Control: 6.2.5 Ensure 'log_hostname' database flag for Cloud SQL PostgreSQL instance is set appropriately

Description

PostgreSQL logs only the IP address of the connecting hosts. The log_hostname flag controls the logging of hostnames in addition to the IP addresses logged. The performance hit is dependent on the configuration of the environment and the host name resolution setup. This parameter can only be set in the postgresql.conf file or on the server command line.

Logging hostnames allows for the association of hostname to IP address at the time of connection. This information can aid with incident response efforts particularly in an environment that utilized dynamic IP addresses. Logging hostnames may incur overhead on server performance as for each statement logged, DNS resolution will be required to convert IP address to hostname. Depending on the setup, this may be non-negligible. This recommendation is applicable to PostgreSQL database instances.

Remediation

From Console:

Go to the Cloud SQL Instances page in the Google Cloud Console by visiting https://console.cloud.google.com/sql/instances.
Select the PostgreSQL instance for which you want to enable the database flag.
Click Edit.
Scroll down to the Flags section.
To set a flag that has not been set on the instance before, click Add item, choose the flag log_hostname from the drop-down menu and the value to On.
Click Save to save your changes.
Confirm your changes under Flags on the Overview page.

From Command Line:

Configure the log_hostname database flag for every Cloud SQL PosgreSQL database instance using the below command.

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

Note: This command will overwrite all database flags previously set. To keep those and add new ones, include the values for all flags you want 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 ("=").

Usage

Run the control in your terminal:

powerpipe control run gcp_compliance.control.cis_v130_6_2_5

Snapshot and share results via Turbot Pipes:

powerpipe login
powerpipe control run gcp_compliance.control.cis_v130_6_2_5 --share

SQL

This control uses a named query:

select
  self_link resource,
  case
    when database_version not like 'POSTGRES%' then 'skip'
    when database_flags @> '[{"name":"log_hostname","value":"on"}]' then 'ok'
    else 'alarm'
  end as status,
  case
    when database_version not like 'POSTGRES%'
      then title || ' not a PostgreSQL database.'
    when database_flags is null or not (database_flags @> '[{"name":"log_hostname"}]')
      then title || ' ''log_hostname'' database flag not set.'
    when database_flags @> '[{"name":"log_hostname","value":"on"}]'
      then title || ' ''log_hostname'' database flag set to ''on''.'
    else title || ' ''log_hostname'' database flag set to ''off''.'
  end as reason
  
  , location as location, project as project
from
  gcp_sql_database_instance;