Throw exception on Store+Descriptor entries

Author: piksel

src/ICSharpCode.SharpZipLib/Zip/ZipInputStream.cs

@@ -493,6 +493,14 @@ private int ReadingNotSupported(byte[] destination, int offset, int count)
 			throw new ZipException("The compression method for this entry is not supported");
 		}
 
+		/// <summary>
+		/// Handle attempts to read from this entry by throwing an exception
+		/// </summary>
+		private int StoredDescriptorEntry(byte[] destination, int offset, int count) =>
+			throw new StreamUnsupportedException(
+				"The combination of Stored compression method and Descriptor flag is not possible to read using ZipInputStream");
+		
+
 		/// <summary>
 		/// Perform the initial read on an entry which may include
 		/// reading encryption headers and setting up inflation.
@@ -544,13 +552,22 @@ private int InitialRead(byte[] destination, int offset, int count)
 				inputBuffer.CryptoTransform = null;
 			}
 
-			if ((csize > 0) || ((flags & (int)GeneralBitFlags.Descriptor) != 0))
+			var usesDescriptor = (flags & (int) GeneralBitFlags.Descriptor) != 0;
+
+			if ((csize > 0) || usesDescriptor)
 			{
 				if ((method == CompressionMethod.Deflated) && (inputBuffer.Available > 0))
 				{
 					inputBuffer.SetInflaterInput(inf);
 				}
 
+				// It's not possible to know how many bytes to read when using "Stored" compression (unless using encryption)
+				if (!entry.IsCrypted && method == CompressionMethod.Stored && usesDescriptor)
+				{
+					internalReader = StoredDescriptorEntry;
+					return StoredDescriptorEntry(destination, offset, count);
+				}
+
 				internalReader = new ReadDataHandler(BodyRead);
 				return BodyRead(destination, offset, count);
 			}

test/ICSharpCode.SharpZipLib.Tests/Zip/StreamHandling.cs

@@ -502,5 +502,41 @@ public void ShouldBeAbleToReadEntriesWithInvalidFileNames()
 				}
 			}
 		}
+
+		[Test]
+		[Category("Zip")]
+		public void ShouldThrowDescriptiveExceptionOnUncompressedDescriptorEntry()
+		{
+			using (var ms = new MemoryStreamWithoutSeek())
+			{
+				using (var zos = new ZipOutputStream(ms))
+				{
+					zos.IsStreamOwner = false;
+					var entry = new ZipEntry("testentry");
+					entry.CompressionMethod = CompressionMethod.Stored;
+					entry.Flags |= (int)GeneralBitFlags.Descriptor;
+					zos.PutNextEntry(entry);
+					zos.Write(new byte[1], 0, 1);
+					zos.CloseEntry();
+				}
+
+				// Patch the Compression Method, since ZipOutputStream automatically changes it to Deflate when descriptors are used
+				ms.Seek(8, SeekOrigin.Begin);
+				ms.WriteByte((byte)CompressionMethod.Stored);
+				ms.Seek(0, SeekOrigin.Begin);
+
+				using (var zis = new ZipInputStream(ms))
+				{
+					zis.IsStreamOwner = false;
+					var buf = new byte[32];
+					zis.GetNextEntry();
+
+					Assert.Throws(typeof(StreamUnsupportedException), () =>
+					{
+						zis.Read(buf, 0, buf.Length);
+					});
+				}
+			}
+		}
 	}
 }