An Ounce of Prevention: Software hardening for securing IoT devices

March 16, 2016 Bill Graham


Every IoT and embedded device manufacturer endeavors to field secure and safe products. However, even with the robust development processes, it's difficult to ensure complete security in finished products more so in legacy products. As the ever-expanding IoT marketplace puts a bigger emphasis on embedded device security, better techniques are required to improve security. I wrote a blog series this fall on improving IoT security with source-based static analysis and binary static analysis coupled with software hardening, but I focused primarily on the static analysis part of the equation. GrammaTech's software hardening techniques complement our static analysis know-how to greatly improve the current and future robustness of embedded software. 


Binary Analysis and Static Rewriting

Analyzing application binaries allows GrammaTech's rewriting tools to discover the use of potentially problematic code patterns, libraries, or OS functions. The rewritten binaries have wrappers around such code to prevent erroneous behavior. For example, function call stack usage can be instrumented to prevent stack overflow and subsequent code injection. Another example would be preventing calls to known problematic library functions like strcpy() from causing buffer overflow errors.

Rewriting a binary executable into a robust hardened version provides quality and security assurance for any version of the application -- current and future versions are protected.

GrammaTech Software Hardening

GrammaTech's hardening tools static rewrite binaries into more robust and secure applications.

Confinement and Diversification: Binary Rewriting Techniques

The goal of confinement is to prevent undetected vulnerabilities from causing a failure in an executing application. Techniques to detect and prevent certain specific classes of vulnerabilities already exist to some extent, but often lead to a program failure state -- which, in turn, leads to a denial of service. Although an attack might be prevented, these consequences are unacceptable in critical systems. GrammaTech has been researching sophisticated confinement techniques that allow applications to detect the same kinds of attacks, but continue operation (while still containing the vulnerability). Combining binary analysis to detect the potential vulnerability with static rewriting to confine the exploit, it's possible to greatly reduce and even eliminate the impact.

Diversification techniques are used to alter the default code and memory layout to prevent potential exploits. By rearranging the subroutine calling sequence, stack, heap, and global data layout, it's possible to prevent vulnerabilities from being exploited. Stack overflow errors that lead to code injection exploits, for example, can be thwarted with these techniques. 

Protection Now and in the Future

Binary analysis and rewriting by nature doesn't require source and is version-independent. As such, IoT device manufacturers can use GrammaTech's hardening techniques on every release of their applications, making software hardening a standard procedure in the software release process. In doing so, organizations can assure better robustness and security for even minor upgrades, without huge re-testing costs. 


Security defines the success of IoT. Good software development techniques are a good start, but adding software hardening is even better. GrammaTech's software hardening techniques provide version-independent protection from vulnerabilities and runtime errors while maintaining system functionality. In addition to the improved security and safety provided, software hardening offers compelling reductions in cost, risk, and time savings. 


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