sys.fn_check_object_signatures (Transact-SQL)

Article
02/28/2023

Applies to: SQL Server Azure SQL Managed Instance Analytics Platform System (PDW)

Returns a list of all signable objects and indicates whether an object is signed by a specified certificate or asymmetric key. If the object is signed by the specified certificate or asymmetric key signed, it also returns whether the object's signature is valid.

Transact-SQL syntax conventions

Syntax

  
fn_ check_object_signatures (   
    { '@class' } , { @thumbprint }   
  )

Arguments

{ '@class' }
Identifies the type of thumbprint being provided:

'certificate'
'asymmetric key'

@class is sysname.

{ @thumbprint }
SHA-1 hash of the certificate with which the key is encrypted, or the GUID of the asymmetric key with which the key is encrypted. @thumbprint is varbinary(20).

Tables Returned

The following table lists the columns that fn_check_object_signatures returns.

Column	Type	Description
type	nvarchar(120)	Returns type description or assembly.
entity_id	int	Returns the object id of the object being evaluated.
is_signed	int	Returns 0 when the object is not signed by the provided thumbprint. Returns 1 when the object is signed by the provided thumbprint.
is_signature_valid	int	When the is_signed value is 1, returns 0 when the signature is not valid. Returns 1 when the signature is valid. When the is_signed value is 0, always returns 0.

Remarks

Use fn_check_object_signatures to confirm that malicious users have not tampered with objects.

Permissions

Requires VIEW DEFINITION on the certificate or asymmetric key.

Examples

The following example finds the schema signing certificate for the master database, and returns the is_signed value of 1 and the is_signature_valid value of 1 for those objects that are signed by the schema signing certificate and which have valid signatures.

USE master;  
-- Declare a variable to hold the thumbprint.  
DECLARE @thumbprint varbinary(20) ;  
-- Populate the thumbprint variable with the master database schema signing certificate.  
SELECT @thumbprint = thumbprint   
FROM sys.certificates   
WHERE name LIKE '%SchemaSigningCertificate%' ;  
-- Evaluates the objects signed by the schema signing certificate  
SELECT type, entity_id, OBJECT_NAME(entity_id) AS [object name], is_signed, is_signature_valid  
FROM sys.fn_check_object_signatures ('certificate', @thumbprint) ;  
GO

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