SQL Server 2008 R2 – How to Find Encrypted Columns Quickly

dmvencryptioninformation-schemasql serversql-server-2008-r2

Is there a quick way to find all columns in SQL Server 2008 R2 that are encrypted/have encrypted data?

I need to nullify the data in all encrypted columns in a development server (according to our business rules). I know most of the columns because we use them regularly, but I want to be thorough and also I want to be able to prove that I've found them all.

I've searched the web, looked in INFORMATION_SCHEMA and checked the DMVs I thought would be useful and also sys.columns and sys.objects — but so far no luck.

Best Answer

Assuming you are talking about data that is encrypted with SQL Server keys, there is way to find these columns.

The Key_name() Function will return the name of the key used for the encryption for that particular value and will return NULL if there isn't anything encrypted with a "known" key (3rd party, or simple not encrypted).

With that knowlegde we can test every column to see if it contains at least one row which has a varbinary value that returns a key name

functionality of key_name()

--create a test database
CREATE DATABASE [Test_ENCR]
GO

--change context
USE [Test_ENCR]
GO


--because it's possible to encrypt different rows with different keys I'll create 2 keys for this demo
-- Create a symmetric key
CREATE SYMMETRIC KEY symmetricKey1
   WITH ALGORITHM = AES_128
   ENCRYPTION BY PASSWORD = 'password01!';
GO

-- Create a second key
CREATE SYMMETRIC KEY symmetricKey2 
   WITH ALGORITHM = AES_128
   ENCRYPTION BY PASSWORD = 'password02!';
GO



--create a table that will have a column holding:
--1: encrypted row with key1
--2: encrypted row with key2
--3: a non encrypted just varbinary value

CREATE TABLE encryptedTable
(ID int IDENTITY PRIMARY KEY,
EncryptedCol varbinary(256) NOT NULL);
GO


-- open key1
OPEN SYMMETRIC KEY symmetricKey1 
    DECRYPTION BY PASSWORD = 'password01!';
GO

-- open key2
OPEN SYMMETRIC KEY symmetricKey2 
    DECRYPTION BY PASSWORD = 'password02!';
GO

--insert encrypted data with key1
INSERT INTO encryptedTable(encryptedCol)
VALUES ( ENCRYPTBYKEY (Key_GUID('symmetricKey1'), 'EncryptedText1'));
GO

--insert encrypted data with key2
INSERT INTO encryptedTable(encryptedCol)
VALUES ( ENCRYPTBYKEY (Key_GUID('symmetricKey2'), 'EncryptedText2'));
GO


--insert just varbinary data
INSERT INTO encryptedTable(encryptedCol)
VALUES (CONVERT(varbinary(256),'NotEncryptedTextJustVarBinary'))



--have a look, without the key, all varbinary for you.
SELECT * FROM encryptedTable
GO

results:

enter image description here 

--Return all key_names
SELECT DISTINCT     key_name(encryptedcol), 
                    EncryptedCol 
FROM encryptedTable;

results:

enter image description here

How to implement it to find encrypted columns

--How do we dynamically find all the columns that have at least one row with a encrypted value?

-- first we will find all tables and column with a varbinary datatype
-- then we will test all those columns with a simple select
-- If the key_name() function returns a value, the column and table name are stored together with the keyname

--create a table to hold all varbinary columns and tables
CREATE TABLE #TablesWithVarbinCols (    ID int IDENTITY,
                                TableName nvarchar(128),
                                ColumnName nvarchar(128)
                                );

--create a table to hold the end result
CREATE TABLE #TablesWithEncryption (
                                TableName nvarchar(128),
                                ColumnName nvarchar(128),
                                KeyName varchar(128)
                                );


--find and store all table and column names of user tables containing a varbinary column
INSERT INTO #TablesWithVarbinCols (TableName,ColumnName)
SELECT      o.[name] as TableName,
            c.[name] as ColumnName
FROM        sys.objects o
INNER JOIN  sys.columns c
ON          o.[object_id]=c.[object_id] 
INNER JOIN  sys.types t
ON          c.system_type_id=t.system_type_id
WHERE       o.[type]='U'
AND         t.name=N'varbinary'
AND         c.max_length > -1;


DECLARE @col nvarchar(256)
DECLARE @tab nvarchar(256)
DECLARE @c int = 1
DECLARE @MaxC int
DECLARE @SQL varchar(max)

SELECT @MaxC=MAX(ID)
FROM #TablesWithVarbinCols

--loop the previous result and create a simple select statement with a key_name() is not null where clause. 
--If you have a result, store the details
WHILE @c <= @MaxC
BEGIN
    SELECT  @Tab=TableName,
         @col=ColumnName
    FROM    #TablesWithVarbinCols
    WHERE   ID=@c

    SET @SQL='  INSERT INTO #TablesWithEncryption (TableName, ColumnName, KeyName)
                SELECT DISTINCT '''+@Tab +''',''' +@col +''', key_name('+@Col +') from '+ @tab +' 
                WHERE key_name('+@Col +') is not null;'
    exec (@SQL)

    DELETE
    FROM #TablesWithVarbinCols
    WHERE id=@c;
    SET @c=@c+1
END

--select the result
SELECT * FROM #TablesWithEncryption;

results:

enter image description here

--cleanup
DROP TABLE #TablesWithVarbinCols;
DROP TABLE #TablesWithEncryption;
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