Improve the behaviour of ZipInputStream when reading zip entries with…

… BZip2 compression.
icsharpcode · Apr 1, 2019 · b02b844 · b02b844
1 parent afcccb0
commit b02b844
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Showing 2 changed files with 43 additions and 5 deletions.
diff --git a/src/ICSharpCode.SharpZipLib/Zip/ZipInputStream.cs b/src/ICSharpCode.SharpZipLib/Zip/ZipInputStream.cs
@@ -131,10 +131,21 @@ public bool CanDecompressEntry
 		{
 			get
 			{
-				return (entry != null) && entry.CanDecompress;
+				return (entry != null) && IsEntryCompressionMethodSupported(entry) && entry.CanDecompress;
 			}
 		}
 
+		/// <summary>
+		/// Is the compression method for the specified entry supported?
+		/// </summary>
+		/// <param name="entry"></param>
+		/// <returns></returns>
+		private static bool IsEntryCompressionMethodSupported(ZipEntry entry)
+		{
+			return entry.CompressionMethod == CompressionMethod.Deflated ||
+				   entry.CompressionMethod == CompressionMethod.Stored;
+		}
+
 		/// <summary>
 		/// Advances to the next entry in the archive
 		/// </summary>
@@ -206,10 +217,9 @@ public ZipEntry GetNextEntry()
 
 			string name = ZipStrings.ConvertToStringExt(flags, buffer);
 
-			entry = new ZipEntry(name, versionRequiredToExtract)
+			entry = new ZipEntry(name, versionRequiredToExtract, ZipConstants.VersionMadeBy, (CompressionMethod)method)
 			{
-				Flags = flags,
-				CompressionMethod = (CompressionMethod)method
+				Flags = flags
 			};
 
 			if ((flags & 8) == 0)
@@ -272,7 +282,7 @@ public ZipEntry GetNextEntry()
 			}
 
 			// Determine how to handle reading of data if this is attempted.
-			if (entry.IsCompressionMethodSupported())
+			if (IsEntryCompressionMethodSupported(entry))
 			{
 				internalReader = new ReadDataHandler(InitialRead);
 			}

diff --git a/test/ICSharpCode.SharpZipLib.Tests/Zip/StreamHandling.cs b/test/ICSharpCode.SharpZipLib.Tests/Zip/StreamHandling.cs
@@ -324,5 +324,33 @@ public void SingleLargeEntry()
 				}
 			);
 		}
+
+		const string BZip2CompressedZip =
+			"UEsDBC4AAAAMAEyxgU5p3ou9JwAAAAcAAAAFAAAAYS5kYXRCWmg5MUFZJlNZ0buMcAAAAkgACABA" + 
+			"ACAAIQCCCxdyRThQkNG7jHBQSwECMwAuAAAADABMsYFOad6LvScAAAAHAAAABQAAAAAAAAAAAAAA" + 
+			"AAAAAAAAYS5kYXRQSwUGAAAAAAEAAQAzAAAASgAAAAAA";
+
+		/// <summary>
+		/// Should fail to read a zip with BZip2 compression
+		/// </summary>
+		[Test]
+		[Category("Zip")]
+		public void ShouldReadBZip2EntryButNotDecompress()
+		{
+			var fileBytes = System.Convert.FromBase64String(BZip2CompressedZip);
+
+			using (var input = new MemoryStream(fileBytes, false))
+			{
+				var zis = new ZipInputStream(input);
+				var entry = zis.GetNextEntry();
+
+				Assert.That(entry.Name, Is.EqualTo("a.dat"), "Should be able to get entry name");
+				Assert.That(entry.CompressionMethod, Is.EqualTo(CompressionMethod.BZip2), "Entry should be BZip2 compressed");
+				Assert.That(zis.CanDecompressEntry, Is.False, "Should not be able to decompress BZip2 entry");
+
+				var buffer = new byte[1];
+				Assert.Throws<ZipException>(() => zis.Read(buffer, 0, 1), "Trying to read the stream should throw");
+			}
+		}
 	}
 }