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Example demonstrating use of Azure Key Vault provider with Always Encrypted enabled with secure enclaves

Applies to: SQL Server 2019 (15.x) and later versions on Windows Azure SQL Database

This example shows you how you can use the Azure Key Vault provider with Always Encrypted with secure enclaves. The script will create a column master key in the database based on the Azure Key Vault URL. Secondly, a column encryption key is created. Once the keys are created, a table with encrypted columns will be created, a few records will be inserted and read again from the table.

AzureKeyVaultProvider v2.0+

using System.Collections.Generic;
using System.Security.Cryptography;
using Azure.Identity;
using Microsoft.Data.SqlClient;
using Microsoft.Data.SqlClient.AlwaysEncrypted.AzureKeyVaultProvider;

namespace AKVEnclaveExample_2_0
{
    class Program
    {
        static readonly string s_algorithm = "RSA_OAEP";

        // ********* Provide details here ***********
        static readonly string s_akvUrl = "https://{KeyVaultName}.vault.azure.net/keys/{Key}/{KeyIdentifier}";
        static readonly string s_connectionString = "Server={Server}; Database={database}; Integrated Security=true; Column Encryption Setting=Enabled; Attestation Protocol=HGS; Enclave Attestation Url = {attestation_url_for_HGS};";
        // ******************************************

        static void Main(string[] args)
        {
            // Initialize Token Credential instance using InteractiveBrowserCredential. For other authentication options,
            // see classes derived from TokenCredential: https://docs.microsoft.com/dotnet/api/azure.core.tokencredential
            InteractiveBrowserCredential interactiveBrowserCredential = new InteractiveBrowserCredential();
            
            // Initialize AKV provider
            SqlColumnEncryptionAzureKeyVaultProvider akvProvider = new SqlColumnEncryptionAzureKeyVaultProvider(interactiveBrowserCredential);

            // Register AKV provider
            SqlConnection.RegisterColumnEncryptionKeyStoreProviders(customProviders: new Dictionary<string, SqlColumnEncryptionKeyStoreProvider>(capacity: 1, comparer: StringComparer.OrdinalIgnoreCase)
                {
                    { SqlColumnEncryptionAzureKeyVaultProvider.ProviderName, akvProvider}
                });
            Console.WriteLine("AKV provider Registered");

            // Create connection to database
            using (SqlConnection sqlConnection = new SqlConnection(s_connectionString))
            {
                string cmkName = "CMK_WITH_AKV";
                string cekName = "CEK_WITH_AKV";
                string tblName = "AKV_TEST_TABLE";

                CustomerRecord customer = new CustomerRecord(1, @"Microsoft", @"Corporation");

                try
                {
                    sqlConnection.Open();

                    // Drop Objects if exists
                    dropObjects(sqlConnection, cmkName, cekName, tblName);

                    // Create Column Master Key with AKV Url
                    createCMK(sqlConnection, cmkName, akvProvider);
                    Console.WriteLine("Column Master Key created.");

                    // Create Column Encryption Key
                    createCEK(sqlConnection, cmkName, cekName, akvProvider);
                    Console.WriteLine("Column Encryption Key created.");

                    // Create Table with Encrypted Columns
                    createTbl(sqlConnection, cekName, tblName);
                    Console.WriteLine("Table created with Encrypted columns.");

                    // Insert Customer Record in table
                    insertData(sqlConnection, tblName, customer);
                    Console.WriteLine("Encryted data inserted.");

                    // Read data from table
                    verifyData(sqlConnection, tblName, customer);
                    Console.WriteLine("Data validated successfully.");
                }
                finally
                {
                    // Drop table and keys
                    dropObjects(sqlConnection, cmkName, cekName, tblName);
                    Console.WriteLine("Dropped Table, CEK and CMK");
                }

                Console.WriteLine("Completed AKV provider Sample.");
            }
        }

        private static void createCMK(SqlConnection sqlConnection, string cmkName, SqlColumnEncryptionAzureKeyVaultProvider sqlColumnEncryptionAzureKeyVaultProvider)
        {
            string KeyStoreProviderName = SqlColumnEncryptionAzureKeyVaultProvider.ProviderName;

            byte[] cmkSign = sqlColumnEncryptionAzureKeyVaultProvider.SignColumnMasterKeyMetadata(s_akvUrl, true);
            string cmkSignStr = string.Concat("0x", BitConverter.ToString(cmkSign).Replace("-", string.Empty));

            string sql =
                $@"CREATE COLUMN MASTER KEY [{cmkName}]
                    WITH (
                        KEY_STORE_PROVIDER_NAME = N'{KeyStoreProviderName}',
                        KEY_PATH = N'{s_akvUrl}',
                        ENCLAVE_COMPUTATIONS (SIGNATURE = {cmkSignStr})
                    );";

            using (SqlCommand command = sqlConnection.CreateCommand())
            {
                command.CommandText = sql;
                command.ExecuteNonQuery();
            }
        }

        private static void createCEK(SqlConnection sqlConnection, string cmkName, string cekName, SqlColumnEncryptionAzureKeyVaultProvider sqlColumnEncryptionAzureKeyVaultProvider)
        {
            string sql =
                    $@"CREATE COLUMN ENCRYPTION KEY [{cekName}] 
                        WITH VALUES (
                            COLUMN_MASTER_KEY = [{cmkName}],
                            ALGORITHM = '{s_algorithm}', 
                            ENCRYPTED_VALUE = {GetEncryptedValue(sqlColumnEncryptionAzureKeyVaultProvider)}
                        )";

            using (SqlCommand command = sqlConnection.CreateCommand())
            {
                command.CommandText = sql;
                command.ExecuteNonQuery();
            }
        }

        private static string GetEncryptedValue(SqlColumnEncryptionAzureKeyVaultProvider sqlColumnEncryptionAzureKeyVaultProvider)
        {
            byte[] plainTextColumnEncryptionKey = new byte[32];
            RandomNumberGenerator rng = RandomNumberGenerator.Create();
            rng.GetBytes(plainTextColumnEncryptionKey);

            byte[] encryptedColumnEncryptionKey = sqlColumnEncryptionAzureKeyVaultProvider.EncryptColumnEncryptionKey(s_akvUrl, s_algorithm, plainTextColumnEncryptionKey);
            string EncryptedValue = string.Concat("0x", BitConverter.ToString(encryptedColumnEncryptionKey).Replace("-", string.Empty));
            return EncryptedValue;
        }

        private static void createTbl(SqlConnection sqlConnection, string cekName, string tblName)
        {
            string ColumnEncryptionAlgorithmName = @"AEAD_AES_256_CBC_HMAC_SHA_256";

            string sql =
                    $@"CREATE TABLE [dbo].[{tblName}]
                (
                    [CustomerId] [int] ENCRYPTED WITH (COLUMN_ENCRYPTION_KEY = [{cekName}], ENCRYPTION_TYPE = RANDOMIZED, ALGORITHM = '{ColumnEncryptionAlgorithmName}'),
                    [FirstName] [nvarchar](50) COLLATE Latin1_General_BIN2 ENCRYPTED WITH (COLUMN_ENCRYPTION_KEY = [{cekName}], ENCRYPTION_TYPE = RANDOMIZED, ALGORITHM = '{ColumnEncryptionAlgorithmName}'),
                    [LastName] [nvarchar](50) COLLATE Latin1_General_BIN2 ENCRYPTED WITH (COLUMN_ENCRYPTION_KEY = [{cekName}], ENCRYPTION_TYPE = RANDOMIZED, ALGORITHM = '{ColumnEncryptionAlgorithmName}')
                )";

            using (SqlCommand command = sqlConnection.CreateCommand())
            {
                command.CommandText = sql;
                command.ExecuteNonQuery();
            }
        }

        private static void insertData(SqlConnection sqlConnection, string tblName, CustomerRecord customer)
        {
            string insertSql = $"INSERT INTO [{tblName}] (CustomerId, FirstName, LastName) VALUES (@CustomerId, @FirstName, @LastName);";

            using (SqlTransaction sqlTransaction = sqlConnection.BeginTransaction())
            using (SqlCommand sqlCommand = new SqlCommand(insertSql,
            connection: sqlConnection, transaction: sqlTransaction,
            columnEncryptionSetting: SqlCommandColumnEncryptionSetting.Enabled))
            {
                sqlCommand.Parameters.AddWithValue(@"CustomerId", customer.Id);
                sqlCommand.Parameters.AddWithValue(@"FirstName", customer.FirstName);
                sqlCommand.Parameters.AddWithValue(@"LastName", customer.LastName);

                sqlCommand.ExecuteNonQuery();
                sqlTransaction.Commit();
            }
        }

        private static void verifyData(SqlConnection sqlConnection, string tblName, CustomerRecord customer)
        {
            // Test INPUT parameter on an encrypted parameter
            using (SqlCommand sqlCommand = new SqlCommand($"SELECT CustomerId, FirstName, LastName FROM [{tblName}] WHERE FirstName = @firstName", sqlConnection))
            {
                SqlParameter customerFirstParam = sqlCommand.Parameters.AddWithValue(@"firstName", @"Microsoft");
                customerFirstParam.Direction = System.Data.ParameterDirection.Input;
                customerFirstParam.ForceColumnEncryption = true;

                using (SqlDataReader sqlDataReader = sqlCommand.ExecuteReader())
                {
                    ValidateResultSet(sqlDataReader);
                }
            }
        }

        private static void ValidateResultSet(SqlDataReader sqlDataReader)
        {
            Console.WriteLine(" * Row available: " + sqlDataReader.HasRows);

            while (sqlDataReader.Read())
            {
                if (sqlDataReader.GetInt32(0) == 1)
                {
                    Console.WriteLine(" * Employee Id received as sent: " + sqlDataReader.GetInt32(0));
                }
                else
                {
                    Console.WriteLine("Employee Id didn't match");
                }

                if (sqlDataReader.GetString(1) == @"Microsoft")
                {
                    Console.WriteLine(" * Employee Firstname received as sent: " + sqlDataReader.GetString(1));
                }
                else
                {
                    Console.WriteLine("Employee FirstName didn't match.");
                }

                if (sqlDataReader.GetString(2) == @"Corporation")
                {
                    Console.WriteLine(" * Employee LastName received as sent: " + sqlDataReader.GetString(2));
                }
                else
                {
                    Console.WriteLine("Employee LastName didn't match.");
                }
            }
        }

        private static void dropObjects(SqlConnection sqlConnection, string cmkName, string cekName, string tblName)
        {
            using (SqlCommand cmd = sqlConnection.CreateCommand())
            {
                cmd.CommandText = $@"IF EXISTS (select * from sys.objects where name = '{tblName}') BEGIN DROP TABLE [{tblName}] END";
                cmd.ExecuteNonQuery();
                cmd.CommandText = $@"IF EXISTS (select * from sys.column_encryption_keys where name = '{cekName}') BEGIN DROP COLUMN ENCRYPTION KEY [{cekName}] END";
                cmd.ExecuteNonQuery();
                cmd.CommandText = $@"IF EXISTS (select * from sys.column_master_keys where name = '{cmkName}') BEGIN DROP COLUMN MASTER KEY [{cmkName}] END";
                cmd.ExecuteNonQuery();
            }
        }

        private class CustomerRecord
        {
            internal int Id { get; set; }
            internal string FirstName { get; set; }
            internal string LastName { get; set; }

            public CustomerRecord(int id, string fName, string lName)
            {
                Id = id;
                FirstName = fName;
                LastName = lName;
            }
        }
    }
}

AzureKeyVaultProvider v1.x

using System.Collections.Generic;
using System.Security.Cryptography;
using System.Threading.Tasks;
using Microsoft.Data.SqlClient;
using Microsoft.Data.SqlClient.AlwaysEncrypted.AzureKeyVaultProvider;
using Microsoft.IdentityModel.Clients.ActiveDirectory;

namespace AKVEnclaveExample
{
    class Program
    {
        static readonly string s_algorithm = "RSA_OAEP";

        // ********* Provide details here ***********
        static readonly string s_akvUrl = "https://{KeyVaultName}.vault.azure.net/keys/{Key}/{KeyIdentifier}";
        static readonly string s_clientId = "{Application_Client_ID}";
        static readonly string s_clientSecret = "{Application_Client_Secret}";
        static readonly string s_connectionString = "Server={Server}; Database={database}; Integrated Security=true; Column Encryption Setting=Enabled; Attestation Protocol=HGS; Enclave Attestation Url = {attestation_url_for_HGS};";
        // ******************************************

        static void Main(string[] args)
        {
            // Initialize AKV provider
            SqlColumnEncryptionAzureKeyVaultProvider sqlColumnEncryptionAzureKeyVaultProvider = new SqlColumnEncryptionAzureKeyVaultProvider(AzureActiveDirectoryAuthenticationCallback);

            // Register AKV provider
            SqlConnection.RegisterColumnEncryptionKeyStoreProviders(customProviders: new Dictionary<string, SqlColumnEncryptionKeyStoreProvider>(capacity: 1, comparer: StringComparer.OrdinalIgnoreCase)
                {
                    { SqlColumnEncryptionAzureKeyVaultProvider.ProviderName, sqlColumnEncryptionAzureKeyVaultProvider}
                });
            Console.WriteLine("AKV provider Registered");

            // Create connection to database
            using (SqlConnection sqlConnection = new SqlConnection(s_connectionString))
            {
                string cmkName = "CMK_WITH_AKV";
                string cekName = "CEK_WITH_AKV";
                string tblName = "AKV_TEST_TABLE";

                CustomerRecord customer = new CustomerRecord(1, @"Microsoft", @"Corporation");

                try
                {
                    sqlConnection.Open();

                    // Drop Objects if exists
                    dropObjects(sqlConnection, cmkName, cekName, tblName);

                    // Create Column Master Key with AKV Url
                    createCMK(sqlConnection, cmkName, sqlColumnEncryptionAzureKeyVaultProvider);
                    Console.WriteLine("Column Master Key created.");

                    // Create Column Encryption Key
                    createCEK(sqlConnection, cmkName, cekName, sqlColumnEncryptionAzureKeyVaultProvider);
                    Console.WriteLine("Column Encryption Key created.");

                    // Create Table with Encrypted Columns
                    createTbl(sqlConnection, cekName, tblName);
                    Console.WriteLine("Table created with Encrypted columns.");

                    // Insert Customer Record in table
                    insertData(sqlConnection, tblName, customer);
                    Console.WriteLine("Encryted data inserted.");

                    // Read data from table
                    verifyData(sqlConnection, tblName, customer);
                    Console.WriteLine("Data validated successfully.");
                }
                finally
                {
                    // Drop table and keys
                    dropObjects(sqlConnection, cmkName, cekName, tblName);
                    Console.WriteLine("Dropped Table, CEK and CMK");
                }

                Console.WriteLine("Completed AKV provider Sample.");

                Console.ReadKey();
            }
        }

        // Maintain an instance of the ClientCredential object to take advantage of underlying token caching
        private static ClientCredential clientCredential = new ClientCredential(s_clientId, s_clientSecret);

        public static async Task<string> AzureActiveDirectoryAuthenticationCallback(string authority, string resource, string scope)
        {
            var authContext = new AuthenticationContext(authority);
            AuthenticationResult result = await authContext.AcquireTokenAsync(resource, clientCredential);
            if (result == null)
            {
                throw new InvalidOperationException($"Failed to retrieve an access token for {resource}");
            }

            return result.AccessToken;
        }

        private static void createCMK(SqlConnection sqlConnection, string cmkName, SqlColumnEncryptionAzureKeyVaultProvider sqlColumnEncryptionAzureKeyVaultProvider)
        {
            string KeyStoreProviderName = SqlColumnEncryptionAzureKeyVaultProvider.ProviderName;

            byte[] cmkSign = sqlColumnEncryptionAzureKeyVaultProvider.SignColumnMasterKeyMetadata(s_akvUrl, true);
            string cmkSignStr = string.Concat("0x", BitConverter.ToString(cmkSign).Replace("-", string.Empty));

            string sql =
                $@"CREATE COLUMN MASTER KEY [{cmkName}]
                    WITH (
                        KEY_STORE_PROVIDER_NAME = N'{KeyStoreProviderName}',
                        KEY_PATH = N'{s_akvUrl}',
                        ENCLAVE_COMPUTATIONS (SIGNATURE = {cmkSignStr})
                    );";

            using (SqlCommand command = sqlConnection.CreateCommand())
            {
                command.CommandText = sql;
                command.ExecuteNonQuery();
            }
        }

        private static void createCEK(SqlConnection sqlConnection, string cmkName, string cekName, SqlColumnEncryptionAzureKeyVaultProvider sqlColumnEncryptionAzureKeyVaultProvider)
        {
            string sql =
                $@"CREATE COLUMN ENCRYPTION KEY [{cekName}] 
                    WITH VALUES (
                        COLUMN_MASTER_KEY = [{cmkName}],
                        ALGORITHM = '{s_algorithm}', 
                        ENCRYPTED_VALUE = {GetEncryptedValue(sqlColumnEncryptionAzureKeyVaultProvider)}
                    )";

            using (SqlCommand command = sqlConnection.CreateCommand())
            {
                command.CommandText = sql;
                command.ExecuteNonQuery();
            }
        }

        private static string GetEncryptedValue(SqlColumnEncryptionAzureKeyVaultProvider sqlColumnEncryptionAzureKeyVaultProvider)
        {
            byte[] plainTextColumnEncryptionKey = new byte[32];
            RandomNumberGenerator rng = RandomNumberGenerator.Create();
            rng.GetBytes(plainTextColumnEncryptionKey);

            byte[] encryptedColumnEncryptionKey = sqlColumnEncryptionAzureKeyVaultProvider.EncryptColumnEncryptionKey(s_akvUrl, s_algorithm, plainTextColumnEncryptionKey);
            string EncryptedValue = string.Concat("0x", BitConverter.ToString(encryptedColumnEncryptionKey).Replace("-", string.Empty));
            return EncryptedValue;
        }

        private static void createTbl(SqlConnection sqlConnection, string cekName, string tblName)
        {
            string ColumnEncryptionAlgorithmName = @"AEAD_AES_256_CBC_HMAC_SHA_256";

            string sql =
                    $@"CREATE TABLE [dbo].[{tblName}]
                (
                    [CustomerId] [int] ENCRYPTED WITH (COLUMN_ENCRYPTION_KEY = [{cekName}], ENCRYPTION_TYPE = RANDOMIZED, ALGORITHM = '{ColumnEncryptionAlgorithmName}'),
                    [FirstName] [nvarchar](50) COLLATE Latin1_General_BIN2 ENCRYPTED WITH (COLUMN_ENCRYPTION_KEY = [{cekName}], ENCRYPTION_TYPE = RANDOMIZED, ALGORITHM = '{ColumnEncryptionAlgorithmName}'),
                    [LastName] [nvarchar](50) COLLATE Latin1_General_BIN2 ENCRYPTED WITH (COLUMN_ENCRYPTION_KEY = [{cekName}], ENCRYPTION_TYPE = RANDOMIZED, ALGORITHM = '{ColumnEncryptionAlgorithmName}')
                )";

            using (SqlCommand command = sqlConnection.CreateCommand())
            {
                command.CommandText = sql;
                command.ExecuteNonQuery();
            }
        }

        private static void insertData(SqlConnection sqlConnection, string tblName, CustomerRecord customer)
        {
            string insertSql = $"INSERT INTO [{tblName}] (CustomerId, FirstName, LastName) VALUES (@CustomerId, @FirstName, @LastName);";

            using (SqlTransaction sqlTransaction = sqlConnection.BeginTransaction())
            using (SqlCommand sqlCommand = new SqlCommand(insertSql,
            connection: sqlConnection, transaction: sqlTransaction,
            columnEncryptionSetting: SqlCommandColumnEncryptionSetting.Enabled))
            {
                sqlCommand.Parameters.AddWithValue(@"CustomerId", customer.Id);
                sqlCommand.Parameters.AddWithValue(@"FirstName", customer.FirstName);
                sqlCommand.Parameters.AddWithValue(@"LastName", customer.LastName);

                sqlCommand.ExecuteNonQuery();
                sqlTransaction.Commit();
            }
        }

        private static void verifyData(SqlConnection sqlConnection, string tblName, CustomerRecord customer)
        {
            // Test INPUT parameter on an encrypted parameter
            using (SqlCommand sqlCommand = new SqlCommand($"SELECT CustomerId, FirstName, LastName FROM [{tblName}] WHERE FirstName = @firstName",
                                                            sqlConnection))
            {
                SqlParameter customerFirstParam = sqlCommand.Parameters.AddWithValue(@"firstName", @"Microsoft");
                customerFirstParam.Direction = System.Data.ParameterDirection.Input;
                customerFirstParam.ForceColumnEncryption = true;

                using (SqlDataReader sqlDataReader = sqlCommand.ExecuteReader())
                {
                    ValidateResultSet(sqlDataReader);
                }
            }
        }

        private static void ValidateResultSet(SqlDataReader sqlDataReader)
        {
            Console.WriteLine(" * Row available: " + sqlDataReader.HasRows);

            while (sqlDataReader.Read())
            {
                if (sqlDataReader.GetInt32(0) == 1)
                {
                    Console.WriteLine(" * Employee Id received as sent: " + sqlDataReader.GetInt32(0));
                }
                else
                {
                    Console.WriteLine("Employee Id didn't match");
                }

                if (sqlDataReader.GetString(1) == @"Microsoft")
                {
                    Console.WriteLine(" * Employee Firstname received as sent: " + sqlDataReader.GetString(1));
                }
                else
                {
                    Console.WriteLine("Employee FirstName didn't match.");
                }

                if (sqlDataReader.GetString(2) == @"Corporation")
                {
                    Console.WriteLine(" * Employee LastName received as sent: " + sqlDataReader.GetString(2));
                }
                else
                {
                    Console.WriteLine("Employee LastName didn't match.");
                }
            }
        }

        private static void dropObjects(SqlConnection sqlConnection, string cmkName, string cekName, string tblName)
        {
            using (SqlCommand cmd = sqlConnection.CreateCommand())
            {
                cmd.CommandText = $@"IF EXISTS (select * from sys.objects where name = '{tblName}') BEGIN DROP TABLE [{tblName}] END";
                cmd.ExecuteNonQuery();
                cmd.CommandText = $@"IF EXISTS (select * from sys.column_encryption_keys where name = '{cekName}') BEGIN DROP COLUMN ENCRYPTION KEY [{cekName}] END";
                cmd.ExecuteNonQuery();
                cmd.CommandText = $@"IF EXISTS (select * from sys.column_master_keys where name = '{cmkName}') BEGIN DROP COLUMN MASTER KEY [{cmkName}] END";
                cmd.ExecuteNonQuery();
            }
        }

        private class CustomerRecord
        {
            internal int Id { get; set; }
            internal string FirstName { get; set; }
            internal string LastName { get; set; }

            public CustomerRecord(int id, string fName, string lName)
            {
                Id = id;
                FirstName = fName;
                LastName = lName;
            }
        }
    }
}

Note

  • To use Always Encrypted with secure enclaves for .NET Standard application, Microsoft.Data.SqlClient version 2.1.0 or higher is required. The supported .NET Standard version is 2.1 or higher.

  • To use Always Encrypted with secure enclaves on Linux and macOS, Microsoft.Data.SqlClient version 2.1.0 or higher is required.

  • To use Always Encrypted with VBS enclaves without attestation, Microsoft.Data.SqlClient version 4.1.0 or higher is required.

See also

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