verify rar CRC on header and file data

adamhathcock · Apr 4, 2017 · 97d5e0a · 97d5e0a
1 parent 356c977
commit 97d5e0a
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Showing 9 changed files with 146 additions and 16 deletions.
diff --git a/src/SharpCompress/Common/Rar/Headers/RarHeader.cs b/src/SharpCompress/Common/Rar/Headers/RarHeader.cs
@@ -1,4 +1,5 @@
-using System.IO;
+using System;
+using System.IO;
 using SharpCompress.IO;
 
 namespace SharpCompress.Common.Rar.Headers
@@ -18,14 +19,14 @@ private void FillBase(RarHeader baseHeader)
             ReadBytes = baseHeader.ReadBytes;
         }
 
-        internal static RarHeader Create(MarkingBinaryReader reader)
+        internal static RarHeader Create(RarCrcBinaryReader reader)
         {
             try
             {
                 RarHeader header = new RarHeader();
 
                 reader.Mark();
-                header.ReadFromReader(reader);
+                header.ReadStartFromReader(reader);
                 header.ReadBytes += reader.CurrentReadByteCount;
 
                 return header;
@@ -36,9 +37,10 @@ internal static RarHeader Create(MarkingBinaryReader reader)
             }
         }
 
-        protected virtual void ReadFromReader(MarkingBinaryReader reader)
+        private void ReadStartFromReader(RarCrcBinaryReader reader)
         {
-            HeadCRC = reader.ReadInt16();
+            HeadCRC = reader.ReadUInt16();
+            reader.ResetCrc();
             HeaderType = (HeaderType)(reader.ReadByte() & 0xff);
             Flags = reader.ReadInt16();
             HeaderSize = reader.ReadInt16();
@@ -48,7 +50,11 @@ protected virtual void ReadFromReader(MarkingBinaryReader reader)
             }
         }
 
-        internal T PromoteHeader<T>(MarkingBinaryReader reader)
+        protected virtual void ReadFromReader(MarkingBinaryReader reader) {
+            throw new NotImplementedException();
+        }
+
+        internal T PromoteHeader<T>(RarCrcBinaryReader reader)
             where T : RarHeader, new()
         {
             T header = new T();
@@ -65,9 +71,21 @@ internal T PromoteHeader<T>(MarkingBinaryReader reader)
                 reader.ReadBytes(headerSizeDiff);
             }
 
+            VerifyHeaderCrc(reader.GetCrc());
+
             return header;
         }
 
+        private void VerifyHeaderCrc(ushort crc) {
+            if (HeaderType != HeaderType.MarkHeader) 
+            {
+                if (crc != HeadCRC) 
+                {
+                    throw new InvalidFormatException("rar header crc mismatch");
+                }
+            }
+        }
+
         protected virtual void PostReadingBytes(MarkingBinaryReader reader)
         {
         }
@@ -77,7 +95,7 @@ protected virtual void PostReadingBytes(MarkingBinaryReader reader)
         /// </summary>
         protected long ReadBytes { get; private set; }
 
-        protected short HeadCRC { get; private set; }
+        protected ushort HeadCRC { get; private set; }
 
         internal HeaderType HeaderType { get; private set; }
 

diff --git a/src/SharpCompress/Common/Rar/Headers/RarHeaderFactory.cs b/src/SharpCompress/Common/Rar/Headers/RarHeaderFactory.cs
@@ -129,7 +129,7 @@ private RarHeader ReadNextHeader(Stream stream)
                 reader.InitializeAes(salt);
             }
 #else
-            var reader = new MarkingBinaryReader(stream);
+            var reader = new RarCrcBinaryReader(stream);
 
 #endif
 
@@ -247,4 +247,4 @@ private RarHeader ReadNextHeader(Stream stream)
             }
         }
     }
-}
+}
diff --git a/src/SharpCompress/Common/Rar/RarCrcBinaryReader.cs b/src/SharpCompress/Common/Rar/RarCrcBinaryReader.cs
@@ -0,0 +1,40 @@
+using System.IO;
+using SharpCompress.Compressors.Rar;
+using SharpCompress.IO;
+
+namespace SharpCompress.Common.Rar {
+    internal class RarCrcBinaryReader : MarkingBinaryReader {
+        private uint currentCrc;
+
+        public RarCrcBinaryReader(Stream stream) : base(stream)
+        {
+        }
+
+        public ushort GetCrc() 
+        {
+            return (ushort)~this.currentCrc;
+        }
+
+        public void ResetCrc()
+        {
+            this.currentCrc = 0xffffffff;
+        }
+
+        protected void UpdateCrc(byte b) 
+        {
+            this.currentCrc = RarCRC.CheckCrc(this.currentCrc, b);
+        }
+
+        protected byte[] ReadBytesNoCrc(int count)
+        {
+            return base.ReadBytes(count);
+        }
+
+        public override byte[] ReadBytes(int count)
+        {
+            var result = base.ReadBytes(count);
+            this.currentCrc = RarCRC.CheckCrc(this.currentCrc, result, 0, result.Length);
+            return result;
+        }
+    }
+}
diff --git a/src/SharpCompress/Common/Rar/RarCryptoBinaryReader.cs b/src/SharpCompress/Common/Rar/RarCryptoBinaryReader.cs
@@ -6,19 +6,36 @@
 
 namespace SharpCompress.Common.Rar
 {
-    internal class RarCryptoBinaryReader : MarkingBinaryReader
+    internal class RarCryptoBinaryReader : RarCrcBinaryReader
     {
         private RarRijndael rijndael;
         private byte[] salt;
         private readonly string password;
         private readonly Queue<byte> data = new Queue<byte>();
+        private long readCount;
 
         public RarCryptoBinaryReader(Stream stream, string password )
             : base(stream)
         {
             this.password = password;
         }
 
+        // track read count ourselves rather than using the underlying stream since we buffer
+        public override long CurrentReadByteCount {
+            get 
+            {
+                return this.readCount;
+            }
+            protected set 
+            {
+                // ignore
+            }
+        }
+
+        public override void Mark() {
+            this.readCount = 0;
+        }
+
         protected bool UseEncryption
         {
             get { return salt != null; }
@@ -36,6 +53,7 @@ public override byte[] ReadBytes(int count)
             {
                 return ReadAndDecryptBytes(count);
             }
+            this.readCount += count;
             return base.ReadBytes(count);
         }
 
@@ -50,7 +68,7 @@ private byte[] ReadAndDecryptBytes(int count)
                 for (int i = 0; i < alignedSize / 16; i++)
                 {
                     //long ax = System.currentTimeMillis();
-                    byte[] cipherText = base.ReadBytes(16);
+                    byte[] cipherText = base.ReadBytesNoCrc(16);
                     var readBytes = rijndael.ProcessBlock(cipherText);
                     foreach (var readByte in readBytes)
                         data.Enqueue(readByte);
@@ -63,8 +81,11 @@ private byte[] ReadAndDecryptBytes(int count)
 
             for (int i = 0; i < count; i++)
             {
-                decryptedBytes[i] = data.Dequeue();
+                var b = data.Dequeue();
+                decryptedBytes[i] = b;
+                UpdateCrc(b);
             }
+            this.readCount += count;
             return decryptedBytes;
         }
 

diff --git a/src/SharpCompress/Compressors/Rar/MultiVolumeReadOnlyStream.cs b/src/SharpCompress/Compressors/Rar/MultiVolumeReadOnlyStream.cs
@@ -19,6 +19,7 @@ internal class MultiVolumeReadOnlyStream : Stream
 
         private long currentPartTotalReadBytes;
         private long currentEntryTotalReadBytes;
+        private uint currentCrc;
 
         internal MultiVolumeReadOnlyStream(IEnumerable<RarFilePart> parts, IExtractionListener streamListener)
         {
@@ -59,6 +60,8 @@ private void InitializeNextFilePart()
 
             currentPartTotalReadBytes = 0;
 
+            currentCrc = filePartEnumerator.Current.FileHeader.FileCRC;
+
             streamListener.FireFilePartExtractionBegin(filePartEnumerator.Current.FilePartName,
                                                        filePartEnumerator.Current.FileHeader.CompressedSize,
                                                        filePartEnumerator.Current.FileHeader.UncompressedSize);
@@ -119,6 +122,8 @@ public override int Read(byte[] buffer, int offset, int count)
 
         public override bool CanWrite { get { return false; } }
 
+        public uint CurrentCrc { get { return this.currentCrc; } }
+
         public override void Flush()
         {
             throw new NotSupportedException();

diff --git a/src/SharpCompress/Compressors/Rar/RarCRC.cs b/src/SharpCompress/Compressors/Rar/RarCRC.cs
@@ -6,6 +6,10 @@ internal static class RarCRC
     {
         private static readonly uint[] crcTab;
 
+        public static uint CheckCrc(uint startCrc, byte b) {
+                return (crcTab[((int) ((int) startCrc ^ (int) b)) & 0xff] ^ (startCrc >> 8));
+        }
+
         public static uint CheckCrc(uint startCrc, byte[] data, int offset, int count)
         {
             int size = Math.Min(data.Length - offset, count);

diff --git a/src/SharpCompress/Compressors/Rar/RarCrcStream.cs b/src/SharpCompress/Compressors/Rar/RarCrcStream.cs
@@ -0,0 +1,42 @@
+using System.IO;
+using SharpCompress.Common;
+using SharpCompress.Common.Rar.Headers;
+
+namespace SharpCompress.Compressors.Rar {
+    internal class RarCrcStream : RarStream {
+        private readonly MultiVolumeReadOnlyStream readStream;
+        private uint currentCrc;
+
+        public RarCrcStream(Unpack unpack, FileHeader fileHeader, MultiVolumeReadOnlyStream readStream) : base(unpack, fileHeader, readStream)
+        {
+            this.readStream = readStream;
+            ResetCrc();
+        }
+
+        public uint GetCrc()
+        {
+            return ~this.currentCrc;
+        }
+
+        public void ResetCrc()
+        {
+            this.currentCrc = 0xffffffff;
+        }
+
+
+        public override int Read(byte[] buffer, int offset, int count)
+        {
+            var result = base.Read(buffer, offset, count);
+            if (result != 0) 
+            {
+                this.currentCrc = RarCRC.CheckCrc(this.currentCrc, buffer, offset, result);
+            } 
+            else if (GetCrc() != this.readStream.CurrentCrc)
+            {
+                // NOTE: we use the last FileHeader in a multipart volume to check CRC
+                throw new InvalidFormatException("file crc mismatch");
+            }
+            return result;
+        }
+    }
+}
diff --git a/src/SharpCompress/IO/MarkingBinaryReader.cs b/src/SharpCompress/IO/MarkingBinaryReader.cs
@@ -12,9 +12,9 @@ public MarkingBinaryReader(Stream stream)
         {
         }
 
-        public long CurrentReadByteCount { get; private set; }
+        public virtual long CurrentReadByteCount { get; protected set; }
 
-        public void Mark()
+        public virtual void Mark()
         {
             CurrentReadByteCount = 0;
         }

diff --git a/src/SharpCompress/Readers/Rar/RarReader.cs b/src/SharpCompress/Readers/Rar/RarReader.cs
@@ -69,9 +69,9 @@ protected virtual IEnumerable<FilePart> CreateFilePartEnumerableForCurrentEntry(
 
         protected override EntryStream GetEntryStream()
         {
-            return CreateEntryStream(new RarStream(pack, Entry.FileHeader,
+            return CreateEntryStream(new RarCrcStream(pack, Entry.FileHeader,
                                                    new MultiVolumeReadOnlyStream(
                                                                                  CreateFilePartEnumerableForCurrentEntry().Cast<RarFilePart>(), this)));
         }
     }
-}
+}