保护有状态的Web服务

Question

We are planning on developing a layer of REST services to expose services hosted on a legacy system. These services will be used by a classic web application and native mobile phone applications.

This legacy system is secured in such a way that an initial username + password authentication is required (a process that can take 5 to 10 seconds). After the initial authentication, a time-constrained token is returned. This token must then be included in all further requests or else requests will be rejected.

Due to a security requirement, the legacy security token cannot be returned outside of the REST service layer. This means that the REST service layer needs to keep this token in some form of user session, or else the expensive username + password authentication process would need to be repeated for every call to the legacy system.

The REST service layer will be implemented using a Java 6 + Spring 3 + Spring Security 3 stack. At first sight, it looks like this setup will run fine: Spring-based REST services will be secured using a rather standard Spring Security configuration, the legacy security token will be stored in the user's HTTP session and every call will retrieve this token using the user's session and send it to the legacy system.

But there lies the question: how will REST clients send the necessary data so that the user's HTTP session is retrieved properly? This is normally done transparently by the web browser using the JSESSIONID cookie, but no browser is involved in this process. Sure, REST clients could add cookie management to their code, but is this an easy task for all Spring RestTemplate, iPhone, BlackBerry and Android clients?

The alternative would be to bypass the HTTP session at the REST service layer and use some other form of user session, maybe using a database, that would be identified using some key that would be sent by REST clients through a HTTP header or simple request query. The question then becomes, how can Spring Security be configured to use this alternative session mechanism instead of the standard Servlet HttpSession?

Surely I am not the first dealing with this situation. What am I missing?

Thanks!

Answer 1

There's nothing magical about cookies. They're just strings in HTTP headers . Any decent client API can handle them, although many require explicit configuration to enable cookie processing.

An alternative to using cookies is to put the JSESSIONID into the URL. I don't know anything about spring-security, but it seems that that's actually the default for at least some types of URL requests, unless disable-url-rewriting is explicitly set to true . This can be considered as ecurity weakness , though.

Answer 2

Unfortunately authentication is highly problematic -- a bit of a blind spot in terms of web standards and browser implementations. You are right that cookies are not considered "RESTful" but purists, but even on fully-featured browsers avoiding takes quite a bit of hackery, as described in this article: Rest based authentication .

Unfortunately I haven't done any mobile development, so I can't suggest what the best compromise is. You might want to start by checking what authentication models each of your targetted platforms does support. In particular, two main options are:

• HTTP authentication (ideally "digest", not "basic")
• Cookies

One possibility would be to provide both options. Obviously not ideal from a technical or security point of view, but could have merits in terms of usability.