Welcome!

Java IoT Authors: Gerardo A Dada, Xenia von Wedel, Elizabeth White, Yeshim Deniz, Carmen Gonzalez

Related Topics: Open Source Cloud, Java IoT, Microservices Expo, Apache

Open Source Cloud: Article

Valve, JAAS and Filter in Tomcat

Their usages and relationships

Tomcat is a widely popular lightweight application server. When securing Tomcat web applications, Valve, JAAS and Filter are used in various scenarios. The challenges for developers are when to use each of these methods and how to integrate them together if more than one method is chosen. For example, the WebSeal agent discussed in the article [1] uses Valve. If a customer needs to integrate WebSeal and its own JAAS-based authentication module, they will need to know how to configure Tomcat to use both the WebSeal Agent Valve and the JAAS module and how to pass information between them.

In this article, we will explain the concepts of Valve, JAAS and Filter, and their relationships such as the order that they get called. Through an example application, we will explain how you can use them together and pass information among them for an authentication process. How to configure and run the example application using Tomcat 7 will also be discussed.

The Concepts
Valve

A Valve is a piece of Java code that can be inserted into the request processing pipeline. The Valve can be defined on a different scope such as Engine, Host and Context. Tomcat comes with a set of pre-built valves that can be found here [2]. However, developers can write their own Valve and participate in the processing of the Valve chain. The main requirements for a Valve are:

  • It needs to extend ValveBase
  • It needs to call getNext().invoke(request, response) to chain other Valves.

For example, Listing 1 is a simple Valve. (Listings 1 - 5 can be downloaded here.) That Valve also has a method that may call an external policy server to verify the user. It may retrieve the user information passed in as a token in the HTTP header field such as the one used in [1]. You can ignore the ThreadLocale part in the Listing 1, which will be discussed later.

JAAS
Java Authentication and Authorization Service (JAAS) [3] is a security framework that allows a user's program to participate in the authentication and authorization process. JAAS also serves as an integration point to allow different user-specific security implementations to be used. JAAS is supported in Tomcat through its JAASRealm interface [4].

When JAASRealm is used, a user will need to provide a login module and the appropriate configurations: a configuration file and a security configuration in the web.xml. Once it's configured properly, the login module will be called and managed by the Tomcat.

Listing 2 has a sample JAAS login module. This login module will use a callback to get the userid and password. It will check whether the password is the reverse of the userid. If the check succeeds, it will create a principal based on the username and assign the role "jvalve" to the principal.

Filter
A filter is part of the Java Servlet specification [5]. A filter can be inserted into the request processing pipeline. It will be executed before the servlet is called and invoked again when the servlet process is done. Multiple filters can be chained together and thus can be used as an integration point for different users who want to use the filter to accomplish certain cross-cutting functions. The main requirements for a filter are:

  • It needs to extend javax.servlet.Filter.
  • It needs to call chain.doFilter(request, response).

Listing 3 shows an example filter. This filter simply calculates the time used to complete the request.

The Relationships
All three technologies, Valve, JAAS and Filter, have the following commonalities:

  • Run before the servlet is invoked
  • Allow cross-cutting functions to be implemented.
  • Provide integration points to allow multiple Valves, login modules and filters to be defined by different users.
  • Provide a common place for implementing security features.

Even though JAAS is the official method for providing security implementations, Valve and filter have been used to implement securities frequently. Especially in the Tomcat case, it is relatively hard to get a Subject in the application code (JBoss has a SharedState, WebLogic and WebSphere all provide a static method to make the "Subject" available for the application code). Implementations may use Valve for the authentication and then set the authenticated principal on the request for the filter and application code to use.

However, it's also important to understand their differences especially if you want to use them together.

  • The order that they get invoked is as follows: Valve, JAAS module, Filter and then Servlet.
  • Valve and Filter have access to a request/response/session, etc. However, JAAS only has access to the shared state. It can interact with the Tomcat container to retrieve such things as security information, but can only do so through callbacks.

Because of the above differences, it becomes a challenge if you want to use all three of them together and pass information among them. Consider the following example. Tivilo WebSeal provides a Valve engine that will set an authenticated user on the request. Your company has been using the JAAS module for the additional authentication purpose. The JAAS module will want to retrieve that authenticated user from the Valve. Tomcat will not help in this case. In the next session, we'll discuss a ThreadLocale [6] solution to address this issue.

The Sample Application
The sample application uses the Valve, the JAAS login module and the filter in Listings 1, 2, and 3. However, we want to retrieve a key in the Valve and pass it to the JAAS login module. We will use the ThreadLocale to accomplish this. Listing 4 shows the ThreadLocale class.

In Listing 1, we have set the "key" to the ThreadLocale. In Listing 2 of the JAAS code, we have code to retrieve the "key" from the ThreadLocale (it is commented out). We define the value of the password as the reverse of the username plus the key (it's commented out in Listing 2 as well).

The web.xml, which protects the secured resource and defines the filter, is listed in Listing 5.

The JAAS login module can be defined in the following login.config file:

MyAccess {
com.sas.tcserver.SampleLoginModule required
debug=true;
};

This same ThreadLocale concept can be used if a user wants to pass information from the JAAS login module to the filter.

Issues with Tomcat 6
If you are using Tomcat 6 and plan to create a user principal at the Valve, the JAAS login module will not be called by Tomcat.

For example, you have the following code in your Valve's "invoke()" method:

GenericPrincipal genericprincipal = new
GenericPrincipal(request.getContext().getRealm(), "user", null,
arraylist
, null);
request.setUserPrincipal(genericprincipal);

This problem does not occur at Tomcat 7. It should note that the construct for GenericPrincipal has been changed from 6 to 7. In Tomcat 7, you will do:

GenericPrincipal genericprincipal = new
GenericPrincipal("user", null, arraylist, null);
request.setUserPrincipal(genericprincipal);

Configure and Run the Sample Application
The sample application is packaged into the following files: 1) A src folder, which contains all source code; 2) securityvalve.jar; 3) loginmodule war file, which includes the sampleloginmodule.jar and timerfilter.jar. The files can be downloaded from here.

To run the application, complete the following process:

  • Download and install Tomcat 7.
  • Unzip the downloaded file.
  • Copy securityvalve.jar into Tomcat lib directory
  • Copy loginmodule war (in exploded format) into Tomcat webapps directory
  • Add the following xml piece into Tomcat conf/server.xml file inside Services -> Engine -> Host:

<Context path="/loginmodule">
<Realm
className="org.apache.catalina.realm.JAASRealm           
appName="MyAccess"          
userClassNames="com.sas.tcserver.SampleUserPrincipal"        
roleClassNames="com.sas.tcserver.SampleRolePrincipal"/>

<Valve className="com.sas.tcserver.SecurityValve"
debugTrace="true"/>
</Context>

  • Create login.config file in Tomcat conf directory using the content in the previous section.
  • Update Tomcat startup command to add the following parameter:

-Djava.security.auth.login.config=%CATALINA_BASE%\conf\login.config

  • Start Tomcat
  • Access the application in Web browser using the following URL: http://localhost:8080/loginmodule/index.html. When prompted, type in "jvalve/velavjsas" as username/password, you should see the following output in the Tomcat console:

Security Valve: invoke
SampleLoginModule: initialize
SampleLoginModule - initialize - subject: Subject:

SampleLoginModule - initialize - sharedState: {}
SampleLoginModule: login
SampleUserPrincipal
SampleLoginModule: commit
SampleRolePrincipal
SampleLoginModule: commit successful
TimerFilter: Time to execute request: 2 milliseconds
Security Valve: exit invoke

In the above output, you may notice that the Valve works like filters but is called before and after JAAS and the filters. We use the password "velavjsas", which is the reverse of username "jvalve" plus the key that is passed from the Valve to the JAAS module using the ThreadLocale.

Conclusion
Valve, JAAS and Filter are common technologies in Tomcat. However, to configure and use them together requires a basic understanding of their relationships. This article explained the concepts and demonstrated their usages and relationships through a sample application. The sample application can be easily expanded and used in various authentication processes.

The concept discussed here can also be used in other Tomcat based application servers such as the VMware vFabric tc Server [7].

Resources

  1. How do I integrate SSO on Apache Tomcat
  2. Apache Tomcat 7: The Valve Component
  3. All that JAAS
  4. Tomcat Class JAASRealm
  5. The Essentials of Filters
  6. ThreadLocale
  7. VMware vFabric tc Server

More Stories By Zhiyong Li

Zhiyong Li is a senior manager of SAS Platform Division and the chair of the Java Technology Board at SAS institute. He started coding in Java in 1995 as a Sun’s development staff. He worked at IBM and iBiomatics as lead architect and developer for several enterprises Java applications. He holds a Ph.D from Computer Science Department of Duke University. He has published many papers in AI, parallel computation and program languages. He has also published several patents.

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
An IoT product’s log files speak volumes about what’s happening with your products in the field, pinpointing current and potential issues, and enabling you to predict failures and save millions of dollars in inventory. But until recently, no one knew how to listen. In his session at @ThingsExpo, Dan Gettens, Chief Research Officer at OnProcess, discussed recent research by Massachusetts Institute of Technology and OnProcess Technology, where MIT created a new, breakthrough analytics model for ...
In his keynote at 18th Cloud Expo, Andrew Keys, Co-Founder of ConsenSys Enterprise, provided an overview of the evolution of the Internet and the Database and the future of their combination – the Blockchain. Andrew Keys is Co-Founder of ConsenSys Enterprise. He comes to ConsenSys Enterprise with capital markets, technology and entrepreneurial experience. Previously, he worked for UBS investment bank in equities analysis. Later, he was responsible for the creation and distribution of life sett...
Successful digital transformation requires new organizational competencies and capabilities. Research tells us that the biggest impediment to successful transformation is human; consequently, the biggest enabler is a properly skilled and empowered workforce. In the digital age, new individual and collective competencies are required. In his session at 19th Cloud Expo, Bob Newhouse, CEO and founder of Agilitiv, drew together recent research and lessons learned from emerging and established compa...
20th Cloud Expo, taking place June 6-8, 2017, at the Javits Center in New York City, NY, will feature technical sessions from a rock star conference faculty and the leading industry players in the world. Cloud computing is now being embraced by a majority of enterprises of all sizes. Yesterday's debate about public vs. private has transformed into the reality of hybrid cloud: a recent survey shows that 74% of enterprises have a hybrid cloud strategy.
Whether your IoT service is connecting cars, homes, appliances, wearable, cameras or other devices, one question hangs in the balance – how do you actually make money from this service? The ability to turn your IoT service into profit requires the ability to create a monetization strategy that is flexible, scalable and working for you in real-time. It must be a transparent, smoothly implemented strategy that all stakeholders – from customers to the board – will be able to understand and comprehe...
DevOps is being widely accepted (if not fully adopted) as essential in enterprise IT. But as Enterprise DevOps gains maturity, expands scope, and increases velocity, the need for data-driven decisions across teams becomes more acute. DevOps teams in any modern business must wrangle the ‘digital exhaust’ from the delivery toolchain, "pervasive" and "cognitive" computing, APIs and services, mobile devices and applications, the Internet of Things, and now even blockchain. In this power panel at @...
Extracting business value from Internet of Things (IoT) data doesn’t happen overnight. There are several requirements that must be satisfied, including IoT device enablement, data analysis, real-time detection of complex events and automated orchestration of actions. Unfortunately, too many companies fall short in achieving their business goals by implementing incomplete solutions or not focusing on tangible use cases. In his general session at @ThingsExpo, Dave McCarthy, Director of Products...
Businesses and business units of all sizes can benefit from cloud computing, but many don't want the cost, performance and security concerns of public cloud nor the complexity of building their own private clouds. Today, some cloud vendors are using artificial intelligence (AI) to simplify cloud deployment and management. In his session at 20th Cloud Expo, Ajay Gulati, Co-founder and CEO of ZeroStack, will discuss how AI can simplify cloud operations. He will cover the following topics: why clou...
SYS-CON Events has announced today that Roger Strukhoff has been named conference chair of Cloud Expo and @ThingsExpo 2017 New York. The 20th Cloud Expo and 7th @ThingsExpo will take place on June 6-8, 2017, at the Javits Center in New York City, NY. "The Internet of Things brings trillions of dollars of opportunity to developers and enterprise IT, no matter how you measure it," stated Roger Strukhoff. "More importantly, it leverages the power of devices and the Internet to enable us all to im...
With major technology companies and startups seriously embracing IoT strategies, now is the perfect time to attend @ThingsExpo 2016 in New York. Learn what is going on, contribute to the discussions, and ensure that your enterprise is as "IoT-Ready" as it can be! Internet of @ThingsExpo, taking place June 6-8, 2017, at the Javits Center in New York City, New York, is co-located with 20th Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry p...
Internet-of-Things discussions can end up either going down the consumer gadget rabbit hole or focused on the sort of data logging that industrial manufacturers have been doing forever. However, in fact, companies today are already using IoT data both to optimize their operational technology and to improve the experience of customer interactions in novel ways. In his session at @ThingsExpo, Gordon Haff, Red Hat Technology Evangelist, will share examples from a wide range of industries – includin...
"We build IoT infrastructure products - when you have to integrate different devices, different systems and cloud you have to build an application to do that but we eliminate the need to build an application. Our products can integrate any device, any system, any cloud regardless of protocol," explained Peter Jung, Chief Product Officer at Pulzze Systems, in this SYS-CON.tv interview at @ThingsExpo, held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA.
Internet of @ThingsExpo has announced today that Chris Matthieu has been named tech chair of Internet of @ThingsExpo 2017 New York The 7th Internet of @ThingsExpo will take place on June 6-8, 2017, at the Javits Center in New York City, New York. Chris Matthieu is the co-founder and CTO of Octoblu, a revolutionary real-time IoT platform recently acquired by Citrix. Octoblu connects things, systems, people and clouds to a global mesh network allowing users to automate and control design flo...
With 15% of enterprises adopting a hybrid IT strategy, you need to set a plan to integrate hybrid cloud throughout your infrastructure. In his session at 18th Cloud Expo, Steven Dreher, Director of Solutions Architecture at Green House Data, discussed how to plan for shifting resource requirements, overcome challenges, and implement hybrid IT alongside your existing data center assets. Highlights included anticipating workload, cost and resource calculations, integrating services on both sides...
"We're a cybersecurity firm that specializes in engineering security solutions both at the software and hardware level. Security cannot be an after-the-fact afterthought, which is what it's become," stated Richard Blech, Chief Executive Officer at Secure Channels, in this SYS-CON.tv interview at @ThingsExpo, held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA.
Unless your company can spend a lot of money on new technology, re-engineering your environment and hiring a comprehensive cybersecurity team, you will most likely move to the cloud or seek external service partnerships. In his session at 18th Cloud Expo, Darren Guccione, CEO of Keeper Security, revealed what you need to know when it comes to encryption in the cloud.
According to Forrester Research, every business will become either a digital predator or digital prey by 2020. To avoid demise, organizations must rapidly create new sources of value in their end-to-end customer experiences. True digital predators also must break down information and process silos and extend digital transformation initiatives to empower employees with the digital resources needed to win, serve, and retain customers.
The WebRTC Summit New York, to be held June 6-8, 2017, at the Javits Center in New York City, NY, announces that its Call for Papers is now open. Topics include all aspects of improving IT delivery by eliminating waste through automated business models leveraging cloud technologies. WebRTC Summit is co-located with 20th International Cloud Expo and @ThingsExpo. WebRTC is the future of browser-to-browser communications, and continues to make inroads into the traditional, difficult, plug-in web co...
In his general session at 19th Cloud Expo, Manish Dixit, VP of Product and Engineering at Dice, discussed how Dice leverages data insights and tools to help both tech professionals and recruiters better understand how skills relate to each other and which skills are in high demand using interactive visualizations and salary indicator tools to maximize earning potential. Manish Dixit is VP of Product and Engineering at Dice. As the leader of the Product, Engineering and Data Sciences team at D...
The Internet of Things (IoT) promises to simplify and streamline our lives by automating routine tasks that distract us from our goals. This promise is based on the ubiquitous deployment of smart, connected devices that link everything from industrial control systems to automobiles to refrigerators. Unfortunately, comparatively few of the devices currently deployed have been developed with an eye toward security, and as the DDoS attacks of late October 2016 have demonstrated, this oversight can ...