ZeroMemory for sensetive buffer clear

src/DataProtection/Cryptography.Internal/src/CryptoUtil.cs

@@ -91,6 +91,22 @@ public static bool TimeConstantBuffersAreEqual(byte* bufA, byte* bufB, uint coun
 #endif
     }
 
+#if NET || NETSTANDARD2_1_OR_GREATER
+    // CryptographicOperations.ZeroMemory is itself [NoInlining | NoOptimization];
+    // inlining this wrapper just leaves a direct call
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+#else
+    [MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.NoOptimization)]
+#endif
+    public static void ZeroMemory(byte[] buffer)
+    {
+#if NET || NETSTANDARD2_1_OR_GREATER
+        CryptographicOperations.ZeroMemory(buffer);
+#else
+        Array.Clear(buffer, 0, buffer.Length);
+#endif
+    }
+
     [MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.NoOptimization)]
     public static bool TimeConstantBuffersAreEqual(ReadOnlySpan<byte> bufA, ReadOnlySpan<byte> bufB)
     {

src/DataProtection/Cryptography.KeyDerivation/src/PBKDF2/ManagedPbkdf2Provider.cs

@@ -86,7 +86,7 @@ private static KeyedHashAlgorithm PrfToManagedHmacAlgorithm(KeyDerivationPrf prf
         finally
         {
             // The HMAC ctor makes a duplicate of this key; we clear original buffer to limit exposure to the GC.
-            Array.Clear(passwordBytes, 0, passwordBytes.Length);
+            CryptoUtil.ZeroMemory(passwordBytes);
         }
     }
 

src/DataProtection/DataProtection/src/AuthenticatedEncryption/ConfigurationModel/SecretExtensions.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Xml.Linq;
+using Microsoft.AspNetCore.Cryptography;
 
 namespace Microsoft.AspNetCore.DataProtection.AuthenticatedEncryption.ConfigurationModel;
 
@@ -30,7 +31,7 @@ public static XElement ToMasterKeyElement(this ISecret secret)
             }
             finally
             {
-                Array.Clear(unprotectedSecretRawBytes, 0, unprotectedSecretRawBytes.Length);
+                CryptoUtil.ZeroMemory(unprotectedSecretRawBytes);
             }
         }
 
@@ -56,7 +57,7 @@ public static Secret ToSecret(this string base64String)
             }
             finally
             {
-                Array.Clear(unprotectedSecret, 0, unprotectedSecret.Length);
+                CryptoUtil.ZeroMemory(unprotectedSecret);
             }
         }
     }

src/DataProtection/DataProtection/src/Cng/DpapiSecretSerializerHelper.cs

@@ -58,7 +58,7 @@ public static byte[] ProtectWithDpapi(ISecret secret, bool protectToLocalMachine
             finally
             {
                 // To limit exposure to the GC.
-                Array.Clear(plaintextSecret, 0, plaintextSecret.Length);
+                CryptoUtil.ZeroMemory(plaintextSecret);
             }
         }
     }
@@ -136,7 +136,7 @@ public static byte[] ProtectWithDpapiNG(ISecret secret, NCryptDescriptorHandle p
             finally
             {
                 // Limits secret exposure to garbage collector.
-                Array.Clear(plaintextSecret, 0, plaintextSecret.Length);
+                CryptoUtil.ZeroMemory(plaintextSecret);
             }
         }
     }

src/DataProtection/DataProtection/src/Managed/ManagedAuthenticatedEncryptor.cs

@@ -377,8 +377,8 @@ public byte[] Encrypt(ArraySegment<byte> plaintext, ArraySegment<byte> additiona
                 }
                 finally
                 {
-                    Array.Clear(keyModifier, 0, keyModifierLength);
-                    Array.Clear(decryptedKdk, 0, decryptedKdk.Length);
+                    CryptoUtil.ZeroMemory(keyModifier);
+                    CryptoUtil.ZeroMemory(decryptedKdk);
                 }
             }
         }
@@ -453,7 +453,7 @@ private void CalculateAndValidateMac(
         }
         finally
         {
-            Array.Clear(correctHashArray, 0, correctHashArray.Length);
+            CryptoUtil.ZeroMemory(correctHashArray);
         }
     }
 #endif
@@ -573,7 +573,7 @@ public byte[] Decrypt(ArraySegment<byte> protectedPayload, ArraySegment<byte> ad
                 {
                     // delete since these contain secret material
                     validationSubkey.Clear();
-                    Array.Clear(decryptedKdk, 0, decryptedKdk.Length);
+                    CryptoUtil.ZeroMemory(decryptedKdk);
                 }
             }
         }

src/DataProtection/DataProtection/src/XmlEncryption/XmlEncryptionExtensions.cs

@@ -173,7 +173,7 @@ public static Secret ToSecret(this XElement element)
             }
             finally
             {
-                Array.Clear(underlyingBuffer, 0, underlyingBuffer.Length);
+                CryptoUtil.ZeroMemory(underlyingBuffer);
             }
         }
     }
@@ -194,7 +194,7 @@ public static XElement ToXElement(this Secret secret)
             }
             finally
             {
-                Array.Clear(plaintextSecret, 0, plaintextSecret.Length);
+                CryptoUtil.ZeroMemory(plaintextSecret);
             }
         }
     }