Agile Computing Authors: Elizabeth White, Yeshim Deniz, Pat Romanski, Michel Courtoy, ManageEngine IT Matters

Related Topics: Agile Computing, Machine Learning

Agile Computing: Article

JavaScript Hijacking: Only 1 Out 12 Popular AJAX Frameworks Prevents It

The first class of vulnerability specific to rich Web apps

Declining Malicious Requests
From the server's perspective, a JavaScript Hijacking attack looks like an attempt at cross-site request forgery, and defenses against cross-site request forgery will also defeat JavaScript Hijacking attacks.

To make it easy to detect malicious requests, every request should include a parameter that is hard for an attacker to guess. One approach is to add the session cookie to the request as a parameter. When the server gets such a request, it can check to be certain the session cookie matches the value in the request parameter. Malicious code does not have access to the session cookie (cookies are also subject to the Same Origin Policy), so there is no easy way for the attacker to craft a request that will pass this test. A different secret can also be used in place of the session cookie. As long as the secret is hard to guess and appears in a context that is accessible to the legitimate application and not accessible from a different domain, it will prevent an attacker from making a valid request.

Some frameworks run only on the client side. In other words, they are written entirely in JavaScript and have no knowledge of the workings of the server. This implies that they do not know the name of the session cookie. Even without knowing the name of the session cookie, they can participate in a cookie-based defense by adding all of the cookies to each request to the server. The following JavaScript fragment outlines this "blind client" strategy:

var httpRequest = new XMLHttpRequest();
var cookies="cookies="+escape(document.cookie);
http_request.open(‘POST', url, true);

The server could also check the HTTP referrer header to make sure the request has originated from the legitimate application and not from a malicious application. Historically speaking, the referrer header has not been reliable, so we don't recommend using it as the basis for any security mechanism.

A server can mount a defense against JavaScript Hijacking by responding only to HTTP POST requests and not responding to HTTP GET requests. This is a defensive technique because the <script> tag always uses GET to load JavaScript from external sources. This defense is also error-prone. The use of GET for better performance is encouraged by Web application experts from Sun and elsewhere. Even frameworks that use POST requests internally, such as GWT, document the steps necessary to support GET requests without mentioning any potential security ramifications. This missing connection between the choice of HTTP methods and security means that, at some point, a programmer may mistake this lack of functionality for an oversight rather than a security precaution and modify the application to respond to GET requests.

Preventing Direct Execution of the Response
To make it impossible for a malicious site to execute a response that includes JavaScript, the legitimate client application can take advantage of the fact that it is allowed to modify the data it receives before executing it, while a malicious application can only execute it using a <script> tag. When the server serializes an object, it should include a prefix (and potentially a suffix) that makes it impossible to execute the JavaScript using a <script> tag. The legitimate client application can remove this extraneous data before running the JavaScript. There are many possible implementations of this approach. We will outline two.

First, the server could prefix each message with the statement:


Unless the client removes this prefix, evaluating the message will send the JavaScript interpreter into an infinite loop. This is the technique Google used to fix the vulnerability Grossman identified. The client searches for and removes the prefix like this:

var object;
var req = new XMLHttpRequest();
req.open("GET", "/object.json",true);
req.onreadystatechange = function () {
if (req.readyState == 4) {
var txt = req.responseText;
if (txt.substr(0,9) == "while(1);") {
txt = txt.substring(10);
object = eval("(" + txt + ")");
req = null;

Second, the server can include comment characters around the JavaScript that have to be removed before the JavaScript is sent to eval(). The following JSON object has been enclosed in a block comment:

[{"fname":"Brian", "lname":"Chess", "phone":"6502135600",
"purchases":60000.00, "email":"[email protected]" }

The client can search for and remove the comment characters like this:

var object;
var req = new XMLHttpRequest();
req.open("GET", "/object.json",true);
req.onreadystatechange = function () {
if (req.readyState == 4) {
var txt = req.responseText;if (txt.substr(0,2) == "/*") {
txt = txt.substring(2, txt.length - 2);
object = eval("(" + txt + ")");
req = null;

Any malicious site that retrieves the sensitive JavaScript via a <script> tag will not gain access to the data it contains.

Conclusion and Recommendations
The JavaScript implementations contained in popular Web browsers have been the source of numerous security problems, so JavaScript Hijacking follows a distinguished list of older attacks, including cross-site scripting and cross-site request forgery. (Bugs in JavaScript implementations have also led to no shortage of browser vulnerabilities.) The fundamental issue that allows JavaScript Hijacking, an eccentricity in the Web browser Same Origin Policy, is also used by benevolent programmers to create legitimate advertisements and application mashups, so it is unlikely that the Same Origin Policy will change in the near future.

The solutions and best practices proposed in this article have been cobbled together in much the same way that rich Web interfaces and mashup concepts have been cobbled together. The Web programming community has stretched the existing technology well past its original purposes, so it is not surprising that we occasionally encounter an unexpected side effect. These workarounds and hacks will be necessary until popular Web browsers support standards that allow for things like secure cross-domain requests and JavaScript sandboxing. Until then, we need to make programmers aware of the risks inherent in communicating confidential data via JavaScript.

To that end, we recommend that all programs that communicate using JavaScript take the following defensive measures:

  • Include a hard-to-guess identifier, such as the session identifier, as part of each request that will return JavaScript. This defeats cross-site request forgery attacks by allowing the server to validate the origin of the request.
  • Include characters in the response that prevent it from being successfully handed off to a JavaScript interpreter without modification. This prevents an attacker from using a <script> tag to witness the execution of the JavaScript.

We need to encourage Web application frameworks to be secure by default. For server-integrated toolkits, this is a matter of changing both the server-side and client-side components. Purely client-side libraries cannot defend against JavaScript Hijacking without support from server-side code, but they can still improve security by making the JavaScript Hijacking risk clear to developers and by including features that make it easy to implement secure server-side code.

If programmers want to create applications that can participate as part of a mashup, they should be required to explicitly disable a security constraint, and the framework should make them aware of the consequences of their actions.

We would like to extend special thanks to a number of people for their feedback on early versions of this article. We thank Jeremiah Grossman for his valuable comments on the technical content of the report, Joe Walker - for a great discussion of DWR security, Alex Russell - for a discussion of the Dojo framework and for highlighting important points missing from the original draft, and Bob Ippolito - for a discussion of the MochiKit framework and suggestions on how to address the issue. Eddie Lee, Adam Murray, and Erik Cabetas helped us proofread the draft and provided insight into their experience with AJAX and AJAX frameworks.

More Stories By Yekaterina Tsipenyuk O'Neil

Yekaterina Tsipenyuk O'Neil is the founding member of the Security Research Group at Fortify Software. She is responsible for performing code audits, identifying and analyzing insecure coding patterns, providing security content for Fortify's software security products, and researching ways to improve the quality of the tools. Yekaterina has a B.S. and an M.S. in computer science from the University of California, San Diego. Her thesis work focused on mobile agent security.

More Stories By Brian Chess

Brian Chess is a founder of Fortify Software and serves as Fortify's chief scientist, where his work focuses on practical methods for creating secure systems. His book, Secure Programming with Static Analysis, shows how static source code analysis is an indispensable tool for getting security right. Brian holds a Ph.D. in computer engineering from the University of California at Santa Cruz. Before settling on security, Brian spent a decade in Silicon Valley working at huge companies and small startups. He has done research on a broad set of topics, ranging from integrated circuit design all the way to delivering software as a service.

More Stories By Jacob West

Jacob West manages Fortify Software’s Security Research Group, which is responsible for building security knowledge into Fortify's products. He brings expertise in numerous programming languages, frameworks and styles together with knowledge about how real-world systems can fail. In addition, he recently co-authored a book, "Secure Programming with Static Analysis," which was published in June 2007. Before joining Fortify, Jacob worked with Professor David Wagner, at the University of California at Berkeley, to develop MOPS (MOdel Checking Programs for Security properties), a static analysis tool used to discover security vulnerabilities in C programs. When he is away from the keyboard, Jacob spends time speaking at conferences and working with customers to advance their understanding of software security.

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
SYS-CON Events announced today that Enzu will exhibit at SYS-CON's 21st Int\ernational Cloud Expo®, which will take place October 31-November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Enzu’s mission is to be the leading provider of enterprise cloud solutions worldwide. Enzu enables online businesses to use its IT infrastructure to their competitive advantage. By offering a suite of proven hosting and management services, Enzu wants companies to focus on the core of their ...
With major technology companies and startups seriously embracing Cloud strategies, now is the perfect time to attend 21st Cloud Expo October 31 - November 2, 2017, at the Santa Clara Convention Center, CA, and June 12-14, 2018, at the Javits Center in New York City, NY, and learn what is going on, contribute to the discussions, and ensure that your enterprise is on the right path to Digital Transformation.
Internet of @ThingsExpo, taking place October 31 - November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 21st Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The Internet of Things (IoT) is the most profound change in personal and enterprise IT since the creation of the Worldwide Web more than 20 years ago. All major researchers estimate there will be tens of billions devic...
SYS-CON Events announced today that Cloud Academy named "Bronze Sponsor" of 21st International Cloud Expo which will take place October 31 - November 2, 2017 at the Santa Clara Convention Center in Santa Clara, CA. Cloud Academy is the industry’s most innovative, vendor-neutral cloud technology training platform. Cloud Academy provides continuous learning solutions for individuals and enterprise teams for Amazon Web Services, Microsoft Azure, Google Cloud Platform, and the most popular cloud com...
Amazon started as an online bookseller 20 years ago. Since then, it has evolved into a technology juggernaut that has disrupted multiple markets and industries and touches many aspects of our lives. It is a relentless technology and business model innovator driving disruption throughout numerous ecosystems. Amazon’s AWS revenues alone are approaching $16B a year making it one of the largest IT companies in the world. With dominant offerings in Cloud, IoT, eCommerce, Big Data, AI, Digital Assista...
When growing capacity and power in the data center, the architectural trade-offs between server scale-up vs. scale-out continue to be debated. Both approaches are valid: scale-out adds multiple, smaller servers running in a distributed computing model, while scale-up adds fewer, more powerful servers that are capable of running larger workloads. It’s worth noting that there are additional, unique advantages that scale-up architectures offer. One big advantage is large memory and compute capacity...
No hype cycles or predictions of zillions of things here. IoT is big. You get it. You know your business and have great ideas for a business transformation strategy. What comes next? Time to make it happen. In his session at @ThingsExpo, Jay Mason, Associate Partner at M&S Consulting, presented a step-by-step plan to develop your technology implementation strategy. He discussed the evaluation of communication standards and IoT messaging protocols, data analytics considerations, edge-to-cloud tec...
"When we talk about cloud without compromise what we're talking about is that when people think about 'I need the flexibility of the cloud' - it's the ability to create applications and run them in a cloud environment that's far more flexible,” explained Matthew Finnie, CTO of Interoute, in this SYS-CON.tv interview at 20th Cloud Expo, held June 6-8, 2017, at the Javits Center in New York City, NY.
SYS-CON Events announced today that MobiDev, a client-oriented software development company, will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place October 31-November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. MobiDev is a software company that develops and delivers turn-key mobile apps, websites, web services, and complex software systems for startups and enterprises. Since 2009 it has grown from a small group of passionate engineers and business...
SYS-CON Events announced today that GrapeUp, the leading provider of rapid product development at the speed of business, will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place October 31-November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Grape Up is a software company, specialized in cloud native application development and professional services related to Cloud Foundry PaaS. With five expert teams that operate in various sectors of the market acr...
SYS-CON Events announced today that Ayehu will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on October 31 - November 2, 2017 at the Santa Clara Convention Center in Santa Clara California. Ayehu provides IT Process Automation & Orchestration solutions for IT and Security professionals to identify and resolve critical incidents and enable rapid containment, eradication, and recovery from cyber security breaches. Ayehu provides customers greater control over IT infras...
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
With the introduction of IoT and Smart Living in every aspect of our lives, one question has become relevant: What are the security implications? To answer this, first we have to look and explore the security models of the technologies that IoT is founded upon. In his session at @ThingsExpo, Nevi Kaja, a Research Engineer at Ford Motor Company, discussed some of the security challenges of the IoT infrastructure and related how these aspects impact Smart Living. The material was delivered interac...
Artificial intelligence, machine learning, neural networks. We’re in the midst of a wave of excitement around AI such as hasn’t been seen for a few decades. But those previous periods of inflated expectations led to troughs of disappointment. Will this time be different? Most likely. Applications of AI such as predictive analytics are already decreasing costs and improving reliability of industrial machinery. Furthermore, the funding and research going into AI now comes from a wide range of com...
In his session at Cloud Expo, Alan Winters, an entertainment executive/TV producer turned serial entrepreneur, presented a success story of an entrepreneur who has both suffered through and benefited from offshore development across multiple businesses: The smart choice, or how to select the right offshore development partner Warning signs, or how to minimize chances of making the wrong choice Collaboration, or how to establish the most effective work processes Budget control, or how to ma...
IoT solutions exploit operational data generated by Internet-connected smart “things” for the purpose of gaining operational insight and producing “better outcomes” (for example, create new business models, eliminate unscheduled maintenance, etc.). The explosive proliferation of IoT solutions will result in an exponential growth in the volume of IoT data, precipitating significant Information Governance issues: who owns the IoT data, what are the rights/duties of IoT solutions adopters towards t...
In his session at @ThingsExpo, Eric Lachapelle, CEO of the Professional Evaluation and Certification Board (PECB), provided an overview of various initiatives to certify the security of connected devices and future trends in ensuring public trust of IoT. Eric Lachapelle is the Chief Executive Officer of the Professional Evaluation and Certification Board (PECB), an international certification body. His role is to help companies and individuals to achieve professional, accredited and worldwide re...
SYS-CON Events announced today that CA Technologies has been named "Platinum Sponsor" of SYS-CON's 21st International Cloud Expo®, which will take place October 31-November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. CA Technologies helps customers succeed in a future where every business - from apparel to energy - is being rewritten by software. From planning to development to management to security, CA creates software that fuels transformation for companies in the applic...
SYS-CON Events announced today that IBM has been named “Diamond Sponsor” of SYS-CON's 21st Cloud Expo, which will take place on October 31 through November 2nd 2017 at the Santa Clara Convention Center in Santa Clara, California.
The current age of digital transformation means that IT organizations must adapt their toolset to cover all digital experiences, beyond just the end users’. Today’s businesses can no longer focus solely on the digital interactions they manage with employees or customers; they must now contend with non-traditional factors. Whether it's the power of brand to make or break a company, the need to monitor across all locations 24/7, or the ability to proactively resolve issues, companies must adapt to...