PostgreSQL Hardening
Tested on: Ubuntu 24.04 LTS, PostgreSQL 16.x (apt package from pgdg repository). Commands assume the default data directory at /etc/postgresql/16/main/. Why this matters PostgreSQL ships with defaults that are reasonable for a development laptop and wrong for an internet-exposed server. Three settings in particular cause most real-world incidents: listen_addresses = 'localhost' is fine — until someone changes it to '*' for “convenience” and the database is suddenly reachable from anywhere the firewall lets through. pg_hba.conf defaults still allow trust and md5 in some packaging. trust is no authentication. md5 is no longer considered safe and should be replaced with scram-sha-256. TLS is off by default. Application traffic to the database — including passwords and query results — travels in cleartext on the loopback or on the LAN. This guide fixes those three problems and tightens a handful of related items. It does not cover row-level security, backup hardening, or replication — those get their own guides. ...