PR icsharpcode#554 skip CRC calculation for AES zip entries

Author: HowToDoThis

src/ICSharpCode.SharpZipLib/Zip/ZipFile.cs

@@ -949,6 +949,8 @@ public bool TestArchive(bool testData, TestStrategy strategy, ZipTestResultHandl
 
 					if (testing && testData && this[entryIndex].IsFile)
 					{
+						var checkCRC = this[entryIndex].AESKeySize == 0;
+
 						if (resultHandler != null)
 						{
 							status.SetOperation(TestOperation.EntryData);
@@ -964,7 +966,8 @@ public bool TestArchive(bool testData, TestStrategy strategy, ZipTestResultHandl
 							int bytesRead;
 							while ((bytesRead = entryStream.Read(buffer, 0, buffer.Length)) > 0)
 							{
-								crc.Update(new ArraySegment<byte>(buffer, 0, bytesRead));
+								if (checkCRC)
+									crc.Update(new ArraySegment<byte>(buffer, 0, bytesRead));
 
 								if (resultHandler != null)
 								{
@@ -975,13 +978,16 @@ public bool TestArchive(bool testData, TestStrategy strategy, ZipTestResultHandl
 							}
 						}
 
-						if (this[entryIndex].Crc != crc.Value)
+						if (checkCRC)
 						{
-							status.AddError();
+							if (this[entryIndex].Crc != crc.Value)
+							{
+								status.AddError();
 
-							resultHandler?.Invoke(status, "CRC mismatch");
+								resultHandler?.Invoke(status, "CRC mismatch");
 
-							testing &= strategy != TestStrategy.FindFirstError;
+								testing &= strategy != TestStrategy.FindFirstError;
+							}
 						}
 
 						if ((this[entryIndex].Flags & (int)GeneralBitFlags.Descriptor) != 0)
@@ -991,10 +997,13 @@ public bool TestArchive(bool testData, TestStrategy strategy, ZipTestResultHandl
 
 							helper.ReadDataDescriptor(this[entryIndex].LocalHeaderRequiresZip64, data);
 
-							if (this[entryIndex].Crc != data.Crc)
+							if (checkCRC)
 							{
-								status.AddError();
-								resultHandler?.Invoke(status, "Descriptor CRC mismatch");
+								if (this[entryIndex].Crc != data.Crc)
+								{
+									status.AddError();
+									resultHandler?.Invoke(status, "Descriptor CRC mismatch");
+								}
 							}
 
 							if (this[entryIndex].CompressedSize != data.CompressedSize)
@@ -2633,6 +2642,8 @@ private void AddEntry(ZipFile workFile, ZipUpdate update)
 					source = updateDataSource_.GetSource(update.Entry, update.Filename);
 			}
 
+			var useCrc = update.Entry.AESKeySize == 0;
+
 			if (source != null)
 			{
 				using (source)
@@ -2653,7 +2664,7 @@ private void AddEntry(ZipFile workFile, ZipUpdate update)
 
 					using (Stream output = workFile.GetOutputStream(update.OutEntry))
 					{
-						CopyBytes(update, output, source, sourceStreamLength, true);
+						CopyBytes(update, output, source, sourceStreamLength, useCrc);
 					}
 
 					long dataEnd = workFile.baseStream_.Position;

src/ICSharpCode.SharpZipLib/Zip/ZipHelperStream.cs

@@ -450,7 +450,7 @@ public int WriteDataDescriptor(ZipEntry entry)
 			if ((entry.Flags & (int)GeneralBitFlags.Descriptor) != 0)
 			{
 				// The signature is not PKZIP originally but is now described as optional
-				// in the PKZIP Appnote documenting trhe format.
+				// in the PKZIP Appnote documenting the format.
 				WriteLEInt(ZipConstants.DataDescriptorSignature);
 				WriteLEInt(unchecked((int)(entry.Crc)));
 
@@ -484,7 +484,7 @@ public void ReadDataDescriptor(bool zip64, DescriptorData data)
 			int intValue = ReadLEInt();
 
 			// In theory this may not be a descriptor according to PKZIP appnote.
-			// In practise its always there.
+			// In practice its always there.
 			if (intValue != ZipConstants.DataDescriptorSignature)
 			{
 				throw new ZipException("Data descriptor signature not found");

src/ICSharpCode.SharpZipLib/Zip/ZipOutputStream.cs

@@ -496,6 +496,9 @@ public void PutNextEntry(ZipEntry entry)
 		/// <summary>
 		/// Closes the current entry, updating header and footer information as required
 		/// </summary>
+		/// <exception cref="ZipException">
+		/// Invalid entry field values.
+		/// </exception>
 		/// <exception cref="System.IO.IOException">
 		/// An I/O error occurs.
 		/// </exception>
@@ -526,7 +529,7 @@ public void CloseEntry()
 			}
 			else if (curMethod == CompressionMethod.Stored)
 			{
-				// This is done by Finsh() for Deflated entries, but we need to do it
+				// This is done by Finish() for Deflated entries, but we need to do it
 				// ourselves for Stored ones
 				GetAuthCodeIfAES();
 			}
@@ -535,6 +538,19 @@ public void CloseEntry()
 			if (curEntry.AESKeySize > 0)
 			{
 				baseOutputStream_.Write(AESAuthCode, 0, 10);
+				// Always use 0 as CRC for AE-2 format
+				curEntry.Crc = 0;
+			}
+			else
+			{
+				if (curEntry.Crc < 0)
+				{
+					curEntry.Crc = crc.Value;
+				}
+				else if (curEntry.Crc != crc.Value)
+				{
+					throw new ZipException($"crc was {crc.Value}, but {curEntry.Crc} was expected");
+				}
 			}
 
 			if (curEntry.Size < 0)
@@ -543,7 +559,7 @@ public void CloseEntry()
 			}
 			else if (curEntry.Size != size)
 			{
-				throw new ZipException("size was " + size + ", but I expected " + curEntry.Size);
+				throw new ZipException($"size was {size}, but {curEntry.Size} was expected");
 			}
 
 			if (curEntry.CompressedSize < 0)
@@ -552,16 +568,7 @@ public void CloseEntry()
 			}
 			else if (curEntry.CompressedSize != csize)
 			{
-				throw new ZipException("compressed size was " + csize + ", but I expected " + curEntry.CompressedSize);
-			}
-
-			if (curEntry.Crc < 0)
-			{
-				curEntry.Crc = crc.Value;
-			}
-			else if (curEntry.Crc != crc.Value)
-			{
-				throw new ZipException("crc was " + crc.Value + ", but I expected " + curEntry.Crc);
+				throw new ZipException($"compressed size was {csize}, but {curEntry.CompressedSize} expected");
 			}
 
 			offset += csize;
@@ -709,7 +716,10 @@ public override void Write(byte[] buffer, int offset, int count)
 				throw new ArgumentException("Invalid offset/count combination");
 			}
 
-			crc.Update(new ArraySegment<byte>(buffer, offset, count));
+			// Only update CRC if AES is not enabled
+			if (curEntry.AESKeySize == 0)
+				crc.Update(new ArraySegment<byte>(buffer, offset, count));
+
 			size += count;
 
 			switch (curMethod)