Service: secure coding

RESEARCH | January 11, 2018

SCADA and Mobile Security in the IoT Era

By Alexander Bolshev & Ivan Yushkevich
Two years ago, we assessed 20 mobile applications that worked with ICS software and hardware. At that time, mobile technologies were widespread, but Internet of Things (IoT) mania was only starting. Our research concluded the combination of SCADA systems and mobile applications had the potential to be a very dangerous and vulnerable cocktail. In the introduction of our paper, we stated “convenience often wins over security. Nowadays, you can monitor (or even control!) your ICS from a brand-new Android [device].”


Today, no one is surprised at the appearance of an IIoT. The idea of putting your logging, monitoring, and even supervisory/control functions in the cloud does not sound as crazy as it did several years ago. If you look at mobile application offerings today, many more ICS- related applications are available than two years ago. Previously, we predicted that the “rapidly growing mobile development environment” would redeem the past sins of SCADA systems.
The purpose of our research is to understand how the landscape has evolved and assess the security posture of SCADA systems and mobile applications in this new IIoT era.

SCADA and Mobile Applications
ICS infrastructures are heterogeneous by nature. They include several layers, each of which is dedicated to specific tasks. Figure 1 illustrates a typical ICS structure.

Figure 1: Modern ICS infrastructure including mobile apps

Mobile applications reside in several ICS segments and can be grouped into two general families: Local (control room) and Remote.


Local Applications
Local applications are installed on devices that connect directly to ICS devices in the field or process layers (over Wi-Fi, Bluetooth, or serial).

 Remote Applications
Remote applications allow engineers to connect to ICS servers using remote channels, like the Internet, VPN-over-Internet, and private cell networks. Typically, they only allow monitoring of the industrial process; however, several applications allow the user to control/supervise the process. Applications of this type include remote SCADA clients, MES clients, and remote alert applications. 

 In comparison to local applications belonging to the control room group, which usually operate in an isolated environment, remote applications are often installed on smartphones that use Internet connections or even on personal devices in organizations that have a BYOD policy. In other words, remote applications are more exposed and face different threats.

Typical Threats And     Attacks

In this section, we discuss the typical threats to this heterogeneous landscape of applications and how attacks could be conducted. We also map the threats to the application types.
 
Threat Types
There are three main possible ICS threat types:
  • Unauthorized physical access to the device or “virtual” access to device data
  • Communication channel compromise (MiTM)
  • Application compromise

Table 1 summarizes the threat types.

Table 1: SCADA mobile client threat list
 
Attack Types
Based on the threats listed above, attacks targeting mobile SCADA applications can be sorted into two groups.
 
Directly/indirectly influencing an industrial process or industrial network infrastructure
This type of attack could be carried out by sending data that would be carried over to the field segment devices. Various methods could be used to achieve this, including bypassing ACL/ permissions checks, accessing credentials with the required privileges, or bypassing data validation.
 
Compromising a SCADA operator to unwillingly perform a harmful action on the system
The core idea is for the attacker to create environmental circumstances where a SCADA system operator could make incorrect decisions and trigger alarms or otherwise bring the system into a halt state.
 
Testing Approach
Similar to the research we conducted two years ago, our analysis and testing approach was based on the OWASP Mobile Top 10 2016. Each application was tested using the following steps:
  • Perform analysis and fill out the test checklist
  • Perform client and backend fuzzing
  • If needed, perform deep analysis with reverse engineering
We did not alter the fuzzing approach since the last iteration of this research. It was discussed in depth in our previous whitepaper, so its description is omitted for brevity.
We improved our test checklist for this assessment. It includes:
  • Application purpose, type, category, and basic information 
  • Permissions
  • Password protection
  • Application intents, exported providers, broadcast services, etc.
  • Native code
  • Code obfuscation
  • Presence of web-based components
  • Methods of authentication used to communicate with the backend
  • Correctness of operations with sessions, cookies, and tokens 
  • SSL/TLS connection configuration
  • XML parser configuration
  • Backend APIs
  • Sensitive data handling
  • HMI project data handling
  • Secure storage
  • Other issues
Reviewed Vendors
We analyzed 34 vendors in our research, randomly selecting  SCADA application samples from the Google Play Store. We did, however, favor applications for which we were granted access to the backend hardware or software, so that a wider attack surface could be tested.
 
Additionally, we excluded applications whose most recent update was before June 2015, since they were likely the subject of our previous work. We only retested them if there had been an update during the subsequent two years.
 
Findings
We identified 147 security issues in the applications and their backends. We classified each issue according to the OWASP Top Ten Mobile risks and added one additional category for backend software bugs.
 
Table 4 presents the distribution of findings across categories. The “Number of Issues” column reports the number of issues belonging to each category, while the “% of Apps” column reports how many applications have at least one vulnerability belonging to each category.
Table 4. Vulnerabilities statistics

In our white paper, we provide an in-depth analysis of each category, along with examples of the most significant vulnerabilities we identified. Please download the white paper for a deeper analysis of each of the OWASP category findings.

 Remediation And Best Practices
In addition to the well-known recommendations covering the OWASP Top 10 and OWASP Mobile Top 10 2016 risks, there are several actions that could be taken by developers of mobile SCADA clients to further protect their applications and systems.

 In the following list, we gathered the most important items to consider when developing a mobile SCADA application:

  • Always keep in mind that your application is a gateway to your ICS systems. This should influence all of your design decisions, including how you handle the inputs you will accept from the application and, more generally, anything that you will accept and send to your ICS system.
  • Avoid all situations that could leave the SCADA operators in the dark or provide them with misleading information, from silent application crashes to full subverting of HMI projects.
  • Follow best practices. Consider covering the OWASP Top 10, OWASP Mobile Top 10 2016, and the 24 Deadly Sins of Software Security.
  • Do not forget to implement unit and functional tests for your application and the backend servers, to cover at a minimum the basic security features, such as authentication and authorization requirements.
  • Enforce password/PIN validation to protect against threats U1-3. In addition, avoid storing any credentials on the device using unsafe mechanisms (such as in cleartext) and leverage robust and safe storing mechanisms already provided by the Android platform.
  • Do not store any sensitive data on SD cards or similar partitions without ACLs at all costs Such storage mediums cannot protect your sensitive data.
  • Provide secrecy and integrity for all HMI project data. This can be achieved by using authenticated encryption and storing the encryption credentials in the secure Android storage, or by deriving the key securely, via a key derivation function (KDF), from the application password.
  • Encrypt all communication using strong protocols, such as TLS 1.2 with elliptic curves key exchange and signatures and AEAD encryption schemes. Follow best practices, and keep updating your application as best practices evolve. Attacks always get better, and so should your application.
  • Catch and handle exceptions carefully. If an error cannot be recovered, ensure the application notifies the user and quits gracefully. When logging exceptions, ensure no sensitive information is leaked to log files.
  • If you are using Web Components in the application, think about preventing client-side injections (e.g., encrypt all communications, validate user input, etc.).
  • Limit the permissions your application requires to the strict minimum.
  • Implement obfuscation and anti-tampering protections in your application.

Conclusions
Two years have passed since our previous research, and things have continued to evolve. Unfortunately, they have not evolved with robust security in mind, and the landscape is less secure than ever before. In 2015 we found a total of 50 issues in the 20 applications we analyzed and in 2017 we found a staggering 147 issues in the 34 applications we selected. This represents an average increase of 1.6 vulnerabilities per application. 

 We therefore conclude that the growth of IoT in the era of “everything is connected” has not led to improved security for mobile SCADA applications. According to our results, more than 20% of the discovered issues allow attackers to directly misinform operators and/or directly/ indirectly influence the industrial process.

In 2015, we wrote:

SCADA and ICS come to the mobile world recently, but bring old approaches and weaknesses. Hopefully, due to the rapidly developing nature of mobile software, all these problems will soon be gone.

We now concede that we were too optimistic and acknowledge that our previous statement was wrong.

 Over the past few years, the number of incidents in SCADA systems has increased and the systems become more interesting for attackers every year. Furthermore, widespread implementation of the IoT/IIoT connects more and more mobile devices to ICS networks.

 Thus, the industry should start to pay attention to the security posture of its SCADA mobile applications, before it is too late.

 For the complete analysis, please download our white paper here.

 Acknowledgments

Many thanks to Dmitriy Evdokimov, Gabriel Gonzalez, Pau Oliva, Alfredo Pironti, Ruben Santamarta, and Tao Sauvage for their help during our work on this research.
 
About Us
Alexander Bolshev
Alexander Bolshev is a Security Consultant for IOActive. He holds a Ph.D. in computer security and works as an assistant professor at Saint-Petersburg State Electrotechnical University. His research interests lie in distributed systems, as well as mobile, hardware, and industrial protocol security. He is the author of several white papers on topics of heuristic intrusion detection methods, Server Side Request Forgery attacks, OLAP systems, and ICS security. He is a frequent presenter at security conferences around the world, including Black Hat USA/EU/UK, ZeroNights, t2.fi, CONFIdence, and S4.
 
Ivan Yushkevich
Ivan is the information security auditor at Embedi (http://embedi.com). His main area of interest is source code analysis for applications ranging from simple websites to enterprise software. He has vast experience in banking systems and web application penetration testing.
 
IOActive
IOActive is a comprehensive, high-end information security services firm with a long and established pedigree in delivering elite security services to its customers. Our world-renowned consulting and research teams deliver a portfolio of specialist security services ranging from penetration testing and application code assessment through to semiconductor reverse engineering. Global 500 companies across every industry continue to trust IOActive with their most critical and sensitive security issues. Founded in 1998, IOActive is headquartered in Seattle, USA, with global operations through the Americas, EMEA and Asia Pac regions. Visit for more information. Read the IOActive Labs Research Blog. Follow IOActive on Twitter.
 
Embedi
Embedi expertise is backed up by extensive experience in security of embedded devices, with special emphasis on attack and exploit prevention. Years of research are the genesis of the software solutions created. Embedi developed a wide range of security products for various types of embedded/smart devices used in different fields of life and industry such as: wearables, smart home, retail environments, automotive, smart buildings, ICS, smart cities, and others. Embedi is headquartered in Berkeley, USA. Visit for more information and follow Embedi on Twitter.
RESEARCH | October 18, 2016

Let’s Terminate XML Schema Vulnerabilities

By Fernando Arnaboldi

XML eXternal Entity (XXE) attacks are a common threat to applications using XML schemas, either actively or unknowingly. That is because we continue to use XML schemas that can be abused in multiple ways. Programming languages and libraries use XML schemas to define the expected contents of XML documents, SAML authentications or SOAP messages. XML schemas were intended to constrain document definitions, yet they have introduced multiple attack avenues.

XML parsers should be prepared to manage two types of problematic XML documents: malformed files and invalid files. Malformed files do not follow the World Wide Web Consortium (W3C) specification. This results in unexpected consequences for any software that parses the file. Invalid files abuse XML schemas and exploit actions that are built into programming languages and libraries. This may unwillingly put any software relying on these technologies at risk.

I analyzed possible attacks affecting XML and discovered new attacks in the previous categories. Among them:

  • Schema version disclosure: Parsers may disclose type and version information when retrieving remote schemas.
  • Unrestrictive schemas: Major companies still rely on schemas that cannot provide the restrictions required for their XML documents. DTD schemas continue to be common, even though they are often unable to accomplish their goal.
  • Improper data validation: As companies move away from DTD schemas and attempt to implement better restrictions, they may provide incomplete protection for their systems. XML schemas provide highly granular constraints, and if they are not properly defined, the approved document may affect the underlying security of applications.

Some of the proposed examples provided by the W3C include vulnerable methods of defining XML documents. To illlustrate with a basic example, the W3C states that an application can use a DTD to verify that XML data is valid, and provides the following example:

<?xml version=”1.0″?>
<!DOCTYPE note [
  <!ELEMENT note (to,from,heading,body)>
  <!ELEMENT to (#PCDATA)>
  <!ELEMENT from (#PCDATA)>
  <!ELEMENT heading (#PCDATA)>
  <!ELEMENT body (#PCDATA)>
]>
<note>
  <to>Tove</to>
  <from>Jani</from>
  <heading>Reminder</heading>
  <body>Don’t forget me this weekend</body>
</note>

This example document contains an embedded DTD that constrains the contents to the previously defined elements. However, those elements do not provide a constraint on how large they are or what type of data they contain. Moreover, since the DTD declaration can simply be changed or removed from the previous document, you can even have a valid, well-formed document without an XML schema.

For more details and greater depth on this topic, view the full white paper, Assessing and Exploiting XML Schema’s Vulnerabilities.

As always, we would love to hear from other security types who might have a differing opinion. All of our positions are subject to change through exposure to compelling arguments and/or data.