ARM

Getting Shellcode from ARM Binaries

For x86 and x86_64 there are already commands for extracting shellcode and printing them nicely formatted. But when it comes to ARM none of them work would because of the way objdump would dump the opcodes. For example if this is my sample program:

.section .text

.global _start



_start:



    .code 32

    # Thumb-Mode on

    add     r6, pc, #1

    bx  r6



    .code   16

    # _write()

    mov     r2, #7

    mov r1, pc

    add r1, #12

    mov     r0, $0x1

    mov     r7, $0x4

    svc     0



    # _exit()

    sub r0, r0, r0

    mov     r7, $0x1

    svc 0



.ascii "Osanda\n"

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Running Shellcode in your Raspberry Pi

I was interested in learning ARM assembly language for developing small applications for microcontrollers. I wrote this small piece of shellcode which will write “127.0.0.1 google.lk” inside the /etc/hosts file in a Linux system. I used my Raspberry Pi model B+ for this 🙂
Image result for raspberry pi b+
We will be needing the following syscalls.

[code language=”c”]
#define __NR_exit (__NR_SYSCALL_BASE+ 1)
#define __NR_write (__NR_SYSCALL_BASE+ 4)
#define __NR_open (__NR_SYSCALL_BASE+ 5)
#define __NR_close (__NR_SYSCALL_BASE+ 6)
[/code]

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