Merge pull request #23852 from prathamesh-sonpatki/hsts-subdomains

Enable HSTS with IncludeSubdomains header by default for new apps

1 files changed, 12 insertions, 1 deletions

diff --git a/actionpack/lib/action_dispatch/middleware/ssl.rb b/actionpack/lib/action_dispatch/middleware/ssl.rb
index 735b5939dd..d6a0fe650c 100644
--- a/actionpack/lib/action_dispatch/middleware/ssl.rb
+++ b/actionpack/lib/action_dispatch/middleware/ssl.rb
@@ -23,7 +23,7 @@ module ActionDispatch
   #     preload lists is `18.weeks`.
   #   * `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 `false`.
+  #     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
@@ -57,6 +57,17 @@ module ActionDispatch
       end
 
       @secure_cookies = secure_cookies
+
+      if hsts != true && hsts != false && hsts[:subdomains].nil?
+        hsts[:subdomains] = false
+
+        ActiveSupport::Deprecation.warn <<-end_warning.strip_heredoc
+          In Rails 5.1, The `:subdomains` option of HSTS config will be treated as true if
+          unspecified. Set `config.ssl_options = { hsts: { subdomains: false }}` to opt out
+          of this behavior.
+        end_warning
+      end
+
       @hsts_header = build_hsts_header(normalize_hsts_options(hsts))
     end