilla’s list of root CA’s. If this is the case your certificate should work as you expect for many browsers.

If you have uploaded a certificate that was signed by a root authority but you get the message that it is not trusted, then something is wrong with the certificate. For example, it may be missing intermediary certificates. If so, download the intermediary certificates from your SSL provider and re-run the certs:add command.

Internal server error

If you get an Internal server error when adding your certificate, it may be that you have an outdated version of the Heroku CLI.

$ heroku certs:add server.crt server.key --type endpoint
Adding SSL endpoint to example... failed
! Internal server error.
! Run 'heroku status' to check for known platform issues.

Verify your CLI installation and update it to the latest version with heroku update.

SSL file types

Many different file types are produced and consumed when creating an SSL certificate.

• A .csr file is a certificate signing request, which initiates your certificate request with a certificate provider and contains administrative information about your organization.
• A .key file is the private key used for your site’s SSL-enabled requests.
• .pem and .crt extensions are often used interchangeably and are both base64 ASCII encoded files. The technical difference is that .pem files contain both the certificate and key whereas a .crt file only contains the certificate. In reality this distinction is often ignored.