NTFSVolume: Added ability to mount as readonly

Author: TalAloni

DiskAccessLibrary/FileSystems/FileSystemHelper.cs

@@ -1,4 +1,4 @@
-/* Copyright (C) 2014-2016 Tal Aloni <[email protected]>. All rights reserved.
+/* Copyright (C) 2014-2019 Tal Aloni <[email protected]>. All rights reserved.
  * 
  * You can redistribute this program and/or modify it under the terms of
  * the GNU Lesser Public License as published by the Free Software Foundation,
@@ -15,10 +15,15 @@ namespace DiskAccessLibrary.FileSystems
     public class FileSystemHelper
     {
         public static FileSystem ReadFileSystem(Volume volume)
+        {
+            return ReadFileSystem(volume, false);
+        }
+
+        public static FileSystem ReadFileSystem(Volume volume, bool isReadOnly)
         {
             try
             {
-                return new NTFSFileSystem(volume);
+                return new NTFSFileSystem(volume, isReadOnly);
             }
             catch (InvalidDataException)
             {

DiskAccessLibrary/FileSystems/NTFS/Adapters/NTFSFileSystem.cs

@@ -19,9 +19,9 @@ public class NTFSFileSystem : FileSystem, IExtendableFileSystem
         private NTFSVolume m_volume;
         private Dictionary<long, List<NTFSFileStream>> m_openStreams = new Dictionary<long, List<NTFSFileStream>>();
 
-        public NTFSFileSystem(Volume volume)
+        public NTFSFileSystem(Volume volume, bool isReadOnly)
         {
-            m_volume = new NTFSVolume(volume);
+            m_volume = new NTFSVolume(volume, isReadOnly);
         }
 
         public NTFSFileSystem(NTFSVolume volume)

DiskAccessLibrary/FileSystems/NTFS/NTFSVolume.cs

@@ -24,6 +24,7 @@ namespace DiskAccessLibrary.FileSystems.NTFS
     public partial class NTFSVolume : IExtendableFileSystem
     {
         private Volume m_volume;
+        private bool m_isReadOnly;
         private NTFSBootRecord m_bootRecord; // Partition's boot record
         private MasterFileTable m_mft;
         private LogFile m_logFile;
@@ -39,9 +40,14 @@ public NTFSVolume(Volume volume) : this(volume, false)
         { 
         }
 
-        public NTFSVolume(Volume volume, bool useMftMirror)
+        public NTFSVolume(Volume volume, bool isReadOnly) : this(volume, isReadOnly, false)
+        {
+        }
+
+        public NTFSVolume(Volume volume, bool isReadOnly, bool useMftMirror)
         {
             m_volume = volume;
+            m_isReadOnly = volume.IsReadOnly || isReadOnly;
 
             byte[] bootSector = m_volume.ReadSector(0);
             m_bootRecord = NTFSBootRecord.ReadRecord(bootSector);
@@ -358,13 +364,16 @@ protected internal virtual byte[] ReadClusters(long clusterLCN, int count, Conte
             long firstSectorIndex = clusterLCN * m_bootRecord.SectorsPerCluster;
             int sectorsToRead = m_bootRecord.SectorsPerCluster * count;
 
-            byte[] result = m_volume.ReadSectors(firstSectorIndex, sectorsToRead);
-
-            return result;
+            return m_volume.ReadSectors(firstSectorIndex, sectorsToRead);
         }
 
         protected internal virtual void WriteClusters(long clusterLCN, byte[] data, ContentType contentType)
         {
+            if (IsReadOnly)
+            {
+                throw new UnauthorizedAccessException("Attempted to perform write on a filesystem mounted for readonly access");
+            }
+
             long firstSectorIndex = clusterLCN * m_bootRecord.SectorsPerCluster;
             m_volume.WriteSectors(firstSectorIndex, data);
         }
@@ -376,6 +385,11 @@ protected internal virtual byte[] ReadSectors(long sectorIndex, int sectorCount,
 
         protected internal virtual void WriteSectors(long sectorIndex, byte[] data, ContentType contentType)
         {
+            if (IsReadOnly)
+            {
+                throw new UnauthorizedAccessException("Attempted to perform write on a filesystem mounted for readonly access");
+            }
+
             m_volume.WriteSectors(sectorIndex, data);
         }
 
@@ -492,7 +506,7 @@ public bool IsReadOnly
         {
             get
             {
-                return m_volume.IsReadOnly;
+                return m_isReadOnly;
             }
         }