This middleware is added to the stack when config.force_ssl = true, and is passed the options set in config.ssl_options. It does three jobs to enforce secure HTTP requests:

  1. TLS redirect: Permanently redirects http:// requests to https:// with the same URL host, path, etc. Enabled by default. Set config.ssl_options to modify the destination URL (e.g. redirect: { host: "secure.widgets.com", port: 8080 }), or set redirect: false to disable this feature.

    Requests can opt-out of redirection with exclude:

    config.ssl_options = { redirect: { exclude: -> request { request.path =~ /healthcheck/ } } }

    Cookies will not be flagged as secure for excluded requests.

  2. Secure cookies: Sets the secure flag on cookies to tell browsers they must not be sent along with http:// requests. Enabled by default. Set config.ssl_options with secure_cookies: false to disable this feature.

  3. HTTP Strict Transport Security (HSTS): Tells the browser to remember this site as TLS-only and automatically redirect non-TLS requests. Enabled by default. Configure config.ssl_options with hsts: false to disable.

    Set config.ssl_options with hsts: { ... } to configure HSTS:

    • expires: How long, in seconds, these settings will stick. The minimum required to qualify for browser preload lists is 1 year. Defaults to 1 year (recommended).

    • subdomains: Set to true to tell the browser to apply these settings to all subdomains. This protects your cookies from interception by a vulnerable site on a subdomain. Defaults to true.

    • preload: Advertise that this site may be included in browsers' preloaded HSTS lists. HSTS protects your site on every visit except the first visit since it hasn't seen your HSTS header yet. To close this gap, browser vendors include a baked-in list of HSTS-enabled sites. Go to hstspreload.org to submit your site for inclusion. Defaults to false.

    To turn off HSTS, omitting the header is not enough. Browsers will remember the original HSTS directive until it expires. Instead, use the header to tell browsers to expire HSTS immediately. Setting hsts: false is a shortcut for hsts: { expires: 0 }.