Symptoms

• The following error appears in the SQL Server log:

  Login failed for user 'confuser'. Reason: Login-based server access validation failed with an infrastructure error. Check for previous errors. [Client: 127.0.0.1]
  Error: 18456, Severity: 14, State: 12

• The following appears in the atlassian-confluence.log:
  

  2013-02-25 15:09:44,445 ERROR [http-8090-2] [atlassian.config.bootstrap.DefaultAtlassianBootstrapManager] getTestDatabaseConnection Could not successfully test your database: 
   -- referer: http://<confluence-url>/setup/setupstandarddb-start.action?database=mssql | url: /setup/setupstandarddb.action | userName: anonymous | action: setupstandarddb
  java.sql.SQLException: Login failed for user 'confuser'.

Cause

Error: 18456, Severity: 14, State: 12 means that the authentication is successful, but the server access fails due to permission.

Resolution

• Ensure that the SQL Server Authentication mode is enabled.

• Assuming that the SQL Server username is confuser, run the following SQL query in a master database, to give the permission to connect via TCP/IP

  GRANT CONNECT SQL TO "confuser"
  GRANT CONNECT ON ENDPOINT::"TSQL Default TCP" TO "confuser";