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)

By default it uses Marshal to serialize the message. If you want to use another serialization method, you can set the serializer attribute to something that responds to dump and load, e.g.:

@verifier.serializer = YAML
Show files where this class is defined (1 file)
Register or log in to add new notes.
March 29, 2010
0 thanks

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)
August 14, 2011
0 thanks

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.

May 4, 2014
0 thanks


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.