The next step in my playing with chroot escapes is crafting some shellcode. Recently my main dev machine is a MacBook running OS X, so it felt reasonable to fiddle with making system calls of that platform.
By the way, a system call is a function of the kernel invoked by a userspace program and it can be something like writing to a file descriptor, or even exiting. Usually, these are wrapped by C functions in the standard library.
First, users should look for the Boot Camp icon in the Windows tool bar. After finding the icon, double-click the icon to bring up the Boot Camp Control Panel. In the Boot Camp Control Panel, select the operating system you want to use by default. In the example below, we have selected Mac OS X as the default operating system. Pros and Cons of Mac Os. Following are some of the Pros (Advantages) and Cons (Disadvantages) of Mac OS. Mac OS has a built-in program called BootCamp. It allows you to install windows, Linux or any other operating system in addition to OS X. Setting up the boot camp in OS X is also very easy. And switching between them is. Recently my main dev machine is a MacBook running OS X, so it felt reasonable to fiddle with making system calls of that platform. By the way, a system call is a function of the kernel invoked by a userspace program and it can be something like writing to a file descriptor, or even exiting.
The system calls
First, we need to know what system call we want to make, and what arguments it pretends. Ordeals of december mac os.
Meteor madness (charliemort games) mac os. A full list is hosted by Apple here. The header also hints at the fact that they are inherited from BSD. Yeah, that makes sense.
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So, to write our proverbial Hello world we will pick the syscall 4
32-bit
Let's start easy. A cute 32-bit program, written in NASM assembler language. Compile with nasm or yasm, output format MachO, and link with ld.
32-bit
Let's start easy. A cute 32-bit program, written in NASM assembler language. Compile with nasm or yasm, output format MachO, and link with ld.
I'm on a Intel machine, so what we are looking for is the x86 syscall calling conventions for the OS X or BSD platform. They are pretty simple:
- arguments passed on the stack, pushed right-to-left
- stack 16-bytes aligned
- syscall number in the
eaxregister - call by interrupt
0x80
So what we have to do to print a 'Hello world' is:
- push the length of the string (
int) to the stack - push a pointer to the string to the stack
- push the stdout file descriptor (1) to the stack
- align the stack by moving the stack pointer 4 more bytes (16 - 4 * 3)
- set the
eaxregister to thewritesyscall number (4) - interrupt
0x80
64-bit
64-bit is a bit cleaner, but completely different: OS X (and GNU/Linux and everyone except Windows) on 64 architectures adopt the System V AMD64 ABI reference. Jump to section A.2.1 for the syscall calling convention.
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- arguments are passed on the registers
rdi,rsi,rdx,r10,r8andr9 - syscall number in the
raxregister - the call is done via the
syscallinstruction - what OS X contributes to the mix is that you have to add
0x20000000to the syscall number (still have to figure out why)
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So, here is the (IMHO) much more clean 64-bit 'Hello world'. Ah, if you want to do this at home and have it actually run, generate a macho64 object with a new version of NASM or with YASM, and link with ld as usual.
