This module can be used to obtain a list of all logins from a SQL Server with any login. Selecting all of the logins from the master..syslogins table is restricted to sysadmins. However, logins with the PUBLIC role (everyone) can quickly enumerate all SQL Server logins using the SUSER_SNAME function by fuzzing the principal_id parameter. This is pretty simple, because the principal IDs assigned to logins are incremental. Once logins have been enumerated they can be verified via sp_defaultdb error analysis. This is important, because not all of the principal IDs resolve to SQL logins (some resolve to roles instead). Once logins have been enumerated, they can be used in dictionary attacks.
To display the available options, load the module within the Metasploit console and run the commands 'show options' or 'show advanced':
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