Mass Assignment: General Mass Assignment
ID |
ruby.checkmassassignment |
Severity |
high |
Resource |
Mass Assignment |
Language |
Ruby |
Description
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.
Remediation
Follow secure coding practices for Ruby on Rails applications. Review the references below for detailed remediation guidance.