Why is it that I cannot find a definition of a rolling authentication token anywhere? Let me provide my own then: a rolling token is a security (authentication) token that can only be used for a single successful authentication. After a successful authentication, the used token is always replaced by a new one, therefore the token is said to be rolling. There, now we can talk. I’ve always disliked typical rememberMe implementations for the weak security they provide and I still admire this eight year old blog post by Charles Miller. Let me quote from “Persistent Login Cookie Best Practice”:
Persistent login cookies are the cookies that are stored with your browser when you click the “remember me” button on the login form. I would like to be able to say that such cookies are obselete, and we have a better way of handling user logins, but they aren’t, and we don’t.
The following recipe for persistent cookies requires no crypto more powerful than a good random number generator.
- Cookies are vulnerable. Between common browser cookie-theft vulnerabilities and cross-site scripting attacks, we must accept that cookies are not safe
- Persistent login cookies are on their own sufficient authentication to access a website. They are the equivalent of both a valid username and password rolled into one
- Users reuse passwords. Hence, any login cookie from which you can recover the user’s password holds significantly more potential for harm than one from which you can not
- Binding persistent cookies to a particular IP address makes them not particularly persistent in many common cases
- A user may wish to have persistent cookies on multiple web browsers on different machines simultaneously
With all this in mind, I’ve always implemented rememberMe based on rolling tokens in the various web applications I’ve worked on. However, I’ve never attempted to provide it as a reusable module until one day a few months ago while I was working on federatedaccounts it hit me: rolling tokens can be thought of as just another “remote” authentication provider that can be federated with the main account. For some months now, we’ve happily been using tynamo-federatedaccounts-rollingtokens in production. I added some quick documentation for it at the end of the generic tynamo-federatedaccounts guide, have (secure) fun with it!