def signin
    if request.post?
      begin
        session[:user] = User.authenticate(params[:username], params[:password]).id
        redirect_to :action => session[:intended_action], :controller => session[:intended_controller]
      rescue RuntimeError => boom
        flash[:notice] = boom
        redirect_to :action => :signin
      end
    end
  end

##user model
require 'digest/sha2'
class User < ActiveRecord::Base
  has_and_belongs_to_many :restaurants

  def password=(pass)
    salt = [Array.new(6){rand(256).chr}.join].pack("m").chomp
    self.password_salt, self.password_hash = salt, Digest::SHA256.hexdigest(pass + salt)
  end

  def self.authenticate(username, password)
    user = User.find(:first, :conditions => ['username = ?', username])
    if user.blank? || Digest::SHA256.hexdigest(password + user.password_salt) != user.password_hash
      raise "Username or password invalid"
    end
    user
  end

end

##session dump
---
:intended_action: index
:intended_controller: restaurants
:user: 1
flash: !map:ActionController::Flash::FlashHash
  :notice: !ruby/exception:RuntimeError
    message: Username or password invalid

##full trace
vendor/rails/actionpack/lib/action_controller/session/cookie_store.rb:91:in `close'
/usr/local/lib/ruby/1.8/cgi/session.rb:330:in `close'
vendor/rails/actionpack/lib/action_controller/base.rb:1221:in `close_session'
vendor/rails/actionpack/lib/action_controller/base.rb:1265:in `process_cleanup_without_flash'
vendor/rails/actionpack/lib/action_controller/flash.rb:180:in `process_cleanup_without_session_management_support'
vendor/rails/actionpack/lib/action_controller/session_management.rb:132:in `process_cleanup_without_components'
vendor/rails/actionpack/lib/action_controller/components.rb:161:in `process_cleanup'
vendor/rails/actionpack/lib/action_controller/base.rb:502:in `process_without_filters'
vendor/rails/actionpack/lib/action_controller/filters.rb:747:in `process_without_session_management_support'
vendor/rails/actionpack/lib/action_controller/session_management.rb:122:in `process'
vendor/rails/actionpack/lib/action_controller/base.rb:346:in `process'
vendor/rails/railties/lib/dispatcher.rb:39:in `dispatch'
/usr/local/lib/ruby/gems/1.8/gems/mongrel-1.0.1/lib/mongrel/rails.rb:78:in `process'
/usr/local/lib/ruby/gems/1.8/gems/mongrel-1.0.1/lib/mongrel/rails.rb:76:in `process'
/usr/local/lib/ruby/gems/1.8/gems/mongrel-1.0.1/lib/mongrel.rb:618:in `process_client'
/usr/local/lib/ruby/gems/1.8/gems/mongrel-1.0.1/lib/mongrel.rb:617:in `process_client'
/usr/local/lib/ruby/gems/1.8/gems/mongrel-1.0.1/lib/mongrel.rb:736:in `run'
/usr/local/lib/ruby/gems/1.8/gems/mongrel-1.0.1/lib/mongrel.rb:736:in `run'
/usr/local/lib/ruby/gems/1.8/gems/mongrel-1.0.1/lib/mongrel.rb:720:in `run'
/usr/local/lib/ruby/gems/1.8/gems/mongrel-1.0.1/lib/mongrel/configurator.rb:271:in `run'
/usr/local/lib/ruby/gems/1.8/gems/mongrel-1.0.1/lib/mongrel/configurator.rb:270:in `run'
/usr/local/lib/ruby/gems/1.8/gems/mongrel-1.0.1/bin/mongrel_rails:127:in `run'
/usr/local/lib/ruby/gems/1.8/gems/mongrel-1.0.1/lib/mongrel/command.rb:211:in `run'
/usr/local/lib/ruby/gems/1.8/gems/mongrel-1.0.1/bin/mongrel_rails:243
vendor/rails/activesupport/lib/active_support/dependencies.rb:488:in `load'
vendor/rails/activesupport/lib/active_support/dependencies.rb:342:in `new_constants_in'
vendor/rails/activesupport/lib/active_support/dependencies.rb:488:in `load'
vendor/rails/railties/lib/commands/servers/mongrel.rb:64
/usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in `require'
vendor/rails/activesupport/lib/active_support/dependencies.rb:495:in `require'
vendor/rails/activesupport/lib/active_support/dependencies.rb:342:in `new_constants_in'
vendor/rails/activesupport/lib/active_support/dependencies.rb:495:in `require'
vendor/rails/railties/lib/commands/server.rb:39
script/server:3

##log
Processing HomeController#signin (for 127.0.0.1 at 2007-06-18 14:10:02) [POST]
  Session ID: BAh7CToUaW50ZW5kZWRfYWN0aW9uIgppbmRleDoYaW50ZW5kZWRfY29udHJv%0AbGxlciIQcmVzdGF1cmFudHM6CXVzZXJpBiIKZmxhc2hJQzonQWN0aW9uQ29u%0AdHJvbGxlcjo6Rmxhc2g6OkZsYXNoSGFzaHsABjoKQHVzZWR7AA%3D%3D--dc0e44157f47130094778e3423e343ebbae55a17
  Parameters: {"commit"=>"Sign in", "/home/signin"=>nil, "username"=>"chad", "action"=>"signin", "controller"=>"home", "password"=>""}


CGI::Session::CookieStore::CookieOverflow (CGI::Session::CookieStore::CookieOverflow):
    /vendor/rails/actionpack/lib/action_controller/session/cookie_store.rb:91:in `close'
    /usr/local/lib/ruby/1.8/cgi/session.rb:330:in `close'
    /vendor/rails/actionpack/lib/action_controller/base.rb:1221:in `close_session'
    /vendor/rails/actionpack/lib/action_controller/base.rb:1265:in `process_cleanup_without_flash'
    /vendor/rails/actionpack/lib/action_controller/flash.rb:180:in `process_cleanup_without_session_management_support'
    /vendor/rails/actionpack/lib/action_controller/session_management.rb:132:in `process_cleanup_without_components'
    /vendor/rails/actionpack/lib/action_controller/components.rb:161:in `process_cleanup'
    /vendor/rails/actionpack/lib/action_controller/base.rb:502:in `process_without_filters'
    /vendor/rails/actionpack/lib/action_controller/filters.rb:747:in `process_without_session_management_support'
    /vendor/rails/actionpack/lib/action_controller/session_management.rb:122:in `process'
    /vendor/rails/actionpack/lib/action_controller/base.rb:346:in `process'
    /vendor/rails/railties/lib/dispatcher.rb:39:in `dispatch'
    /usr/local/lib/ruby/gems/1.8/gems/mongrel-1.0.1/lib/mongrel/rails.rb:78:in `process'
    /usr/local/lib/ruby/gems/1.8/gems/mongrel-1.0.1/lib/mongrel/rails.rb:76:in `process'
    /usr/local/lib/ruby/gems/1.8/gems/mongrel-1.0.1/lib/mongrel.rb:618:in `process_client'
    /usr/local/lib/ruby/gems/1.8/gems/mongrel-1.0.1/lib/mongrel.rb:617:in `process_client'
    /usr/local/lib/ruby/gems/1.8/gems/mongrel-1.0.1/lib/mongrel.rb:736:in `run'
    /usr/local/lib/ruby/gems/1.8/gems/mongrel-1.0.1/lib/mongrel.rb:736:in `run'
    /usr/local/lib/ruby/gems/1.8/gems/mongrel-1.0.1/lib/mongrel.rb:720:in `run'
    /usr/local/lib/ruby/gems/1.8/gems/mongrel-1.0.1/lib/mongrel/configurator.rb:271:in `run'
    /usr/local/lib/ruby/gems/1.8/gems/mongrel-1.0.1/lib/mongrel/configurator.rb:270:in `run'
    /usr/local/lib/ruby/gems/1.8/gems/mongrel-1.0.1/bin/mongrel_rails:127:in `run'
    /usr/local/lib/ruby/gems/1.8/gems/mongrel-1.0.1/lib/mongrel/command.rb:211:in `run'
    /usr/local/lib/ruby/gems/1.8/gems/mongrel-1.0.1/bin/mongrel_rails:243
    /vendor/rails/activesupport/lib/active_support/dependencies.rb:488:in `load'
    /vendor/rails/activesupport/lib/active_support/dependencies.rb:342:in `new_constants_in'
    /vendor/rails/activesupport/lib/active_support/dependencies.rb:488:in `load'
    /vendor/rails/railties/lib/commands/servers/mongrel.rb:64
    /usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in `require'
    /vendor/rails/activesupport/lib/active_support/dependencies.rb:495:in `require'
    /vendor/rails/activesupport/lib/active_support/dependencies.rb:342:in `new_constants_in'
    /vendor/rails/activesupport/lib/active_support/dependencies.rb:495:in `require'
    /vendor/rails/railties/lib/commands/server.rb:39
    script/server:3