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代码注入是一种向目标进程插入独立运行代码并使之运行的技术，它一般调用CreateRemoteThread()API以远程线程形式运行插入的代码，所以也被称为线程注入。
和DLL注入相比代码注入占用内存少并难以查找痕迹。所以DLL注入技术主要用在代码量大且复杂的时候，而代码注入技术则适用于代码量小且简单的情况比如shellcode。下面我们先测试一下代码。
运行notepad.exe并查看PID。
在命令行窗口中输入命令与参数。
notepad.exe弹出一个消息框，如图所示。
我们来分析一下源代码，看看是怎么实现的。
首先看一下main函数。main函数用来调用InjectCode()函数，传入的函数参数为目标进程的PID。
int main(int argc, char *argv[])
{
DWORD dwPID = 0;
if( argc != 2 )
{
printf("\n USAGE : %s <pid>\n", argv[0]);
return 1;
}
// change privilege
if( !SetPrivilege(SE_DEBUG_NAME, TRUE) )
return 1;
// code injection
dwPID = (DWORD)atol(argv[1]);
InjectCode(dwPID);
return 0;
}
分析InjectCode()函数之前，先看一下要注入的目标进程的代码。函数中并未直接调用相关API，也未直接定义使用字符串，它们都通过THREAD_PARAM结构体以线程参数的形式传递调用。typedef struct _THREAD_PARAM
{
FARPROC pFunc[2]; // LoadLibraryA(), GetProcAddress()
char szBuf[4][128]; // "user32.dll", "MessageBoxA", "www.reversecore.com", "ReverseCore"
} THREAD_PARAM, *PTHREAD_PARAM;
typedef HMODULE (WINAPI *PFLOADLIBRARYA)
(
LPCSTR lpLibFileName
);
typedef FARPROC (WINAPI *PFGETPROCADDRESS)
(
HMODULE hModule,
LPCSTR lpProcName
);
typedef int (WINAPI *PFMESSAGEBOXA)
(
HWND hWnd,
LPCSTR lpText,
LPCSTR lpCaption,
UINT uType
);
DWORD WINAPI ThreadProc(LPVOID lParam)
{
PTHREAD_PARAM pParam = (PTHREAD_PARAM)lParam;
HMODULE hMod = NULL;
FARPROC pFunc = NULL;
// LoadLibrary()
hMod = ((PFLOADLIBRARYA)pParam->pFunc[0])(pParam->szBuf[0]); // "user32.dll"
if( !hMod )
return 1;
// GetProcAddress()
pFunc = (FARPROC)((PFGETPROCADDRESS)pParam->pFunc[1])(hMod, pParam->szBuf[1]); // "MessageBoxA"
if( !pFunc )
return 1;
// MessageBoxA()
((PFMESSAGEBOXA)pFunc)(NULL, pParam->szBuf[2], pParam->szBuf[3], MB_OK);
return 0;
}
InjectCode()是代码注入技术的核心部分。两次调用VirtualAllocEx和WriteProcessMemory，第一次调用分配内存空间并写入远程线程的数据，第二次调用分配内存空间并写入远程线程的代码。这是代码注入的一个非常重要的特征。
BOOL InjectCode(DWORD dwPID)
{
HMODULE hMod = NULL;
THREAD_PARAM param = {0,};
HANDLE hProcess = NULL;
HANDLE hThread = NULL;
LPVOID pRemoteBuf[2] = {0,};
DWORD dwSize = 0;
hMod = GetModuleHandleA("kernel32.dll");
// set THREAD_PARAM
param.pFunc[0] = GetProcAddress(hMod, "LoadLibraryA");
param.pFunc[1] = GetProcAddress(hMod, "GetProcAddress");
strcpy_s(param.szBuf[0], "user32.dll");
strcpy_s(param.szBuf[1], "MessageBoxA");
strcpy_s(param.szBuf[2], "www.reversecore.com");
strcpy_s(param.szBuf[3], "ReverseCore");
// Open Process
if ( !(hProcess = OpenProcess(PROCESS_ALL_ACCESS, // dwDesiredAccess
FALSE, // bInheritHandle
dwPID)) ) // dwProcessId
{
printf("OpenProcess() fail : err_code = %d\n", GetLastError());
return FALSE;
}
// Allocation for THREAD_PARAM
dwSize = sizeof(THREAD_PARAM);
if( !(pRemoteBuf[0] = VirtualAllocEx(hProcess, // hProcess
NULL, // lpAddress
dwSize, // dwSize
MEM_COMMIT, // flAllocationType
PAGE_READWRITE)) ) // flProtect
{
printf("VirtualAllocEx() fail : err_code = %d\n", GetLastError());
return FALSE;
}
if( !WriteProcessMemory(hProcess, // hProcess
pRemoteBuf[0], // lpBaseAddress
(LPVOID)m, // lpBuffer
dwSize, // nSize
NULL) ) // [out] lpNumberOfBytesWritten
{
printf("WriteProcessMemory() fail : err_code = %d\n", GetLastError());
return FALSE;
}
// Allocation for ThreadProc()
dwSize = (DWORD)InjectCode - (DWORD)ThreadProc;
if( !(pRemoteBuf[1] = VirtualAllocEx(hProcess, // hProcess
NULL, // lpAddress
dwSize, // dwSize
MEM_COMMIT, // flAllocationType
PAGE_EXECUTE_READWRITE)) ) // flProtect
{
printf("VirtualAllocEx() fail : err_code = %d\n", GetLastError());
return FALSE;
}
if( !WriteProcessMemory(hProcess, // hProcess
pRemoteBuf[1], // lpBaseAddress
(LPVOID)ThreadProc, // lpBuffer
dwSize, // nSize
NULL) ) // [out] lpNumberOfBytesWritten
{
printf("WriteProcessMemory() fail : err_code = %d\n", GetLastError());
return FALSE;
}
if( !(hThread = CreateRemoteThread(hProcess, // hProcess
NULL, // lpThreadAttributes
0, // dwStackSize
(LPTHREAD_START_ROUTINE)pRemoteBuf[1], // dwStackSize
pRemoteBuf[0], // lpParameter
0, // dwCreationFlags
NULL)) ) // lpThreadId
{
printf("CreateRemoteThread() fail : err_code = %d\n", GetLastError());
return FALSE;
}
WaitForSingleObject(hThread, INFINITE);
CloseHandle(hThread);
CloseHandle(hProcess);
return TRUE;
}
完整的代码如下。// CodeInjection.cpp
// reversecore@gmail.com
// http://www.reversecore.com
#include "windows.h"
#include "stdio.h"
typedef struct _THREAD_PARAM
{
FARPROC pFunc[2]; // LoadLibraryA(), GetProcAddress()
char szBuf[4][128]; // "user32.dll", "MessageBoxA", "www.reversecore.com", "ReverseCore"
} THREAD_PARAM, *PTHREAD_PARAM;
typedef HMODULE (WINAPI *PFLOADLIBRARYA)
(
LPCSTR lpLibFileName
);
typedef FARPROC (WINAPI *PFGETPROCADDRESS)
(
HMODULE hModule,
LPCSTR lpProcName
);
typedef int (WINAPI *PFMESSAGEBOXA)
(
HWND hWnd,
LPCSTR lpText,
LPCSTR lpCaption,
UINT uType
);
DWORD WINAPI ThreadProc(LPVOID lParam)
{
PTHREAD_PARAM pParam = (PTHREAD_PARAM)lParam;
HMODULE hMod = NULL;
FARPROC pFunc = NULL;
// LoadLibrary()
hMod = ((PFLOADLIBRARYA)pParam->pFunc[0])(pParam->szBuf[0]); // "user32.dll"
if( !hMod )
return 1;
// GetProcAddress()
pFunc = (FARPROC)((PFGETPROCADDRESS)pParam->pFunc[1])(hMod, pParam->szBuf[1]); // "MessageBoxA"
if( !pFunc )
return 1;
// MessageBoxA()
((PFMESSAGEBOXA)pFunc)(NULL, pParam->szBuf[2], pParam->szBuf[3], MB_OK);
return 0;
}
BOOL InjectCode(DWORD dwPID)
{
HMODULE hMod = NULL;
THREAD_PARAM param = {0,};
HANDLE hProcess = NULL;
HANDLE hThread = NULL;
LPVOID pRemoteBuf[2] = {0,};
DWORD dwSize = 0;
hMod = GetModuleHandleA("kernel32.dll");
// set THREAD_PARAM
param.pFunc[0] = GetProcAddress(hMod, "LoadLibraryA");
param.pFunc[1] = GetProcAddress(hMod, "GetProcAddress");
strcpy_s(param.szBuf[0], "user32.dll");
strcpy_s(param.szBuf[1], "MessageBoxA");
strcpy_s(param.szBuf[2], "www.reversecore.com");
strcpy_s(param.szBuf[3], "ReverseCore");
// Open Process
if ( !(hProcess = OpenProcess(PROCESS_ALL_ACCESS, // dwDesiredAccess
FALSE, // bInheritHandle
dwPID)) ) // dwProcessId
{
printf("OpenProcess() fail : err_code = %d\n", GetLastError());
return FALSE;
}
// Allocation for THREAD_PARAM
dwSize = sizeof(THREAD_PARAM);
if( !(pRemoteBuf[0] = VirtualAllocEx(hProcess, // hProcess
NULL, // lpAddress
dwSize, // dwSize
MEM_COMMIT, // flAllocationType
PAGE_READWRITE)) ) // flProtect
{
printf("VirtualAllocEx() fail : err_code = %d\n", GetLastError());
return FALSE;
}
if( !WriteProcessMemory(hProcess, // hProcess
pRemoteBuf[0], // lpBaseAddress
(LPVOID)m, // lpBuffer
dwSize, // nSize
NULL) ) // [out] lpNumberOfBytesWritten
{
printf("WriteProcessMemory() fail : err_code = %d\n", GetLastError());
return FALSE;
}
// Allocation for ThreadProc()
dwSize = (DWORD)InjectCode - (DWORD)ThreadProc;
if( !(pRemoteBuf[1] = VirtualAllocEx(hProcess, // hProcess
NULL, // lpAddress
dwSize, // dwSize
MEM_COMMIT, // flAllocationType
PAGE_EXECUTE_READWRITE)) ) // flProtect
{
printf("VirtualAllocEx() fail : err_code = %d\n", GetLastError());
return FALSE;
}
if( !WriteProcessMemory(hProcess, // hProcess
pRemoteBuf[1], // lpBaseAddress
(LPVOID)ThreadProc, // lpBuffer
dwSize, // nSize
NULL) ) // [out] lpNumberOfBytesWritten
{
printf("WriteProcessMemory() fail : err_code = %d\n", GetLastError());
return FALSE;
}
if( !(hThread = CreateRemoteThread(hProcess, // hProcess
NULL, // lpThreadAttributes
0, // dwStackSize
(LPTHREAD_START_ROUTINE)pRemoteBuf[1], // dwStackSize
pRemoteBuf[0], // lpParameter
0, // dwCreationFlags
NULL)) ) // lpThreadId
{
printf("CreateRemoteThread() fail : err_code = %d\n", GetLastError());
return FALSE;
}
WaitForSingleObject(hThread, INFINITE);
CloseHandle(hThread);
CloseHandle(hProcess);
return TRUE;
}
BOOL SetPrivilege(LPCTSTR lpszPrivilege, BOOL bEnablePrivilege)
{
TOKEN_PRIVILEGES tp;
HANDLE hToken;
LUID luid;
if( !OpenProcessToken(GetCurrentProcess(),
TOKEN_ADJUST_PRIVILEGES | TOKEN_QUERY,
&hToken) )
{
printf("OpenProcessToken error: %u\n", GetLastError());
return FALSE;
}
if( !LookupPrivilegeValue(NULL, // lookup privilege on local system
lpszPrivilege, // privilege to lookup
&luid) ) // receives LUID of privilege
{
printf("LookupPrivilegeValue error: %u\n", GetLastError() );
return FALSE;
}
tp.PrivilegeCount = 1;
tp.Privileges[0].Luid = luid;
if( bEnablePrivilege )
tp.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;
else
tp.Privileges[0].Attributes = 0;
// Enable the privilege or disable all privileges.
if( !AdjustTokenPrivileges(hToken,
FALSE,
&tp,
sizeof(TOKEN_PRIVILEGES),
(PTOKEN_PRIVILEGES) NULL,
(PDWORD) NULL) )
{
printf("AdjustTokenPrivileges error: %u\n", GetLastError() );
return FALSE;
}
if( GetLastError() == ERROR_NOT_ALL_ASSIGNED )
{
printf("The token does not have the specified privilege. \n");
return FALSE;
}
return TRUE;
}
int main(int argc, char *argv[])
{
DWORD dwPID = 0;
if( argc != 2 )
{
printf("\n USAGE : %s <pid>\n", argv[0]);
return 1;
}
// change privilege
if( !SetPrivilege(SE_DEBUG_NAME, TRUE) )
return 1;
// code injection
dwPID = (DWORD)atol(argv[1]);
InjectCode(dwPID);
return 0;
}
说到shellcode，我们还可以把ThreadProc()的代码写成汇编的形式，效果是一样的。
// CodeInjection2.cpp
// reversecore@gmail.com
// http://www.reversecore.com
#include "windows.h"
#include "stdio.h"
typedef struct _THREAD_PARAM
{
FARPROC pFunc[2]; // LoadLibraryA(), GetProcAddress()
} THREAD_PARAM, *PTHREAD_PARAM;
BYTE g_InjectionCode[] =
{
0x55, 0x8B, 0xEC, 0x8B, 0x75, 0x08, 0x68, 0x6C, 0x6C, 0x00,
0x00, 0x68, 0x33, 0x32, 0x2E, 0x64, 0x68, 0x75, 0x73, 0x65,
0x72, 0x54, 0xFF, 0x16, 0x68, 0x6F, 0x78, 0x41, 0x00, 0x68,
0x61, 0x67, 0x65, 0x42, 0x68, 0x4D, 0x65, 0x73, 0x73, 0x54,
0x50, 0xFF, 0x56, 0x04, 0x6A, 0x00, 0xE8, 0x0C, 0x00, 0x00,
0x00, 0x52, 0x65, 0x76, 0x65, 0x72, 0x73, 0x65, 0x43, 0x6F,
0x72, 0x65, 0x00, 0xE8, 0x14, 0x00, 0x00, 0x00, 0x77, 0x77,
0x77, 0x2E, 0x72, 0x65, 0x76, 0x65, 0x72, 0x73, 0x65, 0x63,
0x6F, 0x72, 0x65, 0x2E, 0x63, 0x6F, 0x6D, 0x00, 0x6A, 0x00,
0xFF, 0xD0, 0x33, 0xC0, 0x8B, 0xE5, 0x5D, 0xC3
};
/*
004010ED 55 PUSH EBP
004010EE 8BEC MOV EBP,ESP
004010F0 8B75 08 MOV ESI,DWORD PTR SS:[EBP+8] ; ESI = pParam
004010F3 68 6C6C0000 PUSH 6C6C
004010F8 68 33322E64 PUSH 642E3233
004010FD 68 75736572 PUSH 72657375
00401102 54 PUSH ESP ; - "user32.dll"
00401103 FF16 CALL DWORD PTR DS:[ESI] ; LoadLibraryA("user32.dll")
00401105 68 6F784100 PUSH 41786F
0040110A 68 61676542 PUSH 42656761
0040110F 68 4D657373 PUSH 7373654D
00401114 54 PUSH ESP ; - "MessageBoxA"
00401115 50 PUSH EAX ; - hMod
00401116 FF56 04 CALL DWORD PTR DS:[ESI+4] ; GetProcAddress(hMod, "MessageBoxA")
00401119 6A 00 PUSH 0 ; - MB_OK (0)
0040111B E8 0C000000 CALL 0040112C
00401120 <ASCII> ; - "ReverseCore", 0
0040112C E8 14000000 CALL 00401145
00401131 <ASCII> ; - "www.reversecore.com", 0
00401145 6A 00 PUSH 0 ; - hWnd (0)
00401147 FFD0 CALL EAX ; MessageBoxA(0, "www.reversecore.com", "ReverseCore", 0)
00401149 33C0 XOR EAX,EAX
0040114B 8BE5 MOV ESP,EBP
0040114D 5D POP EBP
0040114E C3 RETN
*/
BOOL SetPrivilege(LPCTSTR lpszPrivilege, BOOL bEnablePrivilege)
{
TOKEN_PRIVILEGES tp;
HANDLE hToken;
LUID luid;
if( !OpenProcessToken(GetCurrentProcess(),
TOKEN_ADJUST_PRIVILEGES | TOKEN_QUERY,
&hToken) )
{
printf("OpenProcessToken error: %u\n", GetLastError());
return FALSE;
}
if( !LookupPrivilegeValue(NULL, // lookup privilege on local system
lpszPrivilege, // privilege to lookup
&luid) ) // receives LUID of privilege
{
printf("LookupPrivilegeValue error: %u\n", GetLastError() );
return FALSE;
}
tp.PrivilegeCount = 1;
tp.Privileges[0].Luid = luid;
if( bEnablePrivilege )
tp.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;
else
tp.Privileges[0].Attributes = 0;
// Enable the privilege or disable all privileges.
if( !AdjustTokenPrivileges(hToken,
FALSE,
&tp,
sizeof(TOKEN_PRIVILEGES),
(PTOKEN_PRIVILEGES) NULL,
(PDWORD) NULL) )
{
printf("AdjustTokenPrivileges error: %u\n", GetLastError() );
return FALSE;
}
if( GetLastError() == ERROR_NOT_ALL_ASSIGNED )
{
printf("The token does not have the specified privilege. \n");
return FALSE;
}
return TRUE;
}
BOOL InjectCode(DWORD dwPID)
{
HMODULE hMod = NULL;
THREAD_PARAM param = {0,};
HANDLE hProcess = NULL;
HANDLE hThread = NULL;
LPVOID pRemoteBuf[2] = {0,};
hMod = GetModuleHandleA("kernel32.dll");
// set THREAD_PARAM
param.pFunc[0] = GetProcAddress(hMod, "LoadLibraryA");
param.pFunc[1] = GetProcAddress(hMod, "GetProcAddress");
// Open Process
if ( !(hProcess = OpenProcess(PROCESS_ALL_ACCESS, // dwDesiredAccess
FALSE, // bInheritHandle
dwPID)) ) // dwProcessId
{
printf("OpenProcess() fail : err_code = %d\n", GetLastError());
return FALSE;
}
// Allocation for THREAD_PARAM
if( !(pRemoteBuf[0] = VirtualAllocEx(hProcess, // hProcess
NULL, // lpAddress
sizeof(THREAD_PARAM), // dwSize
MEM_COMMIT, // flAllocationType
PAGE_READWRITE)) ) // flProtect
{
printf("VirtualAllocEx() fail : err_code = %d\n", GetLastError());
return FALSE;
}
if( !WriteProcessMemory(hProcess, // hProcess
pRemoteBuf[0], // lpBaseAddress
(LPVOID)m, // lpBuffer
sizeof(THREAD_PARAM), // nSize
NULL) ) // [out] lpNumberOfBytesWritten
{
printf("WriteProcessMemory() fail : err_code = %d\n", GetLastError());
return FALSE;
}
// Allocation for ThreadProc()
if( !(pRemoteBuf[1] = VirtualAllocEx(hProcess, // hProcess
NULL, // lpAddress
sizeof(g_InjectionCode), // dwSize
MEM_COMMIT, // flAllocationType
PAGE_EXECUTE_READWRITE)) ) // flProtect
{
printf("VirtualAllocEx() fail : err_code = %d\n", GetLastError());
return FALSE;
}
if( !WriteProcessMemory(hProcess, // hProcess
pRemoteBuf[1], // lpBaseAddress
(LPVOID)&g_InjectionCode, // lpBuffer
sizeof(g_InjectionCode), // nSize
NULL) ) // [out] lpNumberOfBytesWritten
{
printf("WriteProcessMemory() fail : err_code = %d\n", GetLastError());
return FALSE;
}
if( !(hThread = CreateRemoteThread(hProcess, // hProcess
NULL, // lpThreadAttributes
0, // dwStackSize
(LPTHREAD_START_ROUTINE)pRemoteBuf[1],
pRemoteBuf[0], // lpParameter
0, // dwCreationFlags
NULL)) ) // lpThreadId
{
printf("CreateRemoteThread() fail : err_code = %d\n", GetLastError());
return FALSE;
}
WaitForSingleObject(hThread, INFINITE);
CloseHandle(hThread);
CloseHandle(hProcess);
return TRUE;
}
int main(int argc, char *argv[])
{
DWORD dwPID = 0;
if( argc != 2 )
{
printf("\n USAGE : %s <pid>\n", argv[0]);
return 1;
}
// change privilege
if( !SetPrivilege(SE_DEBUG_NAME, TRUE) )
return 1;
// code injection
dwPID = (DWORD)atol(argv[1]);
InjectCode(dwPID);
return 0;
}
可以看到，_THREAD_PARAM结构体中并不包含字符串成员，并且图中的指令字节数组(g_InjectionCode)替代了用C语言编写的ThreadProc()函数。
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