Permit same-origin connections by default

WebSocket always defers the decision to the server, because it didn't
have to deal with legacy compatibility... but the same-origin policy is
still a reasonable default.

Origin checks do not protect against a directly connecting attacker --
they can lie about their host, but can also lie about their origin.
Origin checks protect against a connection from 3rd-party controlled
script in a context where a victim browser's cookies will be passed
along. And if an attacker has breached that protection, they've already
compromised the HTTP session, so treating the WebSocket connection in
the same way seems reasonable.

In case this logic proves incorrect (or anyone just wants to be more
paranoid), we retain a config option to disable it.

2 files changed, 3 insertions, 3 deletions

diff --git a/actioncable/lib/action_cable/connection/base.rb b/actioncable/lib/action_cable/connection/base.rb
index 2596635701..dfee123ea2 100644
--- a/actioncable/lib/action_cable/connection/base.rb
+++ b/actioncable/lib/action_cable/connection/base.rb
@@ -196,9 +196,9 @@ module ActionCable
           return true if server.config.disable_request_forgery_protection
 
           proto = Rack::Request.new(env).ssl? ? "https" : "http"
-          if Array(server.config.allowed_request_origins).any? { |allowed_origin|  allowed_origin === env["HTTP_ORIGIN"] }
+          if server.config.allow_same_origin_as_host && env["HTTP_ORIGIN"] == "#{proto}://#{env['HTTP_HOST']}"
             true
-          elsif server.config.allow_same_origin_as_host && env["HTTP_ORIGIN"] == "#{proto}://#{env['HTTP_HOST']}"
+          elsif Array(server.config.allowed_request_origins).any? { |allowed_origin|  allowed_origin === env["HTTP_ORIGIN"] }
             true
           else
             logger.error("Request origin not allowed: #{env['HTTP_ORIGIN']}")
diff --git a/actioncable/lib/action_cable/server/configuration.rb b/actioncable/lib/action_cable/server/configuration.rb
index aa8d10b3d4..17e0dee064 100644
--- a/actioncable/lib/action_cable/server/configuration.rb
+++ b/actioncable/lib/action_cable/server/configuration.rb
@@ -15,7 +15,7 @@ module ActionCable
         @worker_pool_size = 4
 
         @disable_request_forgery_protection = false
-        @allow_same_origin_as_host = false
+        @allow_same_origin_as_host = true
       end
 
       # Returns constant of subscription adapter specified in config/cable.yml.