I'm looking at page 162 in *Agile Web Development with Rails* and in there they do the following once they find that a user has logged in with the right name and password:
- - - def login if request.post? user = User.authenticate(params[:username], params[:password]) if user session[:user_id] = user.id redirect_to(:action => "index") else flash.now[:notice] = "Invalid user/password combination" end end end - - -
The line that concerns me is session[:user_id] = user.id
The authors write
Ralph Shnelvar wrote:
The line that concerns me is session[:user_id] = user.id ... Given that the session data is likely to be stored in cookies, and given that user.id is likely to be a relatively small number (less than a million) ... how secure is this as a flag to indicate that someone is an authorized user of a store??? Couldn't an unauthorized user create the session[:user_id] = user.id and then get access?
A good question! You are thinking the right way. Fortunately this question has been asked already and the answer is that the session is a signed piece of data using an HMAC. This means that if an attacker tries to change the values in the session store that the signature will fail. The signature check in Rails will catch this and the user will see a 422 error. Try it!
Note that the session is only signed and not encrypted. So don't store anything there that you don't want the user to be able to see. It is only protected from modification and not protected from being seen.
Here is a good guide for further information.
Securing Rails Applications — Ruby on Rails Guides
Bob
Bob Proulx wrote:
Here is a good guide for further information.
Securing Rails Applications — Ruby on Rails Guides
Bob
I must have read that guide over the last sdevera; months a half a dozen times.
Your two-paragraph explanation made it snap into focus for me .... finally!
Thanks!
Ralph