### Home Classes Methods

### In Files

- lib/ramaze/helper/csrf.rb

### Methods

- #csrf_protection
- #generate_csrf_token
- #get_csrf_token
- #validate_csrf_token

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# Ramaze::Helper::CSRF

A relatively basic yet useful helper that can be used to protect your application from CSRF attacks/exploits. Note that this helper merely generates the required data, and provides several methods. You still need to manually add the token to each form.

The reason for this is because this is quite simple. Ramaze is meant as a framework that works with any given helper, ORM, template engine and so on. If we were to automatically load this helper and include (a perhaps more advanced) CSRF system that would mean that every form helper, official or third-party, would have to support that specific system. However, there's no need to panic as it's very easy to setup a basic anti CSRF system.

## Usage

In order to enable CSRF protection we need to do two things. Load the helper and create a before_all block in a controller. Take a look at the following code:

    class BaseController < Ramaze::Controller
      before_all do
        puts "Hello, before_all!"
      end
    end

This would output "Hello, before_all!" to the console upon each request. Not very useful but it does show what the before_all block can do. On to actual CSRF related code!

    class BaseController < Ramaze::Controller
      before_all do
        csrf_protection :save do
          # ....
        end
      end
    end

This example introduces an extra block that validates the current request. Whenever a user requests a controller that either extends BaseController or has it's own before_all block Ramaze will check if the current request data contains a CSRF token. Of course an if/end isn't very useful if it doesn't do anything, let's add some code.

    class BaseController < Ramaze::Controller
      before_all do
        csrf_protection :save do
          puts "Hello, unsafe data!"
        end
      end
    end

The code above checks if the current method is "save" (or any other of the provided methods) and checks if an CSRF token is supplied if the method matches. Protected methods require a token in ALL HTTP requests (GET, POST, etc). While this may seem weird since GET is generally used for safe actions it actually makes sense. Ramaze stores both the POST and GET parameters in the request.params hash. While this makes it easy to work with POST/GET data this also makes it easier to spoof POST requests using a GET request, thus this helper protects ALL request methods.

If you're a lazy person you can copy-paste the example below and adapt it to your needs.

    class BaseController < Ramaze::Controller
      before_all do
        csrf_protection :save do
          respond("The supplied CSRF token is invalid.", 401)
        end
      end
    end

@author Yorick Peterse

### Public Instance Methods

csrf_protection(*methods, &block) click to toggle source

Method that can be used to protect the specified methods against CSRF exploits. Each protected method will require the token to be stored in a field called "csrf_token". This method will then validate that token against the current token in the session.

@author Yorick Peterse @param [Strings/Symbol] *methods Methods that will be

    protected/unprotected.

@param [Block] Block that will be executed if the token is invalid. @example

    # Protect "create" and "save" against CSRF exploits
    before_all do
      csrf_protection :create, :save do
        respond("GET TO DA CHOPPA!", 401)
      end
    end

    # File lib/ramaze/helper/csrf.rb, line 99
    def csrf_protection(*methods, &block)
      # Only protect the specified methods
      if methods.include?(action.name) or methods.include?(action.name.to_sym)
        # THINK: For now the field name is hard-coded to "csrf_token". While
        # this is perfectly fine in most cases it might be a good idea
        # to allow developers to change the name of this field (for whatever the reason).
        yield unless validate_csrf_token(request.params['csrf_token'])
      end
    end

generate_csrf_token(args = {}) click to toggle source

Generate a new token and create the session array that will be used to validate the client. The following items are stored in the session:

- token: An unique hash that will be stored in each form

- agent: The visitor's user agent

- ip: The IP address of the visitor

- time: Timestamp that indicates at what time the data was generated.

Note that this method will be automatically called if no CSRF token exists.

@author Yorick Peterse @param [Hash] Additional arguments that can be set such as the TTL.

    # File lib/ramaze/helper/csrf.rb, line 123
    def generate_csrf_token(args = {})
      # Default TTL is 15 minutes
      ttl = args[:ttl] || (15 * 60)

      # Get some good entropy
      random = SecureRandom.random_bytes(512)
      # and some not so good entropy
      time = Time.now.to_f

      # Hash it together
      token = Digest::SHA512.hexdigest(random + time.to_s)

      # Time to store all the data we want to check later.
      session[:_csrf] = {
        :time  => time.to_i,
        :token => token,
        :ip    => request.env['REMOTE_ADDR'],
        :agent => request.env['HTTP_USER_AGENT'],
        :host  => request.env['REMOTE_HOST'],
        :ttl   => ttl
      }

      # Prevent this method from returning any value (it isn't needed anyway)
      return
    end

get_csrf_token() click to toggle source

Retrieves the current value of the CSRF token.

@author Yorick Peterse @return [String] The current CSRF token. @example

    form(@data, :method => :post) do |f|
      f.input_hidden :csrf_token, get_csrf_token()
    end

    # File lib/ramaze/helper/csrf.rb, line 159
    def get_csrf_token
      if !session[:_csrf] || !self.validate_csrf_token(session[:_csrf][:token])
        self.generate_csrf_token
      end

      # Land ho!
      return session[:_csrf][:token]
    end

validate_csrf_token(input_token) click to toggle source

Validates the request based on the current session date stored in _csrf. The following items are verified:

- Do the user agent, ip and token match those supplied by the visitor?

- Has the token been expired? (after 15 minutes).

If any of these checks fail this method will return FALSE. It's your job to take action based on the results of this method.

@author Yorick Peterse @param [String] input_token The CSRF token to validate. @return [TrueClass|FalseClass] @example

    before_all do
      if validate_csrf_token(request.params['csrf_token']) != true
        respond("Invalid CSRF token", 401)
      end
    end

    # File lib/ramaze/helper/csrf.rb, line 188
    def validate_csrf_token(input_token)
      # Check if the CSRF data has been generated and generate it if this
      # hasn't been done already (usually on the first request).
      if !session[:_csrf] or session[:_csrf].empty?
        self.generate_csrf_token
      end

      _csrf = session[:_csrf]

      # Mirror mirror on the wall, who's the most secure of them all?
      session[:_csrf][:token] == input_token &&
        (Time.now.to_f - _csrf[:time]) <= _csrf[:ttl] &&
        _csrf[:host] == request.env['REMOTE_HOST'] &&
        _csrf[:ip] == request.env['REMOTE_ADDR'] &&
        _csrf[:agent] == request.env['HTTP_USER_AGENT']
    end

[Validate]

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