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 ; ..............