sys.fn_check_object_signatures (Transact-SQL)
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