Container Security Checklist: From the image to the workload 18/01/2024, 08:38
Container Security Checklist: From the image to
the workload
Table Of Contents
Cloud Native challenges
Container Threat Model
Container Security Checklist
Supply Chain Security
Secure the Build
Secure Supply Chain
Hardening Code - Secure SDLC (Software Development Life Cycle)
Secure the Image - Hardening
Image Scanning
Image Signing
Secure the Container Registry
Registry Resources
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Container Security Checklist: From the image to the workload 18/01/2024, 08:38
Secure the Container Runtime
Why is important Runtime Security?
Constraints
Docker Security
Secure the Infrastructure
Secure the Data
Secrets Management Tools
Secure the Workloads... Running the containers
Common Containers Attacks
Container Security Guides
Further reading
Collaborate
Cloud Native challenges
Cloud Native Cloud Native
Legacy apps
apps Security
Shifting left with
frequent releases,
Discrete, infrequent releases automated
using CI/CD
testing
SCA - Software
Open source
Very little open source composition
everywhere
analysis
Proprietary code,
Open source, Software supply
Proprietary software
Third-party chain risk
software
Ephemeral
workloads.
Ensure that your Runtime controls
Persistent workloads containers are that follow the
stateless and workload
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Container Security Checklist: From the image to the workload 18/01/2024, 08:38
immutable
Enforce least
Shared kernel,
Hypervisor or hardware isolation privilege on each
obscured OS
workload
Orchestrated
containers.
Kubernetes
Identity-based
Permanent address creates DNS
segmentation
records for
services and
pods
Detecting cloud
services
Vertical control of the stack multi-cloud
misconfigurations
(CSPM)
Cloud native apps
Networking monitoring and threat detection Using eBPF
the traffic is
tools were based on auditd, syslog, dead-disk programs, you
encrypted.
forensics, and it used to get the full contents of collect the events
Packet captures
network packets to disk "packet captures". in real time
are too costly and
Capturing packets sotes every packet in a without
ineffective for
network to disk and runs custom pattern disruption to the
cloud native
matching on each packet to identify an attack. app.
environments.
Table by Aqua Cloud Native Security Platform, more details download here
Container Threat Model
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Container Security Checklist: From the image to the workload 18/01/2024, 08:38
Figure by Container Security by Liz Rice
Insecure Host
Misconfiguration container
Vulnerable application
Supply chain attacks
Expose secrets
Insecure networking
Integrity and confidentiality of OS images
Container escape vulnerabilities
Container Security Checklist
Checklist to build and secure the images across the following phases:
Secure the Build
Secure the Container Registry
Secure the Container Runtime
Secure the Infrastructure
Secure the Data
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Container Security Checklist: From the image to the workload 18/01/2024, 08:38
Secure the Workloads
Figure by cncf/tag-security
Supply Chain Security
Enforce image trust with Image signing: Container Signing, Verification and Storage in an
OCI registry.
Image Signing
Sign and verify images to mitigate a man in the middle (MITM) attack. Docker offers a Content
Trust mechanism that allows you to cryptographically sign images using a private key. This
guarantees the image, and its tags, have not been modified.
Notary. Implementation of TUF specification.
sigstore/Cosign
Sigstore: A Solution to Software Supply Chain Security
Zero-Trust supply chains with Sigstore and SPIFFE/SPIRE
Secure the Build
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Container Security Checklist: From the image to the workload 18/01/2024, 08:38
Hardening Code - Secure SDLC (Software Development Life Cycle)
[x] Do a static analysis of the code and libraries used by the code to surface any
vulnerabilities in the code and its dependencies.
Improve the security and quality of their code. OWASP Open Source Application
Security tools: SAST, IAST.
Secure the Image - Hardening
You can build the container images using Docker, Kaniko.
Reduce the attack surface
Package a single application per container. Small container images. Minimize the number of
layers.
Use the minimal OS image:
Alpine images
Scratch images
Distroless images
Use OS optimized for running containers:
Flatcar images
CodeOS by Fedora replaced the Project Atomic.
Bottlerocket by Aws
k3os by Rancher
Container-Optimized OS - COS by Google, based on Chromium-os used by Google
Do you use Alpine, distroless or vanilla images? ...
7 Google best practices for building containers
Multi-staged builds.
A well-designed multi-stage build contains only the minimal binary files and dependencies
required for the final image, with no build tools or intermediate files. Optimize cache.
[x] Use official base images.
Avoid unknown public images.
[x] Rootless. Run as a non-root user. Least privileged user
[x] Create a dedicated user and group on the image.
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Do not use a UID below 10,000. For best security, always run your processes as a UID
above 10,000. Remove setuid and setgid permissions from the images
[x] Avoid privileged containers, which lets a container run as root on the local machine.
[x] Use only the necessary Privileged Capabilities.
Drop kernel modules, system time, trace processes (CAP_SYS_MODULE,
CAP_SYS_TIME, CAP_SYS_PTRACE ).
[x] Enable the --read-only mode in docker, if it's possible.
[x] Don't leave sensitive information (secrets, tokens, keys, etc) in the image.
[x] Not mounting Host Path.
[x] Use Metadata Labels for Images, such as licensing information, sources, names of
authors, and relation of containers to projects or components.
[x] Used fixed image tag for inmutability.
Tagging using semantic versioning.
Not use mutable tags(latest,staging,etc). Use Inmutable tags(SHA-256, commit).
The challengue of uniquely identifying your images
Pulling images by digest
docker images --digests
docker pull alpine@sha256:b7233dafbed64e3738630b69382a8b231726aa1014ccaabc1947c5308a891
[x] Enabled Security profiles: SELinux, AppArmor, Seccomp.
[x] Static code analysis tool for Dockerfile like a linter. Detect misconfigurations
Hadolint
Packers (including encrypters), and downloaders are all able to evade static scanning
by, for example, encrypting binary code that is only executed in memory, making the
malware active only in runtime.
Trivy detect missconfigurations
Image Scanning
[x] Scan image for Common Vulnerabilities and Exposures (CVE)
[x] Check image for secrets
[x] Prevent attacks using the Supply Chain Attack
[x] Used dynamic analysis techniques for containers to prevent runtime bad behaviours.
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Container Security Checklist: From the image to the workload 18/01/2024, 08:38
Container Security Scanners
Trivy by AquaSecurity
Clair by Quay
Anchore
Dagda
GitGuardian Shield
Comparing the container scanners results:
Container Vulnerability Scanning Fun by Rory
Comparison – Anchore Engine vs Clair vs Trivy by Alfredo Pardo
More Material about build containers
Azure best practices for build containers
Docker best practices for build containers
Google best practices for build containers
Secure the Container Registry
Best configurations with ECR, ACR, Harbor, etc. Best practices.
[x] Lock down access to the image registry (who can push/pull) to restrict which users can
upload and download images from it. Uses Role Based Access Control (RBAC)
There is no guarantee that the image you are pulling from the registry is trusted. It may
unintentionally contain security vulnerabilities, or may have intentionally been replaced with
an image compromised by attackers.
[x] Use a private registry deployed behind firewall, to reduce the risk of tampering.
Registry Resources
Azure ACR
Azure best practices for Azure Container Registry
Amazon ECR
Google Artifact Registry
Harbor
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Container Security Checklist: From the image to the workload 18/01/2024, 08:38
Secure the Container Runtime
See the following container runtimes, there are three main types of container runtimes—low-
level runtimes, high-level runtimes, and virtualized runtimes or sandboxed.
1. Low-Level Container Runtimes:
runC
crun
containerd
2. High-Level Container Runtimes
Docker Engine
Podman
CRI-O - OCI-based implementation of Kubernetes Container Runtime Interface
Mirantes Container Runtime
3. Sandboxed and Virtualized Container Runtimes
gVisor
nabla-containers
kata-containers
Why is important Runtime Security?
Detection of IOC (Indicator Of Compromise)
Detect Zero Days attack
Compliance requirement
Recommended in highly dynamic environments
Constraints
Event context
Safety
Low overhead
Wide support of kernels
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Container Security Checklist: From the image to the workload 18/01/2024, 08:38
Enable detection of anomalous behaviour in applications.
[x] Applied the secure configurations in the container runtime. By default is insecure.
[x] Restrict access to container runtime daemon/APIs
[x] Use if it's possible in Rootless Mode.
Docker Security
[x] Avoid misconfigured exposed Docker API Ports, attackers used the misconfigured port
to deploy and run a malicious image that contained malware that was specifically designed
to evade static scanning.
[x] TLS encryption between the Docker client and daemon. Do not expose the Docker
engine using Unix socket or remotely using http.
Never make the daemon socket available for remote connections, unless you are using
Docker’s encrypted HTTPS socket, which supports authentication.
[x] Limit the usage of mount Docker socket in a container in an untrusted environment.
[x] Do not run Docker images with an option that exposes the socket in the container.
-v /var/run/docker.sock://var/run/docker.sock
The Docker daemon socket is a Unix network socket that facilitates communication with
the Docker API. By default, this socket is owned by the root user. If anyone else obtains
access to the socket, they will have permissions equivalent to root access to the host.
[x] Run Docker in Rootless Mode. docker context use rootless
[x] Enable the user namespaces.
[x] Enable Docker Content Trust. Docker. DOCKER_CONTENT_TRUST=1 . Docker Content Trust
implements The Update Framework (TUF) . Powered by Notary, an open-source TUF-client
and server that can operate over arbitrary trusted collections of data.
[x] Do not run Docker without the default seccomp profile: seccomp=unconfined
Seccomp enabled by default. See the Docker profile here
Hardening Docker and Kubernetes with seccomp
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Container Security Checklist: From the image to the workload 18/01/2024, 08:38
More Material about Docker Security
Docker Security Labs
CIS Docker Bench.
Content trust in Docker
Docker Security Playground - DSP - Network Security and Penetration Test techniques
Secure the Infrastructure
Risk:
If host is compromised, the container will be too.
Kernel exploits
Best practices:
[x] Keep the host kernel patched to prevent a range of known vulnerabilities, many of which
can result in container escape. Since the kernel is shared by the container and the host, the
kernel exploits when an attacker manages to run on a container can directly affect the host.
[x] Use CIS-Benchmark for the operating system.
[x] Use secure computing (seccomp) to restrict host system call (syscall) access from
containers.
[x] Use Security-Enhanced Linux (SELinux) to further isolate containers.
Secure the Data
[x] Don't leak sensitive info in the images, avoid using environment variables for your
sensitive information.
Secrets are Digital credentials:
passwords
API keys & Tokens
SSH keys
Private certificates for secure communication, transmitting and receiving data (TLS,
SSL, and so on)
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Container Security Checklist: From the image to the workload 18/01/2024, 08:38
Private encryption keys for systems like PGP
Database names or connection strings.
Sensitive configuration settings (email address, usernames, debug flags, etc.)
[x] Use a proper filesystem encryption technology for container storage
[x] Use volume mounts to pass secrets to a container at runtime
[x] Provide write/execute access only to the containers that need to modify the data in a
specific host filesystem path
[x] OPA to write controls like only allowing Read-only Root Filesystem access, listing allowed
host filesystem paths to mount, and listing allowed Flex volume drivers.
[x] Automatically scan container images for sensitive data such as credentials, tokens, SSH
keys, TLS certificates, database names or connection strings and so on, before pushing
them to a container registry (can be done locally and in CI).
[x] Limit storage related syscalls and capabilities to prevent runtime privilege escalation.
[x] Implement RBAC, or role-based access control. Every human or application only needs
the minimum secrets required to operate, nothing more. Principle of Least Privilege.
[x] Run audits regularly. Centralized audit trails are the key to knowing all the key security
events.
[x] Rotate secrets, a standard security practice.
[x] Automatically create and store secrets
Secrets Management Tools
Open source tools:
detect-secrets by Yelp: detecting and preventing secrets in code.
git-secrets by awslabs: Prevents you from committing secrets and credentials into git
repositories
Cloud Provider Key Management
AWS Secrets Manager
Azure Key Vault
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Container Security Checklist: From the image to the workload 18/01/2024, 08:38
Google Secret Manager
Enterprise secrets vault:
HashiCorp Vault
CyberArk Conjur
Secure the Workloads... Running the containers
[x] Avoid privileged containers
• Root access to all devices • Ability to tamper with Linux security modules like AppArmor
and SELinux • Ability to install a new instance of the Docker platform, using the host’s kernel
capabilities, and run Docker within Docker.
To check if the container is running in privileged mode docker inspect --format =’{{.
HostConfig.Privileged}}’[container_id]
[x] Limit container resources.
When a container is compromised, attackers may try to make use of the underlying host
resources to perform malicious activity. Set memory and CPU usage limits to minimize the
impact of breaches for resource-intensive containers.
docker run -d --name container-1 --cpuset-cpus 0 --cpu-shares 768 cpu-stress
[x] Preventing a fork bomb. docker run --rm -it --pids-limit 200 debian:jessie
[x] Segregate container networks.
The default bridge network exists on all Docker hosts—if you do not specify a different
network, new containers automatically connect to it.
Use custom bridge networks to control which containers can communicate between
them, and to enable automatic DNS resolution from container name to IP address.
Ensure that containers can connect to each other only if absolutely necessary, and
avoid connecting sensitive containers to public-facing networks.
Docker provides network drivers that let you create your own bridge network, overlay
network, or macvlan network. If you need more control, you can create a Docker
network plugin.
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Container Security Checklist: From the image to the workload 18/01/2024, 08:38
[x] Improve container isolation.
Protecting a container is exactly the same as protecting any process running on Linux.
Ideally, the operating system on a container host should protect the host kernel from
container escapes, and prevent mutual influence between containers.
[x] Set filesystem and volumes to Read only.
This can prevent malicious activity such as deploying malware on the container or
modifying configuration. docker run --read-only alpine
[x] Complete lifecycle management restrict system calls from Within Containers
[x] Monitor Container Activity. Analyze collected events to detect suspicious behaviourial
patterns.
[x] Create an incident response process to ensure rapid response in the case of an attack.
[x] Apply automated patching
[x] Confirms Inmutability. Implement drift prevention to ensure container inmutability.
[x] Ensure you have robust auditing and forensics for quick troubleshooting and compliance
reporting.
Common Containers Attacks
Unsecured Docker daemons
Cetus: Cryptojacking Worm Targeting Docker Daemons
Black-T: New Cryptojacking Variant from TeamTNT
Container Security Guides
SP 800-190 - Application Container Security Guide by NIST
Further reading:
Linux Capabilities: making them work, published in hernel.org 2008.
Using seccomp to limit the kernel attack surface
Docker Security Best Practices by Rani Osnat - AquaSecurity
Applying devsecops in a Golang app with trivy-github-actions by Daniel Pacak -
AquaSecurity
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Container Security Checklist: From the image to the workload 18/01/2024, 08:38
21 Docker Security Best Practices – Deamon, Image & Container by James Walker -
Spacelift
Collaborate
If you find any typos, errors, outdated resources; or if you have a different point of view. Please
open a pull request or contact me.
Pull requests and stars are always welcome
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