Cis Docker 4.7
DevOps & Securitycis-docker-4.7Cis Docker 4.7 is an Agent Skill for devops & security published in the CyberStrikeus/CyberStrike repository on GitHub: a SKILL.md instruction file an AI agent can load to do this task.
Ensure update instructions are not used alone in Dockerfiles
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4.7 Ensure update instructions are not used alone in Dockerfiles (Manual)
Profile Applicability
- Level 1 - Docker - Linux
Description
You should not use OS package manager update instructions such as apt-get update or yum update either alone or in a single line in any Dockerfiles used to generate images under review.
Rationale
Adding update instructions in a single line on the Dockerfile will cause the update layer to be cached. When you then build any image later using the same instruction, this will cause the previously cached update layer to be used, potentially preventing any fresh updates from being applied to later builds.
Impact
None
Audit Procedure
Step 1: Run the command below to get the list of images:
docker images
Step 2: Run the command below against each image in the list above, looking for any update instructions which are incorporated in a single line:
docker history <Image_ID>
Alternatively, if you have access to the Dockerfile for the image, you should verify that there are no update instructions configured as described above.
Remediation
You should use update instructions together with install instructions and version pinning for packages while installing them. This will prevent caching and force the extraction of the required versions.
Alternatively, you could use the --no-cache flag during the docker build process to avoid using cached layers.
Default Value
By default, Docker does not enforce any restrictions on using update instructions.
References
CIS Controls
v8
16.7 Use Standard Hardening Configuration Templates for Application Infrastructure
Use standard, industry-recommended hardening configuration templates for application infrastructure components. This includes underlying servers, databases, and web servers, and applies to cloud containers, Platform as a Service (PaaS) components, and SaaS components. Do not allow in-house developed software to weaken configuration hardening.
v7
5.2 Maintain Secure Images
Maintain secure images or templates for all systems in the enterprise based on the organization's approved configuration standards. Any new system deployment or existing system that becomes compromised should be imaged using one of those images or templates.