In a previous post CryptedHelloWorld: App with encrypted mach-o sections, I created a simple macOS app CryptedHelloWorld with its (__TEXT, __text) section encrypted. The section is decrypted by a constructor function.
This post explains how to dump the decrypted app. A common way is to attach the app with a debugger (GDB, LLDB) and manually dump the decrypted memory to disk.
In the following article I will describe a simple method to inject code into executables on Mac OS X 10.8 using the DYLD_INSERT_LIBRARIES environment variable.