continuous delivery of runtime-protected code

Memory layouts have evolved a lot over time, but there are still fundamental problems that have plagued them all. On the left is the memory layout representative of a program built in the late 90s. Each time a program was executed, or library loaded, the memory addresses of each program were the same. In the early 2000s most OSes began adopting Address Space Layout Randomization (ASLR) to help prevent attackers from always knowing where . ASLR randomizes the base address of a program each time it is executed, but has an inherent weakness in that the whole program is moved as one unit. Introduction of ASLR made exploitation of memory corruption vulnerabilities more difficult, but ASLR can be defeated easily by one information leak. Alkemist:Source improves upon the ASLR concept by randomizing each function within a program. An important aspect of Alkemist:Source is that while functions move around in memory, the functionality of the program stays identical. One way to assess functionality is to look at the call graph of a program. Let’s consider a simple program with five functions with a call graph shown in the left of the figure below. The call graph would read: Function 1 calls Function 3, Function 3 calls Function 2, Function 2 calls Function 4, and Function 4 calls Function 5. For simplicity’s sake, consider all functions to be contiguous in memory in the order shown in the figure. On the right is the same program, with the same five functions, after the program is executed and Alkemist:Source randomizes the functions in memory. You will see that while the functions are not in the same location, the call graph is the same. By building Alkemist:Source into your software, you deprive the attacker the ability to reliably exploit your software because the code they need to execute is never in the same place twice. Additionally, any failed attempts to exploit Alkemist:Source-protected software result in the program crashing. When the software is launched again, any information an attacker could gain from the previous failed exploit attempt would not be useful because the program will have been randomized again. Alkemist:Source allows you to continue using your existing compiler and linker. We accomplish this by sitting in front of the linker, making the modifications needed, and then calling your linker. This process can be seen in the figure below. The top path through the process is what a normal build looks like, abstracting away the infinite complexities that build systems bring. Alkemist:Source has been proven to work with builds as simple as a “Hello, World” example built with GCC all the way to a complex Yocto-based build using different compilers per project. With Alkemist:Source in the mix, compilation takes a slightly different path at the linking stage, where we inject information needed to accomplish our runtime randomization.

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