Check crc on tar header

src/SharpCompress/Common/Tar/Headers/TarHeader.cs

@@ -134,6 +134,13 @@ internal sealed class TarHeader
             hasLongValue = false;
         } while (hasLongValue);
 
+        var crc = ReadAsciiInt64Base8(buffer, 148, 7);
+
+        if (crc != RecalculateChecksum(buffer))
+        {
+            return false;
+        }
+
         Name = longName ?? ArchiveEncoding.Decode(buffer, 0, 100).TrimNulls();
         EntryType = entryType;
         Size = ReadSize(buffer);

tests/SharpCompress.Test/Tar/TarArchiveTests.cs

@@ -217,8 +217,7 @@ public class TarArchiveTests : ArchiveTests
     {
         var archiveFullPath = Path.Combine(TEST_ARCHIVES_PATH, "Tar.Empty.tar");
         using Stream stream = File.OpenRead(archiveFullPath);
-        using var archive = ArchiveFactory.Open(stream);
-        Assert.True(archive.Type == ArchiveType.Tar);
+        Assert.Throws<InvalidOperationException>(() => ArchiveFactory.Open(stream));
     }
 
     [Theory]
@@ -287,4 +286,12 @@ public class TarArchiveTests : ArchiveTests
 
         Assert.Equal(2, numberOfEntries);
     }
+
+    [Fact]
+    public void Tar_Detect_Test()
+    {
+        var isTar = TarArchive.IsTarFile(Path.Combine(TEST_ARCHIVES_PATH, "false.positive.tar"));
+
+        Assert.False(isTar);
+    }
 }