Tuesday, August 21, 2012
XACML and the SDLC (Development): Part Two
JM: Generally speaking, the need for entitlements management tends to be on the radar of savvy information security professionals who realize that they need to invest more time in protecting enterprise applications and the data they hold over simply twiddling with firewalls, SSL and audit policies that look for whether a third party has a clean desk policy and whether there number two pencils are sharpened. When security people know nothing about software development and software development people don’t know anything about security, then bad things can happen. Today’s conversation will be a small attempt in connecting these two concerns. Are you game?
GG: Definitely. I also see a disproportionate amount of time and budget dedicated to security apparatus that does not address the specific security, business or compliance rules that an enterprise must enforce. To do that, you need to address security and access control concerns within the business application directly.
JM: A developer has received the mockups for a user interface from the graphics team and now has to turn it into code using JSPs and Servlets. In this particular tier, how should they incorporate entitlements into the pages as well as do it en-masse if they have hundreds of pages to develop?
FG: That’s an excellent question. Access control can and should happen on multiple layers. As you mention a user interface, that is a good point to control access to individual user interface components. For example: a button might start a particular transaction. Is this user authorized to carry out that transaction? If not, then the button should perhaps not be displayed. We can even think of fine-grained access control here. Suppose you are displaying a list of customer accounts to a user. What details should be visible? Should you perhaps hide some columns?
When we do access control in a holistic manner, we can obviously not stop at the presentation layer. You mentioned servlets here. A servlet operation is another type of action that can be authorized. May this function be executed on this servlet by this user in this particular context? This again is a good question. Let’s assume the user is authorized. What happens then? The servlet probably does some things, perhaps retrieving some data, perhaps kicking off a call to some back-end service. As the servlet does its thing, there other steps that would need to be authorized within the execution code of the running servlet. None of this is actually new. If we look at existing code, we see a lot of “If thens” that check whether something is allowed to happen. What architects should be vigilant about, is the fact that having all these “if thens” causes problems down the line. What if the business policies change? What if new regulations come into force? How can you actually audit what is happening? Because of this, it is important to consider moving access control to a separate layer and externalize authorization.
JM: Developers will also develop reusable web services whenever possible that can be leveraged not only by their enterprise application but others as well. How should they think about incorporating entitlements into a service-oriented architecture?
FG: Hooking entitlements into a service-oriented architecture is actually quite painless. The easiest way – without modifying code – would be to use interceptors that check whether a particular transaction is authorized. This also makes the services simpler because authorization is moved into its own layer.
JM: There are a variety of ways to develop web-based applications ranging from Spring, Struts, Django, etc and each of them come with some sort of security hook functionality. How do I configure this to work with entitlements?
FG: These frameworks support authorization, to a certain degree. Unfortunately though, Authorization is typically quite coarse-grained. In Spring for example, you can authorize access to a class. But if this class implements a lot of logic by itself, Spring doesn’t help you doing these “micro-authorizations” or fine-grained authorization. So it’s likely going to be a lot of “If thens” within those classes. The best approach would be to externalize both the coarse-grained as well as the fine-grained authorizations. But if for any reason that is not practical, then the coarse-grained authorization can already be done through the framework by talking to an externalized authorization layer, such as a XACML policy decision point (PDP).
JM: Being an Enterprise Architect who codes and knows security, I have observed throughout my career that many enterprise applications from a code perspective tend to centralize authentication but spread authorization in almost every module. What guidance do you have for both new and old applications in this regard?
FG: For new code, you have the option of externalizing authorization from the start. There are several ways to do this. Aspect-oriented programming can help automate some of this. You can also implement your own permissions checker interface and then hook that into either a local implementation or an externalized XACML authorization service at run-time, so that it gives you all of the flexibility. There is no perfect answer for all cases, as it really depends on how you are writing your code. Wherever in your code you would otherwise do the hard-coded “If thens” to check whether something should be authorized or not, you should be calling an authorization function. If you can create certain “control points”, then you make your life easier. If you have some other points where you need to authorize, use simple APIs to make a call-out to an authorization service.
For old applications, you will need to check where you can “hook in” the authorization. Perhaps there are some control points where you can install interceptors, inject dependencies, or wrap existing classes. If this is not possible, you might be able to intercept data flows coming in or out of a module, and do your authorization there.
JM: Within my enterprise application, I may have built up a “profile” of the user that contains information I would have retrieved post authentication from a directory service. What is the best practice in using this information to make authorization decisions?
GG: The design issue you are raising is whether the PEP should do attribute lookups or if we should rely on the PDP to perform this function. Generally speaking, it is more efficient for the PDP to look up attributes. Mostly this is because the PDP determines what policies will be evaluated and is able to fetch only the additional attributes it needs for policy evaluation. The PEP is not aware of what policies are going to be evaluated, and therefore may waste processing cycles retrieving attributes that will not be used. That extra processing time could be substantial when considering network time for the retrieval, parsing the response, and converting data to XACML attributes.
However, in your case it appears that the application is collecting attribute data for the profile in its normal course of operation. Seems like these attributes can be forwarded to the PDP in the access request without compromising response time performance. There may be other cases where the attributes are in close proximity to the application and it is better for the PEP to do the lookup.
Each scenario and use case should be analyzed, but our starting position would be to have the PEP include attributes it has already collected and to let the PDP look up the rest through its PIP interface. Attribute retrieval is really an externality for the application and should be left to the authorization service. It is also important to consider what happens when policies change. If too much attribute handling is done by the application, it may require additional code changes to accommodate policy changes. If the developer relies on the authorization service to deal with attribute management, then he/she gets the additional benefit of fewer (if any) code changes when the access policies must be adjusted.
JM: Another form of reuse within that many enterprise applications should consider but are not currently implementing is the notion of supporting multiple tenants. Today, an enterprise may take an application and deploy it redundantly instead of keeping a single instance and allowing multiple tenants to live within it. If I wanted to show development leadership in this regard, how can entitlements help?
GG: Applications have multiple layers or integration points where you must consider authorization for a multi tenant configuration – this also applies to single tenant applications. As you described earlier, access policies need to be applied at the presentation and web services or API layers. Beyond this, you have the data layer, typically a database, to consider. It is likely that enterprises deploy multiple instances of an application and its database because they cannot adequately filter data per tenant with current technologies or approaches. With an XACML entitlements system, you can enforce row, column and field level access controls – providing a consistent enforcement of entitlements from presentation to web service to the database. Axiomatics builds specific database integrations (such as Oracle, Microsoft and others), but customers can also use the API to integrate with their preferred SQL coding mechanisms. We think this is a less costly AND more secure solution than what can be purchased from Oracle, for example.
With the approach just described, enterprises can get some economies of scale by deploying fewer application instances – I know there are reports out there about idle CPU time in data centers. Hopefully this also reduces the operational burden by managing fewer instances, but the operations center has to know more detail about which user communities or customer groups each application is supporting.
JM: Our corporation has been breached on more than a few occasions by Wiley hackers. Every time this happens, the security forensic jamboree blows their trumpets really loud asking for assistance in determining what happened. They attempt to reactively walk through log files. To me, this feels like a ceremonial failure. Can entitlements management make those information security people disappear so that I can focus on developing code that provides business value without listening to their forensic whining?
GG: Audit logs of what HAS happened will always be important when attempting to analyze a breach, incident or even for extreme troubleshooting. I think it can be helpful to investigators if there are fewer access logs to examine – here a central authorization service can provide a lot of benefit. A central authorization system that serves multiple applications gives you a single audit stream and single audit file format. It also relieves developers from at least some of the burdens of security logging – although there may be requirements to log additional context that the authorization system is not aware of.
There is also a proactive side of this coin: what CAN users access in an application. It seems that, as an industry, we’ve been trying to definitively answer auditor questions such as, “Who can update accounting data in the general ledger system?” or “Who can approve internal equity trades when the firm’s accumulated risk position reaches a certain threshold?” First, there is a fundamental failure in application design when business owners, auditors and security officers alike cannot easily answer these questions. Why is it still acceptable to build and buy applications that actually increase the operational risk for an organization? Second, many identity management technologies have only served to mask the problem and, ultimately, enable the problem to continue. For example, user provisioning systems were initially thought to be capable of managing access and entitlements for business applications. It turns out that they are relatively good at creating user accounts, but have limited visibility into application entitlements – those are managed by local admin teams. Access governance tools have a better view of entitlements, but it remains difficult to get a complete view when authorization logic is embedded in the application code.
With XACML policies implemented, auditors can test specific access scenarios to confirm enterprise objectives are being met. A policy language is an infinitely richer model for expressing access control policies, than can be done with ACLs, group lists, or roles. Finally, you can specifically answer those auditor questions of who can access or update applications, transactions, or data.
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