The audit information produced by PostgreSQL must be protected from unauthorized modification.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-72847	PGS9-00-000400	SV-87499r2_rule		Medium

Description
If audit data were to become compromised, then competent forensic analysis and discovery of the true source of potentially malicious system activity is impossible to achieve. To ensure the veracity of audit data the information system and/or the application must protect audit information from unauthorized modification. This requirement can be achieved through multiple methods that will depend upon system architecture and design. Some commonly employed methods include ensuring log files enjoy the proper file system permissions and limiting log data locations. Applications providing a user interface to audit data will leverage user permissions and roles identifying the user accessing the data and the corresponding rights that the user enjoys in order to make access decisions regarding the modification of audit data. Audit information includes all information (e.g., audit records, audit settings, and audit reports) needed to successfully audit information system activity. Modification of database audit data could mask the theft of, or the unauthorized modification of, sensitive data stored in the database.

Description

If audit data were to become compromised, then competent forensic analysis and discovery of the true source of potentially malicious system activity is impossible to achieve. To ensure the veracity of audit data the information system and/or the application must protect audit information from unauthorized modification. This requirement can be achieved through multiple methods that will depend upon system architecture and design. Some commonly employed methods include ensuring log files enjoy the proper file system permissions and limiting log data locations. Applications providing a user interface to audit data will leverage user permissions and roles identifying the user accessing the data and the corresponding rights that the user enjoys in order to make access decisions regarding the modification of audit data. Audit information includes all information (e.g., audit records, audit settings, and audit reports) needed to successfully audit information system activity. Modification of database audit data could mask the theft of, or the unauthorized modification of, sensitive data stored in the database.

STIG	Date
PostgreSQL 9.x Security Technical Implementation Guide	2018-02-27

Details

Check Text ( C-72981r4_chk )
Review locations of audit logs, both internal to the database and database audit logs located at the operating system level. Verify there are appropriate controls and permissions to protect the audit information from unauthorized modification. Note: The following instructions use the PGDATA environment variable. See supplementary content APPENDIX-F for instructions on configuring PGDATA. #### stderr Logging If the PostgreSQL server is configured to use stderr for logging, the logs will be owned by the database owner (usually postgres user) with a default permissions level of 0600. The permissions can be configured in postgresql.conf. To check the permissions for log files in postgresql.conf, as the database owner (shown here as "postgres"), run the following command: $ sudo su - postgres $ grep "log_file_mode" ${PGDATA?}/postgresql.conf If the permissions are not 0600, this is a finding. Next, navigate to where the logs are stored. This can be found by running the following command against postgresql.conf as the database owner (shown here as "postgres"): $ sudo su - postgres $ grep "log_directory" ${PGDATA?}/postgresql.conf With the log directory identified, as the database owner (shown here as "postgres"), list the permissions of the logs: $ sudo su - postgres $ ls -la ${PGDATA?}/pg_log If logs are not owned by the database owner (shown here as "postgres") and are not the same permissions as configured in postgresql.conf, this is a finding. #### syslog Logging If the PostgreSQL server is configured to use syslog for logging, consult the organization syslog setting for permissions and ownership of logs.

Check Text ( C-72981r4_chk )

Review locations of audit logs, both internal to the database and database audit logs located at the operating system level.

Verify there are appropriate controls and permissions to protect the audit information from unauthorized modification.

Note: The following instructions use the PGDATA environment variable. See supplementary content APPENDIX-F for instructions on configuring PGDATA.

#### stderr Logging

If the PostgreSQL server is configured to use stderr for logging, the logs will be owned by the database owner (usually postgres user) with a default permissions level of 0600. The permissions can be configured in postgresql.conf.

To check the permissions for log files in postgresql.conf, as the database owner (shown here as "postgres"), run the following command:

$ sudo su - postgres
$ grep "log_file_mode" ${PGDATA?}/postgresql.conf

If the permissions are not 0600, this is a finding.

Next, navigate to where the logs are stored. This can be found by running the following command against postgresql.conf as the database owner (shown here as "postgres"):

$ sudo su - postgres
$ grep "log_directory" ${PGDATA?}/postgresql.conf

With the log directory identified, as the database owner (shown here as "postgres"), list the permissions of the logs:

$ sudo su - postgres
$ ls -la ${PGDATA?}/pg_log

If logs are not owned by the database owner (shown here as "postgres") and are not the same permissions as configured in postgresql.conf, this is a finding.

#### syslog Logging

If the PostgreSQL server is configured to use syslog for logging, consult the organization syslog setting for permissions and ownership of logs.

Fix Text (F-79289r1_fix)
To ensure that logging is enabled, review supplementary content APPENDIX-C for instructions on enabling logging. Note: The following instructions use the PGDATA environment variable. See supplementary content APPENDIX-F for instructions on configuring PGDATA. #### stderr Logging With stderr logging enabled, as the database owner (shown here as "postgres"), set the following parameter in postgresql.conf: $ vi ${PGDATA?}/postgresql.conf log_file_mode = 0600 To change the owner and permissions of the log files, run the following: $ chown postgres:postgres ${PGDATA?}/ $ chmod 0700 ${PGDATA?}/ $ chmod 600 ${PGDATA?}//.log #### syslog Logging If PostgreSQL is configured to use syslog for logging, the log files must be configured to be owned by root with 0600 permissions. $ chown root:root / $ chmod 0700 $ chmod 0600 /.log

Fix Text (F-79289r1_fix)

To ensure that logging is enabled, review supplementary content APPENDIX-C for instructions on enabling logging.

Note: The following instructions use the PGDATA environment variable. See supplementary content APPENDIX-F for instructions on configuring PGDATA.

#### stderr Logging

With stderr logging enabled, as the database owner (shown here as "postgres"), set the following parameter in postgresql.conf:

$ vi ${PGDATA?}/postgresql.conf
log_file_mode = 0600

To change the owner and permissions of the log files, run the following:

$ chown postgres:postgres ${PGDATA?}/
$ chmod 0700 ${PGDATA?}/
$ chmod 600 ${PGDATA?}//*.log

#### syslog Logging

If PostgreSQL is configured to use syslog for logging, the log files must be configured to be owned by root with 0600 permissions.

$ chown root:root /
$ chmod 0700
$ chmod 0600 /*.log