External Secrets Operator (ESO) Threat Modeling using STRIDE

Spoofing

Threat-01-S - Spoofing of External Secrets Operator

A malicious actor might attempt to impersonate the External System Operator (ESO) to illicitly access confidential information stored in external systems.

  • Implementing mutual TLS (Transport Layer Security) ensures that both the ESO and the external secret management system authenticate each other.
  • Using robust authentication mechanisms, like using API tokens or OAuth, further secure the connection, preventing impersonation.
Threat-02-S - Spoofing of External Secrets

The risk of the External Secrets Operator (ESO) interacting with a fake external secret store represents a significant security threat. In such a scenario, an attacker could set up a counterfeit secret management service, mimicking legitimate services like AWS Secrets Manager or HashiCorp Vault. If ESO is deceived into connecting with this fraudulent service, it could lead to several security breaches, including the leakage of sensitive information, injection of false secrets, or disruption of secret synchronization processes.

  • Certificate Verification: Implement strict SSL/TLS certificate verification for all external secret stores. This ensures that ESO establishes connections only with authenticated and validated services.
  • Endpoint Validation: Configure ESO to connect only to known and verified endpoints of secret stores, possibly using allowlists for trusted URLs and IP addresses.
  • Regular Auditing: Periodically audit and verify the configurations and connections of ESO to external services to detect any anomalies or changes that could indicate a security breach.

Tampering

Threat-03-T - Supply Chain Attacks

An attack can infiltrate the ESO container through various attack vectors. The following are some potential entry points, although this is not an exhaustive list:

  • Source Threats: Unauthorized changes or inclusion of vulnerable code in ESO through code submissions.
  • Build Threats: Creation and distribution of malicious builds of ESO, such as in container registries, Artifact Hub, or Operator Hub.
  • Dependency Threats: Introduction of vulnerable code into ESO dependencies.
  • Deployment and Runtime Threats: Injection of malicious code through compromised deployment processes.
  • CI/CD Security: Secure the Continuous Integration and Continuous Deployment (CI/CD) pipeline with tools that scan for vulnerabilities and unauthorized changes.
  • Dependency Management: Regularly scan and update dependencies to prevent vulnerabilities and use trusted sources for dependencies.
  • Container Image Security: Utilize signed and verified container images, and scan these images for vulnerabilities.
Threat-04-T - Tampering with ESO configuration files

The threat of tampering with External Secrets Operator (ESO) configuration files involves unauthorized modifications to the ESO’s settings, which can lead to security breaches or malfunctioning of the system.

  • File Integrity Monitoring: Implement a system that continuously monitors the ESO configuration files for unauthorized changes. This tool alerts administrators whenever a file is altered, enabling quick detection and response to tampering.
  • Access Controls: Restrict access to ESO configuration files using robust access control mechanisms. Ensure that only authorized personnel have the necessary permissions to modify these files, and enforce multi-factor authentication for added security.

Repudiation

Threat-05-R - Unauthorized Modification Denial

An unauthorized user might modify a secret and subsequently deny their involvement.

  • Implement a robust logging system that captures every interaction with the secrets, including access and modifications. The logs should record user identities, timestamps, and specific changes made to the secrets.
  • Use digital signatures or similar mechanisms to ensure the integrity and non-repudiation of the log entries.
  • Regular audits of these logs can help in quickly identifying and addressing unauthorized changes, thus holding users accountable for their actions.
Threat-06-R - Disputing Synchronization

There could be discrepancies or disputes regarding when a secret was synchronized from the external store to Kubernetes.

  • Maintaining detailed logs with precise timestamps for each synchronization event helps resolve these disputes. These logs should capture when the ESO checks for updates in external secret stores, when it retrieves updates, and when it synchronizes them to Kubernetes Secrets.
  • Timestamps in these logs provide clear and indisputable evidence of the timing of each synchronization, aiding in resolving any disputes or confusion over the timing of updates.

Information Disclosure

Threat-07-I - Unauthorized access to cluster secrets

An attacker can gain unauthorized access to secrets by utilizing the service account token of the ESO core controller Pod or exploiting software vulnerabilities. This unauthorized access allows the attacker to read secrets within the cluster, potentially leading to a cluster takeover.

  • Service Account Security: Secure the service account associated with the ESO core controller Pod. Implement minimal permissions (principle of least privilege) and regularly audit these permissions.
  • Vulnerability Management: Regularly update and patch ESO to address known vulnerabilities. Use vulnerability scanning tools to proactively identify and mitigate potential weaknesses.
  • Network Policies and Pod Security: Implement stringent network policies and pod security measures to restrict and control the communication to and from the ESO core controller Pod.

Denial of Service (DoS)

Threat-08-D - Webhook DOS

Currently, ESO generates an X.509 certificate for webhook registration without authenticating the kube-apiserver. Consequently, if an attacker gains network access to the webhook Pod, they can overload the webhook server and initiate a DoS attack. As a result, modifications to ESO resources may fail, and the ESO core controller may be impacted due to the unavailability of the conversion webhook.

  • Authenticate the kube-apiserver: Ensure that the communication between ESO’s webhook and the kube-apiserver is authenticated, preventing unauthorized entities from interacting with the webhook.
  • Implement Rate Limiting: Introduce rate limiting on the webhook to prevent it from being overwhelmed by excessive requests.
  • Network Security: Strengthen network security policies to restrict access to the webhook Pod, ensuring that only authorized traffic can reach it.
Threat-09-D - Man-in-the-Middle (MITM) attack

An adversary could launch a Man-in-the-Middle (MITM) attack to hijack the webhook pod, enabling them to manipulate the data of the conversion webhook. This could involve injecting malicious resources or causing a Denial-of-Service (DoS) attack.

To mitigate this threat, a mutual authentication mechanism should be enforced for the connection between the Kubernetes API server and the webhook service to ensure that only authenticated endpoints can communicate.

Elevation of Privilege

Threat-10-E - Exploiting Vulnerabilities for Higher Privileges:

Attackers might identify and exploit existing vulnerabilities in the External Secrets Operator (ESO) or the Kubernetes environment. These vulnerabilities could range from software bugs to insecure configurations, allowing attackers to gain unauthorized access or control.

  • Perform regular updates and apply patches to both ESO and Kubernetes, addressing known security issues.
  • Continuously monitor for new vulnerabilities and apply security patches as soon as they are released.
Threat-11-E - Insufficiently Restricted User Roles

In this scenario, users or attackers exploit overly permissive or poorly configured RBAC (Role-Based Access Control) policies in Kubernetes. This can lead to unauthorized access elevation, potentially giving attackers control over sensitive operations or data.

  • Implement and enforce strict RBAC policies, ensuring each role is granted only the minimum necessary permissions.
  • Regularly review and audit RBAC configurations to detect and correct any excess permissions, ensuring they align with the principle of least privilege.
  • Document security best practices for administrators and users on the importance of secure role configuration and management.