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

8 files changed, 47 insertions, 6 deletions

diff --git a/actionpack/CHANGELOG.md b/actionpack/CHANGELOG.md
index 0f0e7b0975..5d4ae16c09 100644
--- a/actionpack/CHANGELOG.md
+++ b/actionpack/CHANGELOG.md
@@ -1,5 +1,7 @@
 ## Rails 4.0.0 (unreleased) ##
 
+*   Malformed query and request parameter hashes now raise ActionController::BadRequest. *Andrew White*
+
 *   Add `divider` option to `grouped_options_for_select` to generate a separator
     `optgroup` automatically, and deprecate `prompt` as third argument, in favor
     of using an options hash. *Nicholas Greenfield*
diff --git a/actionpack/lib/action_controller/metal/exceptions.rb b/actionpack/lib/action_controller/metal/exceptions.rb
index 90648c37ad..8fd8f4797c 100644
--- a/actionpack/lib/action_controller/metal/exceptions.rb
+++ b/actionpack/lib/action_controller/metal/exceptions.rb
@@ -2,6 +2,9 @@ module ActionController
   class ActionControllerError < StandardError #:nodoc:
   end
 
+  class BadRequest < ActionControllerError #:nodoc:
+  end
+
   class RenderError < ActionControllerError #:nodoc:
   end
 
@@ -38,7 +41,7 @@ module ActionController
 
   class UnknownHttpMethod < ActionControllerError #:nodoc:
   end
-  
+
   class UnknownFormat < ActionControllerError #:nodoc:
   end
 end
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
diff --git a/actionpack/test/dispatch/debug_exceptions_test.rb b/actionpack/test/dispatch/debug_exceptions_test.rb
index 11c292d61a..6ff651ad52 100644
--- a/actionpack/test/dispatch/debug_exceptions_test.rb
+++ b/actionpack/test/dispatch/debug_exceptions_test.rb
@@ -35,6 +35,8 @@ class DebugExceptionsTest < ActionDispatch::IntegrationTest
         raise ActionController::InvalidAuthenticityToken
       when "/not_found_original_exception"
         raise ActionView::Template::Error.new('template', AbstractController::ActionNotFound.new)
+      when "/bad_request"
+        raise ActionController::BadRequest
       else
         raise "puke!"
       end
@@ -88,6 +90,10 @@ class DebugExceptionsTest < ActionDispatch::IntegrationTest
     get "/method_not_allowed", {}, {'action_dispatch.show_exceptions' => true}
     assert_response 405
     assert_match(/ActionController::MethodNotAllowed/, body)
+
+    get "/bad_request", {}, {'action_dispatch.show_exceptions' => true}
+    assert_response 400
+    assert_match(/ActionController::BadRequest/, body)
   end
 
   test "does not show filtered parameters" do
diff --git a/actionpack/test/dispatch/request/query_string_parsing_test.rb b/actionpack/test/dispatch/request/query_string_parsing_test.rb
index d14f188e30..c3f009ab15 100644
--- a/actionpack/test/dispatch/request/query_string_parsing_test.rb
+++ b/actionpack/test/dispatch/request/query_string_parsing_test.rb
@@ -105,6 +105,17 @@ class QueryStringParsingTest < ActionDispatch::IntegrationTest
     )
   end
 
+  test "ambiguous query string returns a bad request" do
+    with_routing do |set|
+      set.draw do
+        get ':action', :to => ::QueryStringParsingTest::TestController
+      end
+
+      get "/parse", nil, "QUERY_STRING" => "foo[]=bar&foo[4]=bar"
+      assert_response :bad_request
+    end
+  end
+
   private
     def assert_parses(expected, actual)
       with_routing do |set|
diff --git a/actionpack/test/dispatch/request/url_encoded_params_parsing_test.rb b/actionpack/test/dispatch/request/url_encoded_params_parsing_test.rb
index 568e220b15..e9b59f55a7 100644
--- a/actionpack/test/dispatch/request/url_encoded_params_parsing_test.rb
+++ b/actionpack/test/dispatch/request/url_encoded_params_parsing_test.rb
@@ -126,6 +126,17 @@ class UrlEncodedParamsParsingTest < ActionDispatch::IntegrationTest
     assert_parses expected, query
   end
 
+  test "ambiguous params returns a bad request" do
+    with_routing do |set|
+      set.draw do
+        post ':action', :to => ::UrlEncodedParamsParsingTest::TestController
+      end
+
+      post "/parse", "foo[]=bar&foo[4]=bar"
+      assert_response :bad_request
+    end
+  end
+
   private
     def with_test_routing
       with_routing do |set|
diff --git a/actionpack/test/dispatch/request_test.rb b/actionpack/test/dispatch/request_test.rb
index 94d0e09842..54fc1b208d 100644
--- a/actionpack/test/dispatch/request_test.rb
+++ b/actionpack/test/dispatch/request_test.rb
@@ -561,7 +561,7 @@ class RequestTest < ActiveSupport::TestCase
     begin
       request = stub_request(mock_rack_env)
       request.parameters
-    rescue TypeError
+    rescue ActionController::BadRequest
       # rack will raise a TypeError when parsing this query string
     end
     assert_equal({}, request.parameters)