Merge pull request #1213 from adamhathcock/copilot/fix-compression-type-entry

Fix CompressionType for WinZip AES encrypted ZIP entries

src/SharpCompress/Common/Zip/ZipEntry.cs

@@ -10,6 +10,10 @@ public class ZipEntry : Entry
 {
     private readonly ZipFilePart? _filePart;
 
+    // WinZip AES extra data constants
+    private const int MinimumWinZipAesExtraDataLength = 7;
+    private const int WinZipAesCompressionMethodOffset = 5;
+
     internal ZipEntry(ZipFilePart? filePart, IReaderOptions readerOptions)
         : base(readerOptions)
     {
@@ -33,24 +37,54 @@ public class ZipEntry : Entry
         CreatedTime = times?.UnicodeTimes.Item3;
     }
 
-    public override CompressionType CompressionType =>
-        _filePart?.Header.CompressionMethod switch
+    public override CompressionType CompressionType
+    {
+        get
         {
-            ZipCompressionMethod.BZip2 => CompressionType.BZip2,
-            ZipCompressionMethod.Deflate => CompressionType.Deflate,
-            ZipCompressionMethod.Deflate64 => CompressionType.Deflate64,
-            ZipCompressionMethod.LZMA => CompressionType.LZMA,
-            ZipCompressionMethod.PPMd => CompressionType.PPMd,
-            ZipCompressionMethod.None => CompressionType.None,
-            ZipCompressionMethod.Shrink => CompressionType.Shrink,
-            ZipCompressionMethod.Reduce1 => CompressionType.Reduce1,
-            ZipCompressionMethod.Reduce2 => CompressionType.Reduce2,
-            ZipCompressionMethod.Reduce3 => CompressionType.Reduce3,
-            ZipCompressionMethod.Reduce4 => CompressionType.Reduce4,
-            ZipCompressionMethod.Explode => CompressionType.Explode,
-            ZipCompressionMethod.ZStandard => CompressionType.ZStandard,
-            _ => CompressionType.Unknown,
-        };
+            var compressionMethod = GetActualCompressionMethod();
+            return compressionMethod switch
+            {
+                ZipCompressionMethod.BZip2 => CompressionType.BZip2,
+                ZipCompressionMethod.Deflate => CompressionType.Deflate,
+                ZipCompressionMethod.Deflate64 => CompressionType.Deflate64,
+                ZipCompressionMethod.LZMA => CompressionType.LZMA,
+                ZipCompressionMethod.PPMd => CompressionType.PPMd,
+                ZipCompressionMethod.None => CompressionType.None,
+                ZipCompressionMethod.Shrink => CompressionType.Shrink,
+                ZipCompressionMethod.Reduce1 => CompressionType.Reduce1,
+                ZipCompressionMethod.Reduce2 => CompressionType.Reduce2,
+                ZipCompressionMethod.Reduce3 => CompressionType.Reduce3,
+                ZipCompressionMethod.Reduce4 => CompressionType.Reduce4,
+                ZipCompressionMethod.Explode => CompressionType.Explode,
+                ZipCompressionMethod.ZStandard => CompressionType.ZStandard,
+                _ => CompressionType.Unknown,
+            };
+        }
+    }
+
+    private ZipCompressionMethod GetActualCompressionMethod()
+    {
+        if (_filePart?.Header.CompressionMethod != ZipCompressionMethod.WinzipAes)
+        {
+            return _filePart?.Header.CompressionMethod ?? ZipCompressionMethod.None;
+        }
+
+        // For WinZip AES, the actual compression method is stored in the extra data
+        var aesExtraData = _filePart.Header.Extra.FirstOrDefault(x =>
+            x.Type == ExtraDataType.WinZipAes
+        );
+
+        if (aesExtraData is null || aesExtraData.DataBytes.Length < MinimumWinZipAesExtraDataLength)
+        {
+            return ZipCompressionMethod.WinzipAes;
+        }
+
+        // The compression method is at offset 5 in the extra data
+        return (ZipCompressionMethod)
+            System.Buffers.Binary.BinaryPrimitives.ReadUInt16LittleEndian(
+                aesExtraData.DataBytes.AsSpan(WinZipAesCompressionMethodOffset)
+            );
+    }
 
     public override long Crc => _filePart?.Header.Crc ?? 0;
 

tests/SharpCompress.Test/Zip/ZipArchiveTests.cs

@@ -491,6 +491,56 @@ public class ZipArchiveTests : ArchiveTests
         }
     }
 
+    [Fact]
+    public void Zip_WinzipAES_CompressionType()
+    {
+        // Test that WinZip AES encrypted entries correctly report their compression type
+        using var deflateArchive = ZipArchive.OpenArchive(
+            Path.Combine(TEST_ARCHIVES_PATH, "Zip.deflate.WinzipAES.zip"),
+            new ReaderOptions { Password = "test" }
+        );
+        foreach (var entry in deflateArchive.Entries.Where(x => !x.IsDirectory))
+        {
+            Assert.True(entry.IsEncrypted);
+            Assert.Equal(CompressionType.Deflate, entry.CompressionType);
+        }
+
+        using var lzmaArchive = ZipArchive.OpenArchive(
+            Path.Combine(TEST_ARCHIVES_PATH, "Zip.lzma.WinzipAES.zip"),
+            new ReaderOptions { Password = "test" }
+        );
+        foreach (var entry in lzmaArchive.Entries.Where(x => !x.IsDirectory))
+        {
+            Assert.True(entry.IsEncrypted);
+            Assert.Equal(CompressionType.LZMA, entry.CompressionType);
+        }
+    }
+
+    [Fact]
+    public void Zip_Pkware_CompressionType()
+    {
+        // Test that Pkware encrypted entries correctly report their compression type
+        using var deflateArchive = ZipArchive.OpenArchive(
+            Path.Combine(TEST_ARCHIVES_PATH, "Zip.deflate.pkware.zip"),
+            new ReaderOptions { Password = "test" }
+        );
+        foreach (var entry in deflateArchive.Entries.Where(x => !x.IsDirectory))
+        {
+            Assert.True(entry.IsEncrypted);
+            Assert.Equal(CompressionType.Deflate, entry.CompressionType);
+        }
+
+        using var bzip2Archive = ZipArchive.OpenArchive(
+            Path.Combine(TEST_ARCHIVES_PATH, "Zip.bzip2.pkware.zip"),
+            new ReaderOptions { Password = "test" }
+        );
+        foreach (var entry in bzip2Archive.Entries.Where(x => !x.IsDirectory))
+        {
+            Assert.True(entry.IsEncrypted);
+            Assert.Equal(CompressionType.BZip2, entry.CompressionType);
+        }
+    }
+
     [Fact]
     public void Zip_Read_Volume_Comment()
     {

tests/SharpCompress.Test/Zip/ZipReaderAsyncTests.cs

@@ -224,7 +224,7 @@ public class ZipReaderAsyncTests : ReaderTests
                 {
                     if (!reader.Entry.IsDirectory)
                     {
-                        Assert.Equal(CompressionType.Unknown, reader.Entry.CompressionType);
+                        Assert.Equal(CompressionType.LZMA, reader.Entry.CompressionType);
                         await reader.WriteEntryToDirectoryAsync(SCRATCH_FILES_PATH);
                     }
                 }
@@ -252,7 +252,7 @@ public class ZipReaderAsyncTests : ReaderTests
             {
                 if (!reader.Entry.IsDirectory)
                 {
-                    Assert.Equal(CompressionType.Unknown, reader.Entry.CompressionType);
+                    Assert.Equal(CompressionType.Deflate, reader.Entry.CompressionType);
                     await reader.WriteEntryToDirectoryAsync(SCRATCH_FILES_PATH);
                 }
             }

tests/SharpCompress.Test/Zip/ZipReaderTests.cs

@@ -201,7 +201,7 @@ public class ZipReaderTests : ReaderTests
                 {
                     if (!reader.Entry.IsDirectory)
                     {
-                        Assert.Equal(CompressionType.Unknown, reader.Entry.CompressionType);
+                        Assert.Equal(CompressionType.LZMA, reader.Entry.CompressionType);
                         reader.WriteEntryToDirectory(SCRATCH_FILES_PATH);
                     }
                 }
@@ -223,7 +223,7 @@ public class ZipReaderTests : ReaderTests
             {
                 if (!reader.Entry.IsDirectory)
                 {
-                    Assert.Equal(CompressionType.Unknown, reader.Entry.CompressionType);
+                    Assert.Equal(CompressionType.Deflate, reader.Entry.CompressionType);
                     reader.WriteEntryToDirectory(SCRATCH_FILES_PATH);
                 }
             }