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Fix identifying between FAT12 and FAT16, checking entire FAT validity. Fixes #576

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This commit is contained in:
Natalia Portillo
2021-06-03 23:34:17 +01:00
parent 9fe5353394
commit fcc0211fb6
2 changed files with 133 additions and 9 deletions
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75
Aaru.Filesystems/FAT/Info.cs
View File

@@ -34,6 +34,7 @@ using System;
using System.Diagnostics.CodeAnalysis;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using Aaru.Checksums;
using Aaru.CommonTypes;
@@ -42,6 +43,7 @@ using Aaru.CommonTypes.Interfaces;
using Aaru.Console;
using Aaru.Helpers;
using Schemas;
using Marshal = Aaru.Helpers.Marshal;
namespace Aaru.Filesystems
{
@@ -690,8 +692,79 @@ namespace Aaru.Filesystems
else
clusters = humanBpb.clusters == 0 ? humanBpb.big_clusters : humanBpb.clusters;
// This will walk all the FAT entries and check if they're valid FAT12 or FAT16 entries.
// If the whole table is valid in both senses, it considers the type entry in the BPB.
// BeOS is known to set the type as FAT16 but treat it as FAT12.
if(!isFat12 &&
!isFat16)
{
if(clusters < 4089)
isFat12 = true;
{
ushort[] fat12 = new ushort[clusters];
_reservedSectors = fakeBpb.rsectors;
sectorsPerRealSector = fakeBpb.bps / imagePlugin.Info.SectorSize;
_fatFirstSector = partition.Start + (_reservedSectors * sectorsPerRealSector);
byte[] fatBytes = imagePlugin.ReadSectors(_fatFirstSector, fakeBpb.spfat);
int pos = 0;
for(int i = 0; i + 3 < fatBytes.Length && pos < fat12.Length; i += 3)
{
fat12[pos++] = (ushort)(((fatBytes[i + 1] & 0xF) << 8) + fatBytes[i + 0]);
if(pos >= fat12.Length)
break;
fat12[pos++] = (ushort)(((fatBytes[i + 1] & 0xF0) >> 4) + (fatBytes[i + 2] << 4));
}
bool fat12Valid = fat12[0] >= FAT12_RESERVED && fat12[1] >= FAT12_RESERVED;
foreach(ushort entry in fat12)
{
if(entry >= FAT12_RESERVED ||
entry <= clusters)
continue;
fat12Valid = false;
break;
}
ushort[] fat16 = MemoryMarshal.Cast<byte, ushort>(fatBytes).ToArray();
bool fat16Valid = fat16[0] >= FAT16_RESERVED && fat16[1] >= 0x3FF0;
foreach(ushort entry in fat16)
{
if(entry >= FAT16_RESERVED ||
entry <= clusters)
continue;
fat16Valid = false;
break;
}
isFat12 = fat12Valid;
isFat16 = fat16Valid;
// Check BPB type
if(isFat12 == isFat16)
{
isFat12 = fakeBpb.fs_type != null &&
Encoding.ASCII.GetString(fakeBpb.fs_type) == "FAT12 ";
isFat16 = fakeBpb.fs_type != null &&
Encoding.ASCII.GetString(fakeBpb.fs_type) == "FAT16 ";
}
if(!isFat12 &&
!isFat16)
isFat12 = true;
}
else
isFat16 = true;
}

67
Aaru.Filesystems/FAT/Super.cs
View File

@@ -313,15 +313,66 @@ namespace Aaru.Filesystems
if(!_fat12 &&
!_fat16)
{
ulong clusters;
if(fakeBpb.sectors == 0)
clusters = fakeBpb.spc == 0 ? fakeBpb.big_sectors : fakeBpb.big_sectors / fakeBpb.spc;
else
clusters = fakeBpb.spc == 0 ? fakeBpb.sectors : (ulong)fakeBpb.sectors / fakeBpb.spc;
if(clusters < 4089)
_fat12 = true;
{
ushort[] fat12 = new ushort[clusters];
_reservedSectors = fakeBpb.rsectors;
sectorsPerRealSector = fakeBpb.bps / imagePlugin.Info.SectorSize;
_fatFirstSector = partition.Start + (_reservedSectors * sectorsPerRealSector);
byte[] fatBytes = imagePlugin.ReadSectors(_fatFirstSector, fakeBpb.spfat);
int pos = 0;
for(int i = 0; i + 3 < fatBytes.Length && pos < fat12.Length; i += 3)
{
fat12[pos++] = (ushort)(((fatBytes[i + 1] & 0xF) << 8) + fatBytes[i + 0]);
if(pos >= fat12.Length)
break;
fat12[pos++] = (ushort)(((fatBytes[i + 1] & 0xF0) >> 4) + (fatBytes[i + 2] << 4));
}
bool fat12Valid = fat12[0] >= FAT12_RESERVED && fat12[1] >= FAT12_RESERVED;
foreach(ushort entry in fat12)
{
if(entry >= FAT12_RESERVED ||
entry <= clusters)
continue;
fat12Valid = false;
break;
}
ushort[] fat16 = MemoryMarshal.Cast<byte, ushort>(fatBytes).ToArray();
bool fat16Valid = fat16[0] >= FAT16_RESERVED && fat16[1] >= 0x3FF0;
foreach(ushort entry in fat16)
{
if(entry >= FAT16_RESERVED ||
entry <= clusters)
continue;
fat16Valid = false;
break;
}
_fat12 = fat12Valid;
_fat16 = fat16Valid;
// Check BPB type
if(_fat12 == _fat16)
{
_fat12 = Encoding.ASCII.GetString(fakeBpb.fs_type) == "FAT12 ";
_fat16 = Encoding.ASCII.GetString(fakeBpb.fs_type) == "FAT16 ";
}
}
else
_fat16 = true;
}