SharePoint 2013 Insufficient SQL database permissions for user 'Name: NT AUTHORITY\IUSR SID -The EXECUTE permission was denied on the object

SharePoint 2013 -  Insufficient SQL database permissions for user 'Name: NT AUTHORITY\IUSR SID -The EXECUTE permission was denied on the object

This error basically deals with any SP database. There’s in sufficient access to the account.

“Insufficient SQL database permissions for user 'Name: NT AUTHORITY\IUSR SID: S-1-5-17 ImpersonationLevel: Impersonation' in database 'SharePoint_Admin_Content' on SQL Server instance 'Database Instance'.
Additional error information from SQL Server is included below.
The EXECUTE permission was denied on the object 'proc_SecAddAppPrincipal', database 'SharePoint_Admin_Content', schema 'dbo'.”

Cause:

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Actually “NT Authority\IUSR” refer to application pool identity of SharePoint web app. So whenever user clicks on app related links, it tries to access central admin db(stored procedure) by impersonating privileges using app pool ccount.

 

Solution:

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Check if 'WSS_Content_Application_Pools’ database role have “execute” permission and then grant access on SharePoint central Admin Content Database and specifically on stored procedure "proc_SecAddAppPrincipal", so that any authenticated user can access that object.