Abusing Docker Socket for Privilege Escalation

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There are some occasions were you just have access to the docker socket and you want to use it to escalate privileges. Some actions might be very suspicious and you may want to avoid them, so here you can find different flags that can be useful to escalate privileges:

Via mount

You can mount different parts of the filesystem in a container running as root and access them.
You could also abuse a mount to escalate privileges inside the container.

-v /:/host -> Mount the host filesystem in the container so you can read the host filesystem.
- If you want to feel like you are in the host but being on the container you could disable other defense mechanisms using flags like:
  - --privileged
  - --cap-add=ALL
  - --security-opt apparmor=unconfined
  - --security-opt seccomp=unconfined
  - -security-opt label:disable
  - --pid=host
  - --userns=host
  - --uts=host
  - --cgroupns=host
**--device=/dev/sda1 --cap-add=SYS_ADMIN --security-opt apparmor=unconfined ** -> This is similar to the previous method, but here we are mounting the device disk. Then, inside the container run mount /dev/sda1 /mnt and you can access the host filesystem in /mnt
- Run fdisk -l in the host to find the </dev/sda1> device to mount
-v /tmp:/host -> If for some reason you can just mount some directory from the host and you have access inside the host. Mount it and create a /bin/bash with suid in the mounted directory so you can execute it from the host and escalate to root.

{% hint style="info" %} Note that maybe you cannot mount the folder /tmp but you can mount a different writable folder. You can find writable directories using: find / -writable -type d 2>/dev/null

Note that not all the directories in a linux machine will support the suid bit! In order to check which directories support the suid bit run mount | grep -v "nosuid" For example usually /dev/shm , /run , /proc , /sys/fs/cgroup and /var/lib/lxcfs don't support the suid bit.

Note also that if you can mount /etc or any other folder containing configuration files, you may change them from the docker container as root in order to abuse them in the host and escalate privileges (maybe modifying /etc/shadow) {% endhint %}

Escaping from the container

--privileged -> With this flag you remove all the isolation from the container. Check techniques to escape from privileged containers as root.
--cap-add=<CAPABILITY/ALL> [--security-opt apparmor=unconfined] [--security-opt seccomp=unconfined] [-security-opt label:disable] -> To escalate abusing capabilities, grant that capability to the container and disable other protection methods that may prevent the exploit to work.

Curl

In this page we have discussed ways to escalate privileges using docker flags, you can find ways to abuse these methods using curl command in the page:

{% content-ref url="authz-and-authn-docker-access-authorization-plugin.md" %} authz-and-authn-docker-access-authorization-plugin.md {% endcontent-ref %}