Cis GCP Foundations 6.2.3

6.2.3 Ensure That the 'Log_disconnections' Database Flag for Cloud SQL PostgreSQL Instance Is Set to 'On' (Automated)

Profile Applicability

• Level 1

Description

Enabling the log_disconnections setting logs the end of each session, including the session duration.

Rationale

PostgreSQL does not log session details such as duration and session end by default. Enabling the log_disconnections setting will create log entries at the end of each session which can be useful in troubleshooting issues and determine any unusual activity across a time period. The log_disconnections and log_connections work hand in hand and generally, the pair would be enabled/disabled together. This recommendation is applicable to PostgreSQL database instances.

Impact

Turning on logging will increase the required storage over time. Mismanaged logs may cause your storage costs to increase. Setting custom flags via command line on certain instances will cause all omitted flags to be reset to defaults. This may cause you to lose custom flags and could result in unforeseen complications or instance restarts. Because of this, it is recommended you apply these flags changes during a period of low usage.

Audit

From Google Cloud Console

1. Go to the Cloud SQL Instances page in the Google Cloud Console by visiting https://console.cloud.google.com/sql/instances.
2. Select the instance to open its Instance Overview page
3. Go to the Configuration card.
4. Under Database flags, check the value of log_disconnections flag is configured as expected.

From Google Cloud CLI

1. Ensure the below command returns on for every Cloud SQL PostgreSQL database instance:

gcloud sql instances list --format=json | jq '.[].settings.databaseFlags[] | select(.name=="log_disconnections")|.value'

Remediation

From Google Cloud Console

1. Go to the Cloud SQL Instances page in the Google Cloud Console by visiting https://console.cloud.google.com/sql/instances.
2. Select the PostgreSQL instance where the database flag needs to be enabled.
3. Click Edit.
4. Scroll down to the Flags section.
5. To set a flag that has not been set on the instance before, click Add a Database Flag, choose the flag log_disconnections from the drop-down menu and set the value as on.
6. Click Save.
7. Confirm the changes under Flags on the Overview page.

From Google Cloud CLI

1. Configure the log_disconnections database flag for every Cloud SQL PosgreSQL database instance using the below command:

gcloud sql instances patch <INSTANCE_NAME> --database-flags log_disconnections=on

Note: This command will overwrite all previously set database flags. To keep those and add new ones, include the values for all flags to be set on the instance; any flag not specifically included is set to its default value. For flags that do not take a value, specify the flag name followed by an equals sign ("=").

Default Value

By default log_disconnections is off.

References

1. https://cloud.google.com/sql/docs/postgres/flags
2. https://www.postgresql.org/docs/current/runtime-config-logging.html#GUC-LOG-DISCONNECTIONS

Additional Information

WARNING: This patch modifies database flag values, which may require your instance to be restarted. Check the list of supported flags - https://cloud.google.com/sql/docs/postgres/flags - to see if your instance will be restarted when this patch is submitted.

Note: some database flag settings can affect instance availability or stability and remove the instance from the Cloud SQL SLA. For information about these flags, see Operational Guidelines.

Note: Configuring the above flag does not require restarting the Cloud SQL instance.

CIS Controls