ActiveSupport::MessageVerifier
MessageVerifier makes it easy to generate and verify messages which are signed to prevent tampering.
This is useful for cases like remember-me tokens and auto-unsubscribe links where the session store isn’t suitable or available.
Remember Me:
cookies[:remember_me] = @verifier.generate([@user.id, 2.weeks.from_now])
In the authentication filter:
id, time = @verifier.verify(cookies[:remember_me]) if time < Time.now self.current_user = User.find(id) end
By default it uses Marshal to serialize the message. If you want to use another serialization method, you can set the serializer in the options hash upon initialization:
@verifier = ActiveSupport::MessageVerifier.new('s3Krit', serializer: YAML)
Files
- activesupport/lib/active_support/message_verifier.rb
Nested classes and modules
3Notes
Wrong example
In the authentication filter example above, the time condition should be reversed: we only want to find the user if +time+ is still in the future (because it's the valid-until time).
So the example should look like this:
id, time = @verifier.verify(cookies[:remember_me])
if time > Time.now
self.current_user = User.find(id)
end
Security issue
One thing to note about the code above is that it could have a security issue. If the user changes his/her password, the authentication token should expire. Hence, in a production scenario you should put in the password salt or something to allow the token to become invalidated.
Security
In regards to @aamer's comment on including the password salt this is a bad idea. ActiveSupport::MessageVerifier is NOT encrypted so:
verifier = ActiveSupport::MessageVerifier.new('secret')
id = 'id'
salt = 'salt'
verifier.generate("#{id}-#{salt}") # "BAhJIgxpZC1zYWx0BjoGRVQ=--c880254708d18ce4a686bcd96a25cf0d2117e1e0"
Base64.decode64(token.split("--").first) # "...id-salt..."
Note how the salt and id are both exposed! Instead a different token (reset_passowrd_token) should be used.
