Unsafe Query Generation Affecting activerecord package, versions < 4.2.7.1, >= 4.2.0

ActiveRecord is the Object-Relational Mapping (ORM) that comes out-of-the-box with Rails. It plays the role of Model in the MVC architecture employed by Rails.

There is a vulnerability when ActiveRecord is used in conjunction with JSON parameter parsing.

This vulnerability is similar to CVE-2012-2660, CVE-2012-2694 and CVE-2013-0155.

Details

Due to the way ActiveRecord interprets parameters in combination with the way that JSON parameters are parsed, it is possible for an attacker to issue unexpected database queries with IS NULL or empty WHERE clauses. This issue does not let an attacker insert arbitrary values into an SQL query, however they can cause the query to check for NULL or eliminate a WHERE clause when most users wouldn't expect it.

For example, a system has password reset with token functionality:

    unless params[:token].nil?
      user = User.find_by_token(params[:token])
      user.reset_password!
    end

An attacker can craft a request such that params[:token] will return [nil]. The [nil] value will bypass the test for nil, but will still add an IN ('xyz', NULL) clause to the SQL query.

Similarly, an attacker can craft a request such that params[:token] will return an empty hash. An empty hash will eliminate the WHERE clause of the query, but can bypass the nil? check.

Note that this impacts not only dynamic finders (find_by_*) but also relations (User.where(:name => params[:name])).

• https://groups.google.com/forum/#!topic/rubyonrails-security/rgO20zYW33s