Merge pull request #121 from benshoof/rar_detection_fix

Fix false positives in Rar file detection

SharpCompress.Test/Tar/TarArchiveTests.cs

@@ -145,5 +145,16 @@ namespace SharpCompress.Test
             }
             CompareArchivesByPath(modified, scratchPath);
         }
+
+        [TestMethod]
+        public void Tar_Containing_Rar_Archive()
+        {
+            string archiveFullPath = Path.Combine(TEST_ARCHIVES_PATH, "Tar.ContainsRar.tar");
+            using (Stream stream = File.OpenRead(archiveFullPath))
+            using (IArchive archive = ArchiveFactory.Open(stream))
+            {
+                Assert.IsTrue(archive.Type == ArchiveType.Tar);
+            }
+        }
     }
 }

SharpCompress.Test/Tar/TarReaderTests.cs

@@ -2,6 +2,7 @@
 using System.IO;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using SharpCompress.Common;
+using SharpCompress.Reader;
 using SharpCompress.Reader.Tar;
 
 namespace SharpCompress.Test
@@ -88,5 +89,16 @@ namespace SharpCompress.Test
                 Assert.AreEqual(names.Count, 3);
             }
         }
+
+        [TestMethod]
+        public void Tar_Containing_Rar_Reader()
+        {
+            string archiveFullPath = Path.Combine(TEST_ARCHIVES_PATH, "Tar.ContainsRar.tar");
+            using (Stream stream = File.OpenRead(archiveFullPath))
+            using (IReader reader = ReaderFactory.Open(stream))
+            {
+                Assert.IsTrue(reader.ArchiveType == ArchiveType.Tar);
+            }
+        }
     }
 }

SharpCompress/Archive/ArchiveFactory.cs

@@ -43,7 +43,7 @@ namespace SharpCompress.Archive
                 return GZipArchive.Open(stream, options);
             }
             stream.Seek(0, SeekOrigin.Begin);
-            if(RarArchive.IsRarFile(stream, Options.LookForHeader | Options.KeepStreamsOpen))
+            if (RarArchive.IsRarFile(stream, options))
             {
                stream.Seek(0, SeekOrigin.Begin);
                return RarArchive.Open(stream, options);
@@ -138,7 +138,7 @@ namespace SharpCompress.Archive
                     return GZipArchive.Open(fileInfo, options);
                 }
                 stream.Seek(0, SeekOrigin.Begin);
-                if(RarArchive.IsRarFile(stream, Options.LookForHeader | Options.KeepStreamsOpen))
+                if (RarArchive.IsRarFile(stream, options))
                 {
                    stream.Dispose();
                    return RarArchive.Open(fileInfo, options);

SharpCompress/Archive/Rar/RarArchive.cs

@@ -152,12 +152,8 @@ namespace SharpCompress.Archive.Rar
             try
             {
                 var headerFactory = new RarHeaderFactory(StreamingMode.Seekable, options);
-                RarHeader header = headerFactory.ReadHeaders(stream).FirstOrDefault();
-                if (header == null)
-                {
-                    return false;
-                }
-                return Enum.IsDefined(typeof (HeaderType), header.HeaderType);
+                var markHeader = headerFactory.ReadHeaders(stream).FirstOrDefault() as MarkHeader;
+                return markHeader != null && markHeader.IsValid();
             }
             catch
             {

SharpCompress/Common/Rar/Headers/MarkHeader.cs

@@ -10,48 +10,15 @@ namespace SharpCompress.Common.Rar.Headers
 
         internal bool IsValid()
         {
-            if (!(HeadCRC == 0x6152))
-            {
-                return false;
-            }
-            if (!(HeaderType == HeaderType.MarkHeader))
-            {
-                return false;
-            }
-            if (!(Flags == 0x1a21))
-            {
-                return false;
-            }
-            if (!(HeaderSize == BaseBlockSize))
-            {
-                return false;
-            }
-            return true;
-        }
+            // Rar old signature: 52 45 7E 5E (not supported)
 
-        internal bool IsSignature()
-        {
-            bool valid = false;
-            /*byte[] d = new byte[BaseBlock.BaseBlockSize];
-                BinaryWriter writer = new BinaryWriter();
-                writer.Write(HeadCRC);
-                writer.Write((byte)HeaderType);
-                writer.Write(flags);
-                writer.Write(HeaderSize);
-                writer.Flush
-        
-            if (d[0] == 0x52) {
-                if (d[1]==0x45 && d[2]==0x7e && d[3]==0x5e) {
-                    oldFormat=true;
-                    valid=true;
-                }
-                else if (d[1]==0x61 && d[2]==0x72 && d[3]==0x21 && d[4]==0x1a &&
-                        d[5]==0x07 && d[6]==0x00) {
-                    oldFormat=false;
-                    valid=true;
-                }
-            }*/
-            return valid;
+            // Rar4 signature: 52 61 72 21 1A 07 00
+            return HeadCRC == 0x6152 &&
+                   HeaderType == HeaderType.MarkHeader &&
+                   Flags == 0x1A21 &&
+                   HeaderSize == 0x07;
+
+            // Rar5 signature: 52 61 72 21 1A 07 10 00 (not supported yet)
         }
 
         internal bool OldFormat { get; private set; }