Rails 3: How to intercept any http request

Question

Lets say I have an image at app/assets/images/privateimages/myrestrictedimage1.jpg If I try to go directly to the image via url say with something like

 http://localhost:5555/assets/privateimages/myrestrictedimage1.jpg

I am able to view the image.

I would like to have a way to inspect any http request to decide if the user is allowed access to it.

I know I can use before_filter in controllers to do some preprocessing before continuing onto any of the controller actions but I dont think this will help me because I need to be attempting to do a controller action for this to take effect.

I have heard I might be able to do it with a rake task but after much searching I haven't found anything like what I am trying to do. Perhaps I have to create a ruby gem to do this but I have no clue how to do this.

Can anyone point me in the right direction? Thanks.

score 4 · Accepted Answer · answered Jul 19 '12 at 15:41

I used Rack Middleware

The middleware class looks like this:

class MyChecker  
  def initialize(app)
    @app = app       
  end                

  def call(env)
    if (docheck)
      #do stuff here such as check the path.
      #For example @path = env['PATH_INFO'] and compare against your okay paths  
      #if youre good and are able to continue then
      @app.call(env)
    else
      #redirect such as
      [301, {"Location" => /somewhere, "Content-Type" => "text/html"}, []]
    end
  end  

end

make sure to make your middleware visible by adding the following to application.rb

class Application < Rails::Application
  ...
  config.autoload_paths += %W(#{config.root}/lib)  #if MyChecker is located in lib othewise substitute lib with wherever you have your middleware class
  config.middleware.use "MyChecker"
end

please update your answer as the middleware name can no longer be written in quotes. it will throw an error in Rails version 5. — amitava mozumder, Jan 23 '19 at 06:28

score 2 · Answer 2 · answered Jul 12 '12 at 02:42

2

You want to look at Rack (not rake).

answered Jul 12 '12 at 02:42

olore

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After much reading up on Rack, I believe this is probably the way to go I just have no idea how. So far most of the Rack examples simply display some text using a Rack application. I can't find an example of how to do some other kind of logic with Rack and then continue. So for example, if user goes to http://localhost:3000/* then some code that performs a check on the url is run and if the check passes then the user is able to continue on to /* normally otherwise they are redirected to some other url. – snowleopard Jul 13 '12 at 17:23

Rails 3: How to intercept any http request

2 Answers2

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