[release/9.0-staging] Fix shimmed implementation of TryGetHashAndRese…

…t to handle HMAC.

The TryGetHashAndReset in switches on the algorithm name of IncrementalHash. IncrementalHash prepends "HMAC" in front of the algorithm name, so the shim did not correctly handle the HMAC-prepended algorithm names.


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Co-authored-by: Kevin Jones <[email protected]>
Co-authored-by: Larry Ewing <[email protected]>

src/libraries/Microsoft.Bcl.Cryptography/src/System/Security/Cryptography/NetStandardShims.cs

@@ -100,25 +100,14 @@ internal static bool TryGetHashAndReset(
             Span<byte> destination,
             out int bytesWritten)
         {
-            int hashSize = hash.AlgorithmName.Name switch
-            {
-                nameof(HashAlgorithmName.MD5) => 128 >> 3,
-                nameof(HashAlgorithmName.SHA1) => 160 >> 3,
-                nameof(HashAlgorithmName.SHA256) => 256 >> 3,
-                nameof(HashAlgorithmName.SHA384) => 384 >> 3,
-                nameof(HashAlgorithmName.SHA512) => 512 >> 3,
-                _ => throw new CryptographicException(),
-            };
-
-            if (destination.Length < hashSize)
+            byte[] actual = hash.GetHashAndReset();
+
+            if (destination.Length < actual.Length)
             {
                 bytesWritten = 0;
                 return false;
             }
 
-            byte[] actual = hash.GetHashAndReset();
-            Debug.Assert(actual.Length == hashSize);
-
             actual.AsSpan().CopyTo(destination);
             bytesWritten = actual.Length;
             return true;