Sunday , February 16 2025

PostgreSQL Role Authentication Methods

In today’s article, we will explain the PostgreSQL role authentication methods, including trust, md5, sha256, and ident on pg_hba.conf.

Authentication in PostgreSQL involves the use of both pg_hba.conf and postgresql.conf.

To connect a user to PostgreSQL, the system first checks the pg_hba.conf file. Based on the method defined there, authentication is performed. If authentication is successful, user-password verification follows, and the connection is established if the credentials are correct.

With pg_hba.conf, we can apply restrictions based on IP addresses, IP blocks, or specific users.

TRUST

This method is used for passwordless connections to PostgreSQL. Even if you assign a password to the user, they can still connect without a password as long as the pg_hba.conf file is configured to use the trust method.

If the user connects passwordlessly via pg_hba.conf but has access rights to only a single table within the database cluster, they will be limited to viewing just that table and nothing more.

MD5

MD5 is a cryptographic algorithm designed by MIT Professor Ronald Rivest. It was introduced as a replacement for MD4 after MD4 was proven to be insufficiently secure.

To use the MD5 algorithm in PostgreSQL, you can make the necessary changes in the pg_hba.conf file.

When the MD5 method is configured in pg_hba.conf, passwords are transmitted in encrypted form instead of plain text. This helps prevent password interception during network sniffing attacks.

In PostgreSQL, the pg_authid table stores user information, including MD5-hashed passwords. If the MD5 hash of a user password from pg_authid is compromised, the hash can be cracked, allowing unauthorized access to the system.

Today, MD5 is considered insecure, and SCRAM-SHA-256 is used as a stronger alternative.

SCRAM-SHA-256

SCRAM-SHA-256 is used because MD5 is now considered insecure, and this algorithm offers greater strength than MD5.

To enable SCRAM-SHA-256, you need to modify the password_encryption parameter in the postgresql.conf file.

After this change, you can update the pg_hba.conf file to include the SCRAM-SHA-256 parameter, enabling user passwords to be stored using the SCRAM-SHA-256 algorithm.

Ident

Ident authentication is used to connect PostgreSQL with operating system users.

The methods described above are the most commonly used authentication methods in PostgreSQL.

In addition to these, other methods like PAM Authentication, Certificate Authentication, RADIUS Authentication, and LDAP Authentication can also be used.

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