Applied patch from Anonymous user (https://sourceforge.net/p/acryptoh…

…ashnet/discussion/429867/thread/01c41d58/?limit=25#5dc2)

src/ACryptoHashNet.UnitTests/ACryptoHashNet.UnitTests.csproj

@@ -83,6 +83,7 @@
   </ItemGroup>
   <ItemGroup>
     <Compile Include="BaseHashTest.cs" />
+    <Compile Include="BlockAlgorithmTests.cs" />
     <Compile Include="CounterTests\IntCounterTest.cs" />
     <Compile Include="Haval\Haval128Pass3Test.cs" />
     <Compile Include="Haval\Haval128Pass4Test.cs" />

src/ACryptoHashNet.UnitTests/BlockAlgorithmTests.cs

@@ -0,0 +1,39 @@
+using System.Security.Cryptography;
+using System.Text;
+
+using NUnit.Framework;
+
+namespace Home.Andir.Cryptography.UnitTests
+{
+    [TestFixture]
+    [Category("BlockAlgorithmTests")]
+    public class BlockAlgorithmTests
+    {
+        [Test]
+        public static void BlockAlgorithmTest()
+        {
+            byte[] b1 = Encoding.UTF8.GetBytes("hello");
+            byte[] b2 = Encoding.UTF8.GetBytes(" world");
+
+            HashAlgorithm sha1Managed = new SHA1Managed();
+            sha1Managed.TransformBlock(b1, 0, b1.Length, null, 0);
+            var expected = 
+                sha1Managed.TransformFinalBlock(b2, 0, b2.Length);
+
+            HashAlgorithm sha1 = new SHA1();
+            sha1.TransformBlock(b1, 0, b1.Length, null, 0);
+            byte[] actual = 
+                sha1.TransformFinalBlock(b2, 0, b2.Length);
+
+            if (expected.Length != actual.Length)
+            {
+                Assert.Fail("Final block has wrong lengh");
+            }
+
+            for (int ii = 0; ii < expected.Length; ii++)
+            {
+                Assert.AreEqual(expected[ii], actual[ii], string.Format("Final block differ at {0} position", ii));
+            }
+        }
+    }
+}

src/ACryptoHashNet/Base/BlockHashAlgorithm.cs

@@ -67,33 +67,42 @@ protected override void HashCore(byte[] array, int offset, int length)
             int currentOffset = offset;
             int currentLength = length;
 
-            if (lastBlockLength > 0)
+            int lastBlockRemaining = lastBlock.Length - lastBlockLength;
+            if (lastBlockLength > 0 && length >= lastBlockRemaining)
             {
+                // we were left with a partial block and we have enough data to fill it now
                 Buffer.BlockCopy(
-                    array, currentOffset,
-                    lastBlock, lastBlockLength,
-                    lastBlock.Length - lastBlockLength
-                    );
+                    array,
+                    currentOffset,
+                    lastBlock,
+                    lastBlockLength,
+                    lastBlockRemaining
+                                     );
 
                 ProcessBlock(lastBlock, 0);
 
-                currentOffset += lastBlockLength;
-                currentLength -= lastBlockLength;
+                currentOffset += lastBlockRemaining;
+                currentLength -= lastBlockRemaining;
 
                 lastBlockLength = 0;
             }
 
             int blockCount = currentLength / BlockSize;
-            lastBlockLength = currentLength % BlockSize;
 
             for (int ii = 0; ii < blockCount; ii++, currentOffset += BlockSize)
                 ProcessBlock(array, currentOffset);
 
-            if (lastBlockLength != 0)
+            int blockBoundaryOffset = currentLength % BlockSize;
+            if (blockBoundaryOffset != 0) // current data length does not fall on a block boundary
+            {
                 Buffer.BlockCopy(
-                    array, currentOffset,
-                    lastBlock, 0,
-                    lastBlockLength);
+                    array,
+                    currentOffset,
+                    lastBlock,
+                    lastBlockLength,
+                    blockBoundaryOffset);
+                lastBlockLength += blockBoundaryOffset;
+            }
         }
 
         /// <summary>