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Accepted
aroth
Asked: 2016-04-20 20:48:48 +0800 CST

Ansible 会阻止在 shell 脚本中执行“rm -rf /”吗

  • 772

这是基于这里的这个恶作剧问题。所描述的问题是有一个 bash 脚本，其中包含以下内容：

rm -rf {pattern1}/{pattern2}

rm -rf /...如果两种模式都包含一个或多个空元素，则假设原始命令已正确转录并且 OP 正在执行大括号扩展而不是参数扩展，则该模式将扩展为 的至少一个实例。

在 OP对骗局的解释中，他指出：

命令 [...] 是无害的，但似乎几乎没有人注意到。

Ansible 工具可以防止这些错误，[...] 但是 [...] 似乎没有人知道这一点，否则他们会知道我所描述的不可能发生。

rm -rf /因此，假设您有一个通过大括号扩展或参数扩展发出命令的 shell 脚本，使用Ansible是否会阻止该命令被执行，如果是，它是如何做到的？

rm -rf /只要您使用 Ansible 来执行，以 root 权限执行真的“无害”吗？

linux bash ansible rm

2 个回答

  1. Best Answer

    我有虚拟机，让我们炸毁一堆！为了科学。

    [root@diaf ~]# ansible --version
ansible 2.0.1.0
  config file = /etc/ansible/ansible.cfg
  configured module search path = Default w/o overrides

    第一次尝试：

    [root@diaf ~]# cat killme.yml 
---
- hosts: localhost
  gather_facts: False
  tasks:
    - name: Die in a fire
      command: "rm -rf {x}/{y}"
[root@diaf ~]# ansible-playbook -l localhost -vvv killme.yml
Using /etc/ansible/ansible.cfg as config file
1 plays in killme.yml

PLAY ***************************************************************************

TASK [Die in a fire] ***********************************************************
task path: /root/killme.yml:5
ESTABLISH LOCAL CONNECTION FOR USER: root
localhost EXEC /bin/sh -c '( umask 22 && mkdir -p "` echo $HOME/.ansible/tmp/ansible-tmp-1461128819.56-86533871334374 `" && echo "` echo $HOME/.ansible/tmp/ansible-tmp-1461128819.56-86533871334374 `" )'
localhost PUT /tmp/tmprogfhZ TO /root/.ansible/tmp/ansible-tmp-1461128819.56-86533871334374/command
localhost EXEC /bin/sh -c 'LANG=en_US.UTF-8 LC_ALL=en_US.UTF-8 LC_MESSAGES=en_US.UTF-8 /usr/bin/python /root/.ansible/tmp/ansible-tmp-1461128819.56-86533871334374/command; rm -rf "/root/.ansible/tmp/ansible-tmp-1461128819.56-86533871334374/" > /dev/null 2>&1'
changed: [localhost] => {"changed": true, "cmd": ["rm", "-rf", "{x}/{y}"], "delta": "0:00:00.001844", "end": "2016-04-20 05:06:59.601868", "invocation": {"module_args": {"_raw_params": "rm -rf {x}/{y}", "_uses_shell": false, "chdir": null, "creates": null, "executable": null, "removes": null, "warn": true}, "module_name": "command"}, "rc": 0, "start": "2016-04-20 05:06:59.600024", "stderr": "", "stdout": "", "stdout_lines": [], "warnings": ["Consider using file module with state=absent rather than running rm"]}
 [WARNING]: Consider using file module with state=absent rather than running rm


PLAY RECAP *********************************************************************
localhost                  : ok=1    changed=1    unreachable=0    failed=0

    好的，所以command只是传递文字，没有任何反应。

    我们最喜欢的安全旁路raw怎么样？

    [root@diaf ~]# cat killme.yml
---
- hosts: localhost
  gather_facts: False
  tasks:
    - name: Die in a fire
      raw: "rm -rf {x}/{y}"
[root@diaf ~]# ansible-playbook -l localhost -vvv killme.yml
Using /etc/ansible/ansible.cfg as config file
1 plays in killme.yml

PLAY ***************************************************************************

TASK [Die in a fire] ***********************************************************
task path: /root/killme.yml:5
ESTABLISH LOCAL CONNECTION FOR USER: root
localhost EXEC rm -rf {x}/{y}
ok: [localhost] => {"changed": false, "invocation": {"module_args": {"_raw_params": "rm -rf {x}/{y}"}, "module_name": "raw"}, "rc": 0, "stderr": "", "stdout": "", "stdout_lines": []}

PLAY RECAP *********************************************************************
localhost                  : ok=1    changed=0    unreachable=0    failed=0

    别再去了！删除所有文件有多难？

    哦，但是如果它们是未定义的变量或其他东西怎么办？

    [root@diaf ~]# cat killme.yml
---
- hosts: localhost
  gather_facts: False
  tasks:
    - name: Die in a fire
      command: "rm -rf {{x}}/{{y}}"
[root@diaf ~]# ansible-playbook -l localhost -vvv killme.yml
Using /etc/ansible/ansible.cfg as config file
1 plays in killme.yml

PLAY ***************************************************************************

TASK [Die in a fire] ***********************************************************
task path: /root/killme.yml:5
fatal: [localhost]: FAILED! => {"failed": true, "msg": "'x' is undefined"}

NO MORE HOSTS LEFT *************************************************************
        to retry, use: --limit @killme.retry

PLAY RECAP *********************************************************************
localhost                  : ok=0    changed=0    unreachable=0    failed=1

    好吧，那没有用。

    但是，如果变量已定义但为空怎么办？

    [root@diaf ~]# cat killme.yml 
---
- hosts: localhost
  gather_facts: False
  tasks:
    - name: Die in a fire
      command: "rm -rf {{x}}/{{y}}"
  vars:
    x: ""
    y: ""
[root@diaf ~]# ansible-playbook -l localhost -vvv killme.yml
Using /etc/ansible/ansible.cfg as config file
1 plays in killme.yml

PLAY ***************************************************************************

TASK [Die in a fire] ***********************************************************
task path: /root/killme.yml:5
ESTABLISH LOCAL CONNECTION FOR USER: root
localhost EXEC /bin/sh -c '( umask 22 && mkdir -p "` echo $HOME/.ansible/tmp/ansible-tmp-1461129132.63-211170666238105 `" && echo "` echo $HOME/.ansible/tmp/ansible-tmp-1461129132.63-211170666238105 `" )'
localhost PUT /tmp/tmp78m3WM TO /root/.ansible/tmp/ansible-tmp-1461129132.63-211170666238105/command
localhost EXEC /bin/sh -c 'LANG=en_US.UTF-8 LC_ALL=en_US.UTF-8 LC_MESSAGES=en_US.UTF-8 /usr/bin/python /root/.ansible/tmp/ansible-tmp-1461129132.63-211170666238105/command; rm -rf "/root/.ansible/tmp/ansible-tmp-1461129132.63-211170666238105/" > /dev/null 2>&1'
fatal: [localhost]: FAILED! => {"changed": true, "cmd": ["rm", "-rf", "/"], "delta": "0:00:00.001740", "end": "2016-04-20 05:12:12.668616", "failed": true, "invocation": {"module_args": {"_raw_params": "rm -rf /", "_uses_shell": false, "chdir": null, "creates": null, "executable": null, "removes": null, "warn": true}, "module_name": "command"}, "rc": 1, "start": "2016-04-20 05:12:12.666876", "stderr": "rm: it is dangerous to operate recursively on ‘/’\nrm: use --no-preserve-root to override this failsafe", "stdout": "", "stdout_lines": [], "warnings": ["Consider using file module with state=absent rather than running rm"]}

NO MORE HOSTS LEFT *************************************************************
        to retry, use: --limit @killme.retry

PLAY RECAP *********************************************************************
localhost                  : ok=0    changed=0    unreachable=0    failed=1

    终于有进步了！但它仍然抱怨我没有使用--no-preserve-root.

    当然，它也警告我应该尝试使用file模块和state=absent. 让我们看看这是否有效。

    [root@diaf ~]# cat killme.yml 
---
- hosts: localhost
  gather_facts: False
  tasks:
    - name: Die in a fire
      file: path="{{x}}/{{y}}" state=absent
  vars:
    x: ""
    y: ""
[root@diaf ~]# ansible-playbook -l localhost -vvv killme.yml    
Using /etc/ansible/ansible.cfg as config file
1 plays in killme.yml

PLAY ***************************************************************************

TASK [Die in a fire] ***********************************************************
task path: /root/killme.yml:5
ESTABLISH LOCAL CONNECTION FOR USER: root
localhost EXEC /bin/sh -c '( umask 22 && mkdir -p "` echo $HOME/.ansible/tmp/ansible-tmp-1461129394.62-191828952911388 `" && echo "` echo $HOME/.ansible/tmp/ansible-tmp-1461129394.62-191828952911388 `" )'
localhost PUT /tmp/tmpUqLzyd TO /root/.ansible/tmp/ansible-tmp-1461129394.62-191828952911388/file
localhost EXEC /bin/sh -c 'LANG=en_US.UTF-8 LC_ALL=en_US.UTF-8 LC_MESSAGES=en_US.UTF-8 /usr/bin/python /root/.ansible/tmp/ansible-tmp-1461129394.62-191828952911388/file; rm -rf "/root/.ansible/tmp/ansible-tmp-1461129394.62-191828952911388/" > /dev/null 2>&1'
fatal: [localhost]: FAILED! => {"changed": false, "failed": true, "invocation": {"module_args": {"backup": null, "content": null, "delimiter": null, "diff_peek": null, "directory_mode": null, "follow": false, "force": false, "group": null, "mode": null, "original_basename": null, "owner": null, "path": "/", "recurse": false, "regexp": null, "remote_src": null, "selevel": null, "serole": null, "setype": null, "seuser": null, "src": null, "state": "absent", "validate": null}, "module_name": "file"}, "msg": "rmtree failed: [Errno 16] Device or resource busy: '/boot'"}

NO MORE HOSTS LEFT *************************************************************
        to retry, use: --limit @killme.retry

PLAY RECAP *********************************************************************
localhost                  : ok=0    changed=0    unreachable=0    failed=1

    好消息，大家！它开始试图删除我所有的文件！但不幸的是，它遇到了错误。我将解决这个问题并让剧本使用file模块作为练习来破坏所有内容给读者。

    不要运行任何你看到的超出这一点的剧本！你马上就会明白为什么。

    最后，为了致命一击......

    [root@diaf ~]# cat killme.yml
---
- hosts: localhost
  gather_facts: False
  tasks:
    - name: Die in a fire
      raw: "rm -rf {{x}}/{{y}}"
  vars:
    x: ""
    y: "*"
[root@diaf ~]# ansible-playbook -l localhost -vvv killme.yml
Using /etc/ansible/ansible.cfg as config file
1 plays in killme.yml

PLAY ***************************************************************************

TASK [Die in a fire] ***********************************************************
task path: /root/killme.yml:5
ESTABLISH LOCAL CONNECTION FOR USER: root
localhost EXEC rm -rf /*
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/ansible/executor/process/result.py", line 102, in run
  File "/usr/lib/python2.7/site-packages/ansible/executor/process/result.py", line 76, in _read_worker_result
  File "/usr/lib64/python2.7/multiprocessing/queues.py", line 117, in get
ImportError: No module named task_result

    这个虚拟机是一只前鹦鹉！

    有趣的是，上面没有做任何事情，command而不是raw. file它只是打印了关于使用with的相同警告state=absent。

    我要说的是，如果你不使用它，似乎raw有一些保护可以防止rm失控。但是，您不应该依赖于此。我快速浏览了 Ansible 的代码，虽然我发现了警告，但我没有发现任何实际上会抑制运行该rm命令的内容。

    • 54

  2. Ansible 会阻止rm -rf /在 shell 脚本中执行吗？

    我确实检查了 coreutils rm source，它具有以下内容：

      if (x.recursive && preserve_root)
    {
      static struct dev_ino dev_ino_buf;
      x.root_dev_ino = get_root_dev_ino (&dev_ino_buf);
      if (x.root_dev_ino == NULL)
        error (EXIT_FAILURE, errno, _("failed to get attributes of %s"),
               quoteaf ("/"));
    }

    从根目录擦除的唯一方法是越过此代码块。从这个来源：

    struct dev_ino *
get_root_dev_ino (struct dev_ino *root_d_i)
{
  struct stat statbuf;
  if (lstat ("/", &statbuf))
    return NULL;
  root_d_i->st_ino = statbuf.st_ino;
  root_d_i->st_dev = statbuf.st_dev;
  return root_d_i;
}

    我将此解释为该函数get_root_dev_ino返回 null on /，因此 rm 失败。

    绕过第一个代码块（使用递归）的唯一方法是拥有--no-preserve-root并且它不使用环境变量来覆盖，因此它必须显式传递给 rm。

    我相信这证明除非 Ansible 明确传递--no-preserve-root给rm，否则它不会这样做。

    结论

    我不相信 Ansible 明确阻止rm -rf /，因为rm它本身阻止了它。

    • 3

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