Description:

Service Account keys consist of a key ID (Private_key_Id) and Private key, which are used to sign programmatic requests users make to Google cloud services accessible to that particular service account. It is recommended that all Service Account keys are regularly rotated.

Rationale:

Rotating Service Account keys will reduce the window of opportunity for an access key that is associated with a compromised or terminated account to be used. Service Account keys should be rotated to ensure that data cannot be accessed with an old key that might have been lost, cracked, or stolen.

Each service account is associated with a key pair managed by Google Cloud Platform (GCP). It is used for service-to-service authentication within GCP. Google rotates the keys daily.

GCP provides the option to create one or more user-managed (also called external key pairs) key pairs for use from outside GCP (for example, for use with Application Default Credentials). When a new key pair is created, the user is required to download the private key (which is not retained by Google). With external keys, users are responsible for keeping the private key secure and other management operations such as key rotation. External keys can be managed by the IAM API, gcloud command-line tool, or the Service Accounts page in the Google Cloud Platform Console. GCP facilitates up to 10 external service account keys per service account to facilitate key rotation.

Rotating service account keys will break communication for dependent applications. Dependent applications need to be configured manually with the new key 'ID' displayed in the 'Service account keys' section and the 'private key' downloaded by the user.

ID	Name	CSP	Domain	Severity
AC_GCP_0004	Ensure That There Are Only GCP-Managed Service Account Keys for Each Service Account	GCP	Identity and Access Management	LOW
AC_GCP_0268	Ensure User-Managed/External Keys for Service Accounts Are Rotated Every 90 Days or Fewer	GCP	Identity and Access Management	LOW

Detections

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LOW