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(ArcOpener.OpenEntry): decrypt ASB scripts (the only known key is hard-coded).

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morkt 2015-04-27 21:35:48 +04:00
parent 8ee82a8c31
commit 35ad091adf
1 changed files with 39 additions and 0 deletions
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39
ArcFormats/ArcAZSys.cs
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@ -29,6 +29,7 @@ using System.ComponentModel.Composition;
using System.IO;
using GameRes.Formats.Strings;
using GameRes.Utility;
using ZLibNet;
namespace GameRes.Formats.AZSys
{
@ -83,6 +84,44 @@ namespace GameRes.Formats.AZSys
return new ArcFile (file, this, dir);
}
static readonly uint[] KnownKeys = new uint[] { 0x1de71cb9 }; // Triptych
public override Stream OpenEntry (ArcFile arc, Entry entry)
{
if (entry.Size < 20
|| ".asb" != Path.GetExtension (entry.Name).ToLowerInvariant()
|| !arc.File.View.AsciiEqual (entry.Offset, "ASB\x1a"))
return arc.File.CreateStream (entry.Offset, entry.Size);
uint packed = arc.File.View.ReadUInt32 (entry.Offset+4);
uint unpacked = arc.File.View.ReadUInt32 (entry.Offset+8);
if (12 + packed != entry.Size)
return arc.File.CreateStream (entry.Offset, entry.Size);
uint key = KnownKeys[0] ^ unpacked;
key ^= ((key << 12) | key) << 11;
uint first = arc.File.View.ReadUInt16 (entry.Offset+16);
first = (first - key) & 0xffff;
if (first != 0xda78) // doesn't look like zlib stream
return arc.File.CreateStream (entry.Offset, entry.Size);
byte[] input = new byte[packed];
arc.File.View.Read (entry.Offset+12, input, 0, packed);
unsafe
{
fixed (byte* raw = input)
{
uint* encoded = (uint*)raw;
for (int i = 0; i < input.Length/4; ++i)
encoded[i] -= key;
}
}
// first 4 bytes are CRC32 of the compressed stream
uint checksum = LittleEndian.ToUInt32 (input, 0);
if (checksum != Crc32.Compute (input, 4, input.Length-4))
return arc.File.CreateStream (entry.Offset, entry.Size);
return new ZLibStream (new MemoryStream (input, 4, input.Length-4), CompressionMode.Decompress);
}
internal class IndexReader
{
byte[] m_input;