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84 lines
3.3 KiB
C#
84 lines
3.3 KiB
C#
// /***************************************************************************
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// Aaru Data Preservation Suite
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// ----------------------------------------------------------------------------
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//
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// Filename : Fixup.cs
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// Author(s) : Natalia Portillo <claunia@claunia.com>
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//
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// Component : Microsoft NT File System plugin.
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//
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// --[ License ] --------------------------------------------------------------
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//
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// This library is free software; you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as
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// published by the Free Software Foundation; either version 2.1 of the
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// License, or (at your option) any later version.
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//
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// This library is distributed in the hope that it will be useful, but
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// WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public
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// License along with this library; if not, see <http://www.gnu.org/licenses/>.
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//
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// ----------------------------------------------------------------------------
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// Copyright © 2011-2026 Natalia Portillo
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// ****************************************************************************/
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using System;
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using Aaru.CommonTypes.Enums;
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using Aaru.Helpers;
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using Aaru.Logging;
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namespace Aaru.Filesystems;
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/// <inheritdoc />
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public sealed partial class NTFS
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{
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/// <summary>Applies Update Sequence Array fixups to a multi-sector protected record.</summary>
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/// <param name="record">Record data to fix up in place.</param>
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/// <returns>Error number indicating success or failure.</returns>
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ErrorNumber ApplyUsaFixup(byte[] record)
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{
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if(record.Length < Marshal.SizeOf<NtfsRecordHeader>()) return ErrorNumber.InvalidArgument;
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var usaOffset = BitConverter.ToUInt16(record, 4);
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var usaCount = BitConverter.ToUInt16(record, 6);
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// USA count includes the USN itself, so we have (usaCount - 1) fixup entries
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if(usaCount == 0 || usaOffset + usaCount * 2 > record.Length) return ErrorNumber.InvalidArgument;
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// The first entry of the USA is the Update Sequence Number (USN)
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var usn = BitConverter.ToUInt16(record, usaOffset);
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// Each subsequent entry replaces the last 2 bytes of each sector
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for(var i = 1; i < usaCount; i++)
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{
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int sectorEnd = i * (int)_bytesPerSector - 2;
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if(sectorEnd + 1 >= record.Length) break;
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// Verify the USN at the end of each sector matches
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var sectorUsn = BitConverter.ToUInt16(record, sectorEnd);
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if(sectorUsn != usn)
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{
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AaruLogging.Debug(MODULE_NAME,
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"USA fixup mismatch at sector {0}: 0x{1:X4} != 0x{2:X4}",
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i,
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sectorUsn,
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usn);
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return ErrorNumber.InOutError;
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}
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// Replace with the original data from the USA
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var originalValue = BitConverter.ToUInt16(record, usaOffset + i * 2);
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record[sectorEnd] = (byte)(originalValue & 0xFF);
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record[sectorEnd + 1] = (byte)(originalValue >> 8);
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}
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return ErrorNumber.NoError;
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}
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} |