SkipBlockAlignmentPadding must be executed for all entries (#74396)

src/libraries/System.Formats.Tar/src/System/Formats/Tar/TarReader.cs

@@ -225,10 +225,10 @@ internal void AdvanceDataStreamIfNeeded()
                     {
                         long bytesToSkip = _previouslyReadEntry._header._size - dataStream.Position;
                         TarHelpers.AdvanceStream(_archiveStream, bytesToSkip);
-                        TarHelpers.SkipBlockAlignmentPadding(_archiveStream, _previouslyReadEntry._header._size);
                         dataStream.HasReachedEnd = true; // Now the pointer is beyond the limit, so any read attempts should throw
                     }
                 }
+                TarHelpers.SkipBlockAlignmentPadding(_archiveStream, _previouslyReadEntry._header._size);
             }
         }
 
@@ -267,10 +267,10 @@ internal async ValueTask AdvanceDataStreamIfNeededAsync(CancellationToken cancel
                     {
                         long bytesToSkip = _previouslyReadEntry._header._size - dataStream.Position;
                         await TarHelpers.AdvanceStreamAsync(_archiveStream, bytesToSkip, cancellationToken).ConfigureAwait(false);
-                        await TarHelpers.SkipBlockAlignmentPaddingAsync(_archiveStream, _previouslyReadEntry._header._size, cancellationToken).ConfigureAwait(false);
                         dataStream.HasReachedEnd = true; // Now the pointer is beyond the limit, so any read attempts should throw
                     }
                 }
+                await TarHelpers.SkipBlockAlignmentPaddingAsync(_archiveStream, _previouslyReadEntry._header._size, cancellationToken).ConfigureAwait(false);
             }
         }
 

src/libraries/System.Formats.Tar/tests/TarFile/TarFile.ExtractToDirectory.Stream.Tests.cs

@@ -3,6 +3,7 @@
 
 using System.Collections.Generic;
 using System.IO;
+using System.IO.Compression;
 using System.Linq;
 using Xunit;
 
@@ -145,5 +146,36 @@ private void Extract_LinkEntry_TargetInsideDirectory_Internal(TarEntryType entry
 
             Assert.Equal(2, Directory.GetFileSystemEntries(baseDir).Count());
         }
+
+        [Theory]
+        [InlineData(512)]
+        [InlineData(512 + 1)]
+        [InlineData(512 + 512 - 1)]
+        public void Extract_UnseekableStream_BlockAlignmentPadding_DoesNotAffectNextEntries(int contentSize)
+        {
+            byte[] fileContents = new byte[contentSize];
+            Array.Fill<byte>(fileContents, 0x1);
+
+            using var archive = new MemoryStream();
+            using (var compressor = new GZipStream(archive, CompressionMode.Compress, leaveOpen: true))
+            {
+                using var writer = new TarWriter(compressor);
+                var entry1 = new PaxTarEntry(TarEntryType.RegularFile, "file");
+                entry1.DataStream = new MemoryStream(fileContents);
+                writer.WriteEntry(entry1);
+
+                var entry2 = new PaxTarEntry(TarEntryType.RegularFile, "next-file");
+                writer.WriteEntry(entry2);
+            }
+
+            archive.Position = 0;
+            using var decompressor = new GZipStream(archive, CompressionMode.Decompress);
+            using var reader = new TarReader(decompressor);
+
+            using TempDirectory destination = new TempDirectory();
+            TarFile.ExtractToDirectory(decompressor, destination.Path, overwriteFiles: true);
+
+            Assert.Equal(2, Directory.GetFileSystemEntries(destination.Path, "*", SearchOption.AllDirectories).Count());
+        }
     }
 }

src/libraries/System.Formats.Tar/tests/TarFile/TarFile.ExtractToDirectoryAsync.Stream.Tests.cs

@@ -3,6 +3,7 @@
 
 using System.Collections.Generic;
 using System.IO;
+using System.IO.Compression;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
@@ -174,5 +175,36 @@ private async Task Extract_LinkEntry_TargetInsideDirectory_Internal_Async(TarEnt
                 }
             }
         }
+
+        [Theory]
+        [InlineData(512)]
+        [InlineData(512 + 1)]
+        [InlineData(512 + 512 - 1)]
+        public async Task Extract_UnseekableStream_BlockAlignmentPadding_DoesNotAffectNextEntries_Async(int contentSize)
+        {
+            byte[] fileContents = new byte[contentSize];
+            Array.Fill<byte>(fileContents, 0x1);
+
+            using var archive = new MemoryStream();
+            using (var compressor = new GZipStream(archive, CompressionMode.Compress, leaveOpen: true))
+            {
+                using var writer = new TarWriter(compressor);
+                var entry1 = new PaxTarEntry(TarEntryType.RegularFile, "file");
+                entry1.DataStream = new MemoryStream(fileContents);
+                await writer.WriteEntryAsync(entry1);
+
+                var entry2 = new PaxTarEntry(TarEntryType.RegularFile, "next-file");
+                await writer.WriteEntryAsync(entry2);
+            }
+
+            archive.Position = 0;
+            using var decompressor = new GZipStream(archive, CompressionMode.Decompress);
+            using var reader = new TarReader(decompressor);
+
+            using TempDirectory destination = new TempDirectory();
+            await TarFile.ExtractToDirectoryAsync(decompressor, destination.Path, overwriteFiles: true);
+
+            Assert.Equal(2, Directory.GetFileSystemEntries(destination.Path, "*", SearchOption.AllDirectories).Count());
+        }
     }
 }

src/libraries/System.Formats.Tar/tests/TarReader/TarReader.GetNextEntry.Tests.cs

@@ -250,5 +250,43 @@ public void GetNextEntry_UnseekableArchive_ReplaceDataStream_ExcludeFromDisposin
                 Assert.Equal("Substituted", streamReader.ReadLine());
             }
         }
+
+        [Theory]
+        [InlineData(512)]
+        [InlineData(512 + 1)]
+        [InlineData(512 + 512 - 1)]
+        public void BlockAlignmentPadding_DoesNotAffectNextEntries(int contentSize)
+        {
+            byte[] fileContents = new byte[contentSize];
+            Array.Fill<byte>(fileContents, 0x1);
+
+            using var archive = new MemoryStream();
+            using (var writer = new TarWriter(archive, leaveOpen: true))
+            {
+                var entry1 = new PaxTarEntry(TarEntryType.RegularFile, "file");
+                entry1.DataStream = new MemoryStream(fileContents);
+                writer.WriteEntry(entry1);
+
+                var entry2 = new PaxTarEntry(TarEntryType.RegularFile, "next-file");
+                writer.WriteEntry(entry2);
+            }
+
+            archive.Position = 0;
+            using var unseekable = new WrappedStream(archive, archive.CanRead, archive.CanWrite, canSeek: false);
+            using var reader = new TarReader(unseekable);
+
+            TarEntry e = reader.GetNextEntry();
+            Assert.Equal(contentSize, e.Length);
+
+            byte[] buffer = new byte[contentSize];
+            while (e.DataStream.Read(buffer) > 0) ;
+            AssertExtensions.SequenceEqual(fileContents, buffer);
+
+            e = reader.GetNextEntry();
+            Assert.Equal(0, e.Length);
+
+            e = reader.GetNextEntry();
+            Assert.Null(e);
+        }
     }
 }

src/libraries/System.Formats.Tar/tests/TarReader/TarReader.GetNextEntryAsync.Tests.cs

@@ -288,5 +288,43 @@ public async Task GetNextEntry_UnseekableArchive_ReplaceDataStream_ExcludeFromDi
                 }
             }
         }
+
+        [Theory]
+        [InlineData(512)]
+        [InlineData(512 + 1)]
+        [InlineData(512 + 512 - 1)]
+        public async Task BlockAlignmentPadding_DoesNotAffectNextEntries_Async(int contentSize)
+        {
+            byte[] fileContents = new byte[contentSize];
+            Array.Fill<byte>(fileContents, 0x1);
+
+            using var archive = new MemoryStream();
+            using (var writer = new TarWriter(archive, leaveOpen: true))
+            {
+                var entry1 = new PaxTarEntry(TarEntryType.RegularFile, "file");
+                entry1.DataStream = new MemoryStream(fileContents);
+                await writer.WriteEntryAsync(entry1);
+
+                var entry2 = new PaxTarEntry(TarEntryType.RegularFile, "next-file");
+                await writer.WriteEntryAsync(entry2);
+            }
+
+            archive.Position = 0;
+            using var unseekable = new WrappedStream(archive, archive.CanRead, archive.CanWrite, canSeek: false);
+            using var reader = new TarReader(unseekable);
+
+            TarEntry e = await reader.GetNextEntryAsync();
+            Assert.Equal(contentSize, e.Length);
+
+            byte[] buffer = new byte[contentSize];
+            while (e.DataStream.Read(buffer) > 0) ;
+            AssertExtensions.SequenceEqual(fileContents, buffer);
+
+            e = await reader.GetNextEntryAsync();
+            Assert.Equal(0, e.Length);
+
+            e = await reader.GetNextEntryAsync();
+            Assert.Null(e);
+        }
     }
 }