Testing Docker Images Security All Day DevOps 2017

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jmortega.github.io about.me/jmortegac Software Engineer & Security Researcher

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Introduction to docker security Security best practices Tools for auditing docker images Three Takeaways

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● “Docker containers wrap up a piece of software in a complete filesystem that contains everything it needs to run: code,runtime, system tools, system libraries –anything you can install on a server. This guarantees that it will always run the same,regardless of the environment it is running in.”

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● Docker provides an additional layer of isolation, making your infrastructure safer by default. ● Makes the application lifecycle fast and easier, reducing risks in your applications

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● Docker uses several mechanisms for security: ○ Linux kernel namespaces ○ Linux Control Groups (cgroups) ○ The Docker daemon ○ Linux capabilities (libcap) ○ Linux security mechanisms like AppArmor or SELinux

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● Namespaces:provides an isolated view of the system where processes cannot see other processes in other containers ● Each container also gets its own network stack. ● A container doesn’t get privileged access to the sockets or interfaces of another container.

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● Cgroups: kernel feature that limits and isolates the resource usage(CPU,memory,network) of a collection of processes. ● Linux Capabilities: divides the privileges of root into distinct units and smaller groups of privileges.

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● The docker daemon (/usr/bin/docker) is responsible for managing the control groups, orchestrating the namespaces, and so on so that docker images can be run and secured. ● Because of the need to manage kernel functions, Docker runs with root privileges. ● Limit the users who have control of the Docker Daemon

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● Restrict access to the daemon only to the ones really needing it (users, processes) ● Don’t expose the daemon to the outside your network ● If you do so, make sure you have put this behind a secure proxy, like NGINX

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https://github.com/CenturyLinkLabs/dockerfile-from-image

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● Images are extracted in a chrooted sub process, being the first-step in a wider effort toward privilege separation. ● From Docker 1.10, all images are stored and accessed by the cryptographic checksums of their contents, limiting the possibility of an attacker causing a collision with an existing image Docker Content Trust.

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● Protects against untrusted images ● Can enable signing checks on every managed host ● Signature verification transparent to users ● Guarantee integrity of your images when pulled ● Provides trust from publisher to consumer ● export DOCKER_CONTENT_TRUST=1 ● ~/.docker/trust/trusted-certificates/

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● Do not write secrets(users and passwords). ● Remove unnecessary setuid, setgid permissions (Privilege escalation) ● Download packages securely using GPG and certificates ● Try to restrict an image or container to one service

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● To disable setuid rights, add the following to the Dockerfile of your image

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● Set a specific user. ● Don’t run your applications as root in containers.

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● Don’t run containers with --privileged flag ● The --privileged flag gives all capabilities to the container. ● docker run --privileged … ● docker run --cap-drop=ALL --cap-add= CAP_NET_ADMIN ...

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● Manual management within the container: docker run --cap-add ALL ● Restricted capabilities with root: docker run --cap-drop ALL --cap-add $CAP ● No capabilities: docker run --user

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● We can verify the integrity of the image ● Checksum validation when pulling image from docker hub ● Pulling by digest to enforce consistent

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● Pulling by Docker content trust ● $ export DOCKER_CONTENT_TRUST=1 $ docker pull debian:latest Pull (1 of 1): debian:latest@sha256:a25306f38…

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● Check packages installed in the container

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Docker security is about limiting and controlling the attack surface on the kernel.

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Run filesystems as read-only so that attackers can not overwrite data or save malicious scripts to the image.

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Auditing Docker Images

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● You can scan your images for known vulnerabilities ● There are tools for that, like Docker Security Scanning, Docker Bench Security and CoreOS Clair ● Find known vulnerable binaries

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● Checks based on best practices for hosts and containers ● Find Common Vulnerabilities and Exposures (CVEs) https://docs.docker.com/docker-cloud/builds/image-scan/

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● Checks against CVE database for image layers ● Binary scanning of all components in the image ● Performs binary scan to pick up on statically linked binaries ● Analyses libraries statically compiled in the image ● Generates a reports that shows if there are CVE in the libraries inside the image

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https://www.docker.com/docker-cve-database

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● Vulnerability Static Analysis for Containers ● https://github.com/coreos/clair

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● You've found an image by searching the internet and want to determine if it's safe enough for you to use in production. ● You're regularly deploying into a containerized production environment and want operations to alert or block deployments on insecure software.

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● Checks based on best practices for hosts and containers ● https://github.com/docker/docker-bench-security ● Open-source tool for running automated tests ● Inspired by the CIS Docker 1.11 benchmark ● Runs against containers currently running on same host ● Checks for AppArmor, read-only volumes, etc...

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● The host configuration ● The Docker daemon configuration ● The Docker daemon configuration files ● Container images and build files ● Container runtime ● Docker security operations

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● The Docker daemon configuration ● [WARN] 2.1- Restrict network traffic between containers ● [WARN] 4.1 - Create a user for the container ● [WARN] * Running as root: ● [WARN] 5.4 - Restrict Linux Kernel Capabilities within containers ● [WARN] * Capabilities added: CapAdd=[audit_control] ● [WARN] 5.13 - Mount container's root filesystem as readonly ● [WARN] * Container running with root FS mounted R/W:

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● Lynis ● Dagda ● Anchore

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● https://github.com/CISOfy/lynis-docker ● Lynis is a Linux, Mac and Unix security auditing and system hardening tool that includes a module to audit Dockerfiles. ● lynis audit dockerfile

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● https://github.com/eliasgranderubio/dagda ● Static analysis of known vulnerabilities on Docker containers ● Allows monitoring Docker containers for detecting anomalous activities

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Python 3 MongoDB PyMongo Requests Python-dateutil Joblib Docker-py Flask Flask-cors PyYAML

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● python3 dagda.py check --docker_image ● python3 dagda.py history --id

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Signing ● Secure & sign your source Dependences ● Pin & verify your dependencies Content Trust ● Sign your artifacts with Docker Content Trust Privileges ● Least Privilege configurations

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● https://docs.docker.com/engine/security ● http://www.oreilly.com/webops-perf/free/files/dock er-security.pdf ● http://container-solutions.com/content/uploads/201 5/06/15.06.15_DockerCheatSheet_A2.pdf ● https://www.openshift.com/promotions/docker-sec urity.html

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● Docker Content Trust https://docs.docker.com/engine/security/trust/cont ent_trust ● Docker Security Scanning https://docs.docker.com/docker-cloud/builds/image-scan https://blog.docker.com/2016/04/docker-security http://softwaretester.info/docker-audit