ptrace on iOS 8

Question

I'm trying to call a function on ptrace like thisptrace(PT_DENY_ATTACH, 0, 0, 0); But when I try to import it using #include <sys/ptrace.h>Xcode gives me an error 'sys/ptrace.h' file not found. Am I missing something, do I need to import a library or is this simply unavailable on iOS?

Answer 1

The problem here is that Xcode is prepending its SDK base path to all system header paths (e.g., /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS9.0.sdk/usr/include/). Unfortunately, ptrace.h is not there but is found in /usr/include/sys/. So, to solve this, you need to change your include statement to be:

#include </usr/include/sys/ptrace.h>

I have no idea why ptrace.h is not included in the SDK but the functionality you're looking for does work when it's running on the phone.

Update: While this does allow you to use the ptrace functionality, uploading to Apple will result in app rejection due to:

Non-public API usage:

The app references non-public symbols in <app name>: _ptrace

Answer 2

This seems to be working for me and will prevent attaching the debugger. I have not tested the #ifdef OPTIMIZE if it works in distribution, so let me know if you find any problems.

//#include <sys/ptrace.h>
#import <dlfcn.h>
#import <sys/types.h>

typedef int (*ptrace_ptr_t)(int _request, pid_t _pid, caddr_t _addr, int _data);
#if !defined(PT_DENY_ATTACH)
#define PT_DENY_ATTACH 31
#endif  // !defined(PT_DENY_ATTACH)

void disable_gdb() {
    void* handle = dlopen(0, RTLD_GLOBAL | RTLD_NOW);
    ptrace_ptr_t ptrace_ptr = dlsym(handle, "ptrace");
    ptrace_ptr(PT_DENY_ATTACH, 0, 0, 0);
    dlclose(handle);
}

int main(int argc, char *argv[]) {

//#ifndef DEBUG => use the following instead.
 #ifdef __OPTIMIZE__
    //ptrace(PT_DENY_ATTACH, 0, 0, 0);
    disable_gdb();
#endif