Click here to close now.


Cloud Security Authors: Pat Romanski, Liz McMillan, Sanjay Zalavadia, Ian Khan, Steve Watts

Related Topics: Java IoT, Cloud Security

Java IoT: Article

How to Provide Dynamic Security Permissions

Two approaches

For various reasons, an application may install a security manager. Usually it does so to guard against malicious third-party code either installed or dynamically downloaded at runtime. If the application uses RMI APIs, it's even required by a Java specification that a security manager be installed, otherwise the classloader will not download any classes from remote locations.

The most convenient security manager to use is java.lang.SecurityManager. Once installed, it will work with security policy to control the security permissions granted to different protection domains. For simplicity, it will be referred to as SecurityManager for the rest of this article.

The security policy is statically initialized at application start-up. For Sun's JDK, the security policy is defined in a security policy file. Naturally, this initial security policy cannot be changed at runtime once it's loaded with the application.

What if you want the security permissions to change at runtime? For example, you have a list of hosts from which the socket connection requests should not be accepted by the security manager. This list keeps changing when the application is running and you don't want to shut the application down to make the latest list effective. Or you feel that the expressions allowed in the security policy file are not enough for your application. Sure, it allows wildcards like "*", but you need something more dynamic and powerful, like a regular expression. What can you do?

Before any solution is proposed, let's take a look at how security permissions are managed normally. First, create a security policy that defines a set of security permissions granted to one or more protection domains, then install java.lang.SecurityManager at the start of your application. When the application calls a security-sensitive API, the API first checks with the SecurityManager to determine whether certain operations are allowed. The SecurityManager calls AccessContoller.checkPermission() method, which in turn consults the security policy when making security permission decisions.

It's not difficult to find out from the above that three components work together to provide security permissions - a security manager, a security policy, and the AccessContoller. AccessController is a final class and cannot be dynamically set with the system, so there's nothing we can do about it. SecurityManager and Policy, on the other hand, are extendable and can be set with the system.

It seems there are two approaches - writing your own security manager or writing your own security policy.

Writing Your Own Security Manager
If you take a look at SecurityManager APIs, the bulk of them are two checkPermission() methods and some checkOperation() methods, where Operation is an action like Connect, Listen, SetFactory, etc. If the security permission is granted, these methods simply return without doing anything. Otherwise, they throw SecurityException to indicate that the related security permission is denied. To dynamically control the behavior, just override one or more such APIs. If a method is not overridden, leave the behavior to SecurityManager and essentially the security policy to decide.

So far this seems easy. Is that so? Let's find out with a simple example. In this example, you want to control which properties can be accessed by overriding the checkPropertyAccess(String key) API. It's assumed that the list of accessible properties keeps changing and you get a fresh list each time checkPropertyAccess(String key) is invoked (see Listing 1).

You don't expect to get a security exception because we allow access to "user.home". By the way, if you use a security policy file that grants PropertyPermission to access "user.home" and "user.dir" and install a SecurityManager, TestProperty prints out the value of "user.home" just as expected.

If you run TestProperty with MySecurityManager in Sun's JDK 1.4.2, it prints out the following:

Exception in thread "main" java.lang.ExceptionInInitializerError
at java.lang.System.setSecurityManager0(
at java.lang.System.setSecurityManager(
at TestProperty.main(
Caused by: java.lang.SecurityException: Not allowed!
at MySecurityManager.checkPropertyAccess(
at java.lang.System.getProperty(
at java.lang.Integer.getInteger(
at java.lang.Integer.getInteger(
at Method)
... 3 more

The exception is thrown from System.setSecurityManager() and is caused by a read of property "", which is totally unrelated to our code. Seems like you just shot yourself in the foot, yet you don't know where the bullet came from.

Actually it's not important to know where the check comes from, but it is important to note that the security exception is caused by an AccessController.doPrivileged() call.

When we try the TestProperty application with the standard SecurityManager and security policy, AccessController.doPrivileged doesn't throw a security exception. This is because SecurityManager.checkPropertyAccess() delegates to checkPermission(), which in turn calls AccessController.checkPermission(). AccessController knows how to handle privileged code blocks. When it sees a privileged code block and the associated protection domain has the required permission, it returns without further checking callers of the privileged code block on the call stack. In our case, the privileged code block is in the, which is from the system domain that has all the permissions.

Let's go back to MySecurityManager. There is no way for it to know whether a call is from a privileged code block or the information about the call stack. It grants and denies the same set of permissions to all protection domains, even if the protection domain is the system domain where all permissions should be granted. That's where the problem comes from.

For more details regarding AccessController, I encourage you to check out the JavaDoc for the AccessController and security documentation at spec/security-spec.doc4.html#20389.

It's important to note that MySecurityManager tends to be more restrictive than SecurityManager (or the initial security policy) by specifically disallowing access to most of the properties. On the other hand, an application may need a security manager that is less restrictive than the initial security policy at certain times. In this case, override a SecurityManager's check method in the following manner:

  1. Specifically allow an action by directly returning from the method when a condition is met.
  2. Otherwise delegate to the same checkOperation() method in its super class to get the default behavior controlled by the initial security policy.

More Stories By Xiaozhong Wang

Xiaozhong Wang is a software engineer at Sun where he has solved some security problems in his TCK (Technology Compatibility Kit) work.

Comments (0)

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.

@ThingsExpo Stories
The Internet of Things (IoT) is growing rapidly by extending current technologies, products and networks. By 2020, Cisco estimates there will be 50 billion connected devices. Gartner has forecast revenues of over $300 billion, just to IoT suppliers. Now is the time to figure out how you’ll make money – not just create innovative products. With hundreds of new products and companies jumping into the IoT fray every month, there’s no shortage of innovation. Despite this, McKinsey/VisionMobile data shows "less than 10 percent of IoT developers are making enough to support a reasonably sized team....
Just over a week ago I received a long and loud sustained applause for a presentation I delivered at this year’s Cloud Expo in Santa Clara. I was extremely pleased with the turnout and had some very good conversations with many of the attendees. Over the next few days I had many more meaningful conversations and was not only happy with the results but also learned a few new things. Here is everything I learned in those three days distilled into three short points.
Most of the IoT Gateway scenarios involve collecting data from machines/processing and pushing data upstream to cloud for further analytics. The gateway hardware varies from Raspberry Pi to Industrial PCs. The document states the process of allowing deploying polyglot data pipelining software with the clear notion of supporting immutability. In his session at @ThingsExpo, Shashank Jain, a development architect for SAP Labs, discussed the objective, which is to automate the IoT deployment process from development to production scenarios using Docker containers.
DevOps is about increasing efficiency, but nothing is more inefficient than building the same application twice. However, this is a routine occurrence with enterprise applications that need both a rich desktop web interface and strong mobile support. With recent technological advances from Isomorphic Software and others, rich desktop and tuned mobile experiences can now be created with a single codebase – without compromising functionality, performance or usability. In his session at DevOps Summit, Charles Kendrick, CTO and Chief Architect at Isomorphic Software, demonstrated examples of com...
As organizations realize the scope of the Internet of Things, gaining key insights from Big Data, through the use of advanced analytics, becomes crucial. However, IoT also creates the need for petabyte scale storage of data from millions of devices. A new type of Storage is required which seamlessly integrates robust data analytics with massive scale. These storage systems will act as “smart systems” provide in-place analytics that speed discovery and enable businesses to quickly derive meaningful and actionable insights. In his session at @ThingsExpo, Paul Turner, Chief Marketing Officer at...
In his keynote at @ThingsExpo, Chris Matthieu, Director of IoT Engineering at Citrix and co-founder and CTO of Octoblu, focused on building an IoT platform and company. He provided a behind-the-scenes look at Octoblu’s platform, business, and pivots along the way (including the Citrix acquisition of Octoblu).
In his General Session at 17th Cloud Expo, Bruce Swann, Senior Product Marketing Manager for Adobe Campaign, explored the key ingredients of cross-channel marketing in a digital world. Learn how the Adobe Marketing Cloud can help marketers embrace opportunities for personalized, relevant and real-time customer engagement across offline (direct mail, point of sale, call center) and digital (email, website, SMS, mobile apps, social networks, connected objects).
With all the incredible momentum behind the Internet of Things (IoT) industry, it is easy to forget that not a single CEO wakes up and wonders if “my IoT is broken.” What they wonder is if they are making the right decisions to do all they can to increase revenue, decrease costs, and improve customer experience – effectively the same challenges they have always had in growing their business. The exciting thing about the IoT industry is now these decisions can be better, faster, and smarter. Now all corporate assets – people, objects, and spaces – can share information about themselves and thei...
The Internet of Everything is re-shaping technology trends–moving away from “request/response” architecture to an “always-on” Streaming Web where data is in constant motion and secure, reliable communication is an absolute necessity. As more and more THINGS go online, the challenges that developers will need to address will only increase exponentially. In his session at @ThingsExpo, Todd Greene, Founder & CEO of PubNub, exploreed the current state of IoT connectivity and review key trends and technology requirements that will drive the Internet of Things from hype to reality.
Two weeks ago (November 3-5), I attended the Cloud Expo Silicon Valley as a speaker, where I presented on the security and privacy due diligence requirements for cloud solutions. Cloud security is a topical issue for every CIO, CISO, and technology buyer. Decision-makers are always looking for insights on how to mitigate the security risks of implementing and using cloud solutions. Based on the presentation topics covered at the conference, as well as the general discussions heard between sessions, I wanted to share some of my observations on emerging trends. As cyber security serves as a fou...
The cloud. Like a comic book superhero, there seems to be no problem it can’t fix or cost it can’t slash. Yet making the transition is not always easy and production environments are still largely on premise. Taking some practical and sensible steps to reduce risk can also help provide a basis for a successful cloud transition. A plethora of surveys from the likes of IDG and Gartner show that more than 70 percent of enterprises have deployed at least one or more cloud application or workload. Yet a closer inspection at the data reveals less than half of these cloud projects involve production...
Countless business models have spawned from the IaaS industry – resell Web hosting, blogs, public cloud, and on and on. With the overwhelming amount of tools available to us, it's sometimes easy to overlook that many of them are just new skins of resources we've had for a long time. In his general session at 17th Cloud Expo, Harold Hannon, Sr. Software Architect at SoftLayer, an IBM Company, broke down what we have to work with, discussed the benefits and pitfalls and how we can best use them to design hosted applications.
Discussions of cloud computing have evolved in recent years from a focus on specific types of cloud, to a world of hybrid cloud, and to a world dominated by the APIs that make today's multi-cloud environments and hybrid clouds possible. In this Power Panel at 17th Cloud Expo, moderated by Conference Chair Roger Strukhoff, panelists addressed the importance of customers being able to use the specific technologies they need, through environments and ecosystems that expose their APIs to make true change and transformation possible.
Microservices are a very exciting architectural approach that many organizations are looking to as a way to accelerate innovation. Microservices promise to allow teams to move away from monolithic "ball of mud" systems, but the reality is that, in the vast majority of organizations, different projects and technologies will continue to be developed at different speeds. How to handle the dependencies between these disparate systems with different iteration cycles? Consider the "canoncial problem" in this scenario: microservice A (releases daily) depends on a couple of additions to backend B (re...
Container technology is shaping the future of DevOps and it’s also changing the way organizations think about application development. With the rise of mobile applications in the enterprise, businesses are abandoning year-long development cycles and embracing technologies that enable rapid development and continuous deployment of apps. In his session at DevOps Summit, Kurt Collins, Developer Evangelist at, examined how Docker has evolved into a highly effective tool for application delivery by allowing increasingly popular Mobile Backend-as-a-Service (mBaaS) platforms to quickly crea...
Too often with compelling new technologies market participants become overly enamored with that attractiveness of the technology and neglect underlying business drivers. This tendency, what some call the “newest shiny object syndrome” is understandable given that virtually all of us are heavily engaged in technology. But it is also mistaken. Without concrete business cases driving its deployment, IoT, like many other technologies before it, will fade into obscurity.
We all know that data growth is exploding and storage budgets are shrinking. Instead of showing you charts on about how much data there is, in his General Session at 17th Cloud Expo, Scott Cleland, Senior Director of Product Marketing at HGST, showed how to capture all of your data in one place. After you have your data under control, you can then analyze it in one place, saving time and resources.
The Internet of Things is clearly many things: data collection and analytics, wearables, Smart Grids and Smart Cities, the Industrial Internet, and more. Cool platforms like Arduino, Raspberry Pi, Intel's Galileo and Edison, and a diverse world of sensors are making the IoT a great toy box for developers in all these areas. In this Power Panel at @ThingsExpo, moderated by Conference Chair Roger Strukhoff, panelists discussed what things are the most important, which will have the most profound effect on the world, and what should we expect to see over the next couple of years.
Growth hacking is common for startups to make unheard-of progress in building their business. Career Hacks can help Geek Girls and those who support them (yes, that's you too, Dad!) to excel in this typically male-dominated world. Get ready to learn the facts: Is there a bias against women in the tech / developer communities? Why are women 50% of the workforce, but hold only 24% of the STEM or IT positions? Some beginnings of what to do about it! In her Day 2 Keynote at 17th Cloud Expo, Sandy Carter, IBM General Manager Cloud Ecosystem and Developers, and a Social Business Evangelist, wil...
PubNub has announced the release of BLOCKS, a set of customizable microservices that give developers a simple way to add code and deploy features for realtime apps.PubNub BLOCKS executes business logic directly on the data streaming through PubNub’s network without splitting it off to an intermediary server controlled by the customer. This revolutionary approach streamlines app development, reduces endpoint-to-endpoint latency, and allows apps to better leverage the enormous scalability of PubNub’s Data Stream Network.