Posted on

Method Internals in Swift 5.0

One of the nice things about Swift 5 is the final stabilization of the ABI. This is actually a big deal. The application binary interface defines exactly how data is stored in programs, shared from libraries, things like that. It includes name decoration, class and object definitions, and so on. Now that we have a stable ABI, building tools that analyzed and manipulate these binary representations will become much, well, not easier, but not as much a waste of time. Until now, you were just about guaranteed to have any tools you created broken by new Swift versions. With a stable ABI? This shouldn't happen.

We just covered how classes are defined in Swift 5, and we discovered that they reflect the basic design in Objective-C. There are some key differences though, and one of those is member method definitions.

Posted on

Objective C vs. C/C++: Getting the Message

Most of the time, working in cybersecurity, when we're reverse engineering an application we're working either with C or C++. Both of these languages use function semantics for method or function calls. Objective C is different — instead of using function semantics, where you use a 'call' instruction to pass program execution and state to a specific section of memory, Objective C uses message passing semantics. Let's explore exactly what that is, and how it differs from function semantics. We'll start by outlining exactly what function semantics are and how they work. To do that, we'll need to outline use of the call instruction and name mangling in C++.

C code is pretty straightforward to analyze. A function call in C will look something like this: