PostgreSQL Authentication

Extended authentication supports password authentication through PostgreSQL integration.

Table Structure and Query Statements

The PostgreSQL authenticator can support any table structure, including joint queries across multiple tables or queries from views. Users need to provide a query SQL template and ensure the query results include the following fields:

• password_hash: Required, the plaintext or hashed password field in the database.
• salt: Optional, considered as an empty salt (salt = "") if empty or non-existent.
• is_superuser: Optional. Indicates whether the current client is a superuser. The default is false. When set to true, clients using this username will not be subject to authorization constraints. It is not recommended to set a superuser.

Example table structure:

CREATE TABLE `mqtt_user` (
  `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `username` varchar(100) DEFAULT NULL,
  `password_hash` varchar(100) DEFAULT NULL,
  `salt` varchar(35) DEFAULT NULL,
  `created` datetime DEFAULT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `mqtt_username` (`username`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

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The example above creates an implicit UNIQUE index field (username) to aid in queries. When the system has a large number of users, ensure that the table used for queries is optimized and uses effective indexes to enhance data lookup speed during numerous connections and reduce EMQX load.

Use username as the lookup condition in this table. For example, to add a user with the username emqx_u, password public, salt slat_foo123, hashed with sha256, and superuser flag false:

mysql> INSERT INTO mqtt_user(username, password_hash, salt, is_superuser) VALUES ('emqx_u', SHA2(concat('public', 'slat_foo123'), 256), 'slat_foo123', 0);
Query OK, 1 row affected (0.01 sec)

The corresponding query statement and password hashing method configuration parameters are:

• Password encryption method: sha256
• Salt mode: suffix
• SQL:

SELECT password_hash, salt, is_superuser FROM mqtt_user WHERE username = ${username} LIMIT 1

Configure PostgreSQL Authentication

In the deployment, click Access Control -> Extended Authentication, select PostgreSQL Authentication, and click Configure.

You can complete the related configurations as follows:

• Server: Enter the PostgreSQL server address (host:port).

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  • If the current deployment is a Dedicated edition, create a VPC Peering Connection, and use the internal network address as the server address.
  • If the current deployment is a BYOC edition, create a VPC Peering Connection in your public cloud console. For details, refer to Create VPC Peering Connections. Use the internal network address as the server address.
  • If you see an "Init resource failure!" message, please check if the server address is correct and if the security group is open.

• Database: Enter the PostgreSQL database name.

• Username (Optional): Enter the username.

• Password (Optional): Enter the password.

• Enable TLS: Configure whether to enable TLS.

• Connection Pool Size (Optional): Enter an integer to specify the concurrent connection count from EMQX nodes to the PostgreSQL database; default value: 8.

• Query Timeout: Enter the connection timeout duration; units available: hours, minutes, seconds, milliseconds.

• Password Hash: Select the hashing algorithm used to store the password, such as plain, md5, sha, bcrypt, pbkdf2, etc.

  • For algorithms plain, md5, sha, sha256, or sha512, you also need to configure:
    • Salt Position: Specifies how the salt is combined with the password. This option generally does not need to be changed unless credentials are being migrated from external storage to the EMQX built-in database; options: suffix (add salt at the end of the password), prefix (add salt at the beginning of the password), disable (do not use salt). Note: If choosing plain, the salt mode should be set to disable.
  • For the pbkdf2 algorithm, you also need to configure:
    • Pseudorandom function: Specifies the hashing function used to generate the key, such as sha256.
    • Iteration Count: Specifies the number of hashes, default value: 4096.
    • Derived key length (Optional): Specifies the desired length of the key. If not specified, the key length will be determined by the pseudorandom function.

• SQL: Fill in the query SQL according to the table structure, specific requirements can be found in SQL Table Structure and Query Statements.