# Ensure that the Docker server certificate key file ownership is set to root:root

- Source: https://support.icompaas.com/support/solutions/articles/62000234342-ensure-that-the-docker-server-certificate-key-file-ownership-is-set-to-root-root
- Section: [Solutions](https://support.icompaas.com/support/solutions) › [CIS Docker Benchmark v1.7.0](https://support.icompaas.com/support/solutions/62000112687) › [CIS Docker Benchmark](https://support.icompaas.com/support/solutions/folders/62000169241)
- Last updated: 2026-05-29
- Publisher: iCompaas, Inc. (https://www.icompaas.com)

**Profile Applicability:**

-   **Level 1** 
    

**Description:**

The Docker server certificate key file, which is used for secure TLS communication between the Docker client and Docker daemon, should have its ownership set to root:root. This ensures that only authorized users (i.e., the root user) can modify or replace the certificate key file, protecting it from unauthorized access.

**Rationale:**

The Docker server certificate key file is crucial for secure communication. Unauthorized users with write access to the key file could potentially replace it with a compromised certificate, exposing the Docker daemon to security vulnerabilities. By ensuring the key file is owned by root:root, access is restricted to authorized administrators, minimizing the risk of compromise.

**Impact:**

**Pros:**

-   Secures the Docker server certificate key file by restricting access to root users only.
    
-   Ensures that the integrity of the certificate key is maintained, preventing unauthorized access or tampering.
    

**Cons:**

-   Requires periodic checks to ensure proper ownership is maintained, especially if the certificate is updated or replaced.
    

**Default Value:**

The default ownership for the Docker server certificate key file is typically root:root, but this can be modified during configuration or due to administrative errors.

**Pre-requisites:**

-   Administrative privileges on the Docker host system.
    
-   Access to the file system to inspect and modify ownership.
    

**Remediation:**

**Test Plan:**

**Using AWS Console:**

1.  Log in to the EC2 instance running Docker.
    
2.  Verify the ownership of the Docker server certificate key file (typically located in /etc/docker or /etc/docker/certs.d):  
    
    ls -l /etc/docker/certs.d/<registry>/server-key.pem
    

**Using AWS CLI:**

1.  Connect to the EC2 instance where Docker is running.
    
2.  Run the following command to check the ownership of the server certificate key file:  
    
    ls -l /etc/docker/certs.d/<registry>/server-key.pem
    

**Implementation Plan:**

**Using AWS Console:**

1.  Log in to the EC2 instance.
    
2.  Set the ownership of the Docker server certificate key file to root:root:  
    
    sudo chown root:root /etc/docker/certs.d/<registry>/server-key.pem
    
3.  Restart Docker to ensure the changes take effect:
    

**Using AWS CLI:**

1.  Use SSM to modify the ownership of the Docker server certificate key file and restart Docker:  
    
    aws ssm send-command --document-name "AWS-RunShellScript" --targets "Key=instanceIds,Values=instance\_id" --parameters 'commands=\["sudo chown root:root /etc/docker/certs.d/<registry>/server-key.pem && sudo systemctl restart docker"\]'
    

**Backout Plan:**

**Using AWS Console:**

1.  Log in to the EC2 instance.
    
2.  Revert the ownership of the Docker server certificate key file if necessary:  
    
    sudo chown <previous-owner>:<previous-group> /etc/docker/certs.d/<registry>/server-key.pem
    
3.  Restart Docker to apply the changes:
    

**Using AWS CLI:**

1.  Use SSM to revert the ownership and restart Docker:  
    
    aws ssm send-command --document-name "AWS-RunShellScript" --targets "Key=instanceIds,Values=instance\_id" --parameters 'commands=\["sudo chown <previous-owner>:<previous-group> /etc/docker/certs.d/<registry>/server-key.pem && sudo systemctl restart docker"\]'
    

**References:**

-   [Docker TLS Security](https://docs.docker.com/engine/security/https/)
    
-   [Docker Insecure Registry Reference  
      
      
    ](https://docs.docker.com/registry/insecure/)

## Related compliance guidance

- [SOC 2 compliance: a practical implementation guide for cloud-native SaaS teams](https://support.icompaas.com/compliance/soc-2-trust-services-criteria): Configuration checks like this one are the technical half of a SOC 2 / ISO 27001 programme — the guide shows where they fit, what else an auditor expects, and how to evidence them.
- [ISO/IEC 27001:2022 compliance: a practical implementation guide](https://support.icompaas.com/compliance/iso-27001-2022): ISO 27001 Annex A.8 (technological controls) is where cloud hardening evidence lands; the guide shows how to run the ISMS around it.