Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Data/System/Data/SqlClient/SqlClientSymmetricKey.cs

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+//------------------------------------------------------------------------------
+// <copyright file="SqlException.cs" company="Microsoft">
+//     Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>
+// <owner current="true" primary="true">balnee</owner>
+// <owner current="true" primary="false">krishnib</owner>
+//------------------------------------------------------------------------------
+namespace System.Data.SqlClient
+{
+    using System;
+    using System.Data.SqlClient;
+    using System.Security.Cryptography;
+
+    /// <summary>
+    /// Base class containing raw key bytes for symmetric key algorithms. Some encryption algorithms can use the key directly while others derive sub keys from this.
+    /// If an algorithm needs to derive more keys, have a derived class from this and use it in the corresponding encryption algorithm.
+    /// </summary>
+    internal class SqlClientSymmetricKey
+    {
+        /// <summary>
+        /// DPAPI protected key
+        /// </summary>
+        protected readonly byte[] _rootKey;
+
+        /// <summary>
+        /// Constructor that initializes the root key.
+        /// </summary>
+        /// <param name="rootKey">root key</param>
+        internal SqlClientSymmetricKey(byte[] rootKey)
+        {
+            // Key validation
+            if (rootKey == null || rootKey.Length == 0) {
+                throw SQL.NullColumnEncryptionKeySysErr();
+            }
+
+            _rootKey = rootKey;
+        }
+
+        /// <summary>
+        /// Returns a copy of the plain text key
+        /// This is needed for actual encryption/decryption.
+        /// </summary>
+        internal virtual byte[] RootKey
+        {
+            get 
+            {
+                return _rootKey; 
+            }
+        }
+
+        /// <summary>
+        /// Computes SHA256 value of the plain text key bytes
+        /// </summary>
+        /// <returns>A string containing SHA256 hash of the root key</returns>
+        internal virtual string GetKeyHash()
+        {
+            return SqlSecurityUtility.GetSHA256Hash(RootKey);
+        }
+
+        /// <summary>
+        /// Gets the length of the root key
+        /// </summary>
+        /// <returns>
+        /// Returns the length of the root key
+        /// </returns>
+        internal virtual int Length()
+        {
+            // Note: DPAPI preserves the original byte length
+            // so for now, this is as same as returning the length of the raw key.
+            return _rootKey.Length;
+        }
+    }
+}