Raise ActionController::BadRequest for malformed parameter hashes.

Currently Rack raises a TypeError when it encounters a malformed or
ambiguous hash like `foo[]=bar&foo[4]=bar`. Rather than pass this
through to the application this commit captures the exception and
re-raises it using a new ActionController::BadRequest exception.

The new ActionController::BadRequest exception returns a 400 error
instead of the 500 error that would've been returned by the original
TypeError. This allows exception notification libraries to ignore
these errors if so desired.

Closes #3051

2 files changed, 12 insertions, 4 deletions

diff --git a/actionpack/lib/action_dispatch/http/request.rb b/actionpack/lib/action_dispatch/http/request.rb
index 56908b5794..aa5ba3e8a5 100644
--- a/actionpack/lib/action_dispatch/http/request.rb
+++ b/actionpack/lib/action_dispatch/http/request.rb
@@ -231,17 +231,24 @@ module ActionDispatch
 
     # Override Rack's GET method to support indifferent access
     def GET
-      @env["action_dispatch.request.query_parameters"] ||= (normalize_parameters(super) || {})
+      begin
+        @env["action_dispatch.request.query_parameters"] ||= (normalize_parameters(super) || {})
+      rescue TypeError => e
+        raise ActionController::BadRequest, "Invalid query parameters: #{e.message}"
+      end
     end
     alias :query_parameters :GET
 
     # Override Rack's POST method to support indifferent access
     def POST
-      @env["action_dispatch.request.request_parameters"] ||= (normalize_parameters(super) || {})
+      begin
+        @env["action_dispatch.request.request_parameters"] ||= (normalize_parameters(super) || {})
+      rescue TypeError => e
+        raise ActionController::BadRequest, "Invalid request parameters: #{e.message}"
+      end
     end
     alias :request_parameters :POST
 
-
     # Returns the authorization header regardless of whether it was specified directly or through one of the
     # proxy alternatives.
     def authorization
diff --git a/actionpack/lib/action_dispatch/middleware/exception_wrapper.rb b/actionpack/lib/action_dispatch/middleware/exception_wrapper.rb
index a8f49bd3bd..7349b578d2 100644
--- a/actionpack/lib/action_dispatch/middleware/exception_wrapper.rb
+++ b/actionpack/lib/action_dispatch/middleware/exception_wrapper.rb
@@ -12,7 +12,8 @@ module ActionDispatch
       'ActionController::MethodNotAllowed'         => :method_not_allowed,
       'ActionController::NotImplemented'           => :not_implemented,
       'ActionController::UnknownFormat'            => :not_acceptable,
-      'ActionController::InvalidAuthenticityToken' => :unprocessable_entity
+      'ActionController::InvalidAuthenticityToken' => :unprocessable_entity,
+      'ActionController::BadRequest'               => :bad_request
     )
 
     cattr_accessor :rescue_templates