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Short demo app for Rails Security Lunch and Learn
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Rails Security Tips

Filter Log Params

  • By default, all params passed within a Rails model are logged
  • Best practice is to use filter_parameter_logging
  • This is built-in to Rails
  • To filter the password field in standard user authentication, state the following in application_controller.rb
    filter_parameter_logging :password

Cross-site Request Forgery Protection

Protect agains cross-site forgery by ensuring that this line exists in application_controller.rb


  • Inside the form element Rails automatically adds a hidden field called authenticity_token.
  • This field’s value is a key that is unique for each user’s session and is based on a random string stored in the session.
  • Rails will automatically check this key for every single POST, PUT or DELETE request that is made
  • Ensures that the request is made by a user who is actually on our site, rather than by another site pretending to be that user.
  • This token is not checked for GET requests so we need to make sure that GET requests can not change or delete our application’s data.

SQL injection

  • SQL injection is a common tactic used by malicious users to compromise a database
  • Poorly written controller actions can allow a user to see unauthorized data, or modify the database

This is BAD:

@users = User.all(:conditions => "name LIKE '%#{params[:search]}%'")

This is GOOD:
@users = User.all(:conditions => ["name LIKE ?", "%#{params[:search]}%"])


  • Passes the condition as an array rather than as a string
  • Quotes the parameter and escapes any special characters

HTML injection

  • Rails has a built-in h method used to escape HTML
  • Prevents inline HTML from executing


    alert("You've been Hacked!")

  • Rails 3 will automatically escape content on the page making the h method unnecessary
  • When using a CMS, it is necessary to show html content

An alternative to the h method is to use sanitize

  <%= sanitize @article.body %>
  <%= sanitize @article.body, :tags => %w(p br table tr td), :attributes => %w(id class style) %>

Or setup defaults in your environment.rb file do |config|
    config.action_view.sanitized_allowed_tags = 'p', 'br', 'strong', table', 'tr', 'td'

File Uploads

  • Using paperclip with the minimum default options, a user can upload any type of file.
  • File uploads are one of the biggest security threats to any app
  • This is BAD !!
  • Consider a simple upload of phpinfo.php
  • Imagine if this was a malicious PHP or Javascript code!
  • Tighten up your model by only allowing specific files to be uploaded.

Note: When using ImageMagick to resize an upload, it seems to fail unless the upload is an image.

Mass Assignment

  • Only allow the editing of necessary fields
  • Access to other fields (such as foreign keys) can lead to data being compromised
  • A malicious user can use curl to issue a command to the server to alter data
  • Example, the name of the Group a user belongs to can be altered since there is a one-to-many relationship in the model
  • This can be exploited using update_attributes when performing an update action

In script/console:

@group = Group.first
@group.update_attributes(:user_ids => [12])

Unfortunate for us, this is very insecure since anyone with knowledge of using curl can pass this update to the web app. To fix this, we need to define attr_accessible for the Group model.

Further Reading

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