Avoid finalizable internal state for non-FIPS scenarios

Fixes #67995

src/Workspaces/Core/Portable/Workspace/Solution/Checksum_Factory.cs

@@ -5,15 +5,14 @@
 using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
+using System.Diagnostics;
 using System.IO;
-using System.Security.Cryptography;
 using System.Runtime.InteropServices;
+using System.Security.Cryptography;
 using System.Threading;
 using Microsoft.CodeAnalysis.PooledObjects;
 using Microsoft.CodeAnalysis.Serialization;
 using Roslyn.Utilities;
-using System.Diagnostics;
-using System.Runtime.CompilerServices;
 
 namespace Microsoft.CodeAnalysis
 {
@@ -23,8 +22,13 @@ internal partial class Checksum
         // https://github.com/dotnet/runtime/blob/f2db6d6093c54e5eeb9db2d8dcbe15b2db92ad8c/src/libraries/System.Security.Cryptography.Algorithms/src/System/Security/Cryptography/SHA256.cs#L18-L19
         private const int SHA256HashSizeBytes = 256 / 8;
 
+#if NET5_0_OR_GREATER
         private static readonly ObjectPool<IncrementalHash> s_incrementalHashPool =
             new(() => IncrementalHash.CreateHash(HashAlgorithmName.SHA256), size: 20);
+#else
+        private static readonly ObjectPool<SHA256> s_incrementalHashPool =
+            new(SHA256.Create, size: 20);
+#endif
 
 #if !NET5_0_OR_GREATER
         // Dedicated pools for the byte[]s we use to create checksums from two or three existing checksums. Sized to
@@ -53,13 +57,15 @@ public static Checksum Create(IEnumerable<string> values)
             using var pooledBuffer = SharedPools.ByteArray.GetPooledObject();
             var hash = pooledHash.Object;
 
+            hash.Initialize();
             foreach (var value in values)
             {
                 AppendData(hash, pooledBuffer.Object, value);
                 AppendData(hash, pooledBuffer.Object, "\0");
             }
 
-            return From(hash.GetHashAndReset());
+            hash.TransformFinalBlock(Array.Empty<byte>(), 0, 0);
+            return From(hash.Hash);
 #endif
         }
 
@@ -73,10 +79,12 @@ public static Checksum Create(string value)
             using var pooledHash = s_incrementalHashPool.GetPooledObject();
             using var pooledBuffer = SharedPools.ByteArray.GetPooledObject();
             var hash = pooledHash.Object;
+            hash.Initialize();
 
             AppendData(hash, pooledBuffer.Object, value);
 
-            return From(hash.GetHashAndReset());
+            hash.TransformFinalBlock(Array.Empty<byte>(), 0, 0);
+            return From(hash.Hash);
 #endif
         }
 
@@ -109,6 +117,7 @@ public static Checksum Create(Stream stream)
             using var pooledBuffer = SharedPools.ByteArray.GetPooledObject();
 
             var hash = pooledHash.Object;
+            hash.Initialize();
 
             var buffer = pooledBuffer.Object;
             var bufferLength = buffer.Length;
@@ -118,12 +127,13 @@ public static Checksum Create(Stream stream)
                 bytesRead = stream.Read(buffer, 0, bufferLength);
                 if (bytesRead > 0)
                 {
-                    hash.AppendData(buffer, 0, bytesRead);
+                    hash.TransformBlock(buffer, 0, bytesRead, null, 0);
                 }
             }
             while (bytesRead > 0);
 
-            var bytes = hash.GetHashAndReset();
+            hash.TransformFinalBlock(Array.Empty<byte>(), 0, 0);
+            var bytes = hash.Hash;
 
             // if bytes array is bigger than certain size, checksum
             // will truncate it to predetermined size. for more detail,
@@ -174,31 +184,37 @@ public static Checksum Create(Checksum checksum1, Checksum checksum2, Checksum c
 
         private static Checksum CreateUsingByteArrays(Checksum checksum1, Checksum checksum2)
         {
-            using var hash = s_incrementalHashPool.GetPooledObject();
             using var bytes = s_twoChecksumByteArrayPool.GetPooledObject();
 
             var bytesSpan = bytes.Object.AsSpan();
             checksum1.WriteTo(bytesSpan);
             checksum2.WriteTo(bytesSpan.Slice(HashSize));
 
-            hash.Object.AppendData(bytes.Object);
+            using var hash = s_incrementalHashPool.GetPooledObject();
+            hash.Object.Initialize();
+
+            hash.Object.TransformBlock(bytes.Object, 0, bytes.Object.Length, null, 0);
 
-            return From(hash.Object.GetHashAndReset());
+            hash.Object.TransformFinalBlock(Array.Empty<byte>(), 0, 0);
+            return From(hash.Object.Hash);
         }
 
         private static Checksum CreateUsingByteArrays(Checksum checksum1, Checksum checksum2, Checksum checksum3)
         {
-            using var hash = s_incrementalHashPool.GetPooledObject();
             using var bytes = s_threeChecksumByteArrayPool.GetPooledObject();
 
             var bytesSpan = bytes.Object.AsSpan();
             checksum1.WriteTo(bytesSpan);
             checksum2.WriteTo(bytesSpan.Slice(HashSize));
             checksum3.WriteTo(bytesSpan.Slice(2 * HashSize));
 
-            hash.Object.AppendData(bytes.Object);
+            using var hash = s_incrementalHashPool.GetPooledObject();
+            hash.Object.Initialize();
+
+            hash.Object.TransformBlock(bytes.Object, 0, bytes.Object.Length, null, 0);
 
-            return From(hash.Object.GetHashAndReset());
+            hash.Object.TransformFinalBlock(Array.Empty<byte>(), 0, 0);
+            return From(hash.Object.Hash);
         }
 
 #else
@@ -283,7 +299,7 @@ public static Checksum Create(ParseOptions value, ISerializerService serializer)
         }
 
 #if !NET5_0_OR_GREATER
-        private static void AppendData(IncrementalHash hash, byte[] buffer, string value)
+        private static void AppendData(SHA256 hash, byte[] buffer, string value)
         {
             var stringBytes = MemoryMarshal.AsBytes(value.AsSpan());
             Debug.Assert(stringBytes.Length == value.Length * 2);
@@ -295,7 +311,7 @@ private static void AppendData(IncrementalHash hash, byte[] buffer, string value
                 var toCopy = Math.Min(remaining, buffer.Length);
 
                 stringBytes.Slice(index, toCopy).CopyTo(buffer);
-                hash.AppendData(buffer, 0, toCopy);
+                hash.TransformBlock(buffer, 0, toCopy, null, 0);
 
                 index += toCopy;
             }