Make ZipFile.Add throw NotSupportedException when trying to add an AES encrypted entry

src/ICSharpCode.SharpZipLib/Zip/ZipFile.cs

@@ -1850,6 +1850,9 @@ public void Add(ZipEntry entry)
 		/// <param name="dataSource">The source of the data for this entry.</param>
 		/// <param name="entry">The entry to add.</param>
 		/// <remarks>This can be used to add file entries with a custom data source.</remarks>
+		/// <exception cref="NotSupportedException">
+		/// The encryption method specified in <paramref name="entry"/> is unsupported.
+		/// </exception>
 		public void Add(IStaticDataSource dataSource, ZipEntry entry)
 		{
 			if (entry == null)
@@ -1862,6 +1865,13 @@ public void Add(IStaticDataSource dataSource, ZipEntry entry)
 				throw new ArgumentNullException(nameof(dataSource));
 			}
 
+			// We don't currently support adding entries with AES encryption, so throw
+			// up front instead of failing or falling back to ZipCrypto later on
+			if (entry.AESKeySize > 0)
+			{
+				throw new NotSupportedException("Creation of AES encrypted entries is not supported");
+			}
+
 			CheckUpdating();
 
 			AddUpdate(new ZipUpdate(dataSource, entry));

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

@@ -1547,5 +1547,27 @@ public void HostSystemPersistedFromZipFile()
 				}
 			}
 		}
+
+		/// <summary>
+		/// Refs https://github.com/icsharpcode/SharpZipLib/issues/385
+		/// Trying to add an AES Encrypted entry to ZipFile should throw as it isn't supported
+		/// </summary>
+		[Test]
+		[Category("Zip")]
+		public void AddingAnAESEncryptedEntryShouldThrow()
+		{
+			var memStream = new MemoryStream();
+			using (ZipFile zof = new ZipFile(memStream))
+			{
+				var entry = new ZipEntry("test")
+				{
+					AESKeySize = 256
+				};
+
+				zof.BeginUpdate();
+				var exception = Assert.Throws<NotSupportedException>(() => zof.Add(new StringMemoryDataSource("foo"), entry));
+				Assert.That(exception.Message, Is.EqualTo("Creation of AES encrypted entries is not supported"));
+			}
+		}
 	}
 }