3scale/porta

Mass assignment is a feature of Rails which allows an application to create a record from the values of a hash.

Example:

User.new(params[:user])

Unfortunately, if there is a user field called admin which controls administrator access, now any user can make themselves an administrator.

attr_accessible and attr_protected can be used to limit mass assignment. However, Brakeman will warn unless attr_accessible is used, or mass assignment is completely disabled.

There are two different mass assignment warnings which can arise. The first is when mass assignment actually occurs, such as the example above. This results in a warning like

Unprotected mass assignment near line 61: User.new(params[:user])

The other warning is raised whenever a model is found which does not use attr_accessible. This produces generic warnings like

Mass assignment is not restricted using attr_accessible

with a list of affected models.

In Rails 3.1 and newer, mass assignment can easily be disabled:

config.active_record.whitelist_attributes = true

Unfortunately, it can also easily be bypassed:

User.new(params[:user], :without_protection => true)

Brakeman will warn on uses of without_protection.

Duplication occurs when two fragments of code look nearly identical, or when two fragments of code have nearly identical effects at some conceptual level.

Reek implements a check for Duplicate Method Call.

Example

Here's a very much simplified and contrived example. The following method will report a warning:

def double_thing()
  @other.thing + @other.thing
end

One quick approach to silence Reek would be to refactor the code thus:

def double_thing()
  thing = @other.thing
  thing + thing
end

A slightly different approach would be to replace all calls of double_thing by calls to @other.double_thing:

class Other
  def double_thing()
    thing + thing
  end
end

The approach you take will depend on balancing other factors in your code.