21.2. Role Attributes
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## 21.2. Role Attributes #

A database role can have a number of attributes that define its privileges and interact with the client authentication system.

login privilege

  Only roles that have the `LOGIN` attribute can be used as the initial role name for a database connection. A role with the `LOGIN` attribute can be considered the same as a “database user”. To create a role with login privilege, use either:

      CREATE ROLE name LOGIN;
      CREATE USER name;

  (`CREATE USER` is equivalent to `CREATE ROLE` except that `CREATE USER` includes `LOGIN` by default, while `CREATE ROLE` does not.)

superuser status

  A database superuser bypasses all permission checks, except the right to log in. This is a dangerous privilege and should not be used carelessly; it is best to do most of your work as a role that is not a superuser. To create a new database superuser, use `CREATE ROLE `name` SUPERUSER`. You must do this as a role that is already a superuser.

database creation

  A role must be explicitly given permission to create databases (except for superusers, since those bypass all permission checks). To create such a role, use `CREATE ROLE `name` CREATEDB`.

role creation

  A role must be explicitly given permission to create more roles (except for superusers, since those bypass all permission checks). To create such a role, use `CREATE ROLE `name` CREATEROLE`. A role with `CREATEROLE` privilege can alter and drop roles which have been granted to the `CREATEROLE` user with the `ADMIN` option. Such a grant occurs automatically when a `CREATEROLE` user that is not a superuser creates a new role, so that by default, a `CREATEROLE` user can alter and drop the roles which they have created. Altering a role includes most changes that can be made using `ALTER ROLE`, including, for example, changing passwords. It also includes modifications to a role that can be made using the `COMMENT` and `SECURITY LABEL` commands.

  However, `CREATEROLE` does not convey the ability to create `SUPERUSER` roles, nor does it convey any power over `SUPERUSER` roles that already exist. Furthermore, `CREATEROLE` does not convey the power to create `REPLICATION` users, nor the ability to grant or revoke the `REPLICATION` privilege, nor the ability to modify the role properties of such users. However, it does allow `ALTER ROLE ... SET` and `ALTER ROLE ... RENAME` to be used on `REPLICATION` roles, as well as the use of `COMMENT ON ROLE`, `SECURITY LABEL ON ROLE`, and `DROP ROLE`. Finally, `CREATEROLE` does not confer the ability to grant or revoke the `BYPASSRLS` privilege.

initiating replication

  A role must explicitly be given permission to initiate streaming replication (except for superusers, since those bypass all permission checks). A role used for streaming replication must have `LOGIN` permission as well. To create such a role, use `CREATE ROLE `name` REPLICATION LOGIN`.

password

  A password is only significant if the client authentication method requires the user to supply a password when connecting to the database. The `password` and `md5` authentication methods make use of passwords. Database passwords are separate from operating system passwords. Specify a password upon role creation with `CREATE ROLE `name` PASSWORD '`string`'`.

inheritance of privileges

  A role inherits the privileges of roles it is a member of, by default. However, to create a role which does not inherit privileges by default, use `CREATE ROLE `name` NOINHERIT`. Alternatively, inheritance can be overridden for individual grants by using `WITH INHERIT TRUE` or `WITH INHERIT FALSE`.

bypassing row-level security

  A role must be explicitly given permission to bypass every row-level security (RLS) policy (except for superusers, since those bypass all permission checks). To create such a role, use `CREATE ROLE `name` BYPASSRLS` as a superuser.

connection limit

  Connection limit can specify how many concurrent connections a role can make. -1 (the default) means no limit. Specify connection limit upon role creation with `CREATE ROLE `name` CONNECTION LIMIT '`integer`'`.

A role's attributes can be modified after creation with `ALTER ROLE`. See the reference pages for the CREATE ROLE and ALTER ROLE commands for details.

A role can also have role-specific defaults for many of the run-time configuration settings described in Chapter 19. For example, if for some reason you want to disable index scans (hint: not a good idea) anytime you connect, you can use:

    ALTER ROLE myname SET enable_indexscan TO off;

This will save the setting (but not set it immediately). In subsequent connections by this role it will appear as though `SET enable_indexscan TO off` had been executed just before the session started. You can still alter this setting during the session; it will only be the default. To remove a role-specific default setting, use `ALTER ROLE `rolename` RESET `varname``. Note that role-specific defaults attached to roles without `LOGIN` privilege are fairly useless, since they will never be invoked.

When a non-superuser creates a role using the `CREATEROLE` privilege, the created role is automatically granted back to the creating user, just as if the bootstrap superuser had executed the command `GRANT created_user TO creating_user WITH ADMIN TRUE, SET FALSE, INHERIT FALSE`. Since a `CREATEROLE` user can only exercise special privileges with regard to an existing role if they have `ADMIN OPTION` on it, this grant is just sufficient to allow a `CREATEROLE` user to administer the roles they created. However, because it is created with `INHERIT FALSE, SET FALSE`, the `CREATEROLE` user doesn't inherit the privileges of the created role, nor can it access the privileges of that role using `SET ROLE`. However, since any user who has `ADMIN OPTION` on a role can grant membership in that role to any other user, the `CREATEROLE` user can gain access to the created role by simply granting that role back to themselves with the `INHERIT` and/or `SET` options. Thus, the fact that privileges are not inherited by default nor is `SET ROLE` granted by default is a safeguard against accidents, not a security feature. Also note that, because this automatic grant is granted by the bootstrap superuser, it cannot be removed or changed by the `CREATEROLE` user; however, any superuser could revoke it, modify it, and/or issue additional such grants to other `CREATEROLE` users. Whichever `CREATEROLE` users have `ADMIN OPTION` on a role at any given time can administer it.

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