Docker Security.md

Docker Security

Docker security features:

1. Namespace isolation: Docker uses Linux namespaces to isolate containers from each other and the host system. Each container gets its own process, network, mount, user, and IPC namespaces.

2. Control groups (cgroups): Docker uses cgroups to limit and allocate resources, such as CPU, memory, and I/O, to containers. This helps prevent a single container from consuming too many resources and affecting other containers or the host system.

3. Capabilities: Docker drops many Linux capabilities by default, limiting the privileges of processes running inside containers. This reduces the potential impact of container breakout or exploitation.

4. Seccomp: Docker uses Seccomp (Secure Computing Mode) profiles to limit the system calls available to containers, reducing the attack surface.

5. AppArmor/SELinux: Docker supports AppArmor and SELinux, which are mandatory access control (MAC) systems that enforce security policies and limit the actions of processes running inside containers.

6. Docker Content Trust: Docker Content Trust provides a mechanism for signing and verifying images, ensuring that the images you use come from trusted sources and have not been tampered with.

Security best practices

1. Use minimal and trusted base images: Start with minimal base images, like Alpine Linux, and use images from trusted sources, such as official repositories or vendors.

2. Keep images up-to-date: Regularly update your images and their dependencies to address security vulnerabilities.

3. Limit container capabilities: Use the --cap-drop and --cap-add options to remove unnecessary capabilities and grant only the required ones to your containers.

   Example: docker run --cap-drop=all --cap-add=NET_BIND_SERVICE my-image

4. Use read-only file systems: Mount your container's file system as read-only, if possible, to prevent unauthorized modifications.

   Example: docker run --read-only my-image

5. Use user namespaces: Enable user namespace remapping to map the root user inside the container to a non-root user on the host system, reducing the risk of privilege escalation.

6. Limit resource usage: Use cgroups to limit the resources available to containers, preventing resource exhaustion attacks.

   Example: docker run --memory=256m --cpus=1 my-image

7. Secure container networks: Use network segmentation to isolate containers and restrict communication between them. Apply network policies and firewall rules to control traffic.

8. Enable Docker Content Trust: Enable Docker Content Trust to ensure the integrity and authenticity of images.

   Example: export DOCKER_CONTENT_TRUST=1

c. Scanning images for vulnerabilities:

1. Use Docker Scan: Docker Scan is a built-in vulnerability scanner for Docker images, powered by Snyk. It checks your images for known security vulnerabilities in the base image and its dependencies.

   Example: docker scan my-image

2. Use third-party scanners: You can also use third-party scanning tools, like Clair, Anchore Engine, or Aqua Security, to scan your images for vulnerabilities. These tools can provide additional features, like policy enforcement and continuous monitoring.