作者:hitetoshi
前几天和朋友交流技术,提到手工打造微型PE文件,他说现在网上流传的大部分版本在XP SP3下都不能运行,于是心血来潮,拍着胸脯说:“你放心,忙完了帮你做一个。” 后来花了半天时间,终于打造出一个XP下可运行的微型PE,弹出一个对话框,292字节,当然这离极限也许还差得远,不过自己做了一次,还是有些心得,贴出来和大家分享一下。本文介绍的这个MiniPE可以在 下载 : http://download.csdn.net/source/774041
第一步 准备PE文件 先创建一个PE文件,为了尽可能地小,我们用汇编语言来编写。代码如下:
.386 .model flat,stdcall option casemap:none
.data byData db 90h
.code start:
end 代码什么也没做,运行就报错(因为PE文件的EntryPoint实际上指向了不存在的区域),代码我们到后面再来填充它,这个PE文件只包含一个数据节。在Windows XP下,PE文件必须包含至少一个节,否则无法运行,这正是我们为什么要定义byData这个数据的原因。 为了让生成出的PE文件尽可能小,在链接的时候,我们使用/align:4这个选项,指定文件和节为4字节对齐(高版本的Microsoft增量链接器可能不支持4字节对齐,比如我测试的8.0版本,要求至少16字节对齐。所以使用这个选项,应该用低版本的链接器,我用的是MASM32V9自带的链接器,版本是5.12。) 这样生成出来的PE文件只有460字节,这是一个很好的开始,因为大部分极其简单的汇 编程 序生成出来都会在1.5K左右,如果是高级语言编写的,将会更高。文件的内容如下: 00000000h: 4D 5A 90 00 03 00 00 00 04 00 00 00 FF FF 00 00 ; MZ?........ .. 00000010h: B8 00 00 00 00 00 00 00 40 00 00 00 00 00 00 00 ; ?......@....... 00000020h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................ 00000030h: 00 00 00 00 00 00 00 00 00 00 00 00 A8 00 00 00 ; ............?.. 00000040h: 0E 1F BA 0E 00 B4 09 CD 21 B8 01 4C CD 21 54 68 ; ..?.???L?Th 00000050h: 69 73 20 70 72 6F 67 72 61 6D 20 63 61 6E 6E 6F ; is program canno 00000060h: 74 20 62 65 20 72 75 6E 20 69 6E 20 44 4F 53 20 ; t be run in DOS 00000070h: 6D 6F 64 65 2E 0D 0D 0A 24 00 00 00 00 00 00 00 ; mode....$....... 00000080h: 5D 17 1D DB 19 76 73 88 19 76 73 88 19 76 73 88 ; ]..?vs?vs?vs? 00000090h: E5 56 61 88 18 76 73 88 52 69 63 68 19 76 73 88 ; 錠a?vs圧ich.vs? 000000a0h: 00 00 00 00 00 00 00 00 50 45 00 00 4C 01 01 00 ; ........PE..L... 000000b0h: 77 B8 1A 49 00 00 00 00 00 00 00 00 E0 00 0F 01 ; w?I........?.. 000000c0h: 0B 01 05 0C 00 00 00 00 04 00 00 00 00 00 00 00 ; ................ 000000d0h: C8 01 00 00 C8 01 00 00 C8 01 00 00 00 00 40 00 ; ?..?..?....@. 000000e0h: 04 00 00 00 04 00 00 00 04 00 00 00 00 00 00 00 ; ................ 000000f0h: 04 00 00 00 00 00 00 00 CC 01 00 00 C8 01 00 00 ; ........?..?.. 00000100h: 00 00 00 00 02 00 00 00 00 00 10 00 00 10 00 00 ; ................ 00000110h: 00 00 10 00 00 10 00 00 00 00 00 00 10 00 00 00 ; ................ 00000120h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................ 00000130h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................ 00000140h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................ 00000150h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................ 00000160h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................ 00000170h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................ 00000180h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................ 00000190h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................ 000001a0h: 2E 64 61 74 61 00 00 00 01 00 00 00 C8 01 00 00 ; .data.......?.. 000001b0h: 04 00 00 00 C8 01 00 00 00 00 00 00 00 00 00 00 ; ....?.......... 000001c0h: 00 00 00 00 40 00 00 C0 90 00 00 00 ; ....@..缾...
第二步 去掉数据节内容 看到文件的最后4字节,90 00 00 00,这正是我们定义的byData(链接器使用4字节对起,后面3字节填0),这当然不是我们需要的东西,我们定义byData,只是为了让链接器生成PE文件时能至少有一个节。所以我们先把它拿掉,在UltraEdit中直接删除最后4个字节,把000001a8处Section的Virtual Size改为0,这样,文件又少了4个字节。
第三步 去掉DOS Stub 我们的目标是在Windows XP下运行,DOS Stub自然是多余的,可是链接器并没有选项来去掉DOS Stub,只好手工来做这个工作,文件偏移0x3C处(IMAGE_DOS_HEADER的e_lfanew)指定了PE文件头位置,这里是0x000000A8,直接将文件偏移0x3C到0xA8间的数据删除,把后面的数据往前移,再将一些数据适当修正,比如e_lfanew修正为0x40。这里DOS Stub的大小为0xA8-0x40=0x68,拿掉它,我们的文件又小了104字节,内容如下: 00000000h: 4D 5A 90 00 03 00 00 00 04 00 00 00 FF FF 00 00 ; MZ?........ .. 00000010h: B8 00 00 00 00 00 00 00 40 00 00 00 00 00 00 00 ; ?......@....... 00000020h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................ 00000030h: 00 00 00 00 00 00 00 00 00 00 00 00 40 00 00 00 ; ............@... 00000040h: 50 45 00 00 4C 01 01 00 77 B8 1A 49 00 00 00 00 ; PE..L...w?I.... 00000050h: 00 00 00 00 E0 00 0F 01 0B 01 05 0C 00 00 00 00 ; ....?.......... 00000060h: 09 00 00 00 00 00 00 00 60 01 00 00 60 01 00 00 ; ........`...`... 00000070h: 60 01 00 00 00 00 40 00 04 00 00 00 04 00 00 00 ; `.....@......... 00000080h: 04 00 00 00 00 00 00 00 04 00 00 00 00 00 00 00 ; ................ 00000090h: 64 01 00 00 60 01 00 00 00 00 00 00 02 00 00 00 ; d...`........... 000000a0h: 00 00 10 00 00 10 00 00 00 00 10 00 00 10 00 00 ; ................ 000000b0h: 00 00 00 00 10 00 00 00 00 00 00 00 00 00 00 00 ; ................ 000000c0h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................ 000000d0h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................ 000000e0h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................ 000000f0h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................ 00000100h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................ 00000110h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................ 00000120h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................ 00000130h: 00 00 00 00 00 00 00 00 2E 64 61 74 61 00 00 00 ; .........data... 00000140h: 00 00 00 00 60 01 00 00 00 00 00 00 60 01 00 00 ; ....`.......`... 00000150h: 00 00 00 00 00 00 00 00 00 00 00 00 40 00 00 C0 ; ............@..
第四步 重叠DOS文件头和PE文件头 在Windows下,PE装载器只关心DOS文件头的e_magic和e_lfanew,有这么多无用的项目,何不把PE文件头往前挪挪,大家挤一挤,再誊点空间出来。当然,PE文件头的长度超过了DOS文件头,往前移动,肯定是会覆盖到e_lfanew的。e_lfanew是不能随便乱填的,怎么办?我们把PE文件头移动到文件偏移0x04的位置,再把e_lfanew修改为0x04,现在PE装载器可以正确从e_lfanew找到PE文件头的位置了,我们在来看看PE文件头,在PE文件头偏移0x3C-0x4=0x38的位置,刚好是IMAGE_OPETION_HEADER的SectionAlignment――节对齐值,刚刚好,我们的节对齐也是4,讲到这里,如果你链接PE文件时,用的对齐值不是4那么就得修改为4咯。 这一步也很简单,直接把刚才文件偏移0x40的数据拷贝到0x04处,这时候,我们的PE文件总大小为292字节:sizeof(IMAGE_NT_HEADERS)+sizeof(IMAGE_SECTION_HEADER)+4。文件内容如下: 00000000h: 4D 5A 90 00 50 45 00 00 4C 01 01 00 77 B8 1A 49 ; MZ?PE..L...w?I 00000010h: 00 00 00 00 00 00 00 00 E0 00 0F 01 0B 01 05 0C ; ........?...... 00000020h: 00 00 00 00 09 00 00 00 00 00 00 00 60 01 00 00 ; ............`... 00000030h: 60 01 00 00 60 01 00 00 00 00 40 00 04 00 00 00 ; `...`.....@..... 00000040h: 04 00 00 00 04 00 00 00 00 00 00 00 04 00 00 00 ; ................ 00000050h: 00 00 00 00 64 01 00 00 60 01 00 00 00 00 00 00 ; ....d...`....... 00000060h: 02 00 00 00 00 00 10 00 00 10 00 00 00 00 10 00 ; ................ 00000070h: 00 10 00 00 00 00 00 00 10 00 00 00 00 00 00 00 ; ................ 00000080h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................ 00000090h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................ 000000a0h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................ 000000b0h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ................ 000000c0h: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ; ..............
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