|By Jared Day||
|April 5, 2012 10:00 AM EDT||
When we aren't fighting crime, taking over the world, or enjoying a good book by the fire, we here on the eEye Research team like to participate in the Any Means Possible (AMP) Penetration Testing engagements with our clients. For us, it's a great way to interact one-on-one with IT folks and really dig into the security problems that they are facing. We can sharpen our skills with real-world scenarios and practice the academic techniques presented in the industry, all the while helping to connect better with our customers and identify their security needs. During these engagements, we target a number of attack surfaces, ranging from exposed external server interfaces to client-side attacks launched on individual workstations. What I would like to talk about today is centered purely on the web-based attack surface, with a common problem we see consistently during our AMP engagements.
When talking about web vulnerabilities, you can't even begin to breach the subject without someone throwing out Cross-Site Scripting (XSS) or SQL Injection (SQLi). Unfortunately, poor little web services never seem to get any attention in the mix. Web service vulnerabilities are arguably just as widespread and dangerous as the aforementioned classes of vulnerabilities, but with so little talk and discussion around them, very rarely are these issues identified and remediated. Let's fix that.
Figure 1: Demo Microsoft Silverlight application. The left is a failed attempt to login and reveal the user's secret data, the right is a successful login.
Many browser applications, such as Adobe Flash and Microsoft Silverlight, communicate back to the server programmatically using web services. These services are exposed interfaces on the server that can be called directly from custom-written applications. In many situations, these services can expose potentially sensitive and privileged information that would otherwise not be accessible. Figure 1 shows a Microsoft Silverlight application that was constructed for demonstration purposes. This application is not vulnerable to XSS or SQLi and, to the average user, there is nothing about this application that allows someone without a password to access the legitimate user's secret data. However, what a lot of people don't seem to take into consideration is that you have access to anything that is running in your browser. Now, we can't pull the entire project down off of the server, but we can reverse-engineer the application interface running in the browser to see if there is anything potentially sensitive that is being exposed.
The first thing that should be done when auditing web sites is to make sure all requests are being logged through a local request proxy. For this example, I will be using Tamper Data (https://addons.mozilla.org/en-US/firefox/addon/tamper-data/) to log all of the requests that FireFox makes to our target Silverlight application. Right away, we see that the application requests an XAP file, shown in Figure 2. This is a fun thing to play around with that I will come back to later. As soon as we click the button on the page, we see the browser make a request to an SVC file; this is our web services interface and is also shown in Figure 2.
Figure 2: Browser makes requests for an XAP file and an SVC file. The XAP file is loaded immediately into the browser when the application is started and the SVC file is loaded as soon as the user attempts to submit data back to the server.
Now, when we find a site serving up an SVC web services file, it's usually game over for that particular site. The reason is that these interfaces are usually trusted by the developer. Developers will assume that the only thing calling these exposed interfaces is the client application that they wrote. However, browsing to the service file directly in your favorite web browser will usually show you the basic interface of the exposed web service. The next step is creating a custom application to interface with the web service directly. You can use any language that you want as long as it can interface with a web server, but I usually like to use C# in Visual Studio. Creating the application is quite easy - simply create a new C# project and add a service reference to the hosted SVC file. Visual Studio will automatically import all of the references to everything exposed by the service. Figure 3 shows what is exposed by the sample service.
Figure 3: Object Viewer's list of the imported Web Services interface.
This service exports two functions: GetUserSecret and Login. The interesting thing here is that GetUserSecret takes a string and gives back a string, likely representing the secret data associated with that provided user. Now, it's perfectly possible that there is some form of authentication check that happens on the server side when this function is called, which ensures no secrets are disclosed to unauthenticated clients. However, in many situations I have encountered, this is not the case. We can test if code is properly checking for authentication by writing our own custom interface for the exposed web service. The following code snippet instantiates a client and queries for the secret data of two users without first authenticating with the server. Figure 4 shows the output from that program.
LoginService.LoginServiceClient client = new LoginService.LoginServiceClient();
Console.WriteLine("eEyeResearch's secret: "+client.GetUserSecret("eEyeResearch"));
Console.WriteLine("admin's secret: " + client.GetUserSecret("admin"));
Figure 4: Output from the code written to call the example service directly.
The output from our code shows that this exposed service is callable directly, without requiring any authentication. The only information needed is the user's name and, as many of you know from attacks that have made the press over the past year, that information can be acquired through social engineering or brute force style attacks quite easily.
This vulnerability is quite straightforward, but I think many of you would be surprised how often we encounter issues very similar to this in real-world penetration testing scenarios. It's a fairly easy mistake to make, to assume that any malicious tampering of a web page would be done through a browser or front-end web application, but the simple truth is that this is not the case.
If you wanted to take this a bit further, you could examine the manifest files that are used by the client-side browser application. Remember the XAP file mentioned at the beginning? That file is actually a ZIP archive containing manifest information and binary executable files used by the Silverlight application. Examining these files will show you all of the web services APIs that the application can potentially call, even the authenticated ones. This information has proven to be quite useful on various engagements. A simple web application, that wasn't vulnerable to XSS or SQLi, revealed a manifest of previously unknown web services, which eventually allowed downloading all of the information hidden behind the login page. Because these services were only referenced after the user had authenticated through the login screen, these APIs may have never been found with a purely unauthenticated audit had the manifest files not been checked for additional exposed interfaces.
As if freely available manifest information wasn't enough, the DLL files presented in this archive can also prove to be a lot of fun. Ask any professional or hobby reverse-code engineer, languages such as Java or C# are quite easy to decompile. Due to the managed nature of such languages, there are actually freely available tools that do quite a good job of turning the compiled binaries back into the original (or very similar) high-level code. These DLLs only represent the client-side browser code that gets executed by Silverlight in the browser, so you won't be getting the original server code out of this. However, a very common mistake made by programmers is to incorporate some of the application logic into the user interface as well. In these situations, such reversing sessions may yield valuable information about how the application is working behind the scenes. In fact, this has been used in the past to gain all kinds of interesting information about target applications, including default credentials to the authenticated sections of the application, which were set in a button click-event handler of the application's user interface.
Though this entire article has been purely focused on Silverlight, the same concept applies to most other client-side web applications out there. Often times, these applications will rely on web services in order to communicate with the server, for both unauthenticated and authenticated communications alike. Developers often times rely on the client-side application to do all of the relevant filtering and data integrity checking of information being sent to these web services.
Problems centered on web service APIs can potentially be just as dangerous as an SQLi vulnerability. It's somewhat unfortunate that SQLi has become so trendy, taking away any deserved fame or glory from the other interesting web vulnerabilities. It's important to keep in mind that, though this was a very heavily focused Microsoft and Silverlight example, the same issues apply across the board in many different web application technologies. The issue is actually very easy to audit for, especially if you already know exactly what your application should and shouldn't be able to do at every level of authentication.
I recommend if you manage servers hosting websites or you manage the websites that you take a few minutes to sit down and browse through each of these services. Be aware of exactly what is exposed on the external facing interfaces. If anything looks out of place, try connecting directly to the service and see what information is exposed and available to your users. Try preventing the service from displaying its metadata by removing the mex endpoint binding and setting httpGetEnabled for service metadata to false in the web configuration file. This prevents users from reading the web services descriptions and makes it nontrivial to arbitrarily connect and communicate with these services without prior knowledge of the internal workings of the application. These problems are quite easy to identify, potentially trivial to remediate, and can save an organization from a serious compromise if steps are taken to proactively identify and address these issues.
• • •
This article was written by Jared Day, a researcher with eEye's Research Team led by Marc Maiffret.
If you are interested in learning more about our AMP services, you can visit our page here (http://www.eeye.com/services/penetration-testing).
SYS-CON Events announced today that HPM Networks will exhibit at the 17th International Cloud Expo®, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. For 20 years, HPM Networks has been integrating technology solutions that solve complex business challenges. HPM Networks has designed solutions for both SMB and enterprise customers throughout the San Francisco Bay Area.
Aug. 3, 2015 06:45 PM EDT Reads: 532
For IoT to grow as quickly as analyst firms’ project, a lot is going to fall on developers to quickly bring applications to market. But the lack of a standard development platform threatens to slow growth and make application development more time consuming and costly, much like we’ve seen in the mobile space. In his session at @ThingsExpo, Mike Weiner, Product Manager of the Omega DevCloud with KORE Telematics Inc., discussed the evolving requirements for developers as IoT matures and conducted a live demonstration of how quickly application development can happen when the need to comply wit...
Aug. 2, 2015 11:15 AM EDT Reads: 366
The Internet of Everything (IoE) brings together people, process, data and things to make networked connections more relevant and valuable than ever before – transforming information into knowledge and knowledge into wisdom. IoE creates new capabilities, richer experiences, and unprecedented opportunities to improve business and government operations, decision making and mission support capabilities.
Aug. 1, 2015 10:00 AM EDT Reads: 344
Explosive growth in connected devices. Enormous amounts of data for collection and analysis. Critical use of data for split-second decision making and actionable information. All three are factors in making the Internet of Things a reality. Yet, any one factor would have an IT organization pondering its infrastructure strategy. How should your organization enhance its IT framework to enable an Internet of Things implementation? In his session at @ThingsExpo, James Kirkland, Red Hat's Chief Architect for the Internet of Things and Intelligent Systems, described how to revolutionize your archit...
Jul. 30, 2015 07:30 PM EDT Reads: 1,426
MuleSoft has announced the findings of its 2015 Connectivity Benchmark Report on the adoption and business impact of APIs. The findings suggest traditional businesses are quickly evolving into "composable enterprises" built out of hundreds of connected software services, applications and devices. Most are embracing the Internet of Things (IoT) and microservices technologies like Docker. A majority are integrating wearables, like smart watches, and more than half plan to generate revenue with APIs within the next year.
Jul. 30, 2015 02:30 PM EDT Reads: 150
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 Opening Keynote at 16th Cloud Expo, Sandy Carter, IBM General Manager Cloud Ecosystem and Developers, and a Social Business Evangelist, d...
Jul. 30, 2015 12:00 PM EDT Reads: 2,087
In his keynote at 16th Cloud Expo, Rodney Rogers, CEO of Virtustream, discussed the evolution of the company from inception to its recent acquisition by EMC – including personal insights, lessons learned (and some WTF moments) along the way. Learn how Virtustream’s unique approach of combining the economics and elasticity of the consumer cloud model with proper performance, application automation and security into a platform became a breakout success with enterprise customers and a natural fit for the EMC Federation.
Jul. 30, 2015 09:00 AM EDT Reads: 2,177
The Internet of Things is not only adding billions of sensors and billions of terabytes to the Internet. It is also forcing a fundamental change in the way we envision Information Technology. For the first time, more data is being created by devices at the edge of the Internet rather than from centralized systems. What does this mean for today's IT professional? In this Power Panel at @ThingsExpo, moderated by Conference Chair Roger Strukhoff, panelists addressed this very serious issue of profound change in the industry.
Jul. 29, 2015 03:00 PM EDT Reads: 1,300
Discussions about cloud computing are evolving into discussions about enterprise IT in general. As enterprises increasingly migrate toward their own unique clouds, new issues such as the use of containers and microservices emerge to keep things interesting. In this Power Panel at 16th Cloud Expo, moderated by Conference Chair Roger Strukhoff, panelists addressed the state of cloud computing today, and what enterprise IT professionals need to know about how the latest topics and trends affect their organization.
Jul. 29, 2015 02:00 PM EDT Reads: 1,207
It is one thing to build single industrial IoT applications, but what will it take to build the Smart Cities and truly society-changing applications of the future? The technology won’t be the problem, it will be the number of parties that need to work together and be aligned in their motivation to succeed. In his session at @ThingsExpo, Jason Mondanaro, Director, Product Management at Metanga, discussed how you can plan to cooperate, partner, and form lasting all-star teams to change the world and it starts with business models and monetization strategies.
Jul. 28, 2015 04:30 PM EDT Reads: 1,776
Converging digital disruptions is creating a major sea change - Cisco calls this the Internet of Everything (IoE). IoE is the network connection of People, Process, Data and Things, fueled by Cloud, Mobile, Social, Analytics and Security, and it represents a $19Trillion value-at-stake over the next 10 years. In her keynote at @ThingsExpo, Manjula Talreja, VP of Cisco Consulting Services, discussed IoE and the enormous opportunities it provides to public and private firms alike. She will share what businesses must do to thrive in the IoE economy, citing examples from several industry sectors.
Jul. 28, 2015 11:00 AM EDT Reads: 2,052
There will be 150 billion connected devices by 2020. New digital businesses have already disrupted value chains across every industry. APIs are at the center of the digital business. You need to understand what assets you have that can be exposed digitally, what their digital value chain is, and how to create an effective business model around that value chain to compete in this economy. No enterprise can be complacent and not engage in the digital economy. Learn how to be the disruptor and not the disruptee.
Jul. 27, 2015 10:00 AM EDT Reads: 2,047
Akana has released Envision, an enhanced API analytics platform that helps enterprises mine critical insights across their digital eco-systems, understand their customers and partners and offer value-added personalized services. “In today’s digital economy, data-driven insights are proving to be a key differentiator for businesses. Understanding the data that is being tunneled through their APIs and how it can be used to optimize their business and operations is of paramount importance,” said Alistair Farquharson, CTO of Akana.
Jul. 27, 2015 09:00 AM EDT Reads: 337
Business as usual for IT is evolving into a "Make or Buy" decision on a service-by-service conversation with input from the LOBs. How does your organization move forward with cloud? In his general session at 16th Cloud Expo, Paul Maravei, Regional Sales Manager, Hybrid Cloud and Managed Services at Cisco, discusses how Cisco and its partners offer a market-leading portfolio and ecosystem of cloud infrastructure and application services that allow you to uniquely and securely combine cloud business applications and services across multiple cloud delivery models.
Jul. 27, 2015 08:00 AM EDT Reads: 1,914
The enterprise market will drive IoT device adoption over the next five years. In his session at @ThingsExpo, John Greenough, an analyst at BI Intelligence, division of Business Insider, analyzed how companies will adopt IoT products and the associated cost of adopting those products. John Greenough is the lead analyst covering the Internet of Things for BI Intelligence- Business Insider’s paid research service. Numerous IoT companies have cited his analysis of the IoT. Prior to joining BI Intelligence, he worked analyzing bank technology for Corporate Insight and The Clearing House Payment...
Jul. 26, 2015 09:00 PM EDT Reads: 1,592
"Optimal Design is a technology integration and product development firm that specializes in connecting devices to the cloud," stated Joe Wascow, Co-Founder & CMO of Optimal Design, in this SYS-CON.tv interview at @ThingsExpo, held June 9-11, 2015, at the Javits Center in New York City.
Jul. 25, 2015 02:00 PM EDT Reads: 406
SYS-CON Events announced today that CommVault has been named “Bronze Sponsor” of SYS-CON's 17th International Cloud Expo®, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. A singular vision – a belief in a better way to address current and future data management needs – guides CommVault in the development of Singular Information Management® solutions for high-performance data protection, universal availability and simplified management of data on complex storage networks. CommVault's exclusive single-platform architecture gives companies unp...
Jul. 25, 2015 01:00 PM EDT Reads: 1,977
Electric Cloud and Arynga have announced a product integration partnership that will bring Continuous Delivery solutions to the automotive Internet-of-Things (IoT) market. The joint solution will help automotive manufacturers, OEMs and system integrators adopt DevOps automation and Continuous Delivery practices that reduce software build and release cycle times within the complex and specific parameters of embedded and IoT software systems.
Jul. 25, 2015 12:15 PM EDT Reads: 490
"ciqada is a combined platform of hardware modules and server products that lets people take their existing devices or new devices and lets them be accessible over the Internet for their users," noted Geoff Engelstein of ciqada, a division of Mars International, in this SYS-CON.tv interview at @ThingsExpo, held June 9-11, 2015, at the Javits Center in New York City.
Jul. 25, 2015 12:00 PM EDT Reads: 1,559
Internet of Things is moving from being a hype to a reality. Experts estimate that internet connected cars will grow to 152 million, while over 100 million internet connected wireless light bulbs and lamps will be operational by 2020. These and many other intriguing statistics highlight the importance of Internet powered devices and how market penetration is going to multiply many times over in the next few years.
Jul. 25, 2015 09:00 AM EDT Reads: 1,505