Anti-debug trick #1: Abusing Mach-O to crash GDB

I developed this funny trick while trying to find a solution for a problem in a project. It is pretty easy to implement and fun. The trick consists in abusing the offset field in the dylib_command and pointing it to somewhere else. From the Mach-O File Format Reference document, the command structures are: struct dylib_command { uint_32 cmd; uint_32 cmdsize; struct dylib dylib; } struct dylib { union lc_str name; uint_32 timestamp; uint_32 current_version; uint_32 compatibility_version; } union lc_str { uint32_t offset; #ifndef __LP64__ char *ptr; #endif } The definition of the offset field is: [Read More]